CNC Plastic Machining

Great Plastics specializes in high-performance plastics in sheets, round rods, tubes, and many more. Large volumes are in stock to meet different project requirements and specifications. With our extensive line of industrial plastics, our offerings include state-of-the-art CNC machining services.

Faster Lead Times

With instant quotes and rapid production, you can reduce cycle times by as much as 50%.

World-Class Machine Shops

Tap into a highly vetted and managed network of the best machine shops world-wide.

Flexible Pricing

Choose between fast and cost-effective options to find the best price.

Machining routes

CNC Machining Processes for Plastic Parts

Our shop has several CNC Turn / Milling Machines which are backed by years of experience in plastics & composites only CNC machining. We have the experience, personnel & technology to provide reliable supply of high quality CNC machined plastic & composite parts.

CNC milling natural PEEK block, white PEEK chips, 3-axis VMC machining high performance thermoplastic

CNC Milling

Suitable for plates, fixtures, manifolds, pockets, slots, blocks and flat parts machined from sheet or block stock.

CNC Turning

Suitable for bushings, rollers, spacers, sleeves, rings and cylindrical parts machined from rod or tube.

Drilling & Threading

Suitable for holes, threaded plastic features, inserts and mounting patterns added to milled or turned parts.

Materials we machine

Engineering Plastic Materials for CNC Machining

Industry-leading companies in aerospace, automotive, defense, machinery, medical technology, robotics, electronics, oil & gas, industrial automation and more that require high degrees of detail and complexity come to us for rapid prototypes and production parts.

PEEK

High performance

Machined for heat, chemical, wear and strength-critical parts: valve seats, bearing sleeves, electrical spacers and structural components.

High temperature Chemical resistant Wear & load

PPS

Chemical & stable

Chosen for chemical resistance and dimensional stability in fluid handling, pump and valve components at a cost-aware performance level.

Chemical resistant Dimensional stability Cost-aware

PI

High temperature

Polyimide serves parts that must hold load and dimension at sustained high temperatures, including bushings, seals and insulating components.

Sustained heat Load bearing Electrical

PEI

Electrical & stiff

PEI combines electrical insulation, stiffness and flame behaviour for housings, insulators, standoffs and precision fixtures.

Electrical insulation Stiffness Flame behaviour

PAI

Extreme duty

PAI is reviewed for the highest load and temperature demands among common thermoplastics — wear parts, bushings and sealing components.

Extreme load High temperature Wear resistance

Not sure which plastic?

Send the drawing — we review material fit during the engineering review.

Material selection is confirmed with you before any quotation is issued.

Machining CHOOSE

When to use CNC Turn / Milling?

This process is ideal for parts that have both turning and milling steps, high part volume, complex geometries requiring multi-axis machining and tight tolerances.

With its multi-tasking capabilities, it requires only one machine set up and produces parts with faster cycle times when compared to utilizing a separate lathe and milling machine. Another advantage is eliminating multiple set-ups which can also introduce tolerance error.

Premium Surface

Premium Surface Finishing Services

The perfect surface finish can make the difference between a good part and an exceptional one. Our comprehensive finishing services go beyond standard deburring to provide aesthetic appeal, functional improvements, and enhanced performance characteristics tailored to your application.

Available Finishing Options:

Creates uniform matte texture for improved grip and reduced glare. Available in various media grades for different surface textures from fine satin to coarse matte.

Progressive sanding and buffing for high gloss finish on engineering plastics. Ideal for aesthetic components and parts requiring low friction surfaces.

Permanent part identification, serialization, logos, and instructional markings. High contrast marking on most plastic materials without surface damage.

Ra 0.05 μm

Optical Polish Available

100%

Edge Deburring Standard

10+

Finishing Methods

part size&tolerances

Maximum part size

There are several types of CNC milling machines, each with its own distinct maximum part size. 3-axis and 3+2 axis machines have the lowest start-up costs and can produce parts with relatively simple geometries.The more advanced of the milling machine family, 5-axis centers can produce parts with more complex geometries. These machines require fewer machine setups so they are more productive.

