Plastics have many benefits. They're widely available, strong relative to their weight, and compatible with many modern manufacturing methods, including CNC machining, high-precision waterjet cutting, and 3D printing. 

The polymers that make up plastics combine in various ways to yield numerous different materials, each with unique properties and uses. While some applications have requirements that necessitate a specific type of plastic, there are times when you may have flexibility with the plastic you choose—and there are certain plastics that are better for manufacturing than others. 

6 Best Plastics for Manufacturing

When you need plastic machining, consider one of these six materials, ranked from good to better to best. Let the countdown begin! 

6. PEEK

Coming in at number six is PEEK, a high-performance plastic often used for medical applications. This material has an operating temperature of up to 480 degrees Fahrenheit and tends to tolerate all common solvents. While PEEK is incredibly strong and possesses high chemical and heat resistance, it's susceptible to UV light and doesn’t do well with halogens, sodium, and some acids. 

Machining PEEK is expensive. Due to the high cost, you may want to opt for another plastic option for your application. Still, when you need it, it's a great recyclable and biocompatible replacement for metal, and it’s compatible with CNC machining. 

5. Polycarbonate 

Polycarbonate (PC) is a naturally transparent, pliable, heat and impact-resistant plastic commonly used in eyewear, medical devices, automotive components, greenhouses, and more. Clear PC can transmit light as effectively as glass and is a better choice for clear-viewing window applications because of its high impact strength, especially when compared to other transparent plastics like acrylic. If transparency isn't a concern, PC can also be purchased with added colors. 

There are, however, a few notable downsides to using polycarbonate. It yellows after prolonged exposure to UV rays, doesn't perform well around hydrocarbons, and can degrade in water hotter than 160 degrees Fahrenheit. 

4. Polytetrafluoroethylene (PTFE or Teflon)

PTFE, more commonly known as Teflon, has made a name for itself thanks to its non-stick properties. It's often used to coat kitchenware but is also found in the medical and technical industries. In addition to its coveted anti-adhesion characteristics, PTFE is resistant to chemicals, high temperatures, UV rays, weather, light, and water. 

PTFE isn't appropriate for every application, however, as it has low abrasion resistance and is susceptible to creep, which causes dimensional changes in the material over time. 

3. Polypropylene 

Polypropylene is a cost-effective plastic for CNC machining or waterjet cutting services. Benefits include its chemical resistance, slippery surface, and electrical insulation capability. 

This plastic is great for many applications and is commonly found in parts for the packaging industry and electrical and equipment manufacturing. Its resistance to swelling when submerged in water makes polypropylene ideal for end-use environments like labs, kitchens, and medical settings. 

Despite all the benefits of polypropylene, it’s important to note that it has low tensile and impact strengths. 

2. Acrylonitrile butadiene styrene (ABS)

ABS is high on our list for its excellent machinability and strength. It has 60% of the overall strength of the number-one plastic but surpasses our top choice in impact strength. We’ve been known to slam ABS parts on the ground to demonstrate the material’s superior impact strength to customers and colleagues!

ABS is affordable, stable over time, and a good insulator. You'll often see it in electrical applications, rapid prototyping, electronic enclosures, and consumer goods. 

The biggest drawback is that it breaks down in the presence of certain solvents, cleaners, and alcohols. Recently, we had to rule out ABS for process rollers in a printer because the solvent used to clean the printing ink would have degraded the parts over time. 

1. Arbiser Machine's favorite plastic: Acetal 

Acetal (also known as Delrin) is our top plastic choice thanks to its machinability, high strength, and ability to hold size better than other plastics. 

While most plastics are generally quicker to machine than aluminum or steel, achieving tight tolerances can be tricky. If, for example, a plastic part calls for a bearing bore with a tight tolerance, we may need to let the material rest and stabilize between cuts, slowing us down. When machining acetal, however, the material is more likely to retain its size. 

Customers like acetal because it's wear-resistant, naturally slippery, and doesn’t expand when exposed to heat and moisture. While not ideal for parts requiring acid resistance, it's an excellent material for many other uses, including bushings, gears, bearings, and more. 

Dishonorable Mention: Acrylic 

We'll always choose the best material for your part, and if acrylic is the right choice, then we won't think twice about using it. However, the problem is that acrylic is commonly used for clear viewing panels when polycarbonate is likely a better option.

Acrylic has a low impact strength, causing it to chip and crack easily during waterjet cutting and CNC machining services—and, more importantly, in the part’s end-use environment. For these reasons, it’s our least favorite plastic to work with. 

Considerations for Plastic Machining

Every plastic is unique, but some universal considerations should always be taken into account when precision machining plastic. Here's the quick list of rules we follow: 

• Avoid friction wherever possible

• Use coolant and keep heat away from the part when possible to avoid deformation

• Use sharp tools to avoid tearing or melting the part during cutting

• Use soft jaws for fixturing to avoid distorting the part with too much pressure

• Watch out for chip buildup that can affect friction

• Allow for stabilization and cooling when using cutting methods that generate heat, especially with tight tolerance parts

• Use high-precision waterjet with HPX sharp garnet to avoid the introduction of heat and achieve precise finishes and tolerances

If you want to work with a shop skilled in plastic machining, request a quote today!