Final Report Summary - TURNCOAT (Temperature Sensor Coatings for Smart Machining Tools)
Executive Summary:
The project aims to design and development of a smart machining tool with a wear-resistant ceramic thin film temperature sensor, for in-situ, continuous wireless monitoring of the temperature during a machining operation. The main benefit is more sustainable production of machined parts through:
* machining process optimization
* Optimal use of the tools within their temperature range resulting in increased lifetime of the tool
* Detection of end-of-life of the tool: changing tools just in time and minimal scrap production * Avoiding scrap of machined parts due to detection of early failure of the tool
With the project reached results, integration in a Tool Condition Monitoring System for full automated production is foreseeable. The main goal of the project, the development of a machining tool (simple geometry cutting tool) with a ceramic thin film temperature sensor, with a minimum temperature range up to 700°C, deposited onto the clearance plane as close as possible to the cutting edge, with connect lines towards the shaft of the tool, where a connection is established with a wireless data transmitter for continuous monitoring of the temperature during a machining operation. The temperature sensor is stable during the full lifetime of the tool, becoming inoperative only after the wear of the cutting edge becoming also a wear sensor.
Project Context and Objectives:
To survive in worldwide competition in the machining industry, European SME’s have changed their focus on machining high-end materials (e.g. high strength steel alloys, titanium) and products with high added value (e.g. precision components). When looking at the aerospace industry, which is the driver for machining of high-end applications, it is now recognised that its products are too expensive and that the new frontier in high-end machining in the 21st century will be cost.
The pie chart in Figure 1 shows the sources of cost in a typical machined part. Because machine and labour costs are so large, higher productivity and efficiency offer the best chance for significant savings. The table in Figure 1 shows an example that increased productivity by using high quality tools offers more potential in cost reduction than a 30% discount on the tool cost itself
A large step forward in improving tool quality and performance has been the introduction of ceramic (PVD- and CVD-deposited) wear-resistant coatings. These coatings can increase the tool life up to a factor 10 or sometimes even more compared to uncoated tools. These are widely accepted in the tooling and machining industry, especially in the high-end machining. The coating accounts for 30% of the total tool cost. For the majority of the coated tools, the coating is applied by job coaters on tools which are supplied directly by the tool maker/seller or by the machining shops who buy uncoated tools first.
To get the maximum benefit (life-time) out of a coated tool, it is important that it is used in an optimal way. One of the properties that influence the lifetime and the efficiency of the tools is the temperature history of the tool: For machining of advanced materials and alloys, the tools are stressed to the maximum and temperature is flirting with the upper limits of use. If the temperature of the coated tool surface in contact with the work piece is too high for a certain period of time, the coating and/or cutting edge will degrade rapidly, resulting in extensive wear of the tool surface and a blunt tool. Another example is the advanced wear resistant coatings which are based on an aluminium alloy. Aluminium oxide is known as very wear-resistant and is for this type of coatings formed in-situ during tool use but only if they are used above a threshold temperature. If the temperature in a machining operation is not high enough, the phase-change to aluminium oxide will not occur, the coating will wear rapidly and the advantage is lost. Therefore, knowledge of the temperature at the cutting edge is needed but at this moment, it is very difficult to monitor the temperature there.
To further decrease the cost, it is important to produce minimal scrap, especially when machining high cost, advanced materials. This can only be reached when using reliable tools and by changing them before their end-of-life. However, if they are replaced too early, it also is an increase in cost for new tools and longer down times for the machines.
Because tools differ in geometry, composition and are not used in exactly the same way for every machining step, a wide range in life-time of a tool exists. In case of (custom) manual machining operations, the operator decides when the tools are changed. In case of continuous production, tools are changed automatically after a defined period of time. For both processes, this leads to sub-optimal use of the tools. A high percentage is changed too early (with only little wear) and substantial percentage is changed too late. A recent study in different large machining shops in Belgium shows an analysis of the wear on tools after replacement in a fully automatic production line (Figure 2).