3-axis milling

Size Metric units Imperial units
plastics 1500 × 800 × 500 mm 59.0 × 31.4 × 27.5 in
Min. feature size Ø 0.50 mm Ø 0.019 in

3+2 axis milling

Size Metric units Imperial units
plastics 2000 × 1500 × 200 mm 78.7 × 59.0 × 7.8 in
Min. feature size Ø 0.50 mm Ø 0.019 in

5-axis milling

Size Metric units Imperial units
Max. part size for all materials 2000 × 1500 × 200 mm 78.7 × 59.0 × 7.8 in
Min. feature size Ø 0.50 mm Ø 0.019 in

CNC turning

Part size limitations Metric units Imperial units
Maximum part diameter 431 mm 17 in
Maximum part length 990 mm 39 in
Maximum swing over the carriage 350 mm 13.7 in
Maximum spindle through-hole 40 mm 1.5 in

*Maximum speed: 1700RPM, Motor power: 640W

CNC milling & turning tolerances

We follow ISO 2768 standards for CNC machining.

CNC milling

Limits for nominal size Plastics (ISO 2768-m)
0.5 mm* to 3 mm ±0.1 mm
Over 3 mm to 6 mm ±0.1 mm
Over 6 mm to 30 mm ±0.2 mm
Over 30 mm to 120 mm ±0.3 mm
Over 120 mm to 400 mm ±0.5 mm
Over 400 mm to 1000 mm ±0.8 mm
Over 1000 mm to 2000 mm ±1.2 mm
Over 2000 mm to 4000 mm ±2 mm

*Please clearly indicate tolerances for nominal sizes below 0.5 mm on your technical drawing.

CNC turning

Limits for nominal size Plastics (ISO 2768-m)
0.5 mm* to 3 mm ±0.1 mm
Over 3 mm to 6 mm ±0.1 mm
Over 6 mm to 30 mm ±0.2 mm
Over 30 mm to 120 mm ±0.3 mm
Over 120 mm to 400 mm ±0.5 mm
Over 400 mm to 1000 mm ±0.8 mm
Over 1000 mm to 2000 mm ±1.2 mm
Over 2000 mm to 4000 mm ±2 mm

*Please clearly indicate tolerances for nominal sizes below 0.5 mm on your technical drawing.

These are our standard tolerances. Should you require tighter custom tolerances, please contact us for details.

Quality & Inspection

We have high standards for CNC Machining

We manufacture your custom parts according to strict manufacturing standards and ensure all parts and processes adhere to The Protolabs Network Standard.

  • Several surface finishes are available to improve the cosmetic quality of your parts after machining.
  • Every custom part gets checked on site by our manufacturing partners according to our guidelines.
  • Inspection reports and other types of quality documentation are available on request to assure the highest quality and compliance.

Buyer questions

CNC Machining FAQs

We guarantee that our manufacturing partners follow ISO 2768 standards for all CNC machined parts. Parts machined with plastics will follow 2768-m (medium). Geometric tolerances down to ± 0004 in. (0.010 mm) are possible but must be clearly indicated in technical drawings. We can achieve tighter tolerances on shafts with up to H7 fits with manual quoting and on occasion tighter.

A CNC Turning Center performs a turning type operation. CNC lathes, or turning centers, have tooling mounted on a turret which is computer-controlled. CNC Turning is a process in manufacturing where workpieces are rotated as various tools are used to remove material and create the desired shape.

CNC lathes are most often only 2 axis machines with one spindle. They also don’t have high production capabilities and typically don’t have a protective enclosure around the machine. CNC turning centers are more advanced versions of CNC lathes with up to 5 axes and more versatility in cutting ability. They also offer the ability to produce higher volumes and usually integrate milling, drilling, and other capabilities.

In addition to using turning tools, a CNC turning center can also be equipped with rotating cutters such as end mills or drills, which allows for greater freedom in machining, such as having the ability to handle asymmetrical features in parts. This increases production speed and efficiency, cost-effectiveness and safer operations. Several aspects of turning that are unique and different from milling, include the ease of achieving radial symmetry, high precision due to mounting part in chuck, and good surface finish.

If a specific fillet radius is required, please specify. If not, the fillet radii that allow for easy machining will be added based on the machinist’s discretion. For a general idea, internal vertical edge radii could be >1/3*Depth and internal horizontal edges may be left sharp or have a 0.5mm to 1mm radius.

Material selection depends on factors including:

Mechanical properties (strength, hardness and wear resistance)

Environmental conditions (temperature and corrosion)

Weight and cost requirements

Our platform provides instant quoting and DFM feedback, and our team can offer guidance regarding the best material for your application.

Need Custom CNC Plastic Parts Made to Your Drawing?

Share your drawing and operating requirements.

We’ll review the material, part geometry, and critical dimensions to help define the right machining approach.