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CNC Plastics Selection Guide | Machining Materials

CNC machining is a very versatile and efficient manufacturing method widely adopted by numerous companies for producing various components. This high-precision and high-quality production process at a fast pace can handle a diverse array of materials. Metals, woods, composites, and plastics are all viable options, with plastics being quite common. There are numerous types of machinable plastics.


Plastic CNC service can be utilized for different parts, such as prototypes, engineering models, and end-use components. Although plastics may be challenging to machine, their lightweight and density combined with simple geometries often make them more suitable for machining compared to 3D printing or injection molding. Many materials are highly durable, with strong fatigue resistance, inertness, and shock absorption capacity. Some plastics are general-purpose materials that are easier to machine and suitable for low-cost design testing, like ABS. Depending on the nature of the project, machined plastic might be the optimal choice for custom parts.


There are a large variety of commonly used engineering plastics out there, like POM, PP, ABS, PEEK, PU, PA, and PTFE! What on earth do these letters stand for? And how can we tell them apart? Well, let's take a deep dive and explore plastic cnc machining china in detail together right now !

Types of Plastic for CNC Machining

Pom

POM is scientifically known as polyoxymethylene, and people call it "acetal copolymer". It is one of the most common engineering plastics, and generally, there are more in white or black, and red POM is relatively uncommon. It can be used for a long time within the temperature range of -40 to 100 °C. This material has a low price and features high hardness, high rigidity, and high abrasion resistance. It is mainly used for products that play a skeletal role such as gearsbearings, automotive parts, machine tools, and instrument inner parts.

When processing POM, attention should be paid to the cutting temperature. Excessive temperature on the one hand will lead to the deformation of the product, and on the other hand, it will also generate highly irritating formaldehyde gas. Therefore, when processing POM, we will choose very sharp tools and shorten the continuous processing time. If the depth of cut is relatively large, corresponding cooling treatment for the processed product is required.


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PP

PP, that is, polypropylene, appears as white waxy and is flammable. The melting point of this material is 164-170 °C, and it softens around 155 °C. The service environment temperature range is -30 to 140 °C. It can resist the corrosion of acids, alkalis, salt solutions, and a variety of organic solvents below 80 °C. It can decompose under high temperatures and oxidation and has chemical resistance, heat resistance, electrical insulation, high-strength mechanical properties good high wear-resistant processing performance, etc. This material can be widely used in the production of clothing, medical care, automobiles, bicycles, parts, pipelines, chemical containers, etc., and also for food and drug packaging.


The density of PP is relatively low. When processing some products with relatively thin wall thickness, deformation is prone to occur easily. Therefore, when processing PP, the deformation problem of PP must be considered. Generally, before processing, the PP raw materials will be subjected to aging treatment to remove stress. When processing, secondary or even tertiary aging treatment should also be done according to the actual situation to ensure that the product will not be deformed when it is completed. For processing PP, generally, relatively sharp tools such as white steel tools or PCD tools will also be selected.


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ABS

ABS has excellent comprehensive physical and mechanical properties and has good low-temperature impact resistance. This material performs well in terms of dimensional stability, electrical properties, wear resistance, chemical resistance, dyeability, finished product processing, and mechanical processing.


ABS resin is resistant to water, inorganic salts, alkalis, and acids, insoluble in most alcohols and hydrocarbon solvents, and easily soluble in aldehydes, ketones, esters, and certain chlorinated hydrocarbons. ABS is suitable for manufacturing general mechanical parts, anti-friction and wear-resistant parts, transmission parts, and telecommunications parts. ABS is non-toxic, odorless, and has an ivory-colored translucent appearance. ABS has good electrical insulation and is almost unaffected by temperature, humidity, and frequency, and can be used in most environments.


The common processing methods of ABS include CNC turning and milling, and in 3D printing, it is also used as a common consumable to print some parts. ABS is easier to process than the above two materials, and only the corresponding cutting depth and cutting speed need to be controlled. Under normal circumstances, if the surface of ABS is to be relatively fine, a slightly faster rotational speed and cutting speed are required.

 

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PEEK

PEEK, with the scientific name of polyetheretherketone, belongs to a special polymer material. It has physical and chemical properties such as high temperature resistance and resistance to chemical corrosion. It is a type of semi-crystalline polymer material and can be used as a high-temperature resistant structural material and electrical insulation material, and can be compounded with glass fiber or carbon fiber to prepare reinforced materials. It is also a very expensive non-metallic material, dozens of times the price of other plastics. This material has extensive applications in the aerospace field, the medical device field (as an artificial bone to repair bone defects), and the industrial field.

 

Due to its excellent comprehensive performance, PEEK can replace traditional materials such as metals and ceramics in many special fields. The characteristics of this plastic such as high-temperature resistance, self-lubrication, wear resistance, and fatigue resistance make it one of the most popular high-performance engineering plastics today. It is mainly applied in the aerospace, automotive industry, electronic appliances, medical devices, and other fields.


