Final Report Summary - EMLACS (Development of an Efficient Manufacturing of Laser Assisted Colds-Sprayed components for the Automotive Industry)
Executive Summary:
Note : see figure in the attached PDF filed
The EMLACS project is a proof of concept that targets to increase the deposition efficiency and the adhesion of a metallic coating on composite and metal substrates with a non-thermal process by texturing the surfaces by laser radiation. An on-line and real time vision module monitors the laser texturation process in order to insure the quality of the process.
Such coatings will allow new physical properties on specific materials as: electrical and /or thermal conductivity, improving adhesion of tribological coating, weldability between metal and composite materials... Among the possible applications, the growth of a thick metal coating of copper or aluminum on composite/plastic parts that will be machined later on for mechanical handling purposes, or, the use of such layer for joining dissimilar materials like aluminum and plastic for light car bodies are of special interest. This new process will eliminate gluing processes, chemical waste and all costs attached to it and can be an efficient and “green” palliative process.
The targeted fields of use are the Space/Aerospace and the automotive industries but not exclusively. Texturation and coating were done on Aluminum AW5083 (Base AI, 4.4% Mg, 0.7% Mn, 0.15% Cr) used in automotive industry and on Carbon Fiber Reinforced Composite samples (CFRP). Interesting preliminary results were also obtained on polymer parts (PEEK and ABS) which are also widely used in Transport industries.
The analysis of existing technologies already used in industry helped to define the most cost effective concept and gave a better global view of applications. From this survey (WP1), the consortium selected the following technologies:
- Coating technology choice: The Low Pressure Cold Spray process (Figure 1) was selected to perform the coatings. Cold Spray is an emergent technology being used to repair damaged metallic surfaces on molds or to enhance hardness of a mild steel or aluminum parts. It works at 6 bars max, has a small footprint and it’s an affordable coating process (approx. 50 kEuros investment only). Extra costs are linked to the powder material which is a consumable.
➢ - Laser technology choice: Widely used in industry with reliable power sources, the nanosecond (ns) and picosecond (ps) laser technologies for the texturing process were applied. These lasers can be easily integrated with direct optics or with a fiber beam delivery. It provides high flexibility for texturing miscellaneous materials which is clearly appreciated by industrial end users.
Based on the selected processes, the project runs in 2 phases: Phase 1 (WP2, WP3 and WP4) was dedicated to the development of the various individual concepts on lab samples whereas Phase 2 (WP5) aims to validate the overall concept on industrial materials. The following points can be highlighted:
➢- A new laser concept combining ns and ps lasers (Figure 2) has been developed (WP2). The good synchronization of both lasers was validated and the lasers characteristics have been demonstrated.
- A Quality and Control module has been developed (WP3). This module (Figure 3) represents a significant added value for the end-user. The process performances (i.e. coating adhesion mainly) completely rely on the texturation process quality. In order to have a repeatable and reliable process a Real Time Vision system module that monitors the texturation has been integrated. It also gives a GO or NO GO action based on a teach feedback illumination signal. A user interface allows saving the images for further QC and SPC analysis. The quality and control module is assembled on a scanning module (XY galvanometer head) and is driven by a friendly user interface. Pre-defined generic laser patterning (data base) for metal or composite material can be saved and downloaded for the best result of adhesion and efficiency properties for a specific coating material. This module can be used for various texturing applications independently from the cold spray process used in this project.
- Low Pressure Cold Spray (LPCS) coatings (Figure 4) have been obtained on textured lab samples (WP4). The LPCS process has been modeled and the deposition efficiency has been simulated and experimentally measured on a variety of samples. Tests showed that the deposition efficiency is almost uninfluenced by the laser texturing process. Tests analysis led to recommendations about the powder size in order to improve the coating performances. As a result of the investigations it was shown that the coating adhesion is drastically increased by the laser texturing process. Remarkable results were obtained with Aluminum/Alumina, pure Aluminum, Cu/Alumina and pure Copper materials.
➢ - Real industrial materials have been prepared following the complete process (WP5). The metallic substrates exhibit very high adhesion values and are very suitable for industrial applications. No coating could be created on the industrial composite samples provided. Therefore solutions to overcome the identified technical issues have been developed. Very promising results have been obtained on pure PEEK and ABS substrates. These last results make industrial applications possible on plastic parts.
Thanks to these first results based on the EMLACS project, ILS as coordinator and Laser process supplier, will continue and work on a demonstrator that will perform real parts with specific Cold Spray coating sprayed on appropriate laser texturation. The EMLACS concept has proven with remarkable results that the adhesion of such coating obtained by Cold Spray process can be improved up to a factor of 2 when the substrate has been laser textured before (80% for Al203/Cu powder, 105% for Pure Cu powder)! It will certainly open other process opportunities like thermal dissipation or thermal conduction on plastic/composite parts, protection of fragile surfaces where the cosmetic aspect has to be taken into consideration. Military industry will also be an area to investigate where components/modules are used in a very difficult environment conditions and where weight is also a major issue like in space applications.
Project Context and Objectives:
The deposition efficiency of Low Pressure Cold Spray can vary between 30 and 60%, depending on several parameters such as the substrate material, the spraying temperature, the surface roughness or the Cold Spray nozzle geometry.
This low efficiency is unacceptable for an industrial process, especially when it results in spraying expensive particles powder. Our objective with EMLACS is to reach an average deposit efficiency above 60 %.
In order to avoid a thermal stress or surface damages of the substrate (especially on composite and plastics substrate), the coating has to be done with a low temperature spraying process (typ. below 180°C). In order to increase the adhesion, a laser has been selected to generate the surface textures.
The target is to show a process that will be very close to the industrial needs. This means that the process has to be highly efficient, reliable, with short cycle times, affordable and with the lowest running and maintenance costs possible.
Today existing laser technology allow pulse durations from femto, pico or nano second. Femto second lasers are very expensive and do not allow the required throughput. On the other side nano and pico second laser sources are an option. Both technologies are compatible with the required cycle time. The optimal laser would be a mix of a pico to nano configuration in order to combine both process benefits. EMLACS addresses this specific laser combination which was not available at the deposition of the Project.
Some R&D projects are currently using short pulse laser sources to texture the surface of metallic parts in order to join plastic and metal components, by melting the thermoplastic material and pressing it onto the textured metallic surface. The EMLACS project also uses such laser process in order to increase the adhesion of the sprayed coating and to improve the deposit efficiency topo.
As part of the objectives of the first period and according to WP1, the existing technologies were investigated in order to define the starting point of the project roadmap of improvement for each individual process.
First the existing laser technology from ns to ps pulse regime was identified in order to combine it into a “single laser tool” for the EMLACS needs. Then different simulation tools were considered in order to identify the best low pressure cold spray configuration to achieve the best efficiency and adhesion of the coatings. For the quality control device, the necessary components were defined to setup the process control module based on an optical scanning system and integrating real time sensor electronics. Based on these three steps the process parameters for the laser texturation and for the cold spray coating were established. Experimental plans were applied on 2 use cases: for the automotive industry we used EMLACS technology on Aluminum substrates; for the Aerospace industry EMLACS technology was tested on Composite PEEK/Carbon fibers parts.
In WP2, the objective was to develop a laser source capable to deliver pulses from ns to ps. Based on the process parameter resulting from WP1, a Preliminary Technical specification for the combination of such lasers sources from EdgeWave was defined. The work done during this period consisted in identifying and designing the components to couple ps/ns generator as well as being able to switch from one regime to the other. One ps laser and one ns laser were assembled on an optical bench with all the required optical components to combine both laser beams. At this stage laser parameters were demonstrated.
Regardless of the delay due to the ps oscillator malfunctioning (due to the ps oscillator) and parasitic background between 2 pulses found in the short-pulse ns system, leading to major changes on the platform and making it available only from November 2015, the consortium managed to arrange texturation of samples using existing compatible short plus lasers available in the consortium in order not to disturb coating tests and analysis performed by UTBM. In WP3, a monitoring system was defined and developed in order to control the laser pattern geometry process in real time. The optical system was designed for the transmission in the visible spectrum while fully delivering the performance for the processing wavelength in the IR. The layout was based on an optical system equipped with a digital camera and sensors that observe the laser process plasma intensity. This signal was acquired synchronously with the scanner position by an electronic system which interfaces to a frame grabber equipped with an FPGA to transfer the data into a standard Windows ™ 7 based PC. Based on a teach process, this give a GO or NO GO signal. In case of a NO GO signal, an offline QC module integrating the same camera and software will be used to confirm and control the pattern geometry.
In WP4 the objective was to improve the use of low pressure cold spray in order to identify new material combinations. The work started on simulation models in order to confirm the existing technical bases of the Dycomet system and generate appropriate data for process comparison. The work carried out included 3D observation and quantification of surfaces which were irradiated using several laser conditions.
Adhesion test was defined in order to study the coating bonding strength as a function of the laser-structured surface characteristics. Based on the identified use case of the WP1, studies of selected materials combinations were done according to the most attractive industrial applications in order to increase the adhesion and deposition efficiency of the low pressure cold spray process.