For a medium-sized company in the sector, with a yearly tool insert replacement cost of 1 Million Euro, this leads to a sub-optimal use of tools worth 450 kEuro. The figure does not show the cost. The cost for scrap production due to the late replacement of damaged tools is estimated to amount to at least 10% of 450 kEuro. Not only has just-in-time replacement a direct influence on the tool cost and scrap production, but also results in a decreased downtime and labour cost. However, to be able to replace tools just-in-time, continuous monitoring of the machining process is necessary. Different techniques already have been proposed and used for Tool Condition Monitoring (TCM): e.g. force measurements, acoustic emission, vibrations, chip dimensions. There is however one important signal that can give a lot of direct and indirect information on the quality of the tool - the temperature at the cutting edge - but up till now no practical method for use in an industrial environment is found.
Apart from temperature as an indicator for the quality of the tool and as parameter for process optimization, it also is useful as a safety parameter. Machining of titanium and magnesium alloys increases but these materials especially the produced chips, are inflammable, which is a serious threat for the SME’s and makes them reluctant to accept these jobs. By monitoring the temperature of the machining process at the cutting edge, safety can be increased.
From the previous paragraphs, it becomes clear that monitoring the tools in machining becomes inevitable if one wants to increase productivity and decrease the cost. With the development of new advanced materials, the need will further increase. Much research has been performed in the past for setting up a tool monitoring system. The main signals that can be measured in a metal cutting operation are force, surface roughness, chip dimensions, strain and temperature. From these signals, temperature at the cutting edge is a very interesting parameter.
By continuously monitoring the temperature as close as possible to the cutting edge of the tool, excessive heating can be prevented. Changing the machining parameters (speed, cooling …) in time, based on the temperature monitoring, an optimal use of the tools and a maximised lifetime can be achieved. According to an SME in the consortium an increase of at least 10% in spindle performance and spindle efficiency is feasible. As already mentioned above, sub-optimal use of the tools is prevented, resulting in a significant cost reduction in purchasing new tools.
Secondly, sudden changes in the temperature data will indicate that some type of wear is degrading the tool, giving the machine or the operator the chance to stop the process and change the tool before a low quality product is delivered from the machine. The product quality will be more constant and scrap production is minimized. However, all researchers agree that temperature is the most difficult to measure, which explains the number of different methods used over the years. This is also emphasized by following quotes from different sources in literature:
“However, none of the laboratory methods for measuring temperatures reported in the literature is simple and reliable enough for routine testing”.
“Unfortunately, determination of cutting tool temperature distributions are technically difficult and past research has not provided sufficiently accurate temperature data”.
“However, the search for a practical method that can be used in an industrial environment continues”.
Up to today, different techniques (integrated thermocouples, powders, contactless infrared radiation monitoring, thermoluminiscence …) have been investigated but with moderate success. Or the tool itself has to be modified, decreasing the stability of the tool, or during contactless monitoring of the temperature, interference is created by hot chips and sticking of work piece material onto the surface of the tool. Modelling of the temperature profiles has been researched intensively, but it is very difficult to validate the simulation if no accurate experimental data is available.
By using thin film temperature sensors deposited onto the functional surfaces and protected by the traditional wear-resistant coating, the temperature at the cutting edge can be monitored constantly without interference from work piece material or other obstacles and without destabilizing the tool itself. Because of the limited mass of the sensor (thickness in order of µm’s), temperature variations are detected immediately.
During machining, the tools are rotating at high speed, making it impossible to connect wires to the applied temperature sensors. By integrating a wireless data transmitter in the head of the tool which is connected with the interconnect lines of the sensors, the data can be send to the receiver and monitored constantly. This opens up the possibility for direct coupling of the temperature data to the steering software of the machine, creating a feedback operating modus for a full automatic machining process.
