CNC Machining Plastic Parts - A Basic Introduction

Updated: December 04, 2023


If you’re looking for a manufacturing process that can create precision parts with tight tolerances, look no further than CNC machining plastic. This process uses computer-controlled tools to cut or shape parts from a variety of plastic materials. With CNC machining, you can get products that are both accurate and durable.


In this post, we will explore some of the different ways that you can use CNC machining to work with plastic. So if you are interested in learning more about how to use CNC machining to work with plastic, keep reading!

1. Plastic CNC Milling

A wide range of plastic components with tight tolerances required is machined using CNC milling. The process involves fixating solid blocks of plastic materials on a CNC mill’s worktable. Then, a cylindrical rotating tool — milling cutter removes plastic off a solid workpiece forming the end shape. 


CNC machines can belong to one of two main categories: 3-axis mills or multi-axis mills having 3 to as many as 8 or even more axes along which spindles with cutters may move. Left to right, back and forth, up and down, and rotatory are the movements that CNC machines can perform.

The more complicated a piece of machinery is, the higher its machining capabilities are. Yet, some complex designs cannot be produced by means of CNC for different reasons.


Here are some important considerations for machining most types of plastic using mills:

  • Make finish cuts with 2 flute or 4 flute mills. Guide your end choice based on the characteristics of the material.
  • Use carbon tooling in every case you machine thermoplastic or glass reinforced plastic material.
  • Use clamps and other fixes to secure the workpiece.
  • Create rounded internal corners with end mills.
  • Choose optimal feed and speed rates to prevent plastic melting.
  • Ensure that the workpiece is not subject to chatter.


It’s always crucial not to apply extreme stresses on a part being milled to prevent it from failure.

CNC Milling Clear PC part
2. Plastic CNC Turning

CNC turning is another manufacturing process that involves holding a workpiece and cutting material of it using tooling. But in this case, the workpiece rotated against the cutter is either spinning or turning motion. The process is applicable to symmetrical, rounded plastic components mostly.

As for turning centers that suit the best to your purposes, straight or cylindrical turning is optimal for larger cuts. At the same time, CNC turning is sufficient for creating cone-line shapes in the workpiece.

Here is the list of essential aspects to pay attention to when it comes to turning:

  • Reduce rubbing by ensuring that cutting edges have a negative back rake.
  • Use relief angles for cutting edge.
  • Polish outermost surfaces to achieve a better surface finish.
  • Use C-2 grade carbide inserts.
  • Run rough cuts at a feed rate of about 0.015 inches per revolution, and run finish cuts at the rate of 0.005 inches per revolution. 


You may also apply some coolant to the workpiece or freeze it before machining. It’ll prolongate the period during which plastic does not melt. 


Take a look at hat CNC turning ,ay look like I’m the image below.

3. Plastic CNC Drilling

Plastic drilling is the use of drill bits to produce precise holes into plastic workpieces. A spindle that secures the CNC drill lowers onto the block and forms appropriately-size round shapes. You may utilize multiple types of CNC drills, including upright, bench, and radial presses.


The crucial aspect here is that you use sharp drill bits. Plastic is extremely sensitive to worn tooling as it instantly reflects uneven stress in the form of scratches. Tooling problems and performance issues may also arise if you use a cutter that is not sharp enough.


  • Use 90° to 118° drill bit with a 9° to 15° lip angle. In the case of drilling the acrylic, use a 0° rake.
  • Ensure that the chip evacuation is adequate. Drilling generates more heat than turning and milling, so make sure to minimize unnecessary stresses.
  • Use drilling depths that are three to four times the drill diameter.
  • Reduce the feed rate when the material is nearly exited not to damage the outer surface of the plastic once you drilled through.


Besides, you should always support the back side of plastic components. It would help you to prevent chipping of unsupported areas.

4. Types of Plastic for CNC Machining

There is plenty of plastic available for CNC machining. The most popular types are ABS, Acrylic, polycarbonate (PC), or nylon 6 parting lines which have unique properties depending on their chemical makeup as well as how they’re created; i.e. injection molding versus casting with a blow-mold process among other things!


The type of plastic you choose for your project can greatly impact how it turns out and what kind of finish there is. For example, thermoset plastics such as epoxy or polyester will not be able to return to their original state once cut with most CNC machines; however, they offer other benefits like durability which makes them perfect in some instances!


Choosing the right material also means understanding where each piece needs to fit so careful consideration should go into this decision process too since anything less than perfection could result from trying something new without knowing exactly why certain materials don’t work well together (which often leads us down rabbit holes).


ECOREPRAP CNC Machining Plastic
BakeliteFR4G-10Carbon FiberPEI
Check all the machined materials here.
5. Plastic CNC machining with ECOREPRAP

By the end of this post, you should be well aware of how to machine plastic components using turning, milling, and drilling. It’s a good start, but remember, CNC machining is more than some distinct guidelines. Once you are experienced enough, you’ll know how to exploit your manufacturing capabilities in the most rational way.


In case you need CNC manufacturing assistance, contact ECOREPRAP. You’re always eligible for instant quoting or a free strategy session with our professional customer support team. Our machining capabilities are extensive, so we can offer large and small volume machining and a vast array of machining techniques. High-end fabrication, fast shipping, and superior customer experience are the least you should expect from ECOREPRAP. 

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