In WP5 the objective was to integrate the modules developed in WP2 and WP3.
Many tests have been performed by UTBM based in order to validate simulation hypothesis on adhesion and efficiency depending on powders’ geometry, texturation geometry, thermal effects, speed of projection, nozzle design...
Descriptions and conclusions are detailed in Deliverable 5.15
Project Results:
3.1 Period 1
In order to perform a proper surface texturation, it is necessary to control the thermal effects of the laser on the surface. If the process induces too much heat effects on the aluminum surface, it could produce scoriae and this will lead to a lack of adhesion of the sprayed coating. Thermal effect regulation has been a recurring problematic throughout the project. Heat effect on composite parts could delaminate the substrate and totally destroy it even before any coating. Therefore first laser parameters were defined in order to minimize the thermal effect on both materials. The first results were obtained with separate ns and ps laser sources in order to generate several textures to be coated.
Different set of samples in Aluminum and Carbon fiber were sprayed with Aluminum and Copper coating with and without laser texturing in order to compare the adhesion and the deposition efficiency of both surface configurations. In order to optimize the speed of the projected particles, the gas temperature and the nozzles geometry of the cold spray process, the UTBM worked on different types of mathematical simulation.
The first coatings done at the UTBM on the aluminum textured samples has shown promising results and significant improvement on the adhesion of the coating that were increased by a factor of 2 with a preliminary texturation. This confirmed the benefit of the laser texturation. Depending on the granulometry of the used powder, parts that were laser textured with geometries between 90 and 150 microns matrix seems to be the best ones. It was also proven that it is possible to grow coatings of copper and/or aluminum with a thickness of several millimeters on aluminum substrates.
The Cold Spray tests done on the first type of composite samples (carbon fiber) were not yet successful. Regardless of a textured surface, the cold spray process acted like a sand blasting process, with an abrasion of the surface and the destruction of the first layer of fibers. Another kind of Carbon fiber samples from another supplier has shown that depending on the fiber direction and on the thickness of the upper matrix layer, it was possible to obtain some metallic coating without destroying the surface (Figure 5). Deeper investigation and new trials have been done to understand the adhesion process on this specific CFRP material.
Based on these preliminary tests, project results were presented at different exhibitions and conferences. The first composite cold spray parts and aluminum cold spray parts were shown at the 2015 JEC show in Paris (Figure 6), at the 2015 Hannover show and at the 2015 JNPLI conference in Nantes. Major aerospace and automotive companies have shown high interest in the EMLACS project. Some of them have committed to supply to the project new material substrates in order to define new user cases.
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Fairs and press releases for communicating EMLACS project :
o JEC Europe, Paris, March 2016 (EMLACS on Fraunhofer booth)
o Hannover Messe, Hanover, April 2016 (EMLACS on Dycomet booth)
o JNPLI 2016, Liège, Juin 2016 (EMLACS on CLFA booth)
o Industrie 2016, Juune 2016, Villepinte(France)
o Cold Spray Summer School, Barcelona, June 2015 (EMLACS on Dycomet booth)
o Laser-induced surface texturing of metal or organic substrates for structural adhesive bonding (article and presentation at Thermec 2015)
o ILT Press release: Short Laser Pulses for Material Deposition with Cold Spray Technology.
o Thermec 2016, Mai- June, Graz, AuStriA (UTBM)
o AKL June 2016, Aachen, Germany
o MICRONORA September 2016, Besançon, France
o Photonics west, San Francisco 2017, USA.
The first scientific results raised during this first reporting period, confirmed the interest of combining laser texturation with Cold Spray process. The deposition efficiency and adhesion were multiplied by a factor of 2 for Aluminum substrate with a copper coating.
Further work has been done on the CFRP (Carbon Fiber Reinforced Polymer) samples. On some specific CFRP material, the Cold Spray behaves like a sand blasting process and no particle were sticking to the surface. But on some other kind of CFRP a thick coating could be done.
During the second period many tests have been performed on various substrates by UTBM in order to validate the results obtained through simulations regarding Deposition efficiency (DE) and related parameters that may impact. Further, deep analysis and tests have been implemented on Dycomet equipment (included powder dispenser) in order to optimize the parameters and highlight the current limitations.
Each test was also performed on raw and grit-blasted samples in order to compare the results and assess laser texturing interest.
At the end, it was very interesting to note that the experimental results confirmed the results predicted by simulations.
Really good results were obtained regarding “Real time inspection” and Control, which are 2 important components for industrial applications. A consistent quality control module was developed. However additional work should be done to simplify the user interface so that it can be easily handled. As part of the EMLACS applications, such a module (with control purpose) could bring very interesting added value and could be used for texturing application in the watch industry or tribology sector. This will lead to significant improvement in quality rate and process adjustment.
Considering the Aerospace and Automotive Quality Control (QC) specifications, EMLACS project has integrated a real time control of the laser texturation and also an offline QC module. A module was developed to monitor the laser texturation process. A TTLV (Through The Lens Viewing) scanning module, with a digital camera and a specific IR sensor was integrated. Thanks to a separate user interface the system is able to catch images on demand for further QC and SPC analysis.
The real time monitoring process allows a “GO or NO GO” decision according to a teach feedback illumination signal. In order to process the signal the fastest way, DSP electronics was embedded in the processing head. With this scanning module (XY galvanometer head), a generic laser patterning has been defined for the aluminum and for each composite substrate based on the best result of adhesion and efficiency obtained during the tests.
At this stage, the EMLACS “software” still needs to be used with a separate computer. For industrial purpose it should be optimized in order to be placed into an independent processor.
3.3 Details
The following presentation provides detailed information on what has been done during the twenty four months of the EMLACS project. It presents an overview of each work package
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WP1: Definition of the use-case studies and the EMLACS technology requirement specifications. M1 – M3.
T1.1 - Technology assessment
T1.2 - Specification requirements
T1.3 - Identification of the End User cases
In regard of T1.1 we investigated the existing know-how and technologies for the development of a laser to be combined with a low pressure cold-spray system. The principal areas of investigation were related to the multi laser source, optical scanning device and low pressure cold-spray. Ns and a ps laser were identified. The ns laser because it is commonly used in the industry and a ps laser in order to reduce thermal effect, mainly for composite substrate.
As there was no existing laser providing ns and ps frequency at the beginning of the project, the first step was to demonstrate that the combination of a ns and a ps laser in a common platform was reachable and valuable regarding EMLACS objectives.
The ILT investigated the existing components and algorithms for real-time-inspection of the laser-process, verify the structuration quality and optimize it. Components specifications according to the process and to the vision spectrum were identified. The online control aimed at optimizing the structuration in real time, while the offline system was used to validate the information especially in case of bad structuration areas. The pattern was 40 microns diameter and 40 microns deep, on a 50x50 mm zone.
Based on the existing experience of the UTBM, the process parameters for the low pressure cold spray (powder, substrate, etc.) were defined. UTBM investigated the best parameters so that the projections can stick to the substrate, with either calibrated or non-calibrated powder.
In T1.2 as a result of these studies the necessary process parameters were established to define the roadmap and to develop the required laser and cold spray technologies to obtain the EMLACS technical objectives.
For the T1.3 the process parameter of the two first identified user cases were defined: on aluminum parts from the automotive industry and on carbon fiber parts form the aerospace parts.
For the Aerospace sector these samples were provided by SAAB Aerospace: composite carbon fiber part (CFRP), Use-Case: deposit of Cu and/or Al layers on composite parts.
For the Automotive sector these are provided by RENAULT: Plastic parts and Aluminum parts (AW5083),
Use-case: Deposit of Cu and/or Al layers on metallic parts
The results are summarized in the report of the deliverables D1.2.
Additionally new end user cases were identified since:
- AIRBUS: Composite, PEEK-Bronze, MTU: Inconel coating on cast Iron,
- PlasticOmnium: Plastic Parts (composite plastic),
- Coriolis Composite: Application linked to the Aerospace and Automotive industries.
These are the bases to start the WP4.
WP1 started in month 1 and ended in month 3. WP1 was completed. D1.1 and D1.2 were delivered.
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WP2: Development of new innovative Innoslab System combining ns and ps technology
T2.1 Consolidation of laser parameters
T2.2 Design of coupled device
T2.3 Implementation of laser source / experimental investigation and verification of the procured parts and the complete setup
Based on existing technology, this work package develops a laser source able to cover a large range of impulsion from nanosecond to the picosecond. The work carried out in WP2 during the first reporting period covers the consolidation of laser parameters defined in WP1, the design of coupled device and the beginning of the implementation of laser source based on experimental investigation and verification of the complete setup.
In T2.1 technical specifications were provided by Edgewave during month 3, based on existing laser sources. Laser power and pulse length of each version (ps and ns) were specified.
A global proof of concept design, combining ns and ps laser was given (Figure 7).
