Periodic Reporting for period 2 - ProSurf (High Precision Process Chains for the Mass Production of Functional Structured Surfaces)
Período documentado: 2019-07-01 hasta 2021-06-30
The ProSurf project aimed to enhance the surface functionalities of polymer and ceramic parts by using a wide range of high precision manufacturing technologies, such as diamond machining, nanoimprinting and micro electro discharge machining, in combination with accurate replication technologies, like micro injection moulding. Along with dedicated modelling, in-process metrology and quality control the developed process chains enable the mass production of cost effective, structured parts which implement a wide variety of surface functionalities. Six demonstrators were integrated using selected techniques to cover a broad spectrum of possible implementations, ranging from optical to tribological and cohesive applications. With this, ProSurf intended to reach a high impact on several areas of industry and society, e.g. increasing the safety of medical procedures and the performance of moulds for ceramic injection moulding as well as cleaning rolls for electronic parts.
Inital work of ProSurf focused on the specification of the demonstrators, their respective functional surfaces and the applicable metrology. Subsequently, the complete process chain, from mould making over replication to quality control was developed to enable the production of the demonstrators. The final part of the work covered the production of the demonstrators using the developed technologies and techniques as well as their functional and economic assessment.
The main results for the individual demonstrators are:
ProSafety - Surgical lens with holograms for anti-counterfeit and batch tracking
- The nFTS machining process enabled for the production of defined nanostructures on freeform surfaces.
- Reflective holographic identification markers were successfully placed on the struts of an ophthalmic lens, allowing for tracing such parts after replication; Q-coef. of 75%-81% were achieved (based on a pixel-wise comparison of source and reconstruction).
- Transmissive holograms with a freeform base geometry have been machined for the very first time by nFTS turning and polymer injection moulding; the encoded image is recognizable to some extended, but further optimization of the process chain is still required.
ProClean - Substrate contact cleaner
- A new hexagonal microstructure for cleaning rollers has been devised along with a viable manufacturing method for bulk production of such surfaces.
- The rollers manufactured with this type of structure do not wrap 25 µm thick films, the cleaning performance is 20% better and the novel rollers last approx. 3x longer.
- An in-process sensor system for monitoring the roller surface was developed. This is utilized to alert the customer when the roller is nearing its end of life and needs replacement. Thus, no preventive maintenance measures are required during operation.
ProMatte - Multifibre optical connector with anti-reflective surfaces
- Antireflective patterns were successfully nanoimprinted on flat steel moulds, however, the patterned surface degraded very quickly during moulding.
- A novel production sequences for nanoimprinting functional patterns on freeform surfaces (e.g. anti-reflective pattern on micro lenses) has been developed. The process utilizes hierarchically structured stamps that are generated in a multi-step procedure and the structured surfaces are then replicated into coated steel moulds for injection moulding. A replication of these structures in a subsequent polymer injection moulding step, however, was unsuccessful due to delamination of the coating.
ProFlow - Ceramic high-temperature sensor cap
- Using a two-step micro-abrasive blasting technique, the injection pressure required for complete filling of the sensor cap cavity was lowered by 150 bar.
- It was shown that micro structuring of the mould cavity with dimples results in a 27% longer flow length of the ceramic feedstock.
- Niobium Carbide cermet (NbC) was introduced as a novel mould material for ceramic injection moulding. It was shown that a more than 90% reduction in mould wear can be achieved when using this material as compared to the previously applied steel.
ProPatt - Transparent hydrophobic micro-patterned surface
- Virtual spindle based tool servo (VSTS) diamond turning and ultra-precision raster milling were qualified for generating hydrophobic surfaces on mould inserts.
- The manufactured hierarchical structures exhibit an increased contact angle in droplet testing (from 91.7° for unstructured micro grooves to 145.6° for hierarchically structured grooves), indicating a composite wetting state which is favourable for self-cleaning of optical surfaces.
- Sliding and rolling-off of the droplet occurred at 39° and 47° tilt of the surface, respectively, verifying the hydrophobic nature of the surface.
- The transmittance of the moulded COC samples was reduced from 92.1% to 84.2% when applying hierarchical structures. This is a necessary trade-off when embedding micro and nanostructures on a transparent material, but shows that such a surface is still applicable in optical applications.
ProDeco - Surfaces with decorative effects for polymer consumer products
- A complete process chain for injection moulding of nanoimprinted high-aspect-ratio structures was established, enabling the production of high quality decorative surfaces, or other conceivable nanostructure designs whose functionality requires high-aspect ratio features.
- Replication fidelity from master to the nanoimprinting stamp was shown to be >97% for the structure height and >98% for the grating period. After replication into polymer, a 90% fidelity (structure height on insert vs. replica) was achieved.
- The central part of the mould exhibited almost no wear after 8000+ shots.
Results applicable for multiple demonstrators
- Great advances have been reported considering fabrication of diamond tools using FIB and pFIB processing allowing high precision structures, various tool materials and geometries of substrates.
- Metrology equipment and off-line measurement procedures for the quality assessment of each demonstrator have been developed.
- A variety of technical solutions to process monitoring have been identified and tested in each demonstrator for enhancing the processing efficiency, tooling life and product quality. Two prototypes of dispersed reference interferometry (DRI) has been built and tested in manufacturing environment.