Applications

Application situations

Aerospace

It can be processed into various high-precision aircraft parts. Due to its good hydrolysis resistance, corrosion resistance, and flame retardant performance, it can be processed into internal/external parts of aircraft and many parts of rocket engines.

Automotive manufacturing

PPEK has been successfully used in the automobile manufacturing industry all the time. Because it has good friction resistance, it can be used to replace metals (including stainless steel and titanium) to manufacture engine inner covers, automotive bearings, seals brake pads, etc.

Industrial field

Because of its good mechanical properties, high-temperature resistance, wear resistance, and high-pressure resistance, it is often used to manufacture compressor valve plates, piston rings, seals, etc.

Medical devices

It can withstand 3000 cycles of high-pressure sterilization at 134°C. This feature can meet the manufacturing requirements of surgical and dental equipment with high sterilization requirements and repeated use. Coupled with its creep resistance and hydrolysis resistance, it can be used to manufacture various medical devices that require high-temperature steam disinfection. What is particularly important is that PEEK is non-toxic, lightweight, and corrosion-resistant, and is the material closest to human bones. Therefore, PEEK can be used to replace metals to manufacture human bones.

Insulating materials

Because PEEK has excellent electrical performance, and its insulation performance can still be maintained under harsh conditions such as high temperature and high humidity, it is an ideal electrical insulating material, and it is especially widely used in the semiconductor industry.

 

When we process PEEK, we just need to consider its surface roughness well. Under normal circumstances, the surface of PEEK processed by CNC will be very smooth and the smoothness will also be relatively high. Also, when processing PEEK, choosing a relatively sharp tool and a slightly higher rotational speed for cutting can achieve relatively good results.


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PU

PU, whose scientific name is polyurethane, is also called elastomer polyurethane. Products related to this material, such as coatings, adhesives, fabric finishing agents, leather modifiers, flexible polyurethane foam/rigid foam, elastomers, etc., are applied in the fields of construction, aviation, shipping, transportation, medical care, electronics, etc. Flexible polyurethane mainly has a thermoplastic linear structure, which has better stability, chemical resistance, resilience, and mechanical properties than PVC foam materials, and has less compressive deformation.


This material has good heat insulation, sound insulation, shock resistance, and anti-virus performance. Therefore, it is used as packaging, sound insulation, and filtering materials. Rigid polyurethane plastic is lightweight, has excellent sound insulation and heat insulation performance, is resistant to chemicals, and has good electrical performance and low water absorption. It is mainly used in the construction, automotive, and aviation industries as structural materials for heat insulation. The performance of polyurethane elastomer is between that of plastics and rubber, with oil resistance, wear resistance, low-temperature resistance, aging resistance, high hardness, and elasticity. It is mainly used in the mechanical industry and the medical industry. Polyurethane can also be used to make adhesives, coatings, synthetic leather, etc.


Because the texture of PU is very soft, there will be certain difficulties when processing PU with CNC. Firstly, in terms of tools, when processing PU materials, a tool with a relatively small outer diameter and thickness needs to be selected for processing. Because the larger the cutting depth, the corresponding resistance will be greater, and the situation of tool deflection will occur. Tool deflection means that when the tool reaches a certain position, instead of cutting the material, it squeezes the material to one side, and there will be machining residues. To facilitate processing, certain cooling can be carried out on the PU material before processing, but this method is not suitable for relatively precise parts.


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PA

PA, namely nylon, with the scientific name of polyamide. Commonly used nylons in equipment include PA66, PA12, etc. This material has high mechanical strength, high stiffness, hardness and toughness, good aging resistance, mechanical shock absorption ability, good slidability, and excellent wear resistance, and this material has good machining performance. When used for precise and effective control, there is no creep phenomenon, and it has good anti-wear performance and good dimensional stability.


PA is suitable for making wear-resistant parts, transmission structural parts, household appliance parts, automotive manufacturing parts, lead screw anti-mechanical parts, chemical machinery parts, and chemical equipment, such as turbines, gears, bearings, impellers, cranks, instrument panels, drive shafts, valves, blades, lead screws, high-pressure gaskets, screws, nuts, sealing rings, shuttles, sleeves, shaft sleeve connectors, etc.


Although nylon is also relatively soft, it is much easier to process than PU. Just choose a relatively sharp tool for processing. In addition, when clamping, it is necessary to pay attention to controlling the clamping force and the cutting depth to avoid material deformation due to overly tight clamping, or the situation of the workpiece being blown away due to insufficient clamping force.


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PTFE

PTFE, namely polytetrafluoroethylene, is also called the king of plastics, Teflon, etc. This material has the characteristics of being resistant to acids alkalis and various organic solvents and is almost insoluble in all solvents. At the same time, polytetrafluoroethylene has the characteristic of high-temperature resistance, and its friction coefficient is extremely low, so in addition to being used as lubrication, it has also become an ideal material for the inner layer of easy-to-clean water pipes.