The ps source will provide the possibility of precision “cold” machining of small micro structures without melt protrusion. Due to the comparable high power and pulse energies also high ablation rates for large area and high throughput applications become feasible.
For higher ablation rates and efficiencies the pulse parameters especially the pulse length of the ns source was chosen to a target parameter range of 1.5 +/-0.5 ns (fwhm). Such laser source parameter range is unique in the market. It should provide the combination of high ablation rates of conventional ns laser with longer pulse length together with less heat effects during the treatment.
The preliminary technical specifications of the laser system were gathered and summarized in D2.3.
In T2.2 Final technical specification were achieved and given in D2.4. The coupled device was designed and specified.
To approve these specifications, two different systems, based on close-to-series-standard Edgewave modules were setup together with the support of Edgewave personal to show the performance and prove the principle of the two laser sources.
Basic specifications of the ps laser source from EdgeWave: PX Model
Ps oscillator - pulse picker - FI - Amplifier - Power modulator
Power 80 W @ 1 MHz
Max. pulse energy 80 mJ
Fixed pulse duration (12 ps)
Fixed high rep. rate ps oscillator 20 MHz
Power/energy scaling with Innoslab amplifier
Pulse trains with pulse picker, max. modulation rate 1 MHz
Fast power modulation 0-100 % via external modulator, max. modulation rate 30 kHz
Astigmatic beam output ellipticity, <10% in far field, M² =1.3
Beam cleaner integrated
Internal FI
Basic specifications of the ns laser source from EdgeWave: BX Model
Ns oscillator, amplifier, FI
Power 80W@100 kHz
Fixed pulse length ≈ 1.5 +/- 0.5 (fwhm)
Fixed rep rate 100 kHz
Power modulation via pump current, depending on the requirements of beam shape (TBD)
Astigmatic beam output ellipticity, <10% in far field, M² =1.3
Beam cleaner integrated
FI external
These details and the final specifications were discussed to balance the demand from the application side to get the widest possible parameter range with highest flexibility.
In T2.3 optical components were purchased and started to be mounted with the lasers on an optical bench at the ILT lab (Figure 8). The implementation of laser source started and experimental investigation began.
These results in “Final technical specifications” for the ps and ns sources, which are described in the deliverable D2.4 are the bases of the D2.5. WP2 started in month 3 and ends in month 11. D2.3 and D2.4 were delivered.
As mentioned above, the platform has been delivered very late, after month 11. The ps laser of Edgewave was not operating due to oscillator malfunctioning and then the ns laser from ILT was no more available and also needed adjustment.
In that context, the consortium decided very soon (month 7) to use a ns laser from ILS to produce the texturation of sample and to limit waste of time. This allowed UTBM to be provided with substrates in order to implement the tests and analysis planed in WP5.
For instance, using ILS laser source with longer pulses shown an increase of the cold sprayed coating adhesion on metallic substrate. As a consequence, the consortium decided to use a 10 ns laser.
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WP3 Definition and layout of fast and flexible optical scanning device with on-line monitoring
T3.1 Optimized mirror coatings and mirror design
T3.2 Provide real-time position and real-time speed signals for communication of scanner electronics with laser control
T3.3 Development and implementation of suitable detector for process monitoring and TTLV module
T3.4 Development of quality control module/Optical design of highly resolving microscopic objective/Development of illumination strategies/Image processing algorithms for assimilation of processing results
The work carried in WP3 covers the design of an optical scan system allowing the transmission of the visible spectrum without being disturbed by the processing wavelength of the laser. The online monitoring system attached to the scan system is used for document and analyze the texturing process. An offline quality control module has also been designed to evaluate the quality of the structuring result. Both systems are used to check the textured pattern for deviations from the intended pattern.
In T3.1 the standard coatings of the scanning mirrors are usually only optimised for the used laser wavelength and not for process observation. In the present case of the laser wavelength of 1064nm most scanner systems do not transmit in the visible range or in the near infrared range.
This prevents a successful detection of process emissions of the online monitoring system.We defined the spectral reflectivity ranges of the scanner mirrors required to monitor laser structuring based on measured emission spectra of ps texturing of selected materials. In cooperation with the scanner supplier, an appropriate mirror coating for this application was designed (D3.6).
The specifications of this coating are listed below:
Laser wavelength: 1030 – 1090 nm
Maximum average power: 250 W
Maximum energy density for continuous operation: 500 W/cm2
Damage threshold (10ns pulse length, 200 pulses): >5 J/cm2
Reflectivity (45° angle of incidence)
>99.7% @ 1030 – 1090 nm
>65% @ 400 – 500 nm
>99.7% @ 600 – 800 nm
>99.7% @ 1070 – 1600 nm
Further details are given in the D3.6.
In T3.2 and T3.3 the online process monitoring system was developed and set up in two phases. In the first phase a laboratory version based on existing prototypes was set up in order to test all relevant components or functions (D3.7). In the second phase this concept was transferred into a module that integrates the scan system and online monitoring system (D3.8).
Within the first phase a sensor which is capable of monitoring the spectrum, which has been identified in T3.1 was chosen. Specific electronic circuitry was used to amplify and digitize the output of that sensor and to provide the data interface for the real-time acquisition. Signal distribution electronics were designed to capture the scanner position and the sensor signals synchronously in real time. These signals have to be captured synchronously in order to correlate position and sensor signal. The data and signals from the different sources are collected by a software running on the FPGA of a programmable frame grabber. The frame grabber gives the ability to include images of a high speed camera into the data stream in the future.
This sensor and electronics were implemented with an optical relay system for coaxial coupling to the scanning system into a laser processing set up and first tests were performed. The evaluation of the system set up shows good results for monitoring the process (D3.7). The gained knowledge during this evaluation has been incorporated into the design of the “Scan system with integrated monitoring system” and is going to serve bases for the remaining deliverables in this WP (D3.8 & D3.10 to be delivered in month 11).
In the second phase of the development of the online monitoring system the concept and used components evaluated in the first phase were combined with the scanning head (D3.8). The optical relay optics, the sensor including digitizing electronics and the through the lens (coaxial) camera were integrated into a housed module directly mounted at the scanning head. For bright images of the TTLV camera LED illumination spots, positioned around the scanning optics, are used. The signal distribution electronics, frame grabber and scanner control card are mounted into the same PC for shortest signal cabling.
The raw data (scanner position, laser control signals and sensor signal) are stored in the HDF5 data format that is supplied by many software libraries. The recording starts and stops automatically and is controlled by the status of the scanner control card that indicates if a texturing process is running or not. The raw data can be analyzed automatically or manually offline. The analyzing result includes a process intensity image that shows the process emission intensity correlated to the scanner position. This image is independent from the texturing strategy. Furthermore the pattern of the texturing is reconstructed from the data and characteristic values are identified or calculated. These values are saved in table form in a text file. Apart from the data files, the raw data, the process intensity image and the analyzation result can be visualized. This is more convenient for most users.
The online monitoring system delivers quite a large amount of data (approximately 2MB/s). Analyzing this data is very specific to the processing strategy, used laser parameters and textured material. During EMLACS only algorithms for rectangular patterns with the jump and drill processing strategy are implemented. Different processing strategies will need an adaption of the algorithms. Large errors like misalignment of the sample, gaps or mixed materials are very good visible in the process intensity image.
Smaller deviations the user is not directly aware of are concealed within the data. Advanced knowledge is needed to differentiate between signal deviations with still a good process results and process deviations that can be visible in the data. . The visualization of the data gives hints to the user by an easy understandable presentation, but robust decisions still need more enhanced decision making algorithms. To allow industrial use a help decision system that tells the user if the process was successful or not will be required.
Task 3.4 represents the development of the offline quality control module of deliverable D3.9. The hardware consists of a camera with microscopic lens and a LED-illumination. In additional a stepper linear stage is used for adjusting the focus of the camera. The offline monitoring system is used for visual inspection of suspicious locations of the textured pattern. For compatibility the camera is the same camera (Basler acA2500–gm14) used in the TTLV system by ILS. The following table summarizes the specification of the offline monitoring hardware.
Specification Nominal values
Camera resolution 2592 x 1944 pixel
Magnification 2
Pixel size on image 1,1 μm
Optical resolution 3,9 μm
Working distance 47 mm
Field of view 2,851 x 2,193 mm2
Frames per second 14
Travel range of linear axis 50 mm
Resolution axis 150 nm
The offline quality control module can be mounted on any standard optical table with a grid of M6 threads with a grid distance of 25mm or at a vertical plate with or without linear axis. With the interface software, the user can control the camera and the linear stage.
A digital zoom function supports the user analyzing smallest features. With the calibrated point-to-point distance measurement the user can analyze the size of the structured pattern. The image of the offline monitoring system can be saved for further analysis or documentation.
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WP4: Definition of low-pressure cold-gas system (LPCS).
T4.1 Improve existing numerical models to enable their application with LPCS.
T4.2 Characterization of surface morphology, 3D observation and quantification of surfaces which are irradiated using several laser conditions.
