The introduction of material machining processing
Generalization
Unreinforced thermoplastic plastics can use high speed steel for the processing: for enhanced plastics, hard alloy steel is required.
In all of the machining processes, the cutting head has to maintain a certain of sharpness.
As the poor thermal conductivity of the plastic, you must ensure heat loss. The best way of cooling depends on the cutting head.
Dimensional stability
The prerequisite to get high precision is to use semi-finished products with stress processing. The heat generated in the machining process will inevitably result in internal stress release, which brings about parts deformation. If machining larger parts, they will need an annealing treatment after the rough processing to eliminate the stress generated in machining process.
For materials with higher water absorption (e.g. nylon), dehumidification has to be done before the processing.
The plastic dimensional tolerance is bigger than the metal. Therefore, it is worth considering the plastic coefficient of thermal expansion.
Machining method
1.Vehicle Processing
The cutting head should be designed into a wide shape if the part surface requirement is especially high.
When processing thin walls and soft materials, it's best to use the structure of the cutting head like a knife.
2. Milling
If milling a flat surface, a facing cut will be more economical than circumferential milling. For a peripheral mining cutter and a formed milling cutter, it should not have more than two smear metal blades, so that deviation amplitude caused by the blade vibration can be reduced to the minimum. Also insure that there is a sufficient enough gap between tools.
3. Drilling
Twist drill： the scope of the spiral angle should be is between12 ° and 16 °. It insures chip removal and a smooth groove.
When drilling a large diameter hole, use a step by step, a hollow drill or cut directly. When drilling into the solid materials, pay particular attention to use a sharp drill bit or increasing the pressure during the drilling process could split the parts.
As compared to unreinforced materials, enhanced plastics have greater internal stresses in the machining process and the impact strength is lower. Thus, it is more likely to be split. Therefore, if possible, heat section bars to about 120℃ (heating time of every 10 mm thick of parts is an hour) before drilling into enhanced materials. We recommend that heating be done when processing nylon and polyester.
4. Sawing
It is usually better using thinner saw blades to cut through thick components in the sawing process. It is better to use saw blades with a big sharp saw tooth to avoid heat through friction.
5. Tapping
It’s better to use a screwer to process the thread. Using a bidentate flower cutter can also avoid the flash.
We recommend that you do not use the a threading die when tapping because the threading die will cut again when returning back to the knife.
Working allowance should be considered when tapping (working allowance depends on different materials and pore sizes, and the reference value is 0.1 mm).
6. Safety Specification
Following the processing guide, plastic degradation caused by overheating will less likely occur. For example, machining materials like PTFE, air discharge equipment should be used to exhaust the fumes away after the degradation.
Smoking should not be allowed in the workshop as this will help to prevent poisoning.
Suggestions by our application engineers, whether written or oral, are to assist you and third parties without assuming any responsibilities.
We will not be held responsible for any damage in machining process. |
