In the field of mechanical processing, the application of plastic materials is becoming more and more extensive, and the selection of the right processing plastic is directly related to the performance, life, processing efficiency and cost control of the product. This article will start from the importance and selection challenges of plastics in machining, introduce common types of processed plastics, disassemble the core selection factors, provide reference based on practical application cases, and finally give practical selection ideas, and supplement professional FAQs to help you accurately choose the right plastic for machining.
1. Introduction
1.1 Introduce the importance of plastics in machining
Compared with metal materials, plastics have the advantages of light weight, corrosion resistance, good insulation, and low processing energy consumption, occupying an irreplaceable position in machining in various industries such as electronic appliances, automobile manufacturing, medical devices, and aerospace. According to industry data, the global machining plastics market will exceed $80 billion in 2024, with the automotive industry accounting for 35% and the electronics industry accounting for 28%. For example, in the processing of automotive interior parts, the application of plastics reduces the weight of parts by more than 30%, effectively improving vehicle fuel economy; in the processing of precision electronic components, plastics with excellent insulation can avoid short circuits and ensure product stability.
1.2 Challenges in Choosing the Right Plastic
Despite the significant advantages of plastics, choosing the right plastic for machining is not an easy task. On the one hand, there are many types of plastics available for processing on the market, and the performance of different types of plastics varies greatly; on the other hand, the needs of processing scenarios are complex and changeable, such as high-temperature environments requiring materials to have good thermal stability, and scenarios exposed to chemicals have strict requirements for chemical resistance. In addition, factors such as processing difficulty, cost budget, and mass production needs will also affect the choice, and a slight carelessness may lead to product scrapping, low processing efficiency or cost overruns. A small mechanical processing factory once misselected ordinary polystyrene (PS) processing chemical equipment accessories, and due to insufficient chemical resistance of the material, cracking and leakage occurred after 1 month of use, resulting in direct economic losses of more than 100,000 yuan.
2. Common types of machined plastics
Different types of processed plastics have their own emphasis on performance and applicable scenarios, and the following is a comparison of the core information of the 5 most commonly used plastics, so that you can quickly understand:
| Plastic type | Core performance | Applicable to processing scenarios | Processing difficulty |
|---|---|---|---|
| Polyoxymethylene (POM) | High hardness, good wear resistance, strong dimensional stability, and excellent fatigue resistance | Gears, bearings, sliders, precision mechanical parts | Medium |
| Polycarbonate (PC) | Strong impact resistance, high light transmittance (up to 90%), and good thermal stability | Protective covers, optical components, medical device housings | Above average |
| Polypropylene (PP) | Excellent chemical resistance, light weight, good toughness, and low cost | Chemical storage tanks, pipelines, food packaging machinery parts | Simple |
| Polyamide (Nylon, PA) | High strength, good wear resistance, impact resistance, and strong moisture absorption | Mechanical transmission parts, auto parts, textile machinery parts | Medium |
| Polystyrene (PS) | Good rigidity, high light transmittance, excellent processing fluidity, and low cost | Ordinary housings, decorative parts, electronic component trays | Simple |
2.1 Polyoxymethylene (POM)
POM is known as "supersteel" and is one of the plastics with the best overall performance in machining. Its outstanding wear resistance and dimensional stability make it particularly suitable for machining precision parts that require long-term movement. For example, a gear processing plant uses POM to process micro transmission gears, which not only increases the processing efficiency by 40% compared with metal gears, but also reduces the noise of the gears by 25 decibels and extends the service life by 3 times.
2.2 Polycarbonate (PC)
The core advantages of PC are impact resistance and high light transmission, maintaining good toughness even in low temperature environments of -40°C. In the field of medical device processing, PC is often used to make protective covers for surgical instruments, which can not only resist collision damage, but also ensure that medical staff can clearly observe the operation process. It should be noted that PC processing requires high temperature control, and too high a temperature can easily lead to material decomposition.
