Introduction
Plastics have become indispensable in modern machining. They offer advantages metals cannot match: lightweight, corrosion resistance, electrical insulation, and lower processing energy consumption. From automotive interiors to medical devices, from electronic components to aerospace parts, machined plastics are everywhere. Industry data shows the global machining plastics market will exceed $80 billion in 2024 , with automotive accounting for 35% and electronics 28%. But choosing the right plastic is not simple. Different plastics have vastly different properties. Processing scenarios demand specific characteristics—heat resistance, chemical resistance, dimensional stability, or impact strength. A wrong choice can lead to product failure, processing inefficiency, or cost overruns. This guide walks you through common machined plastics, key selection factors, real-world cases, and practical strategies to help you choose the right plastic for your application.
What Are the Common Types of Machined Plastics?
Polyoxymethylene (POM)
Known as “super steel,” POM is one of the best-performing plastics for machining. Its outstanding wear resistance and dimensional stability make it ideal for precision parts requiring long-term movement.
Key properties:
- High hardness
- Excellent wear resistance
- Strong dimensional stability
- Good fatigue resistance
Typical applications: Gears, bearings, sliders, precision mechanical parts
Processing difficulty: Medium
Case example: A gear processing plant switched from metal to POM for micro transmission gears. Results: processing efficiency increased by 40% , gear noise reduced by 25 decibels , service life extended by 3× .
Polycarbonate (PC)
PC offers exceptional impact resistance and high light transmission—up to 90% . It maintains toughness even at -40°C .
Key properties:
- High impact resistance
- High transparency
- Good thermal stability
Typical applications: Protective covers, optical components, medical device housings
Processing difficulty: Above average
Important note: PC requires careful temperature control during processing. Excessive heat can cause material decomposition.
Polypropylene (PP)
PP is a cost-effective plastic with excellent chemical resistance. It withstands acids, alkalis, and many solvents.
Key properties:
- Excellent chemical resistance
- Lightweight
- Good toughness
- Low cost
- Good processing fluidity
Typical applications: Chemical storage tanks, pipelines, food packaging machinery parts
Processing difficulty: Simple
Case example: A chemical company used PP for hydrochloric acid transfer pipes. After 5 years of use, no corrosion or leakage occurred. Traditional metal pipes required replacement every 1–2 years.
Polyamide (Nylon, PA)
PA offers high strength, good wear resistance, and impact resistance. It is widely used in automotive and mechanical applications.
Key properties:
- High strength
- Good wear resistance
- Impact resistance
- High moisture absorption (requires drying before processing)
Typical applications: Mechanical transmission parts, automotive components, textile machinery parts
Processing difficulty: Medium
Warning: An automotive parts factory ignored the drying step for PA. The result: a batch of intake manifolds had dimensional deviations, with a 20% scrap rate.
Polystyrene (PS)
PS is simple to process and low in cost. However, it is brittle and has poor impact resistance.
Key properties:
- Good rigidity
- High light transmittance
- Excellent processing fluidity
- Low cost
- Brittle; poor impact resistance
Typical applications: Ordinary housings, decorative parts, electronic component trays
Processing difficulty: Simple
Comparison of Common Machined Plastics
| Plastic Type | Core Performance | Best For | Processing Difficulty |
|---|---|---|---|
| POM | High hardness, wear resistance, dimensional stability, fatigue resistance | Gears, bearings, sliders, precision parts | Medium |
| PC | High impact resistance, high transparency (90%), thermal stability | Protective covers, optical components, medical housings | Above average |
| PP | Excellent chemical resistance, lightweight, low cost | Chemical tanks, pipelines, food machinery | Simple |
| PA (Nylon) | High strength, wear resistance, impact resistance | Mechanical parts, automotive components | Medium |
| PS | Good rigidity, transparency, low cost | Housings, decorative parts, component trays | Simple |
What Key Factors Should You Consider?
Mechanical Properties
Mechanical properties are the core consideration. Select based on how the part will be stressed:
| Requirement | Recommended Materials |
|---|---|
| Long-term friction (gears, bearings) | POM, PA (wear resistance, fatigue resistance) |
| Impact resistance (covers, housings) | PC, PP (good toughness) |
| Precision positioning | POM (dimensional stability) |
Chemical Resistance
If the part will contact chemicals—acids, alkalis, oils, solvents—ensure the material has appropriate resistance.
| Material | Chemical Resistance |
|---|---|
| PP, PTFE | Best; withstand most acids and alkalis |
| PC | Not resistant to strong alkalis, some solvents |
| PS | Poor; corroded by many solvents |
Example: For petrochemical industry parts, choose PP or PTFE. For office equipment parts, PS or PC may suffice.
Thermal Stability
Thermal stability matters during both processing and service.
| Requirement | Recommended Materials |
|---|---|
| High-temperature environments (engine compartments) | PC, POM (heat deflection temperature >100°C) |
| Room temperature use | PS, PP (adequate) |
Machinability
Machinability affects production efficiency and cost:
| Material | Machinability | Best For |
|---|---|---|
| PP, PS | Simple processing | Small shops, simple equipment |
| PC, POM | Requires more control | Professional equipment, skilled operators |
For mass production, choose materials with good processing stability and low scrap rate—PP and POM are excellent choices.
Cost-Effectiveness
Balance material cost, processing cost, and service life:
| Strategy | Approach |
|---|---|
| Low-cost, low-performance | PP, PS for large-scale products with basic requirements |
| High-performance, long life | POM, PC, PA—higher material cost but better performance, reduced maintenance |
Example: A high-end medical device company chose PC for core components. Material cost was 50% higher than PS, but product failure rate dropped by 60% . Overall benefit was superior.