T4.3 Define the most appropriate adhesion test to study the coating bond strength as a function of the laser-structured surface characteristics.
The work carried out in WP4 covers the Improvement of existing numerical models to enable their application with LPCS. Reports on surface characterization and adhesion test as well as on low pressure cold spray deposition efficiency and nozzle geometry were performed. For the tests different parameters were combined, i.e. pressure, spray type, particle and nozzle geometry and dimensions.
In T4.1 existing numerical models were exploited to enable their application to Low Pressure Cold Spray. The first numerical simulation using a 1D two-phases flow performed on Maltlab (Figure 10) code which takes in account the gas parameters, the nozzle geometry, the particles size and distribution show the possibility of Deposit Efficiency improvement, giving the following main conclusions:
The higher both inlet pressure and temperature of the propellant gas, the better the adhesion and the deposition efficiency, provided that the erosion velocity is not reached.
The highest achieved DE for the standard copper powder would be in the range of 0.10 approximately, unless the powder feedstock mainly contains very fine particles such as 1.5 microns diameter sized particles (DE = 0.9 according to the numerical analysis). A good compromise is found between the DEexp and the DEsim which is total DE of adhering particles accounting for their size distribution.
For the Cu+Al2O3/Cu and Cu+Al2O3/Al powder feedstock/substrate combinations, the experimental measured DE remains low, i.e 0.22 and 0.23 respectively.
There is an optimal ratio of rexit/rthroat that increases with the nozzle diverging part length to improve the deposition efficiency. Moreover the longer the nozzle length, the higher the energy loss. Assuming that energy losses due to wall friction are negligible, high DE may be achieved for low diameter particles. The real DE will however depends on the particle size distribution.
The results using helium as propellant gas lead to the same conclusions.
The only difference lies in the DE that may be greatly improved, up to 1, in the case of nozzle diverging part length of 400 mm, since wall friction effect is negligible and the particle sizes are lower than 15 microns approximately.
In T4.2 & T4.3 experiments were carried out in order to characterize the surface morphology according to different laser texturation conditions. As result the most appropriate adhesion test was defined to study the coating bond strength (Figure 11). Comparing the different surface morphologies induced by the laser treatments, different behaviors were observed at first regarding coating efficiency.
Using the same spraying parameters, experiments were made on composite samples but so far no coating was possible. Instead of coating, spraying particles could be observed on the sample surface destroying the composite and the fibers. Tests on metallic substrates have been carried out showing an increase of the adhesion by a factor of 2.
Results predicted by simulations and real parts demonstrated that there are quite close. Several experimental designs with various materials, powders, substrates...have been implemented to demonstrate the impact on DE (deposition efficiency). Each test was performed using round calibrated and non-calibrated powders, calibrated but non-round powders. “Calibrated” here indicates that the grain powder dimension is controlled and approximately the same.
With the Standard Dycomet equipment, the results regarding DE were about 50% - 60%. The Dycomet equipment is at the maximum of its capacity.
WP4 started in month 3 and ends in month 11. D4.11 and D4.12 were delivered.
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WP 5:
T5.1 Laser integration
T5.2 Test in lab environment
T5.3 Industrial user cases
T5.1: The work has been done on the ns laser only. The platform should have been completed to start the wp5 but it was not available (see above).
T5.2: We create a test scheme to validate the performance of the integrated EMLACS platform and verify the formal hypothesis and texturation parameters. Using the ILS ns laser, the texturation geometry (based on existing UTBM expertise) was defined and the efficiency, the adhesion and electric conductivity tested. Significant improvements have been observed on adherence depending on the powder's geometry, but finally have poor effect on efficiency. EMLACS showed that thermal effects do not have negative impact on adhesion but quite the reverse. Nevertheless, lack of repeatability is stills strong.
Texturation on composite materials with thick layer was tested (PEEK matrix, pure resin without fibers) and on composite plastic material (used in automotive sector). Good results on bonding strength on substrates textured with ns laser were obtained. On the other hand, no positive effect on DE on aluminum substrates was shown and little interest on pure PEEK material. Good results were obtained with industrial materials like plastic used in the automotive industry.
T5.3: Since the beginning of the project, industrial end users provided material samples. Real parts with 3D geometries could not be provide as the machining of the parts require much more sophisticated equipment then the one used in this project. The EMLACS Project however provides a real proof of concept which can be used as basis for further developments to set up a real demonstrator unit.
Numerous trials adapted LPCS conditions to create a metallic coating on industrials polymers. To create a thick and adherent coating, several powder granulometry and specific spraying conditions have to be used. Thanks to these new adapted parameters, good results were obtained with industrial materials like plastic used in the automotive industry. Coatings with reasonable thickness were obtained.
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WP 6:
T6.1 Co-ordination of activities
T6.2 Patent and protection of IPR
T6.3 Knowledge transfer
T6.4 Dissemination and use strategy
The web site will continue to be use to communicate after EMLACS project.
T6.1: Co-ordination of activities: coordinate all knowledge management, dissemination activities and Intellectual Property Rights issues. A video from Dycomet have to be done as sample’s pictures presented in conferences.
T6.2: No invention leads to a patent.
FTO: to be developed
T6.3: The simulation tools developed at UTBM have been adapted in order to transform them into self-running software using opensource FEM systems. These tools have been transferred to Dycomet and a video tutorial has been created in order to simply explain how to use the simulation tool. The tool has been installed on a Dycomet computer and a demo has been done. The tutorial will allow Dycomet to reuse it even a long period of time without using it.
T6.4: There is some possible exploitation, especially regarding the control system. Exploitation of the results needs to go further with the project. Concerning the dissemination, several presentations have been done of the EMLACS results in professional fairs as well as in scientific national and internationals conferences. Papers in international journals have also been written. These presentations allow to disseminate the EMLACS results. Among them, the following points have particularly been highlighted:
- Development of specific simulation tools for Low pressure Cold Spray Deposition efficiency and their experimental validation
- Improvement of the adhesion strength of Al and Cu coatings on Aluminum substrates through optimized laser texturing.
- Creation of a copper coating on polymer substrates using a specific spraying process involving the use of two specific powder sizes to optimize the coating adhesion and coating growth.
A better DE on metallic support using laser texturation is obtained. It allows to provide new solutions to industrial end users which are already doing Cold-spray without laser texturation.
On composite, first conclusions are good but they need to be deeply analyzed.
Potential Impact:
Major aerospace and automotive companies have shown high interest in the EMLACS project. Some of them have committed to supply to the project new material substrates in order to define new user cases.
Thanks to the EMLACS project, we are now able to do simulations of our Cold Spray process which allow us to predict spray parameters with a software tool to optimize the Low Pressure Cold Spray process. This is saving time and money in finding the right parameters and in not having to do as much coating characterizations as before.
A second benefit we have is that we now know what a big impact a laser structured surface can have on the adhesive properties of a Cold Sprayed Coating. Certain customers require more bonding than can be obtained with regular pre-surface treatments.
Automotive and aerospace industries are highly interested since metallic parts and composite parts are really often used and assembled together in new modules in order to save weight and therefore to save energy. Composite parts in the car industry can be plastics with glass fiber or with specific reinforcements.
Aerospace is mainly using Carbon Fibers Reinforced Polymers (CFRP) for big and small parts. Some of these parts have to integrate physical properties that such material don’t have. For instance, electrical /electronic housing need to have thermal properties in order to cool down the electronic devices/components.
Nowadays metallic cooling systems are mechanically added on the composite parts, which induce extra cost and weight. This can be replaced by doing a copper and /or aluminum coating on the right area of a CFRP cabinet. On the other hand this also can also be used to heat up some specific areas of a part.
Automotive industry is running after “green issues”. The main objective is to build light and highly recyclable cars, with the smallest possible energy consumption. Therefore more and more projects are coming out trying to combine metal with composite (or plastic) while trying to avoid gluing processes in order to eliminate a maximum of chemical wastes. EMLACS will open possibilities to assemble dissimilar materials in a green and industrial way.
Partners from automotive industry have expressed their interest. Assembling of a composite and a metallic part using the Cold Spray coating interface could have a major impact on the joining technology of dissimilar materials needed for light car bodies manufacturing or aerospace and space & military parts.
EMLACS allows generating a data base with cycle times of a complete laser texturation combined to a low pressure cold spray for given surface/material substrate and therefore a financial model for the process in relation to the surface and to the coating properties.
Such data base and process will help the automotive and the aerospace industries to select the right material combination for a given application. For instance: grow a thick metal coating of copper or aluminum on composite/plastic parts that will be machined later on for mechanical handling purposes, or, use of such layer for joining dissimilar materials like aluminum and plastic for light car bodies. This will eliminate gluing processes, chemical waste and all costs attached to it.
EMLACS will certainly open other process opportunities like thermal dissipation or thermal conduction on plastic/composite parts, protection of fragile surfaces where the cosmetic aspect has to be taken in consideration. Military industry will be also an area to investigate where components/modules are used in a very difficult environment conditions and where weight is also a major issue like in space applications.
