When choosing materials in plastic CNC machining, you need to consider their mechanical properties, as well as factors such as dimensional stability, processing accuracy, and surface finish. Selecting the right plastic is one of the most important decisions in your product development process.
In this article, we will examine the advantages, disadvantages, and costs of 8 common plastics.
8 Common CNC Machining Plastic Materials
POM
POM (Polyoxymethylene) is a commonly used engineering plastic, also known as Acetal. In CNC plastic processing, POM is one of the common materials.
POM has good dimensional stability, excellent mechanical properties, good machinability, relatively good chemical resistance, and good electrical insulation properties. It is widely used in precision gears, guide rail parts, automation equipment components, sliders, and other products.
However, its high-temperature resistance is limited, its impact resistance is average, its resistance to highly corrosive chemicals is limited, surface treatment is difficult, and there is a risk of deformation during machining. If your application requires long-term exposure to high temperatures, high impact resistance, or complex surface finishes, POM may not be the best choice for your application.
PEEK
PEEK (Polyether Ether Ketone) is a high-performance specialty engineering plastic and an excellent material for CNC machining.
The dimensional stability of PEEK is excellent. It can withstand high temperatures and has a long-term service temperature of approximately 250℃. It has excellent chemical stability and good electrical insulation properties. However, it has a very high cost, is difficult to machine, and offers limited surface finishing options.
If your project requires long-term performance in high-temperature, highly corrosive environments, or high-precision applications, such as aerospace, medical equipment, semiconductors, and other industries, PEEK is an ideal choice.
However, if your project is more focused on cost control, or material performance requirements are not very demanding, then PEEK is often not the most economical choice; you can consider POM and other engineering plastics as an alternative material.
Nylon
Nylon (PA) is a commonly used engineering plastic with excellent overall mechanical properties. It has high strength, good toughness, excellent wear resistance and impact resistance, while being lightweight and offering good chemical resistance.
Therefore, when your parts need to withstand significant mechanical loads, frequent friction, or impact, such as mechanical moving parts, automation equipment components, and automotive functional structural components, Nylon is usually an ideal material choice.
However, Nylon also has some limitations. Due to its high water absorption, prolonged exposure to humid environments may affect its dimensional stability. Additionally, its high-temperature resistance and UV resistance are relatively limited, and there is also a risk of deformation during machining.
PE
PE (Polyethylene) is a lightweight, corrosion-resistant thermoplastic. It has excellent chemical resistance and an extremely low water absorption rate, allowing it to maintain good stability in humid environments or when exposed to corrosive chemicals.
Meanwhile, PE offers excellent impact resistance, wear resistance, and self-lubricating properties, making it suitable for conveying equipment parts, chemical equipment components, and wear-resistant parts. Its good electrical insulation performance can also meet the requirements of some electrical insulation applications.
However, the strength and rigidity of PE are relatively low, and its temperature resistance is limited. Due to its softness, it can be affected by machining parameters and clamping methods during CNC machining, while surface treatment can also be challenging.
Therefore, for CNC-machined parts that require high structural strength, strict dimensional accuracy, or long-term exposure to high temperatures, you need to carefully evaluate whether PE is the right material choice.
PTFE
PTFE (Polytetrafluoroethylene), also known as Teflon, is a high-performance fluoropolymer and a specialty plastic material used in CNC machining.
PTFE has an extremely low coefficient of friction, excellent chemical resistance, and outstanding temperature resistance from -200℃ to 260℃. It is ideal for your parts requiring corrosion resistance, low friction, self-lubrication, or electrical insulation, such as seals, sliding components, and insulation parts.
However, PTFE has relatively low mechanical strength, insufficient rigidity, moderate dimensional stability, and a soft material structure. It is also difficult to machine, has limited surface treatment options, and offers only average wear resistance. Therefore, if your CNC machined parts need to withstand high mechanical loads or require high dimensional accuracy, PTFE may not be the best material choice.
ABS
ABS (Acrylonitrile Butadiene Styrene) is a widely used general-purpose engineering plastic that is commonly applied in CNC plastic machining.
ABS has excellent processing performance, good overall mechanical properties, outstanding surface finishing capabilities, low cost, good dimensional stability, and good electrical insulation properties. However, its temperature resistance is moderate, its chemical resistance is average, and its wear resistance is poor.
