Issues related to machining of CFRP components
Carbon fibre composites are becoming more and more important in automobile and aerospace areas due to their superior properties such as lightweight, high strength, excellent corrosion resistance, and minimal fatigue concerns.
However, problems related to the machining of these materials exist, such as high rejection ratio of the product and severe tool-wear usually due to the mechanical and thermal properties of this fiber-reinforced material. The abrasive nature of CFRP material often leads to a high tool-wear rate and some related defects such as delamination. Thermally-induced damages are another aspect of defect that cannot be ignored. Low thermal conductivity of CFRP would lead to an extremely high cutting temperature and make the expansion of the drill bit, which would influence the dimensional accuracy of the boreholes. Also, degradation would occur in matrix due to the high temperature.
These problems can somewhat be controlled by introducing precision cooling in the machining process. Traditionally there are two cooling conditions: flood cooling and dry (air) cooling.
Using coolants would, to some degree, reduce the cutting temperature, and then reduce the defect related to thermal damage. But, a chemical reaction might happen between the coolant liquid and the CFRP material, which would diminish the properties of the material.
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Furthermore, deployment of cutting fluids counts for about 10-20% of the total cost of machining (as a comparison, costs of tool only account for approximately 2-4%), and treatment of waste cutting fluids also has considerable costs. Moreover, one of the major concerns is the health and environment hazard associated with cutting fluids.
These problems related to cutting fluids can be avoided with dry machining of CFRP, that has become the most widely used cooling condition in drilling CFRP materials. But, on the other hand, dry machining induces thermal damage due to low thermal conductivity of CFRP materials and high cutting temperatures. As a consequence of low thermal conductivity of CFRP, the heat generated during the cutting process could not be effectively transferred. This leads to an extremely high cutting temperature generation, resulting in a severe expansion of cutting tool diameter during drilling CFRP. This overheating problem causes matrix material of carbon fiber reinforced composite to get burned, as well as with a larger deviation on the diameter of the bored holes. These quality control problems, which severely and negatively affect the mechanical properties of parts, are the reasons for a significant rejection rate of machined composite parts. The conduction of the heat up through the CNC machine's electro spindle can also alter the characteristics of the grease used to lubricate the electro spindle bearings. This can already begin to occur at temperatures of ~73째 C thereby causing inefficiency of the bearings and giving rise to potential electro spindle damage.
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That is where Cruing's Aerotech® System comes in.
The Aerotech® System is a tool-holder that works like a jet engine! It has a solid fan turbine which sucks in air up to velocity of 80 meters a second at the point of cut, blowing it out into the CNC machines extraction hood through its fan outlets. This is what makes it so effective at removing hot dust particles while cutting, and at the same time reducing cutting temperatures by over 100° C.
The Aerotech® System effectively air-cools the cutter and material providing the solution to the problems related to machining with coolants and with "traditional" dry cutting.
During a series of heat tests conducted at an Aerospace company located in Europe, thermal camera images confirm that the Aerotech® can reduce machining temperatures A) A conventional tool dry cutting a carbon fibre component
See video at: https://www.youtube.com/watch?v=F1uyeiAEPLI
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B) An Aerotech速 System dry cutting the same carbon fibre component
See video at: https://www.youtube.com/watch?v=8_2K8-9KuCc
Photos A) and B) courtesy of The University of Hamburg, Germany
For more informations and free quotations: visit our websites (www.cruing.com ; www.aircooleddrycutting.com) write us (marketing@cruing.com)
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