Its application fields include making bearings, piston rings, support sliders of steel structure roof trusses, and bridge swivels. At the same time, in modern industry, it is also used as a coating material. After the metal is sprayed with a Teflon coating, a certain anti-sticking effect can be achieved, especially in some places that need to be in direct contact with the rubber surface, generally, Teflon spraying or ceramic plating will be carried out for treatment.


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The above are the characteristics, application fields, and processing techniques of the seven most commonly used non-metallic engineering plastics in equipment. In the actual processing process, we also need to set the corresponding processing parameters and select the appropriate tool for processing according to our specific product requirements.


The appropriate non-metallic materials should also be comprehensively selected according to the working environment, operating mode, and price of the parts. For example, when a certain part of ours requires wear resistance and high-temperature resistance, we cannot directly choose PEEK for processing. We have to evaluate according to the specific temperature during use. Generally, ABS is sufficient. After all, the price of PEEK is dozens of times that of ABS, so the price is also an important factor that we need to consider.


To more intuitively reflect the differences among these several materials, we specially sorted out a table for comparison:

Material

Density (g/ml)

Color

Applicable ambient temperature (℃)

Characteristics

POM

1.42

White/Black

-40—104

High strength, wear resistance, fatigue resistance, solvent resistance, etc.

PP

0.89—0.91

White

-30-140

Thermoplastic, light-specific gravity, resistance to chemical corrosion, etc.

ABS

1.04—1.06

Light ivory

-20-80

Impact resistance, heat resistance, low-temperature resistance, etc.

PEEK

1.35

Brown

-40-260

 

Corrosion resistance, anti-aging, anti-dissolution, stable under high temperature and high pressure.

PU

1.18-1.21

Translucent yellow

-70-80

Oil resistance, wear resistance, low-temperature resistance, aging resistance, flexibility

PA

1.12-1.14

White/Black

-30-80

Cleanability, anti-fouling properties, wear resistance, dust resistance

 

PTFE

2.2

Milky white

-180-220

Stability, solubility, and low-temperature resistance.

 

Key Factors When Selecting Plastics for Your CNC Projects

 

Selecting the appropriate engineering plastic to process products needs to consider multiple factors, including the application environment of the product, performance requirements, cost budget, etc. The following are some key considerations for selecting engineering plastics:

  • Application environment

Consider in what environmental conditions the product will be used, such as high temperature, low temperature, chemical contact, etc. Select engineering plastics with characteristics such as high-temperature resistance and corrosion resistance according to the actual situation.

  • Mechanical properties

According to the mechanical performance requirements of the product, such as strength, stiffness, toughness, etc., select the corresponding engineering plastic. For example, if a high-strength material is needed, glass fiber-reinforced plastics can be used.

  • Wear resistance

 If the product needs to have wear resistance, choose engineering plastics with better wear resistance, such as nylon, polyamide, etc.

  • Chemical properties

If the product needs to be resistant to chemical erosion, choose engineering plastics with good chemical stability, such as polytetrafluoroethylene (PTFE).

Electrical properties: If the product needs to have good electrical properties, choose engineering plastics with insulating properties, such as polystyrene (PS).

  • Cost considerations

Consider the budget limitations of the product and choose engineering plastics with a moderate cost while ensuring that they meet the performance requirements of the product.

  • Processing performance

Consider the processing performance of the engineering plastic, including machinability, thermal stability, etc., to ensure that the selected material can adapt to the expected processing technology.

  • Environmental protection requirements

Consider the environmental protection requirements of the product and choose engineering plastics that meet relevant environmental protection standards, such as materials that meet RoHS, REACH, and other standards.

Richconn: Your Ideal Partner for Non-Metallic CNC Part Manufacturing

If you still cannot clearly distinguish these non-metallic materials and don't know how to choose, you can also find a supplier with relatively rich processing experience in this respect to help you make the selection. For example, choose Richconn which has more than ten years of experience in plastic machining services. It is good at processing and designing non-metallic parts.


Richconn is capable of assisting you in attaining an appearance effect with a finish exceeding 0.8 through means such as precision grinding machines and polishing. Richconn constantly undertakes the challenge of processing highly intricate non-metallic parts and can achieve a non-metallic accuracy of ±0.02mm, thereby fulfilling your requirements for precision parts.


Richconn not only can process non-metallic parts, but also non-metallic gears, bearings, and the like. As long as you have such demands, Richconn will employ every possible means to help you realize them. Richconn can offer you the assistance of recommending appropriate non-metallic materials at your design stage. Once Richconn completes the processing and inspection of your parts, it will promptly hand them over to the international logistics company and track the arrival status, ensuring that you can obtain your product in the shortest possible time.


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