ABS is a CNC plastic material with balanced performance, good machinability, and cost-effectiveness. If your project is mainly used for product development verification, functional prototypes, equipment casings, consumer electronics, or aesthetic structural components, ABS often provides better overall performance.
However, if your parts require long-term exposure to high temperatures, frequent friction and wear conditions, or high mechanical loads, it is recommended to consider other plastics with better performance to ensure part reliability and service life.
PC
PC (Polycarbonate) is a high-performance engineering plastic. It is also one of the most commonly used transparent materials in CNC plastic machining.
PC has extremely high impact resistance, excellent light transmission performance, good dimensional stability, and excellent electrical properties. However, it is prone to surface cracking during processing; its chemical resistance is moderate, its wear resistance is poor, machining is relatively difficult, and proper heat dissipation is required during processing.
PC is a type of engineering plastic with high strength, high transparency, and high impact resistance. If your parts require excellent visual appearance and protective properties, such as protective covers, transparent structural components, electronic equipment casings, and automotive parts, PC is an ideal choice.
However, if your parts are exposed to long-term friction, strong corrosive chemicals, or require high wear resistance and special surface treatments, you should consider other materials during the design stage to better meet your application requirements.
PMMA
PMMA (Polymethyl Methacrylate), also known as Acrylic, is a transparent engineering plastic. In CNC plastic machining, PMMA is also one of the most commonly used transparent materials.
PMMA has high transparency, excellent surface finish, good processing performance, good dimensional stability, and moderate cost. But its impact resistance is poor; the surface is prone to scratches, it can deform at high temperatures, the texture is relatively brittle, and it is easy to crack during machining.
PMMA is a type of engineering plastic that is highly transparent, has a high gloss, and possesses excellent weather resistance. If your project is more focused on appearance, optical effects, or transparent structure requirements, such as transparent appearance components, optical parts, display products, and lamp parts, custom acrylic parts can provide very good visual performance.
However, if your components require high impact resistance or structural strength, especially in applications involving repeated impacts or mechanical loads, you should consider materials with better performance.
Comparison of Common CNC Plastic Materials
| Material | Mechanical properties | Durability | Temperature resistance | Electrical performance | Machinability | Cost |
| POM | Excellent High strength, Good rigidity, Stable dimensions | Excellent | Generally, long-term use up to about 100℃ | Generally | Excellent Easy to process, high precision | Medium |
| PEEK | Excellent High strength, High performance | Excellent | Excellent, long-term use up to about 250℃ | Excellent | Difficult | High |
| Nylon | Excellent High strength, Impact resistance | Excellent | Good | Generally | Good | Medium |
| PE | Generally Low intensity | Good | Poor | Excellent | Good | Low |
| PTFE | Poor Low rigidity | Generally | Excellent, -200℃ to 260℃ | Excellent | Difficult | High |
| ABS | Good Comprehensive performance balance | Poor | Generally | Good | Excellent | Low |
| PC | Excellent High impact resistance | Poor | Good | Good | Generally Processing requires careful control | Medium |
| PMMA | Generally Good rigidity, relatively brittle | Poor | Generally | Good | Good | Medium |
Considerations for Choosing CNC Plastic Materials
Mechanical properties
When you choose CNC plastic materials, you need to consider whether the tensile strength, compressive strength, impact strength, bending strength, hardness, rigidity, wear resistance, etc. of the material itself meet your design requirements.
Different plastic materials have different mechanical properties. Some materials can withstand higher pressure loads, tensile forces, and bending stress, while others offer better resistance to cracking, scratches, deformation, and wear.
PEEK, Nylon, and POM have excellent mechanical properties, including high strength, good rigidity, and excellent wear resistance, making them suitable for your CNC machined parts with high-performance requirements.
Dimensional Stability
Different CNC plastic materials have different thermal expansion rates, moisture absorption levels, internal stresses, and long-term load capacities. For precision assemblies or long-term applications, dimensional stability is critical because the material must maintain its original size and shape during operation.
POM, PEEK, and PC have excellent dimensional stability and can maintain high dimensional accuracy with minimal deformation during use, making them suitable for precision CNC machined parts.