List of Websites:
www.emlacs.eu
Learn more on the EMLACS technology on web site.
Note : see figure in the attached PDF filed
The EMLACS project is a proof of concept that targets to increase the deposition efficiency and the adhesion of a metallic coating on composite and metal substrates with a non-thermal process by texturing the surfaces by laser radiation. An on-line and real time vision module monitors the laser texturation process in order to insure the quality of the process.
Such coatings will allow new physical properties on specific materials as: electrical and /or thermal conductivity, improving adhesion of tribological coating, weldability between metal and composite materials... Among the possible applications, the growth of a thick metal coating of copper or aluminum on composite/plastic parts that will be machined later on for mechanical handling purposes, or, the use of such layer for joining dissimilar materials like aluminum and plastic for light car bodies are of special interest. This new process will eliminate gluing processes, chemical waste and all costs attached to it and can be an efficient and “green” palliative process.
The targeted fields of use are the Space/Aerospace and the automotive industries but not exclusively. Texturation and coating were done on Aluminum AW5083 (Base AI, 4.4% Mg, 0.7% Mn, 0.15% Cr) used in automotive industry and on Carbon Fiber Reinforced Composite samples (CFRP). Interesting preliminary results were also obtained on polymer parts (PEEK and ABS) which are also widely used in Transport industries.
The analysis of existing technologies already used in industry helped to define the most cost effective concept and gave a better global view of applications. From this survey (WP1), the consortium selected the following technologies:
- Coating technology choice: The Low Pressure Cold Spray process (Figure 1) was selected to perform the coatings. Cold Spray is an emergent technology being used to repair damaged metallic surfaces on molds or to enhance hardness of a mild steel or aluminum parts. It works at 6 bars max, has a small footprint and it’s an affordable coating process (approx. 50 kEuros investment only). Extra costs are linked to the powder material which is a consumable.
➢ - Laser technology choice: Widely used in industry with reliable power sources, the nanosecond (ns) and picosecond (ps) laser technologies for the texturing process were applied. These lasers can be easily integrated with direct optics or with a fiber beam delivery. It provides high flexibility for texturing miscellaneous materials which is clearly appreciated by industrial end users.
Based on the selected processes, the project runs in 2 phases: Phase 1 (WP2, WP3 and WP4) was dedicated to the development of the various individual concepts on lab samples whereas Phase 2 (WP5) aims to validate the overall concept on industrial materials. The following points can be highlighted:
➢- A new laser concept combining ns and ps lasers (Figure 2) has been developed (WP2). The good synchronization of both lasers was validated and the lasers characteristics have been demonstrated.
- A Quality and Control module has been developed (WP3). This module (Figure 3) represents a significant added value for the end-user. The process performances (i.e. coating adhesion mainly) completely rely on the texturation process quality. In order to have a repeatable and reliable process a Real Time Vision system module that monitors the texturation has been integrated. It also gives a GO or NO GO action based on a teach feedback illumination signal. A user interface allows saving the images for further QC and SPC analysis. The quality and control module is assembled on a scanning module (XY galvanometer head) and is driven by a friendly user interface. Pre-defined generic laser patterning (data base) for metal or composite material can be saved and downloaded for the best result of adhesion and efficiency properties for a specific coating material. This module can be used for various texturing applications independently from the cold spray process used in this project.
- Low Pressure Cold Spray (LPCS) coatings (Figure 4) have been obtained on textured lab samples (WP4). The LPCS process has been modeled and the deposition efficiency has been simulated and experimentally measured on a variety of samples. Tests showed that the deposition efficiency is almost uninfluenced by the laser texturing process. Tests analysis led to recommendations about the powder size in order to improve the coating performances. As a result of the investigations it was shown that the coating adhesion is drastically increased by the laser texturing process. Remarkable results were obtained with Aluminum/Alumina, pure Aluminum, Cu/Alumina and pure Copper materials.
➢ - Real industrial materials have been prepared following the complete process (WP5). The metallic substrates exhibit very high adhesion values and are very suitable for industrial applications. No coating could be created on the industrial composite samples provided. Therefore solutions to overcome the identified technical issues have been developed. Very promising results have been obtained on pure PEEK and ABS substrates. These last results make industrial applications possible on plastic parts.
Thanks to these first results based on the EMLACS project, ILS as coordinator and Laser process supplier, will continue and work on a demonstrator that will perform real parts with specific Cold Spray coating sprayed on appropriate laser texturation. The EMLACS concept has proven with remarkable results that the adhesion of such coating obtained by Cold Spray process can be improved up to a factor of 2 when the substrate has been laser textured before (80% for Al203/Cu powder, 105% for Pure Cu powder)! It will certainly open other process opportunities like thermal dissipation or thermal conduction on plastic/composite parts, protection of fragile surfaces where the cosmetic aspect has to be taken into consideration. Military industry will also be an area to investigate where components/modules are used in a very difficult environment conditions and where weight is also a major issue like in space applications.
Project Context and Objectives:
The deposition efficiency of Low Pressure Cold Spray can vary between 30 and 60%, depending on several parameters such as the substrate material, the spraying temperature, the surface roughness or the Cold Spray nozzle geometry.
This low efficiency is unacceptable for an industrial process, especially when it results in spraying expensive particles powder. Our objective with EMLACS is to reach an average deposit efficiency above 60 %.
In order to avoid a thermal stress or surface damages of the substrate (especially on composite and plastics substrate), the coating has to be done with a low temperature spraying process (typ. below 180°C). In order to increase the adhesion, a laser has been selected to generate the surface textures.
The target is to show a process that will be very close to the industrial needs. This means that the process has to be highly efficient, reliable, with short cycle times, affordable and with the lowest running and maintenance costs possible.
Today existing laser technology allow pulse durations from femto, pico or nano second. Femto second lasers are very expensive and do not allow the required throughput. On the other side nano and pico second laser sources are an option. Both technologies are compatible with the required cycle time. The optimal laser would be a mix of a pico to nano configuration in order to combine both process benefits. EMLACS addresses this specific laser combination which was not available at the deposition of the Project.
Some R&D projects are currently using short pulse laser sources to texture the surface of metallic parts in order to join plastic and metal components, by melting the thermoplastic material and pressing it onto the textured metallic surface. The EMLACS project also uses such laser process in order to increase the adhesion of the sprayed coating and to improve the deposit efficiency topo.
As part of the objectives of the first period and according to WP1, the existing technologies were investigated in order to define the starting point of the project roadmap of improvement for each individual process.
First the existing laser technology from ns to ps pulse regime was identified in order to combine it into a “single laser tool” for the EMLACS needs. Then different simulation tools were considered in order to identify the best low pressure cold spray configuration to achieve the best efficiency and adhesion of the coatings. For the quality control device, the necessary components were defined to setup the process control module based on an optical scanning system and integrating real time sensor electronics. Based on these three steps the process parameters for the laser texturation and for the cold spray coating were established. Experimental plans were applied on 2 use cases: for the automotive industry we used EMLACS technology on Aluminum substrates; for the Aerospace industry EMLACS technology was tested on Composite PEEK/Carbon fibers parts.
In WP2, the objective was to develop a laser source capable to deliver pulses from ns to ps. Based on the process parameter resulting from WP1, a Preliminary Technical specification for the combination of such lasers sources from EdgeWave was defined. The work done during this period consisted in identifying and designing the components to couple ps/ns generator as well as being able to switch from one regime to the other. One ps laser and one ns laser were assembled on an optical bench with all the required optical components to combine both laser beams. At this stage laser parameters were demonstrated.
Regardless of the delay due to the ps oscillator malfunctioning (due to the ps oscillator) and parasitic background between 2 pulses found in the short-pulse ns system, leading to major changes on the platform and making it available only from November 2015, the consortium managed to arrange texturation of samples using existing compatible short plus lasers available in the consortium in order not to disturb coating tests and analysis performed by UTBM. In WP3, a monitoring system was defined and developed in order to control the laser pattern geometry process in real time. The optical system was designed for the transmission in the visible spectrum while fully delivering the performance for the processing wavelength in the IR. The layout was based on an optical system equipped with a digital camera and sensors that observe the laser process plasma intensity. This signal was acquired synchronously with the scanner position by an electronic system which interfaces to a frame grabber equipped with an FPGA to transfer the data into a standard Windows ™ 7 based PC. Based on a teach process, this give a GO or NO GO signal. In case of a NO GO signal, an offline QC module integrating the same camera and software will be used to confirm and control the pattern geometry.
In WP4 the objective was to improve the use of low pressure cold spray in order to identify new material combinations. The work started on simulation models in order to confirm the existing technical bases of the Dycomet system and generate appropriate data for process comparison. The work carried out included 3D observation and quantification of surfaces which were irradiated using several laser conditions.
Adhesion test was defined in order to study the coating bonding strength as a function of the laser-structured surface characteristics. Based on the identified use case of the WP1, studies of selected materials combinations were done according to the most attractive industrial applications in order to increase the adhesion and deposition efficiency of the low pressure cold spray process.
