How To Get High Quality Machined Plastic Parts

Machined Plastic Parts

Probably, you would like to machine plastic parts for your clients.

Whether you want custom-machined plastic parts or OEM, this guide will show you how to get high-quality parts.

From understanding your manufacturer’s capability to choosing the material type and machining techniques – this guide will help you get the best-machined plastic parts.

Let’s dive right in.

1. Start By Machining Plastic Prototypes

Prototyping is a critical stage in machining plastic components and parts. With prototypes, you can examine and test plastic part designs.

Of course, before eventually starting the mass production process.

Of course, the prototype parts are a replica of the final plastic parts you want to produce during the machining process.

Plastic machining prototype

Plastic machining prototype

2. Adopt CNC Plastic Machining

CNC plastic machining is a computer-controlled process that ensures accuracy and repeatability.

CNC machining can produce complex plastic parts with virtually no errors. Again, it is convenient for mass plastic parts production.

Remember, the advancement in machining technology goes hand in hand with precision, accuracy, and consistency.

3. Have Accurate Drawings For Plastic Parts

You will machine plastic parts and components from engineering drawings.

A technical drawing will help you configure the CNC plastic machining equipment.

Therefore, an accurate engineering drawing will translate into precise and high-quality machined plastic parts.

In most cases, your team should collaborate closely with the manufacturer. It is the only sure way to ensure you get quality parts.

So, countercheck all dimensions and other instructions in the drawing to ensure they are accurate.

4. Choose a Suitable Plastic Machining Technique

With the machining technique, you can produce many parts and components.

For instance, you may wish to produce cylindrical parts, make threads, make holes, etc.

Some of the most common machining technologies include:

CNC plastic machining process

CNC Plastic machining process

Plastic CNC Turning

In CNC turning, you will rotate the plastic material against the cutting tool. It is a perfect method for producing cylindrical to cone-shaped plastic components.

Whenever you are using the plastic CNC turning technique, you should adopt the following guideline:

  • Always ensure the cutting edge of the tooling system has a negative back rake. As a result, it minimizes the possibility of rubbing.
  • Ensure there is no material build-up for a better surface finish
  • A C-2 grade carbide insert guarantees a perfect cutting solution
  • Use a feed rate of 015 IPR for rough cuts and 0.005 IPR for fine cuts

CNC plastic turning process

CNC plastic turning process

CNC Milling Plastic Parts

The plastic milling technique uses a rotary tool moving at high speed to remove unwanted sections from plastic material.

Depending on the types of machined plastic parts, your manufacturer may adopt:

  • 3 axis mills
  • Multi-axis mills

For a successful plastic milling process, you should use carbon tooling. This is critical when handling plastic material reinforced with carbon fibers or glass.

Additionally, use clamps for accurate and high spindle speeds.

Plastic milling

Plastic milling

Drilling Plastic Material

Drilling is a technique we use to create holes in plastic material.

Heat is a problem when drilling plastic material. Therefore, solving the overheating problem will produce high-quality plastic parts.

Remember, plastic drilling is one of those techniques which generate excessive heat.

For high-quality plastic drilling, you should consider the following:

  • Choose the following drill bits: drill point angle should be 90 to 118 degrees, while that with twist angles should be 9 to 18 degrees
  • Always use a sharp drill bit

In addition to these variables, you should balance the plastic cutting speed, and feed rate and use coolant where necessary.

Plastic drilling process

Plastic drilling

Threading Plastics

Threading is a process where you carve threads in or on plastic components. Machined plastic parts manufacturers use thread-chasers with twin teeth. It prevents burring.

Apart from these, other plastic machining techniques are sawing and grinding.

In short, when you choose the best plastic machining technique, you will get high-quality parts.

5. Choosing The Right Material For Machining Process

Machining is a versatile process for making many plastic parts and components. However, you must choose plastic material with suitable properties.

Some of the main properties are:

  • Plastic hardness and strength
  • Moisture absorption properties
  • Corrosion and chemical resistance
  • Insulation properties
  • Strength-to-weight ratio
  • Thermal expansion
  • Heat deflection temperature
  • Optical properties
  • Dimension stability

Some of the most suitable plastic for machining include Acrylonitrile Butadiene Styrene (ABS), Nylon

High-Density Polyethylene (HDPE), Acrylic, Delrin (Acetal), Polyetheretherketone (PEEK) and Polycarbonate, just to mention a few.

Remember, the choice of plastic material will depend on the specific application.

6. Know the Machined Plastic Parts Manufacturer’s Capability

Capability is an important parameter, which determines if your manufacturer will machine the exact parts you want.

These fundamental aspects include:


You use tolerance to measure how machined plastic components can deviate from the intended value.

In most cases, the manufacturer will give this in inches. For instance, a custom plastic machining company may state this value as 0.02”. This value will vary depending on the plastic parts you are machining or the plastic fabrication technique.

Even what some manufacturers refer to as precision machined plastic parts depend on the tolerance or accuracy of the component.

Production Volume

How many parts can the company make within a given time frame?

This will help you determine the turnaround time. Again, this will also vary depending on the number, complexity and size of parts.

Industries The Manufacturers Serve

We have machined plastic parts in virtually all industries. Therefore, the manufacturer must be well-conversant with the industry.

It is the only sure way of meeting various quality standards and specifications.

So, experience matters a lot here.

7. Quality Inspection Of Finished Machined Plastic Parts

Quality inspection and verification are critical processes in plastic fabrication. Through quality inspection of machined plastic parts, you can identify defects and non-compliance.

Quality inspection should be a continuous process. It should start from the time you receive plastic material to the final machined product.

It is at this stage that you will determine if machined plastic parts meet recommended quality standards or not.


In summary, to get a high-quality machined plastic part, you must choose the best material, know the technology you intend to use and understand the manufacturers’ capability, just to mention a few. It is a series of interconnected processes.

At Weprofab, we help guarantee quality, consistent and durable plastic machined parts for your business.

You can tell us the parts you need, and our team will produce exactly that.

Related Resource:

Plastic Machining

Plastic Fabrication

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