The project aims to design and development of a smart machining tool with a wear-resistant ceramic thin film temperature sensor, for in-situ, continuous wireless monitoring of the temperature during a machining operation. The main benefit is more sustainable production of machined parts through:
* machining process optimization
* Optimal use of the tools within their temperature range resulting in increased lifetime of the tool
* Detection of end-of-life of the tool: changing tools just in time and minimal scrap production * Avoiding scrap of machined parts due to detection of early failure of the tool
With the project reached results, integration in a Tool Condition Monitoring System for full automated production is foreseeable (figure 3). The main goal of the project, the development of a machining tool (simple geometry cutting tool) with a ceramic thin film temperature sensor, with a minimum temperature range up to 700°C, deposited onto the clearance plane as close as possible to the cutting edge, with connect lines towards the shaft of the tool, where a connection is established with a wireless data transmitter for continuous monitoring of the temperature during a machining operation. The temperature sensor is stable during the full lifetime of the tool, becoming inoperative only after the wear of the cutting edge becoming also a wear sensor.
Project Results:
The project developed a smart machining tool system with a wear-resistant thin film temperature sensor, for in-situ, continuous wireless monitoring of the temperature during a machining operation and since it becomes inoperative only after the wear of the cutting edge it also functions as a wear warning sensor and cutting edge failure warning. For the delivery of this complete system the main components were designed and developed during the project:
1. Temperature sensor integrated in a PVD coating
2. structure on the cutting edge of a four sensor array
3. Lathe Tool Holder
4. Rotating Tool Holder
5. Wireless transmitter-receiver concept
6. Data Analysis Algorithms
A Temperature sensor integrated in a PVD complete coating stack was designed, developed, prototyped and tested with proper chemical composition and electrical and tribomechanical properties.
A laser structuring procedure and proper sensor structure design on the cutting edge for a four sensor array for accurate cutting edge temperature measurement was designed, developed, prototyped and tested.
A lathe tool holder with proper structured sensor-wireless transmitter connection was designed, developed, prototyped and tested in turning machining operations.
A rotating tool holder with proper structured sensor-wireless transmitter connection was designed, developed, prototyped and tested.
A Wireless transmitter-receiver concept with proper frequency, data transmission/acquisition reliability and speed was designed developed, prototyped and tested to a dimension down to 27x37 mm.
Software tools with proper Data Analysis Algorithms were designed developed, prototyped and tested.
The complete system was tested during machining turning operations with successful in situ real time temperature measurement.
Potential Impact:
By applying a sensor on tools that are coated with PVD technology available at TEandM, they can further pursue their mission and obtain a key role amongst other PVD job coater with an added value to the tool. Zenso is a small start-up company, experienced in sensor design and wireless data communication. Success in this project gives Zenso the opportunity to apply and broaden their experience in sensor and wireless communication development with possible market penetration for cooperation's in TCM Systems. ACTARUS already has commercialized tools with sensor functionalities and with this project will be able to gain a greater percentage of this market. KMWE is an end user of the sensor tools and will gain with this project to be the first to have a temperature monitoring system on their equipment giving them the possibility to optimize the production and lower the cost giving them a head start compared to other machining shops. Together, the SME's cover the full value chain for the development, demonstration and exploitation of the "smart" tools. The sector of cutting tools is linked worldwide with all areas of the manufacturing industry. Europe is characterized by many metal machining SME's producing limited quantities of customized components. Europe counts more than 3000 metal milling shops, of which more than 90% SME's. Manufuture, the European strategic roadmap for manufacturing, stresses the importance of a knowledge based and high value for a sustainable European manufacturing industry. Among others, in situ process control is regarded as an important enabling technology. The top SME's, more than 400 metal machining SME companies will profit from smart tools which can monitor the lifetime of the coating. Beside the current markets for machining in job-shops, machinery and automotive, the big niche growing higher-value-added markets are the wind generation market, the aviation industry as well as high-precision complex tools in the machine construction, motor production, power engineering or hydraulics sectors. The consortium targets the machining of high-end products and advanced or difficult to machine materials by means of expensive cemented-carbide tools. The cost of a tool for advanced, difficult to machine materials is in the order of magnitude from €50 to €100. The cost for special cutting tools can even rise to €200 to €300. The main drivers to acquire and use smart coating tool systems are cost reduction, the increase of production efficiency, flexibility and safety. Whereas the allowable surplus cost of the tool during process development can be 500%, the surplus cost during production of large series is in the order of 50-100%.