In WP5 the objective was to integrate the modules developed in WP2 and WP3.
Many tests have been performed by UTBM based in order to validate simulation hypothesis on adhesion and efficiency depending on powders’ geometry, texturation geometry, thermal effects, speed of projection, nozzle design...
Descriptions and conclusions are detailed in Deliverable 5.15
Project Results:
3.1 Period 1
In order to perform a proper surface texturation, it is necessary to control the thermal effects of the laser on the surface. If the process induces too much heat effects on the aluminum surface, it could produce scoriae and this will lead to a lack of adhesion of the sprayed coating. Thermal effect regulation has been a recurring problematic throughout the project. Heat effect on composite parts could delaminate the substrate and totally destroy it even before any coating. Therefore first laser parameters were defined in order to minimize the thermal effect on both materials. The first results were obtained with separate ns and ps laser sources in order to generate several textures to be coated.
Different set of samples in Aluminum and Carbon fiber were sprayed with Aluminum and Copper coating with and without laser texturing in order to compare the adhesion and the deposition efficiency of both surface configurations. In order to optimize the speed of the projected particles, the gas temperature and the nozzles geometry of the cold spray process, the UTBM worked on different types of mathematical simulation.
The first coatings done at the UTBM on the aluminum textured samples has shown promising results and significant improvement on the adhesion of the coating that were increased by a factor of 2 with a preliminary texturation. This confirmed the benefit of the laser texturation. Depending on the granulometry of the used powder, parts that were laser textured with geometries between 90 and 150 microns matrix seems to be the best ones. It was also proven that it is possible to grow coatings of copper and/or aluminum with a thickness of several millimeters on aluminum substrates.
The Cold Spray tests done on the first type of composite samples (carbon fiber) were not yet successful. Regardless of a textured surface, the cold spray process acted like a sand blasting process, with an abrasion of the surface and the destruction of the first layer of fibers. Another kind of Carbon fiber samples from another supplier has shown that depending on the fiber direction and on the thickness of the upper matrix layer, it was possible to obtain some metallic coating without destroying the surface (Figure 5). Deeper investigation and new trials have been done to understand the adhesion process on this specific CFRP material.
Based on these preliminary tests, project results were presented at different exhibitions and conferences. The first composite cold spray parts and aluminum cold spray parts were shown at the 2015 JEC show in Paris (Figure 6), at the 2015 Hannover show and at the 2015 JNPLI conference in Nantes. Major aerospace and automotive companies have shown high interest in the EMLACS project. Some of them have committed to supply to the project new material substrates in order to define new user cases.
Confidentiel Page 11 / 31
Fairs and press releases for communicating EMLACS project :
o JEC Europe, Paris, March 2016 (EMLACS on Fraunhofer booth)
o Hannover Messe, Hanover, April 2016 (EMLACS on Dycomet booth)
o JNPLI 2016, Liège, Juin 2016 (EMLACS on CLFA booth)
o Industrie 2016, Juune 2016, Villepinte(France)
o Cold Spray Summer School, Barcelona, June 2015 (EMLACS on Dycomet booth)
o Laser-induced surface texturing of metal or organic substrates for structural adhesive bonding (article and presentation at Thermec 2015)
o ILT Press release: Short Laser Pulses for Material Deposition with Cold Spray Technology.
o Thermec 2016, Mai- June, Graz, AuStriA (UTBM)
o AKL June 2016, Aachen, Germany
o MICRONORA September 2016, Besançon, France
o Photonics west, San Francisco 2017, USA.
The first scientific results raised during this first reporting period, confirmed the interest of combining laser texturation with Cold Spray process. The deposition efficiency and adhesion were multiplied by a factor of 2 for Aluminum substrate with a copper coating.
Further work has been done on the CFRP (Carbon Fiber Reinforced Polymer) samples. On some specific CFRP material, the Cold Spray behaves like a sand blasting process and no particle were sticking to the surface. But on some other kind of CFRP a thick coating could be done.
During the second period many tests have been performed on various substrates by UTBM in order to validate the results obtained through simulations regarding Deposition efficiency (DE) and related parameters that may impact. Further, deep analysis and tests have been implemented on Dycomet equipment (included powder dispenser) in order to optimize the parameters and highlight the current limitations.
Each test was also performed on raw and grit-blasted samples in order to compare the results and assess laser texturing interest.
At the end, it was very interesting to note that the experimental results confirmed the results predicted by simulations.
Really good results were obtained regarding “Real time inspection” and Control, which are 2 important components for industrial applications. A consistent quality control module was developed. However additional work should be done to simplify the user interface so that it can be easily handled. As part of the EMLACS applications, such a module (with control purpose) could bring very interesting added value and could be used for texturing application in the watch industry or tribology sector. This will lead to significant improvement in quality rate and process adjustment.
Considering the Aerospace and Automotive Quality Control (QC) specifications, EMLACS project has integrated a real time control of the laser texturation and also an offline QC module. A module was developed to monitor the laser texturation process. A TTLV (Through The Lens Viewing) scanning module, with a digital camera and a specific IR sensor was integrated. Thanks to a separate user interface the system is able to catch images on demand for further QC and SPC analysis.
The real time monitoring process allows a “GO or NO GO” decision according to a teach feedback illumination signal. In order to process the signal the fastest way, DSP electronics was embedded in the processing head. With this scanning module (XY galvanometer head), a generic laser patterning has been defined for the aluminum and for each composite substrate based on the best result of adhesion and efficiency obtained during the tests.
At this stage, the EMLACS “software” still needs to be used with a separate computer. For industrial purpose it should be optimized in order to be placed into an independent processor.
3.3 Details
The following presentation provides detailed information on what has been done during the twenty four months of the EMLACS project. It presents an overview of each work package
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WP1: Definition of the use-case studies and the EMLACS technology requirement specifications. M1 – M3.
T1.1 - Technology assessment
T1.2 - Specification requirements
T1.3 - Identification of the End User cases
In regard of T1.1 we investigated the existing know-how and technologies for the development of a laser to be combined with a low pressure cold-spray system. The principal areas of investigation were related to the multi laser source, optical scanning device and low pressure cold-spray. Ns and a ps laser were identified. The ns laser because it is commonly used in the industry and a ps laser in order to reduce thermal effect, mainly for composite substrate.
As there was no existing laser providing ns and ps frequency at the beginning of the project, the first step was to demonstrate that the combination of a ns and a ps laser in a common platform was reachable and valuable regarding EMLACS objectives.
The ILT investigated the existing components and algorithms for real-time-inspection of the laser-process, verify the structuration quality and optimize it. Components specifications according to the process and to the vision spectrum were identified. The online control aimed at optimizing the structuration in real time, while the offline system was used to validate the information especially in case of bad structuration areas. The pattern was 40 microns diameter and 40 microns deep, on a 50x50 mm zone.
Based on the existing experience of the UTBM, the process parameters for the low pressure cold spray (powder, substrate, etc.) were defined. UTBM investigated the best parameters so that the projections can stick to the substrate, with either calibrated or non-calibrated powder.
In T1.2 as a result of these studies the necessary process parameters were established to define the roadmap and to develop the required laser and cold spray technologies to obtain the EMLACS technical objectives.
For the T1.3 the process parameter of the two first identified user cases were defined: on aluminum parts from the automotive industry and on carbon fiber parts form the aerospace parts.
For the Aerospace sector these samples were provided by SAAB Aerospace: composite carbon fiber part (CFRP), Use-Case: deposit of Cu and/or Al layers on composite parts.
For the Automotive sector these are provided by RENAULT: Plastic parts and Aluminum parts (AW5083),
Use-case: Deposit of Cu and/or Al layers on metallic parts
The results are summarized in the report of the deliverables D1.2.
Additionally new end user cases were identified since:
- AIRBUS: Composite, PEEK-Bronze, MTU: Inconel coating on cast Iron,
- PlasticOmnium: Plastic Parts (composite plastic),
- Coriolis Composite: Application linked to the Aerospace and Automotive industries.
These are the bases to start the WP4.
WP1 started in month 1 and ended in month 3. WP1 was completed. D1.1 and D1.2 were delivered.
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WP2: Development of new innovative Innoslab System combining ns and ps technology
T2.1 Consolidation of laser parameters
T2.2 Design of coupled device
T2.3 Implementation of laser source / experimental investigation and verification of the procured parts and the complete setup
Based on existing technology, this work package develops a laser source able to cover a large range of impulsion from nanosecond to the picosecond. The work carried out in WP2 during the first reporting period covers the consolidation of laser parameters defined in WP1, the design of coupled device and the beginning of the implementation of laser source based on experimental investigation and verification of the complete setup.
In T2.1 technical specifications were provided by Edgewave during month 3, based on existing laser sources. Laser power and pulse length of each version (ps and ns) were specified.
A global proof of concept design, combining ns and ps laser was given (Figure 7).
The ps source will provide the possibility of precision “cold” machining of small micro structures without melt protrusion. Due to the comparable high power and pulse energies also high ablation rates for large area and high throughput applications become feasible.