- Areal texture parameters that are suitable for the assessment of specified structured surfaces in ProSurf have been derived, and in particular, a feature-based surface characterisation has been proposed with developed mathematical foundations.
- The platform and assessment criteria for functional tests have been developed and verified for each demonstrator.
- Two methodologies to simplify the meshing of integrated multi-scale simulations for injection moulding were proposed: the feature-restriction and the feature-refinement method.
The main results for the individual demonstrators are:
ProSafety - Surgical lens with holograms for anti-counterfeit and batch tracking
- The nFTS machining process enabled for the production of defined nanostructures on freeform surfaces.
- Reflective holographic identification markers were successfully placed on the struts of an ophthalmic lens, allowing for tracing such parts after replication; Q-coef. of 75%-81% were achieved (based on a pixel-wise comparison of source and reconstruction).
- Transmissive holograms with a freeform base geometry have been machined for the very first time by nFTS turning and polymer injection moulding; the encoded image is recognizable to some extended, but further optimization of the process chain is still required.
ProClean - Substrate contact cleaner
- A new hexagonal microstructure for cleaning rollers has been devised along with a viable manufacturing method for bulk production of such surfaces.
- The rollers manufactured with this type of structure do not wrap 25 µm thick films, the cleaning performance is 20% better and the novel rollers last approx. 3x longer.
- An in-process sensor system for monitoring the roller surface was developed. This is utilized to alert the customer when the roller is nearing its end of life and needs replacement. Thus, no preventive maintenance measures are required during operation.
ProMatte - Multifibre optical connector with anti-reflective surfaces
- Antireflective patterns were successfully nanoimprinted on flat steel moulds, however, the patterned surface degraded very quickly during moulding.
- A novel production sequences for nanoimprinting functional patterns on freeform surfaces (e.g. anti-reflective pattern on micro lenses) has been developed. The process utilizes hierarchically structured stamps that are generated in a multi-step procedure and the structured surfaces are then replicated into coated steel moulds for injection moulding. A replication of these structures in a subsequent polymer injection moulding step, however, was unsuccessful due to delamination of the coating.
ProFlow - Ceramic high-temperature sensor cap
- Using a two-step micro-abrasive blasting technique, the injection pressure required for complete filling of the sensor cap cavity was lowered by 150 bar.
- It was shown that micro structuring of the mould cavity with dimples results in a 27% longer flow length of the ceramic feedstock.
- Niobium Carbide cermet (NbC) was introduced as a novel mould material for ceramic injection moulding. It was shown that a more than 90% reduction in mould wear can be achieved when using this material as compared to the previously applied steel.
ProPatt - Transparent hydrophobic micro-patterned surface
- Virtual spindle based tool servo (VSTS) diamond turning and ultra-precision raster milling were qualified for generating hydrophobic surfaces on mould inserts.
- The manufactured hierarchical structures exhibit an increased contact angle in droplet testing (from 91.7° for unstructured micro grooves to 145.6° for hierarchically structured grooves), indicating a composite wetting state which is favourable for self-cleaning of optical surfaces.
- Sliding and rolling-off of the droplet occurred at 39° and 47° tilt of the surface, respectively, verifying the hydrophobic nature of the surface.
- The transmittance of the moulded COC samples was reduced from 92.1% to 84.2% when applying hierarchical structures. This is a necessary trade-off when embedding micro and nanostructures on a transparent material, but shows that such a surface is still applicable in optical applications.
ProDeco - Surfaces with decorative effects for polymer consumer products
- A complete process chain for injection moulding of nanoimprinted high-aspect-ratio structures was established, enabling the production of high quality decorative surfaces, or other conceivable nanostructure designs whose functionality requires high-aspect ratio features.
- Replication fidelity from master to the nanoimprinting stamp was shown to be >97% for the structure height and >98% for the grating period. After replication into polymer, a 90% fidelity (structure height on insert vs. replica) was achieved.
- The central part of the mould exhibited almost no wear after 8000+ shots.
Results applicable for multiple demonstrators
- Great advances have been reported considering fabrication of diamond tools using FIB and pFIB processing allowing high precision structures, various tool materials and geometries of substrates.
- Metrology equipment and off-line measurement procedures for the quality assessment of each demonstrator have been developed.
- A variety of technical solutions to process monitoring have been identified and tested in each demonstrator for enhancing the processing efficiency, tooling life and product quality. Two prototypes of dispersed reference interferometry (DRI) has been built and tested in manufacturing environment.
- Areal texture parameters that are suitable for the assessment of specified structured surfaces in ProSurf have been derived, and in particular, a feature-based surface characterisation has been proposed with developed mathematical foundations.
- The platform and assessment criteria for functional tests have been developed and verified for each demonstrator.
- Two methodologies to simplify the meshing of integrated multi-scale simulations for injection moulding were proposed: the feature-restriction and the feature-refinement method.
The state of the art has been significantly advanced in the respective fields of each partner. At the end of the project, the capabilities for mass producing functional structured surfaces have been showcased using the demonstrators developed in ProSurf, which each focus on a different type of functionality. Along with the exhibition of fully functional test parts, all steps of the required process chains were described in a way that industrial partners are able to further devise commercial product from this.