* Batch production will enable to further reduce the production cost of the T-sensor and to increase production volume.
* Target is to reach about 20 larger companies at Year+2 integrating machining and (high-end) component fabrication. The successful application of the technology in the start-up of large series high end production at industrial companies is regarded as a major factor to attract these companies.
* As market penetration may evolve, further expansion can be obtained by licensing the technology to other SME's.
* Batch production of the developed technology will result in an additional cost of the tool for integration of a temperature sensor will be maximum 150% of the tool cost (target for market penetration with tools used in high-end applications) with expected decrease of the additional tool cost below 100% 2 years after projects.
After successful application in large series the technology will gradually evolve towards smaller series (lowering of cost of the tool - gained knowledge from industrial application). The early adopters, larger and well-known companies in their region, play an important role in the adoption of emerging manufacturing technology in their region and supply chains. The consortium will target the SME's through these early adopters. Target is to reach about 100 high tech SME's (Year+3) supplying manufacturing services for high-end components. For a broader market take-up, process (and eventually sensor) development will be required to lower the surplus price further down towards 50% and below. The total European market potential for metal-cutting tools amounts to approximately €5 billion in Europe (source ECTA the European Cutting Tools Association, figures refer to 2010). All in all, the European cutting tools industry has about 50,000 employees. Due to consolidation within tool market some 10 producers of cutting tools (e.g. Sandvik Coromant, Kennametal, SECO Tools and others) now hold a combined total of about two-thirds the world market. The remaining one-third of the market is covered by a large number of niche-oriented SME suppliers that are active in clearly focused markets. Within the manufacturing chain of coated cutting tools, the coating represents 30% of the cost. Most large producers coat their cutting tools themselves; however SME's rely on the competence of job-coaters (and specialized service providers). In Europe more than 80 companies provide Physical Vapour Deposition tool coating services. Among which, a few large companies (e.g. Oerlikon Balzers), but the majority niche-oriented SME tool coaters. The total market for PVD coatings on milling tools is estimated to be worth 750M€. 250M€ is taken by EU SME's job coaters.
Seven results have been reached with IPR protection potential, 3 patents and 4 utility models are foreseen:
1 - Temperature sensor integrated in a PVD coating – patent.
2 - Data Analysis Algorithms – patent.
3 - Wireless transmitter-receiver concept – patent.
4 - 4 point sensor structure - utility model.
5 - Lathe tool holder design - utility model.
6 - Rotating tool holder design - utility model.
7 - Complete monitoring system- utility model.
The constitution of joint venture is foreseen, between the SME partners, with an initial investment of about 2 M€ will break-even in the fifth year making a total sales of 6 M€ in this period and creating 8 jobs.
List of Websites:
The project ebsite adress is: http://turncoat.inform.pt/index.html
The partners contacts are:
- TEandM | Ricardo Alexandre [ricardo@teandm.pt].
- ZENSO | Johan Coosemans [johan.coosemans@zenso.be].
- KMWE | Jan Bruurs [j.bruurs@kmwe.com].
- ACTARUS | Laurent Velnom [laurent.velnom@actarus-sas-88.com].
- SIRRIS | Patrick Cosemans [Patrick.Cosemans@sirris.be].
- WZL | Drazen Veselovac [D.Veselovac@wzl.rwth-aachen.de].
- IPN | Joao Paulo Dias [jpdias@ipn.pt]