What Do Real-World Cases Teach Us?
Success Story: Automotive Micro Gear
Requirement: Lightweight, wear-resistant, low-noise gear for transmission.
Initial approach: Metal gears—difficult to machine, high noise.
Solution: Switched to POM with optimized processing parameters.
Results:
- Weight reduced by 40%
- Processing efficiency increased by 35%
- Noise reduced by 30 decibels
- Service life 2× longer than metal gears
- Annual sales exceeded 1 million units
Failure Story: Electronic Device Housing
Requirement: Housing for small electronic device, needed to withstand minor impacts.
Wrong choice: PS selected to reduce cost.
Result:
- High brittleness; housings cracked easily
- Return rate reached 15%
- Loss exceeded $70,000 (500,000 RMB equivalent)
Lesson: Do not sacrifice performance for cost. Match material properties to application requirements. Conduct small-batch trials when necessary.
How Do Different Industries Apply Machined Plastics?
| Industry | Applications | Common Materials |
|---|---|---|
| Automotive | Engine parts, bumpers, lamp shades | PA, PP, PC |
| Electronics | Component trays, phone housings, keyboard buttons | PS, PC, POM |
| Medical | Surgical instrument covers, infusion set components | PC, PP |
| Chemical | Storage tanks, pipelines, seals | PP, PTFE |
What Practical Selection Strategies Work?
Step 1: Define Requirements
Clarify the part’s use environment and core requirements:
- Mechanical stress (friction, impact, static load)
- Chemical exposure
- Operating temperature
- Dimensional precision needed
- Transparency requirements
Step 2: Screen Material Types
Match requirements to material properties:
| Requirement | Candidate Materials |
|---|---|
| High precision, wear resistance | POM |
| High impact resistance, transparency | PC |
| Chemical resistance, low cost | PP |
| High strength, good wear | PA |
| Simple processing, low cost | PS |
Step 3: Consider Processing
- What equipment do you have?
- What is your production volume?
- What is your team’s skill level?
For small shops, PP and PS are easier to process. For professional facilities, PC and POM offer superior performance.
Step 4: Evaluate Cost-Effectiveness
Calculate total cost:
- Material cost per unit
- Processing cost (time, tooling, scrap rate)
- Service life (replacement frequency, maintenance)
A higher material cost may be justified if it reduces scrap, extends life, or improves performance.
Step 5: Test Before Full Production
For critical applications, conduct small-batch trials to verify:
- Machinability with your equipment
- Dimensional stability
- Performance under actual conditions
What Pre-Treatments Are Needed?
Most plastics require drying before processing. This is especially critical for materials with high moisture absorption.
| Material | Pre-Treatment |
|---|---|
| PA (Nylon), PC | Must be dried; insufficient drying causes bubbles and dimensional deviation |
| POM, PP, PS | Less moisture-sensitive but still benefit from dry storage |
Other preparations:
- Adjust processing equipment temperature and speed based on material type
- Avoid overheating to prevent material decomposition
- Verify processing parameters before production
Conclusion
Choosing the right plastic for machining requires balancing material properties, processing feasibility, and cost-effectiveness. Start by defining your part’s use environment—mechanical stress, chemical exposure, temperature, precision requirements. Screen candidate materials based on these factors: POM for wear resistance and precision, PC for impact resistance and transparency, PP for chemical resistance and low cost, PA for high strength, PS for simple, low-cost applications. Consider your processing equipment and skill level—PP and PS are easier to machine; PC and POM offer superior performance but require more control. Evaluate total cost, not just material price. And when in doubt, test with small batches before full production. With the right approach, you can select a plastic that delivers performance, efficiency, and value.
FAQs
Which plastic should I choose for parts requiring high precision?
POM is the best choice. It has strong dimensional stability and is easy to control during processing. Dimensional deviation after molding is minimal, meeting precision part requirements. PC is a secondary option—with optimized processing, it can also achieve high precision.
How do I balance cost and performance for batch processing?
For batch processing, prioritize materials with low processing difficulty and low scrap rate—PP and POM are excellent choices. If you need to improve performance, consider cost-effective modified plastics (modified PA, modified PP). They are less expensive than pure high-end plastics and meet most performance requirements.
What pre-treatments are needed before plastic processing?
Most plastics require drying before processing, especially materials with high moisture absorption like PA and PC. Insufficient drying causes bubbles and dimensional deviations. Also, adjust processing equipment temperature and speed based on the material type to avoid decomposition or insufficient accuracy.
Which plastic should I choose for food-contact parts?
Choose plastics that meet food-grade standards—food-grade PP, food-grade PC, and POM are suitable. They are non-toxic, odorless, and will not contaminate food. Do not use PS or ordinary PA, which do not meet food-grade standards.
How do I know if a plastic has sufficient chemical resistance?
Review material data sheets for chemical resistance ratings. PP and PTFE offer the broadest chemical resistance. PC is not resistant to strong alkalis. PS has poor chemical resistance. For critical applications, conduct small-scale exposure tests before full production.
Contact Yigu Technology for Custom Manufacturing
At Yigu Technology, we specialize in machining a wide range of plastics—POM, PC, PP, PA, PEEK, and more. Our engineering team helps you select the right material for your application, considering mechanical properties, chemical exposure, thermal stability, and cost. We optimize processing parameters to achieve tight tolerances and excellent surface finishes. Whether you need precision gears, medical device housings, or chemical-resistant components, we deliver plastic parts that perform. Contact us to discuss your plastic machining project.