2.3 Polypropylene (PP)
PP is a cost-effective plastic for machining, especially in scenarios where it is exposed to chemicals such as acids and alkalis. A chemical company used PP to process pipes transporting hydrochloric acid, which did not show corrosion leakage after 5 years of use, while traditional metal pipes usually need to be replaced after 1-2 years. In addition, PP has good processing fluidity and is suitable for mass production of parts with complex shapes.
2.4 Polyamide (Nylon, PA)
PA's high strength and wear resistance make it widely used in the automotive industry, such as valve covers, intake manifolds and other parts of automobile engines. However, PA has strong moisture absorption and needs to be dried before processing, otherwise it will lead to dimensional deviation of the processed parts. An auto parts factory once ignored the drying step of PA, resulting in a batch of intake manifolds with an unqualified size, with a scrap rate of 20%.
2.5 Polystyrene (PS)
PS processing is simple and low-cost, and is suitable for processing ordinary parts that do not require high performance. However, PS is more brittle and has poor impact resistance, making it not suitable for use in scenarios where there is a risk of force or collision. In the electronics industry, PS is often used to make trays of electronic components, because its processing accuracy is easy to control, and it can better protect the components from damage.
3. Key considerations when choosing plastic
3.1 Mechanical properties
Mechanical properties are the core factors in choosing plastic for machining, mainly including strength, hardness, wear resistance, toughness, fatigue resistance, etc. It needs to be selected according to the stress of the parts: if the parts are parts that require long-term friction force such as transmission gears and bearings, POM, PA and other materials with good wear resistance and fatigue resistance should be preferred; If the parts are protective covers, shells and other components that need to resist impact, materials with good toughness such as PC and PP are more suitable; If the part is a precision positioning part, it is necessary to choose a POM with strong dimensional stability.
3.2 Chemical resistance
If the part is exposed to chemicals (such as acids and alkalis, oils, solvents, etc.), it is necessary to ensure that the material has the corresponding chemical resistance. The chemical resistance of different plastics varies significantly: PP and PTFE (polytetrafluoroethylene) have the best chemical resistance and can withstand most acids and alkalis; PC is not resistant to strong alkali and some organic solvents; PS has poor chemical resistance and is easily corroded by a variety of solvents. For example, in the processing of parts in the petrochemical industry, PP or PTFE is preferred; In the processing of ordinary office equipment parts, the requirements for chemical resistance are low, and materials such as PS and PC can be selected.
3.3 Thermal stability
Thermal stability refers to the ability of a material to maintain stable performance at both processing and service temperatures. During processing, the material needs to be able to withstand the high temperature of the processing equipment without decomposing; When used, it is necessary to adapt to the temperature changes of the working environment. For example, for parts working in high-temperature environments (such as around the engine), PC and POM with high thermal deflection temperature should be selected (both thermal deformation temperatures are above 100°C); The parts used in the room temperature environment have low requirements for thermal stability, and materials such as PS and PP can meet the demand.
3.4 Machinability
Machinability directly affects production efficiency and cost, mainly including the cutting performance, fluidity, and forming accuracy of the material. For small processing plants or enterprises with simple processing equipment, PP and PS should be selected with low processing difficulty; For enterprises with professional processing equipment and technology, you can choose PC and POM, which are slightly more difficult to process but have better performance. In addition, during mass production, it is necessary to choose materials with good processing stability and low scrap rate, such as PP and POM.
3.5 Cost-effectiveness
Cost-effectiveness requires a comprehensive consideration of material costs, processing costs, and usage costs. PP, PS and other materials have low cost and simple processing, and are suitable for large-scale products with low performance requirements. POM, PC, PA and other materials have high costs, but excellent performance, can improve product life, reduce subsequent maintenance costs, and are suitable for high-precision and high-demand parts. For example, a high-end medical device company chooses PC processing core components, although the material cost is 50% higher than PS, but the product failure rate is reduced by 60%, and the comprehensive benefits are better.
