1. General description of machining
Thermoplastics that have not been strengthened can be processed with high-speed guillotine tools. The strengthened material should be processed with cemented carbide tools. In any case, sharp knives should be used without any problems. Plastic has low thermal conductivity, so it must have good heat dissipation. The best cooling method is to use plastic chips to dissipate heat.
2. Dimensional accuracy
Stress-free annealing of semi-finished products is a prerequisite to ensure accurate dimensions. Otherwise, the heat generated by machining will inevitably lead to the release of machining stress, which will lead to the deformation of the product. If the machining volume is large, a preliminary annealing should be carried out after the main machining is completed to eliminate the thermal stress that has been generated. . For materials with high water absorption (such as polyamide), it is necessary to check the moisture content before processing. The processing error of plastics is larger than that of metals. In addition to this, the coefficient of thermal expansion is also much larger.
3. Processing technology
Car processing
If the surface quality requirements are particularly high, the tool should be made into the shape of a wide-head thin turning tool. The cutter car used for cutting should be made into an appropriate shape to avoid swelling caused by surplus material. For processing thin-walled and flexible workpieces, it is best to use a turning tool ground into a knife shape.
4. Milling
If it is to process a plane, the end face is more economical than circular milling. The use of circular milling and forming milling cutters directly determines the cutting quality and surface quality.
5. Boring
Under normal circumstances, twist drills can be used, the twist angle should be between 12-16 ℃, and the drill bit should have a good twist groove for chip removal. The large hole diameter should be pre-drilled first, and a hollow drill should be used, or a solid material can be drilled by punching. The drill bit must be sharpened, otherwise the pressure will continue to accumulate until the material is broken. Compared with the plastic that has not been tempered, the tempered plastic has lower impact toughness, but the processing residual stress is higher, so it is easy to crack. This kind of plastic should be drilled as much as possible Previously heated to about 120°C (heating time: about 1 hour per 10mm section). This method is also recommended for polyamide 66 and polyester.
6. Saw
Saw processing usually uses a thinner tool to saw a thicker workpiece. Therefore, unnecessary heat generated by friction should be avoided. It is best to use a saw blade with well-ground serrations and a wide saw path.
7. Tapping
The thread is best processed with a thread cutter. Use a double-toothed knife to avoid flash. It is recommended not to use a die, because you may have to make a cut when you return the knife. Wire pushing usually requires some machining allowance (depending on the material and diameter, reference value: 0.1mm)