For higher ablation rates and efficiencies the pulse parameters especially the pulse length of the ns source was chosen to a target parameter range of 1.5 +/-0.5 ns (fwhm). Such laser source parameter range is unique in the market. It should provide the combination of high ablation rates of conventional ns laser with longer pulse length together with less heat effects during the treatment.
The preliminary technical specifications of the laser system were gathered and summarized in D2.3.
In T2.2 Final technical specification were achieved and given in D2.4. The coupled device was designed and specified.
To approve these specifications, two different systems, based on close-to-series-standard Edgewave modules were setup together with the support of Edgewave personal to show the performance and prove the principle of the two laser sources.
Basic specifications of the ps laser source from EdgeWave: PX Model
Ps oscillator - pulse picker - FI - Amplifier - Power modulator
Power 80 W @ 1 MHz
Max. pulse energy 80 mJ
Fixed pulse duration (12 ps)
Fixed high rep. rate ps oscillator 20 MHz
Power/energy scaling with Innoslab amplifier
Pulse trains with pulse picker, max. modulation rate 1 MHz
Fast power modulation 0-100 % via external modulator, max. modulation rate 30 kHz
Astigmatic beam output ellipticity, <10% in far field, M² =1.3
Beam cleaner integrated
Internal FI
Basic specifications of the ns laser source from EdgeWave: BX Model
Ns oscillator, amplifier, FI
Power 80W@100 kHz
Fixed pulse length ≈ 1.5 +/- 0.5 (fwhm)
Fixed rep rate 100 kHz
Power modulation via pump current, depending on the requirements of beam shape (TBD)
Astigmatic beam output ellipticity, <10% in far field, M² =1.3
Beam cleaner integrated
FI external
These details and the final specifications were discussed to balance the demand from the application side to get the widest possible parameter range with highest flexibility.
In T2.3 optical components were purchased and started to be mounted with the lasers on an optical bench at the ILT lab (Figure 8). The implementation of laser source started and experimental investigation began.
These results in “Final technical specifications” for the ps and ns sources, which are described in the deliverable D2.4 are the bases of the D2.5. WP2 started in month 3 and ends in month 11. D2.3 and D2.4 were delivered.
As mentioned above, the platform has been delivered very late, after month 11. The ps laser of Edgewave was not operating due to oscillator malfunctioning and then the ns laser from ILT was no more available and also needed adjustment.
In that context, the consortium decided very soon (month 7) to use a ns laser from ILS to produce the texturation of sample and to limit waste of time. This allowed UTBM to be provided with substrates in order to implement the tests and analysis planed in WP5.
For instance, using ILS laser source with longer pulses shown an increase of the cold sprayed coating adhesion on metallic substrate. As a consequence, the consortium decided to use a 10 ns laser.
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WP3 Definition and layout of fast and flexible optical scanning device with on-line monitoring
T3.1 Optimized mirror coatings and mirror design
T3.2 Provide real-time position and real-time speed signals for communication of scanner electronics with laser control
T3.3 Development and implementation of suitable detector for process monitoring and TTLV module
T3.4 Development of quality control module/Optical design of highly resolving microscopic objective/Development of illumination strategies/Image processing algorithms for assimilation of processing results
The work carried in WP3 covers the design of an optical scan system allowing the transmission of the visible spectrum without being disturbed by the processing wavelength of the laser. The online monitoring system attached to the scan system is used for document and analyze the texturing process. An offline quality control module has also been designed to evaluate the quality of the structuring result. Both systems are used to check the textured pattern for deviations from the intended pattern.
In T3.1 the standard coatings of the scanning mirrors are usually only optimised for the used laser wavelength and not for process observation. In the present case of the laser wavelength of 1064nm most scanner systems do not transmit in the visible range or in the near infrared range.
This prevents a successful detection of process emissions of the online monitoring system.We defined the spectral reflectivity ranges of the scanner mirrors required to monitor laser structuring based on measured emission spectra of ps texturing of selected materials. In cooperation with the scanner supplier, an appropriate mirror coating for this application was designed (D3.6).
The specifications of this coating are listed below:
Laser wavelength: 1030 – 1090 nm
Maximum average power: 250 W
Maximum energy density for continuous operation: 500 W/cm2
Damage threshold (10ns pulse length, 200 pulses): >5 J/cm2
Reflectivity (45° angle of incidence)
>99.7% @ 1030 – 1090 nm
>65% @ 400 – 500 nm
>99.7% @ 600 – 800 nm
>99.7% @ 1070 – 1600 nm
Further details are given in the D3.6.
In T3.2 and T3.3 the online process monitoring system was developed and set up in two phases. In the first phase a laboratory version based on existing prototypes was set up in order to test all relevant components or functions (D3.7). In the second phase this concept was transferred into a module that integrates the scan system and online monitoring system (D3.8).
Within the first phase a sensor which is capable of monitoring the spectrum, which has been identified in T3.1 was chosen. Specific electronic circuitry was used to amplify and digitize the output of that sensor and to provide the data interface for the real-time acquisition. Signal distribution electronics were designed to capture the scanner position and the sensor signals synchronously in real time. These signals have to be captured synchronously in order to correlate position and sensor signal. The data and signals from the different sources are collected by a software running on the FPGA of a programmable frame grabber. The frame grabber gives the ability to include images of a high speed camera into the data stream in the future.
This sensor and electronics were implemented with an optical relay system for coaxial coupling to the scanning system into a laser processing set up and first tests were performed. The evaluation of the system set up shows good results for monitoring the process (D3.7). The gained knowledge during this evaluation has been incorporated into the design of the “Scan system with integrated monitoring system” and is going to serve bases for the remaining deliverables in this WP (D3.8 & D3.10 to be delivered in month 11).
In the second phase of the development of the online monitoring system the concept and used components evaluated in the first phase were combined with the scanning head (D3.8). The optical relay optics, the sensor including digitizing electronics and the through the lens (coaxial) camera were integrated into a housed module directly mounted at the scanning head. For bright images of the TTLV camera LED illumination spots, positioned around the scanning optics, are used. The signal distribution electronics, frame grabber and scanner control card are mounted into the same PC for shortest signal cabling.
The raw data (scanner position, laser control signals and sensor signal) are stored in the HDF5 data format that is supplied by many software libraries. The recording starts and stops automatically and is controlled by the status of the scanner control card that indicates if a texturing process is running or not. The raw data can be analyzed automatically or manually offline. The analyzing result includes a process intensity image that shows the process emission intensity correlated to the scanner position. This image is independent from the texturing strategy. Furthermore the pattern of the texturing is reconstructed from the data and characteristic values are identified or calculated. These values are saved in table form in a text file. Apart from the data files, the raw data, the process intensity image and the analyzation result can be visualized. This is more convenient for most users.
The online monitoring system delivers quite a large amount of data (approximately 2MB/s). Analyzing this data is very specific to the processing strategy, used laser parameters and textured material. During EMLACS only algorithms for rectangular patterns with the jump and drill processing strategy are implemented. Different processing strategies will need an adaption of the algorithms. Large errors like misalignment of the sample, gaps or mixed materials are very good visible in the process intensity image.
Smaller deviations the user is not directly aware of are concealed within the data. Advanced knowledge is needed to differentiate between signal deviations with still a good process results and process deviations that can be visible in the data. . The visualization of the data gives hints to the user by an easy understandable presentation, but robust decisions still need more enhanced decision making algorithms. To allow industrial use a help decision system that tells the user if the process was successful or not will be required.
Task 3.4 represents the development of the offline quality control module of deliverable D3.9. The hardware consists of a camera with microscopic lens and a LED-illumination. In additional a stepper linear stage is used for adjusting the focus of the camera. The offline monitoring system is used for visual inspection of suspicious locations of the textured pattern. For compatibility the camera is the same camera (Basler acA2500–gm14) used in the TTLV system by ILS. The following table summarizes the specification of the offline monitoring hardware.
Specification Nominal values
Camera resolution 2592 x 1944 pixel
Magnification 2
Pixel size on image 1,1 μm
Optical resolution 3,9 μm
Working distance 47 mm
Field of view 2,851 x 2,193 mm2
Frames per second 14
Travel range of linear axis 50 mm
Resolution axis 150 nm
The offline quality control module can be mounted on any standard optical table with a grid of M6 threads with a grid distance of 25mm or at a vertical plate with or without linear axis. With the interface software, the user can control the camera and the linear stage.
A digital zoom function supports the user analyzing smallest features. With the calibrated point-to-point distance measurement the user can analyze the size of the structured pattern. The image of the offline monitoring system can be saved for further analysis or documentation.
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WP4: Definition of low-pressure cold-gas system (LPCS).
T4.1 Improve existing numerical models to enable their application with LPCS.
T4.2 Characterization of surface morphology, 3D observation and quantification of surfaces which are irradiated using several laser conditions.
T4.3 Define the most appropriate adhesion test to study the coating bond strength as a function of the laser-structured surface characteristics.