4. Application examples and case analysis
4.1 Plastic Applications in Different Industries
- Automotive industry: PA is used to process engine parts, PP to process bumpers, and PC to process lamp shades to achieve lightweight and performance improvement;
- Electronics industry: use PS to process electronic component trays, PC to process mobile phone shells, POM to process keyboard buttons, taking into account insulation and precision;
- Medical device industry: PC processing surgical instrument protective cover, PP processing infusion set components to meet hygiene and disinfection resistance requirements;
- Chemical industry: PP processing chemical storage tanks, pipelines, PTFE processing seals to resist chemical corrosion.
4.2 Sharing of successful cases
An auto parts manufacturer needs to process a micro gear in the gearbox, which requires light weight, good wear resistance, and low noise. In the early stage, the use of metal materials was difficult to process and the noise was high. After choosing POM as plastic for machining, after optimizing the processing parameters, the weight of the gear is reduced by 40%, the processing efficiency is increased by 35%, the noise is reduced by 30 decibels during use, the service life is extended by 2 times compared with metal gears, and the product competitiveness is significantly improved, and the annual sales of this gear exceed 1 million pieces.
4.3 Failure cases and lessons learned
In order to reduce costs, a small electronics factory chose PS to process the shell of a small electronic device, which needs to withstand minor collisions. After the product was put on the market, a large number of users reported that the shell was easy to crack and break, and the return rate reached 15%. After analysis, PS has high brittleness and poor impact resistance, which cannot meet the needs of the shell. This failure resulted in a loss of more than 500,000 yuan for the company, and the lesson is profound: when choosing plastics, you cannot simply pursue low cost, you need to give priority to matching the performance requirements of the usage scenario, and carry out small-batch trial production verification if necessary.
5. Conclusion
Choosing the right plastic for machining requires comprehensive consideration of the type characteristics of the plastic, the performance requirements of the processing scenario (mechanical properties, chemical resistance, thermal stability, etc.), processing feasibility, and cost-effectiveness. First, clarify the use environment and core requirements of the parts, and then screen the qualified plastic types, and refer to the successful cases of similar products if necessary to avoid repeated pitfalls. At the same time, it is necessary to fully understand the processing characteristics of the material before processing, optimize the processing parameters, and ensure product quality.
Yigu Technology Perspective
As an enterprise deeply involved in the field of material processing, Yigu Technology believes that plastic for machiningThe core of the choice is "performance matching + benefit balance". With the development of material technology, the application of modified plastics is becoming more and more extensive, and the strength, temperature resistance, chemical resistance and other properties of plastics can be improved through modification, providing more solutions for the processing needs of complex scenarios. When choosing, enterprises should combine their own product positioning, do not blindly pursue high-end materials, and do not ignore the bottom line of performance, and it is recommended to cooperate with professional material suppliers to obtain targeted selection and processing suggestions to enhance product competitiveness.
FAQ
1. Which plastic for machining parts require high precision to choose? Priority is given to POM with strong dimensional stability and easy control of processing accuracy, which has a small dimensional deviation after molding and can meet the processing requirements of precision parts. Secondly, PC can be selected, and if the processing process is optimized in place, high processing accuracy can also be achieved.
2. How do you balance the cost and performance of plastic for machining in batch processing? When processing in batches, PP, POM and other materials with low processing difficulty and low scrap rate can be given priority to reduce processing costs; If you need to improve performance, you can choose cost-effective modified plastics (such as modified PA and modified PP), which are cheaper than pure high-end plastics and can meet most performance requirements.
3. What pre-treatments are required before plastic processing? Most plastics need to be dried before processing, especially for materials with strong hygroscopicity (such as PA and PC), insufficient drying will lead to bubbles and size deviations in the parts after processing; In addition, it is necessary to adjust the temperature, rotation speed and other parameters of the processing equipment according to the material type to avoid material decomposition or insufficient processing accuracy.
4. Which plastic for machining should be chosen for parts that come into contact with food? It is necessary to choose plastics that meet food-grade standards, such as food-grade PP, food-grade PC, POM, etc., which are non-toxic, odorless, and will not cause pollution to food; It is forbidden to use PS, ordinary PA and other materials that do not meet food grade standards.
