The stiffness, hardness and strength of PTFE material, are relatively small. Its tensile strength is 21-28 MPa, bending strength is 11-14 MPa and elongation is 250%-300%. It will deform under long-term stress and is prone to creep when overloaded. The above performance characteristics of PTFE, leads to unique process characteristics when using PTFE film skiving machine cutting.
1. Small cutting forces. Due to the stiffness, strength, and hardness of PTFE being low, under the same cutting conditions, the main cutting force of cutting 45 steel is 14-20 times that of film skiving PTFE material.
2. PTFE film has a small thermal conductivity, only 0.27W/M-K-1, coupled with a lower heat-resistant temperature, its high heat-resistant temperature is only 250 ℃. If the film skiving volume is too large, the cutting speed is high, and the cutting temperature of the workpiece will rise, which will soften the PTFE material, and even melt, coking, and “sticky knife” phenomenon. Before the cutting process, the blank is cured with a process condition of 30-50 degrees Celsius above the working temperature and a curing time of 24h or more, to stabilize the dimensional accuracy of the film skiving process.
3. Teflon has a large coefficient of thermal expansion. Therefore, PTFE material in the film skiving process will generate a large amount of heat due to friction, easy-to-tool, and workpiece local overheating. This leads to elastic deformation of the PTFE workpiece due to heat, which eventually affects the surface quality and dimensional accuracy of the PTFE workpiece.
4. Compared to metal materials, the modulus of elasticity of PTFE is very low. When the cutting feed is too large or the speed is too fast, the larger processing friction and the force applied to the workpiece by the tool act together. The result is a large deformation of the PTFE workpiece, which affects the machining accuracy of the PTFE workpiece.
5 For film cutting fluids to work well, the following basic conditions must be observed: use of soft water, frequent checking of concentration, regular addition of biocides, cleaning of machine tools, removal of sludge and scale, premixing of cutting fluids
Post time: Nov-25-2022