Efficient manufacture of pieces with compound materials
Say that the new industrial revolution, the third, is cream of the union of the new technologies of the information jointly with the utilisation of new sources of power. In this case, these would be the renewable energies. If we admit this approach and use it like starting point, the respect to the environingingment inserts in the heart of this new revolution when incorporating the concept of sustainability in all his extension. Said respect no only self-evident in the energetic production, but especially, in his responsible consumption in all the fields, being the industrial one of the most affected.
The revolution to the new concepts of product goes through the utilisation of different materials to the known, with properties improved and processes of production and transformation also new. The compound materials are leading in this appearance, and the sectors that sue the application of the technology with greater urgency are the typically industrial manufactureros, with very high production and economic impact in the society and big environingingmental repercussion, for example the car and the aeronautical sector component manufacturing sector component manufacturing. On the base of this positive tendency, the analysts foresee a tax of annual growth composed (CAGR) of 17% in the production of compound CFRP (Carbon Fibre Reinforced plastics) of here to 2020, as it illustrates in the Figure 1, producing a total of 100.000 tonnes for the year 2017 in the world-wide market, in which the European market by himself only represents 25.000 tonnes (25% of the total).
Table. Forecast of the demand of CFRP (Ricardo analysis, Composite World, 2012).
The evolution of the processes of manufacture and transformation of compound materials has the sight in the economic productivity of the installations and in the resolution of problems inside the own process. In this investigation situates the initiative on new technologies for the efficient manufacture of components with compound materials, organised in the project Reform (Ressource-Efficient Factory Of Recyclable Manufacturing composite components).
Reform Is a project begun in 2011 with a length of four years and funded by the 7º Program Mark of the European Commission (Grant agreement Number: 283336). In this project participate 13 partners of 6 different states, between which finds Tecnalia R&I through his Division of Industry and Transport.
The main aim is to develop green and efficient technologies for the manufacture of components of compound materials. The activity of Tecnalia R&I centres in the development of the cut and recanteado of materials composed by means of the technology of stream of water and abrasive (AWJ, Abrasive Water Jet).
Cutting by stream of water and abrasive (AWJ)
The technology of stream of abrasive water (AWJ) has received a considerable attention by part of sectors like the aeronautical sector component manufacturing sector component manufacturing or the one of the automotive sector for the mechanised of compounds, thanks to the specific advantages when they mechanise this type of materials, between which stand out:
Cutting in cold: The water deletes the heat that generates instantly by the impact of the abrasive particles with the material, so that the material does not bear any increase of temperature and does not exist thermal sensors distortion in the piece. That is to say, it does not produce the zone damaged térmicamente (ZAT).The low wear of the tool: In this case the tool of cut is the own stream of water and abrasive, and therefore, the wear that produces in the components where generates the stream (orifice, camera of mixed and filter, see Figure 2), is independent of the material to mechanise. These components can have a length and a cost of roughly 120-150 h and €12 in the case of the orifice, 400-500 h and €90 in the case of the camera of mixed, and 50-100 h and €100 in the case of the filter.The low strengths of cutting: To the not having direct contact between the cabezal of cutting and the piece do not exist problems like the chatter, and besides, the deformations that produce in the piece are minimum and the tie up of piece required is simple.The high productivity with a good quality of cutting: For example, the fibre of carbon of 10 mm of thickness can cut to 2.000 mm/min, obtaining a rugosidad superficial Ra of 10 µm.Amicable with the environingingment: This process does not create neither gases neither toxic sequipment.
Although the cut by AWJ is a mature technology, his employment confronts to several challenges when it treats to cut compound materials, mainly because of the fault of a methodology of research of the parameters of optimum cut for this type of materials. Usually, the manufacturers of machines of cut by water provide a database with the ideal parameters of cut of different types of materials. However, when it treats of materials composed these databases are scarce and, therefore, the capacity to find the parameters of optimum cut depends of the specific knowledge and of the experience of the final users of these machines. The development of a methodology to adapt the parameters of process for each type of material will allow to adjust easily the operations of cut by AWJ to the time that will allow an expansion of the employment of the technology.
Another of the challenges to which confronts the technology AWJ consists in ensuring that the parameters of cut are the adapted along all the operation, as well as detect any problem that can arise during the process, as for example the jam of the abrasive in the tube of transport of abrasive, the break of the orifice, the severe wear in the filter or the aseguramiento of the control of the distance of work, known like stand-off.
Development of models of cut for compound materials
An important part of the activity in the project has consisted in developing databases with the parameters of process optimised to the types of compound materials more usual. Between the partners of the consortium, the final users demandantes of the technology cover several sectors of market with real utilisation of compound materials: Azimut-Benetti (Italy), centred in nautical and yachts of luxury, Acciona Infrastructures (Spain), inside the section of construction, and Diad-Group (Italy), FormTech (United Kingdom) and Teks (France), manufacturers of components for applications advanced of automotive sector and aerospace.
