The Basic Guide Of Plastics CNC machining

Plastic CNC Machining

Plastic CNC machining uses computer numerical control machine tools (CNC) to process plastic materials. In this process, operators use computer software to design the desired shapes and dimensions, then convert CAD files into machine instructions that tell CNC machines to perform operations such as cutting, engraving and drilling on plastic material to complete the desired shapes and dimensions.

The following are the guidelines for Plastic CNC machining:

Drawing Design

Before the CNC machining of plastics, a drawing design is required to determine the desired shape and size. Here are some things to look for:

Plastic parts size

Before the drawing design, it is necessary to accurately measure the size and shape of the parts to be processed. This can be done using measuring tools such as callipers, rulers, and microscopes.

Determine the machining path

Before the drawing design, it is necessary to accurately measure the size and shape of the parts to be processed. This can be done using measuring tools such as callipers, rulers, and microscopes.

Safety distance

We must consider the required parts’ safety distance when drawing a design. Safety distance refers to the minimum distance between the cutting tool and the plastic material in CNC machines to avoid collision and damage.

File format

The designer need to save the drawing in the correct file format to ensure the CNC machine can read and interpret the drawing correctly. Common file formats include DXF, DWG, and STL.

Design feasibility analysis:

Before beginning any machining process, the engineer should conduct a design feasibility analysis to ensure that the CNC machine can process your design. This includes checking that the size, shape and features of the design are feasible and determining the most suitable CNC machine tools and tools for machining the parts.

Material Selection

Selecting the right plastic material is crucial for the successful CNC machining of Plastic. Here are some common plastic materials and their characteristics and applications:

Acrylonitrile Butadiene Styrene (ABS):

ABS is a plastic material with good mechanical properties and chemical resistance. Suitable for manufacturing high-load, high-pressure parts. Nc machining ABS parts can obtain high-precision surface quality.

Polypropylene (PP) :

Polypropylene is a relatively inexpensive plastic with excellent impact and heat resistance. It is commonly used to make lightweight components, bottles and pipes, among other things.

Polyethene (PE) :

Polyethene is a low-density plastic with good elasticity and durability. It is commonly used for baby toys, food packaging, water pipes and household items.

Polystyrene (PS) :

Polystyrene is a lightweight plastic with good impact resistance and insulation. It is commonly used to make casings for household goods, durable goods and electronic devices, among other things.

Polycarbonate (PC) :

PC CNC Machining

Polycarbonate is a high-strength, high-definition plastic with excellent impact and heat resistance. It is commonly used to make car lampshades, electronic devices and glass.

Polyvinyl chloride (PVC) :

Polyvinyl chloride is a plastic with good heat and weather resistance. Often used in building materials, water pipes, wire insulation shells, etc.

Tools Selection

CNC Plastic Machining

Choosing the right tool is an important step in the NC machining of plastics. Here are some common types of tools and their applications:

Straight cutting knife:

Straight cutting knife is one of the most commonly used tool types. It has a sharp cutting edge and can cut plastic parts of various shapes and sizes.

Round head knife:

The round-head knife is suitable for cutting round, arc, and curve shape parts. It has a smooth cutting edge to reduce cutting marks and cutting pressure.


The squeegee can process relatively hard plastic materials, such as polycarbonate. It has a small head radius and a large cutting Angle to achieve deeper cutting depth.

Ball sharp knife:

Ball sharp knife is suitable for machining spherical and curved parts. It has spherical cutting edges that can cut surfaces at different angles.

Drill bit:

The drill bit is suitable for machining holes and hollow parts. It allows rapid cutting depth while reducing cutting force and heat.

CNC Machining Parameter Setting

In CNC machining plastics, some parameters need to be set to ensure the quality and efficiency of processing. Here are some common parameter Settings:

Cutting speed:

Cutting speed refers to the movement speed of the tool during machining. Too high tool speed may lead to tool wear or damage, and too slow speed may reduce machining efficiency. The tool speed setting must be adjusted according to the specific plastic material, tool type, machine tool performance and other factors.

Feed speed:

Feed speed refers to the speed at which the workpiece moves during machining. Too high a feed may result in rough surfaces or excessive heat generation, while too slow a feed may reduce machining efficiency. The feed speed setting must be adjusted according to plastic material, tool type, machine tool performance and other factors.

Depth of cutting:

The depth of cutting refers to the depth of each tool. Too much cutting depth will lead to tool wear or workpiece deformation, and too little will affect machining efficiency. The cutting depth setting must be adjusted according to the plastic material, tool type, machine tool performance and other factors.

Cutting Clearance (Stepover):

The cutting clearance is the distance between two adjacent cuts. Too large a clearance may lead to a rough workpiece surface, and too small a clearance may increase tool wear. The setting of the cutting clearance needs to be adjusted according to the plastic material, tool type and machine tool performance.


Coolant reduces the heat generated during machining, reducing the risk of tool wear and workpiece deformation. In Plastic CNC processing, the need to choose the appropriate type of coolant and, in the process of processing, regularly join.

Plastic CNC Machining

Plastic CNC Machining Parts

Once you are ready, you can begin CNC machining of plastics by following these steps:


Clean the CNC machine and workbench and install the required tools and fixtures.


Load the CNC program into the machine tool controller. The program will guide the machine tool for parts processing.

Load the workpiece:

Use the fixture to secure the workpiece to the workbench and adjust the fixture position and height to ensure the correct distance and position of the workpiece from the tool.

Start Machining:

In the machining process, the machine tool will automatically control the motion of the tool and the table and complete the machining of the parts.

Monitoring machining:

In machining, it is necessary to monitor the status of the tool and workpiece constantly. If tool wear or workpiece problems are found, the processing should be stopped in time for inspection and replacement.

Finish Machining:

Once the parts are finished machining, stop the machine and check the quality and accuracy of the parts. If necessary, subsequent processing or trimming can be carried out.

How to optimize the quality of CNC machining plastic parts?

CNC Machining Plastic

Reduce the internal edges and corners:

Plastic processing is easy to appear edges, and sharp angles will affect the quality and efficiency of processing and increase the processing difficulty. Therefore, parts should avoid internal edges, circular arcs, and other smooth shape.

Design the correct cutting direction:

The cutting direction will affect the part’s surface quality and machining difficulty. The design of parts should be according to the nature of plastic materials and processing requirements to choose the appropriate cutting direction, as far as possible, to avoid reverse or oblique cutting.

Consider material shrinkage:

Plastic materials shrink during cooling, so you need to design parts with a shrinkage rate in mind and design with an appropriate allowance for subsequent processing or assembly.

Reasonable arrangement of process flow:

Before CNC machining, we must determine the process flow, including machine type, tool type, processing sequence, etc. When designing parts, the processing sequence should be considered according to the process flow to ensure the smooth processing of parts and reduce processing errors.

Avoid excessive cutting:

In CNC machining, excessive cutting should be avoided, leading to accelerated tool wear and affecting the quality and efficiency of machining. In the design of parts, one should avoid too much depth or too small a cutting interval to reduce tool wear and machining errors.


Gavin Leo is a technical writer at Aria with 8 years of experience in Engineering, He proficient in machining characteristics and surface finish process of various materials. and participated in the development of more than 100complex injection molding and CNC machining projects. He is passionate about sharing his knowledge and experience.