The work carried out in WP4 covers the Improvement of existing numerical models to enable their application with LPCS. Reports on surface characterization and adhesion test as well as on low pressure cold spray deposition efficiency and nozzle geometry were performed. For the tests different parameters were combined, i.e. pressure, spray type, particle and nozzle geometry and dimensions.
In T4.1 existing numerical models were exploited to enable their application to Low Pressure Cold Spray. The first numerical simulation using a 1D two-phases flow performed on Maltlab (Figure 10) code which takes in account the gas parameters, the nozzle geometry, the particles size and distribution show the possibility of Deposit Efficiency improvement, giving the following main conclusions:
The higher both inlet pressure and temperature of the propellant gas, the better the adhesion and the deposition efficiency, provided that the erosion velocity is not reached.
The highest achieved DE for the standard copper powder would be in the range of 0.10 approximately, unless the powder feedstock mainly contains very fine particles such as 1.5 microns diameter sized particles (DE = 0.9 according to the numerical analysis). A good compromise is found between the DEexp and the DEsim which is total DE of adhering particles accounting for their size distribution.
For the Cu+Al2O3/Cu and Cu+Al2O3/Al powder feedstock/substrate combinations, the experimental measured DE remains low, i.e 0.22 and 0.23 respectively.
There is an optimal ratio of rexit/rthroat that increases with the nozzle diverging part length to improve the deposition efficiency. Moreover the longer the nozzle length, the higher the energy loss. Assuming that energy losses due to wall friction are negligible, high DE may be achieved for low diameter particles. The real DE will however depends on the particle size distribution.
The results using helium as propellant gas lead to the same conclusions.
The only difference lies in the DE that may be greatly improved, up to 1, in the case of nozzle diverging part length of 400 mm, since wall friction effect is negligible and the particle sizes are lower than 15 microns approximately.
In T4.2 & T4.3 experiments were carried out in order to characterize the surface morphology according to different laser texturation conditions. As result the most appropriate adhesion test was defined to study the coating bond strength (Figure 11). Comparing the different surface morphologies induced by the laser treatments, different behaviors were observed at first regarding coating efficiency.
Using the same spraying parameters, experiments were made on composite samples but so far no coating was possible. Instead of coating, spraying particles could be observed on the sample surface destroying the composite and the fibers. Tests on metallic substrates have been carried out showing an increase of the adhesion by a factor of 2.
Results predicted by simulations and real parts demonstrated that there are quite close. Several experimental designs with various materials, powders, substrates...have been implemented to demonstrate the impact on DE (deposition efficiency). Each test was performed using round calibrated and non-calibrated powders, calibrated but non-round powders. “Calibrated” here indicates that the grain powder dimension is controlled and approximately the same.
With the Standard Dycomet equipment, the results regarding DE were about 50% - 60%. The Dycomet equipment is at the maximum of its capacity.
WP4 started in month 3 and ends in month 11. D4.11 and D4.12 were delivered.
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WP 5:
T5.1 Laser integration
T5.2 Test in lab environment
T5.3 Industrial user cases
T5.1: The work has been done on the ns laser only. The platform should have been completed to start the wp5 but it was not available (see above).
T5.2: We create a test scheme to validate the performance of the integrated EMLACS platform and verify the formal hypothesis and texturation parameters. Using the ILS ns laser, the texturation geometry (based on existing UTBM expertise) was defined and the efficiency, the adhesion and electric conductivity tested. Significant improvements have been observed on adherence depending on the powder's geometry, but finally have poor effect on efficiency. EMLACS showed that thermal effects do not have negative impact on adhesion but quite the reverse. Nevertheless, lack of repeatability is stills strong.
Texturation on composite materials with thick layer was tested (PEEK matrix, pure resin without fibers) and on composite plastic material (used in automotive sector). Good results on bonding strength on substrates textured with ns laser were obtained. On the other hand, no positive effect on DE on aluminum substrates was shown and little interest on pure PEEK material. Good results were obtained with industrial materials like plastic used in the automotive industry.
T5.3: Since the beginning of the project, industrial end users provided material samples. Real parts with 3D geometries could not be provide as the machining of the parts require much more sophisticated equipment then the one used in this project. The EMLACS Project however provides a real proof of concept which can be used as basis for further developments to set up a real demonstrator unit.
Numerous trials adapted LPCS conditions to create a metallic coating on industrials polymers. To create a thick and adherent coating, several powder granulometry and specific spraying conditions have to be used. Thanks to these new adapted parameters, good results were obtained with industrial materials like plastic used in the automotive industry. Coatings with reasonable thickness were obtained.
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WP 6:
T6.1 Co-ordination of activities
T6.2 Patent and protection of IPR
T6.3 Knowledge transfer
T6.4 Dissemination and use strategy
The web site will continue to be use to communicate after EMLACS project.
T6.1: Co-ordination of activities: coordinate all knowledge management, dissemination activities and Intellectual Property Rights issues. A video from Dycomet have to be done as sample’s pictures presented in conferences.
T6.2: No invention leads to a patent.
FTO: to be developed
T6.3: The simulation tools developed at UTBM have been adapted in order to transform them into self-running software using opensource FEM systems. These tools have been transferred to Dycomet and a video tutorial has been created in order to simply explain how to use the simulation tool. The tool has been installed on a Dycomet computer and a demo has been done. The tutorial will allow Dycomet to reuse it even a long period of time without using it.
T6.4: There is some possible exploitation, especially regarding the control system. Exploitation of the results needs to go further with the project. Concerning the dissemination, several presentations have been done of the EMLACS results in professional fairs as well as in scientific national and internationals conferences. Papers in international journals have also been written. These presentations allow to disseminate the EMLACS results. Among them, the following points have particularly been highlighted:
- Development of specific simulation tools for Low pressure Cold Spray Deposition efficiency and their experimental validation
- Improvement of the adhesion strength of Al and Cu coatings on Aluminum substrates through optimized laser texturing.
- Creation of a copper coating on polymer substrates using a specific spraying process involving the use of two specific powder sizes to optimize the coating adhesion and coating growth.
A better DE on metallic support using laser texturation is obtained. It allows to provide new solutions to industrial end users which are already doing Cold-spray without laser texturation.
On composite, first conclusions are good but they need to be deeply analyzed.
Potential Impact:
Major aerospace and automotive companies have shown high interest in the EMLACS project. Some of them have committed to supply to the project new material substrates in order to define new user cases.
Thanks to the EMLACS project, we are now able to do simulations of our Cold Spray process which allow us to predict spray parameters with a software tool to optimize the Low Pressure Cold Spray process. This is saving time and money in finding the right parameters and in not having to do as much coating characterizations as before.
A second benefit we have is that we now know what a big impact a laser structured surface can have on the adhesive properties of a Cold Sprayed Coating. Certain customers require more bonding than can be obtained with regular pre-surface treatments.
Automotive and aerospace industries are highly interested since metallic parts and composite parts are really often used and assembled together in new modules in order to save weight and therefore to save energy. Composite parts in the car industry can be plastics with glass fiber or with specific reinforcements.
Aerospace is mainly using Carbon Fibers Reinforced Polymers (CFRP) for big and small parts. Some of these parts have to integrate physical properties that such material don’t have. For instance, electrical /electronic housing need to have thermal properties in order to cool down the electronic devices/components.
Nowadays metallic cooling systems are mechanically added on the composite parts, which induce extra cost and weight. This can be replaced by doing a copper and /or aluminum coating on the right area of a CFRP cabinet. On the other hand this also can also be used to heat up some specific areas of a part.
Automotive industry is running after “green issues”. The main objective is to build light and highly recyclable cars, with the smallest possible energy consumption. Therefore more and more projects are coming out trying to combine metal with composite (or plastic) while trying to avoid gluing processes in order to eliminate a maximum of chemical wastes. EMLACS will open possibilities to assemble dissimilar materials in a green and industrial way.
Partners from automotive industry have expressed their interest. Assembling of a composite and a metallic part using the Cold Spray coating interface could have a major impact on the joining technology of dissimilar materials needed for light car bodies manufacturing or aerospace and space & military parts.
EMLACS allows generating a data base with cycle times of a complete laser texturation combined to a low pressure cold spray for given surface/material substrate and therefore a financial model for the process in relation to the surface and to the coating properties.
Such data base and process will help the automotive and the aerospace industries to select the right material combination for a given application. For instance: grow a thick metal coating of copper or aluminum on composite/plastic parts that will be machined later on for mechanical handling purposes, or, use of such layer for joining dissimilar materials like aluminum and plastic for light car bodies. This will eliminate gluing processes, chemical waste and all costs attached to it.
EMLACS will certainly open other process opportunities like thermal dissipation or thermal conduction on plastic/composite parts, protection of fragile surfaces where the cosmetic aspect has to be taken in consideration. Military industry will be also an area to investigate where components/modules are used in a very difficult environment conditions and where weight is also a major issue like in space applications.
List of Websites:
www.emlacs.eu
Learn more on the EMLACS technology on web site.