Temperature Resistance
During the design process, you need to consider the working temperature of the parts, whether they require continuous high temperature or short-term high temperature, and whether they need to undergo thermal cycles, etc. Different CNC plastic materials have different temperature ranges that they can withstand.
Don’t blindly pursue high-temperature resistance. If your application only operates at normal temperatures, high-temperature-resistant CNC plastic materials can be used, but costs increase. The right material should deliver the required performance while balancing functionality and cost.
PEEK and PTFE have excellent temperature resistance and can maintain stable performance during long-term exposure to high temperatures, making them suitable for high-temperature applications.
Chemical Resistance
Different chemical media can cause different levels of corrosion, and the corrosion rate usually increases as the temperature rises. At the same time, the length of time in contact with the chemical medium can have a significant effect on CNC plastic materials. Different CNC plastic materials have different levels of corrosion resistance.
When designing parts, you also need to consider whether they will be exposed to chemical media, whether the ambient temperature will rise, and whether they are suitable for long-term, stable use. These are all factors that you need to take into account.
PTFE, PEEK, and PE have excellent chemical resistance and can maintain stable performance when exposed to corrosive chemicals and harsh environments, making them suitable for applications with high corrosion resistance requirements.
Electrical Properties
The most important aspects are electrical insulation, dielectric strength, volume resistivity, surface resistivity, and electrostatic performance.
What matters most for most CNC plastic parts is whether the material can safely insulate against current and maintain stable electrical properties over long periods of use.
If you choose the wrong material, it may lead to leakage, short circuits, electrostatic accumulation, electrical insulation failure, etc.
PTFE, PEEK, and ABS have excellent electrical insulation properties and can provide stable insulation performance, making them suitable for electronic parts and electrical applications.
Machinability
Many people will ignore the machining performance when selecting materials for CNC machining parts, but it is a very important factor for CNC machining projects.
When selecting materials for CNC plastic parts, you need to consider more than just the final performance requirements. Factors such as machining difficulty, dimensional accuracy, surface finishing requirements, and cost impact on the project all play an important role in choosing the right material for your project.
For your project, choosing the material with the highest performance does not necessarily mean that you have selected the best solution. A more appropriate choice is often one that meets the required performance, ensures reliable processing, and strikes a good balance between functionality and cost.
ABS and PMMA offer good machinability and cost-effectiveness, making them suitable for projects that require efficient processing and cost control.
FAQ
Q: Which plastic materials for CNC machining offer the best durability and finish?
A: If you need CNC plastic parts with excellent durability, you can choose POM, PEEK, or Nylon, while PMMA and PC are better options when you need a smooth surface finish and high visual quality.
Q: Is plastic suitable for small-batch CNC machining?
A: Yes, it is suitable. CNC machining does not require mold making and is highly suitable for prototype verification during the product development stage, small-batch production, and custom part manufacturing. It can help you quickly validate the design and shorten the development cycle.
Q: How can you reduce CNC plastic machining costs?
A: You can reduce machining costs by choosing the right materials, optimizing part design, avoiding unnecessary high-precision tolerance requirements, and performing DFM in advance.
Selecting CNC suppliers with experience in material selection and processing can also help you reduce trial and error costs.
Q: Can CNC plastic parts achieve the same level of tolerance as metal parts?
A: Yes. CNC plastic machining can achieve high dimensional tolerance, but the final tolerance will be affected by material properties, part structure, size, and processing technology. For high-precision applications, we recommend choosing materials with better dimensional stability, such as POM and PEEK.
Q: What are the common problems in CNC machining plastics?
A: The common problems include dimensional tolerance control, part deformation, insufficient surface finish, difficulty in machining complex structures, and processing cost control. Your project can reduce these problems by choosing the right plastic materials, optimizing the machining process, and working with an experienced CNC machining manufacturer.
Final Thoughts
We provide high-quality CNC plastic machining services with machining tolerances controlled within ±0.01mm-0.05mm. With in-house sandblasting capabilities, prototype services, and strict quality control, we ensure reliable parts that meet your requirements. Contact us and tell us about your needs, and get a solution that fits your plant perfectly in terms of efficiency and reliability.