The technological development carried out in Tecnalia R&I centres in the generation of models of cut for these materials, that base in experimental essays realizar in the machine Byjet L 2030, available in Tecnalia. The materials tested, in total 11, have been of two types:
- Type I: Compound Materials reinforced with fibres;
- Type II: Panels Sandwich.
The form to characterise each one of these types has been different. In the material type I, the cut has characterised with the upper width of cutting (Wtop), the inferior width of cutting (Wbottom), and the inclination of the wall or angle taper (T), as it shows in the Figure 2-c. However, the material type II have characterised through the upper width, the inferior, the maximum width (Wmax) and the depth to which produces the maximum width (h) (Figure 2-d). This is due to the fact that in the panels sándwich (type II), unlike the materials reinforced with fibres (type I), the stream finds with an intermediate layer of a much less dense material and less last once that has crossed the first layer, by what the flow disperses , and goes back to close when it finds with the last layer or when the outside of the stream remains without sufficient power as to follow eroding the intermediate layer.
With the experimental results obtained, have developed models of cutting that allow to predict the characteristics described previously, as well as the deviation of the stream during the cut along the path, and the superficial quality of the piece through the rugosidad superficial (Figure 3). To his time, these models also allow to find the parameters of suitable process for each type of material and thickness.
Development of systems of monitoring for the cut by AWJ
The failures by jams of abrasive are very common in this type of processes and can give place to the occlusion of the filter or to a jam in the pipe of abrasive. In the cases in which it obstructs the pipe of abrasive the machine is still working, but to the not having of abrasive in the stream loses the capacity of cut, by what only achieves mark the pieces and not to cut them, wasting time, prime matter and power. Besides, the wear of the components of the cabezal can produce also a loss of power of cutting of the stream and therefore affect to the final piece. Therefore, the control of the supply of abrasive and of the wear of the components of the cabezal of cut are critical during the process.
For this, has posed a system for the monitoring of the conditions of able cutting to detect of effective form the situations of jam in the pipe of abrasive and in the filter as well as the wear of the orifices.
The most reliable option bases in the monitoring of the depressesion generated in the tube of transport of abrasive because of the effect Venturi that causes the stream of water in the camera of mixed. In proofs carried out inside the project Reform, in which they have miscellaneous the parameters of cut as for example, the pressesure and the discharge of abrasive, and have realizar essays of wear of orifices, has checked that it treats of a suitable method for the detection of the correct supply of abrasive (Figure 4) as well as of the deterioration of the tool (Figure 5). In the Figure 4, shows the signal of the pressesure in the tube of transport of abrasive in a process of taladrado of several holes in compound material, in which they differentiate clearly the zones in which the stream is turned off (pressesure around 1 bar), with regard to when only it has of water (pressesure around 0,95 bar) and when it goes in the abrasive (pressesure around 0,8 bar). it is working So much only with water as with water and abrasive. In the Figure 5, shows the variation of this same signal in the essays of wear of the orifice.
Another of the critical parameters during the process is the control of the distance of work. The stand-off or distance of work between the cabezal of cutting and the piece to mechanise, is a fundamental variable to reach the maximum productivity of the process. Inside the project Reform, Tecnalia is investigating the development of systems of able monitoring to detect this height for what is preparing a comparative between different types of commercial sensors (Figure 6) with the end to analyse advantages and disadvantages of each one of them. To continuation will analyse his implementation in the machine of cut to realizar so much the control so much of height of the cabezal like the depth of mechanised.
Conclusions
The incorporation of the materials composed to our daily life depends almost exclusively of the cheapening of his utilisation, so much in the manufacture of the material as of the processes of mechanised and transformation. Whereas the utilisation of the ironinging and of the steel has thousands of years of experience, the investigation in the processes of manufacture of the composites advances decididamente to the industrial application on a large scale thanks to projects like Reform.
The efforts of Tecnalia R&I inside Reform, centre in the mechanised of this type of materials using the technology of cut by water and abrasive (AWJ) and organised in two lines of work:
- Optimisation parameters of cut by means of the development of models of cutting that allow to know the optimum parameters of the process and allow to compensate the inherent errors to the same process (mainly geometrical errors as for example, the angle taper)
- Systems of monitoring of the process, to avoid problems during the mechanised of this type of materials of high value, controlling the flow of abrasive, the state of tool and the distance of work.
The results obtained in the two lines of work offer already a sample of the levels of improvement and of the increase of profitability of the installations of AWJ, with some very positive values. The results of the work in course, so much inside the project as in other lines of investigation related, will finish to confirm and dimensionar this increase of productivity.
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