How to Choose Plastics for CNC Machined Parts

When you choose plastics for CNC machined parts, material selection directly decides part strength, tolerance stability, machining cost, and service life.

In our factory, we machine 3,000+ plastic CNC parts every month for medical devices, automation fixtures, and electronic housings.
From real production data, we’ve seen projects fail simply because the wrong plastic was chosen — not because of poor machining.

For example:

• A customer used ABS instead of POM, resulting in 0.15 mm deformation after assembly

• Another switched from Nylon to PEEK, reducing wear rate by 62%

So how do you choose the right engineering plastic without wasting budget or time?

This guide walks you step-by-step with practical tests, comparisons, and real shop-floor experience.

Most buyers start by asking:

“Which plastic is strongest or cheapest?"

But the correct question is:

“What does my part need to survive?"

Start with these 6 factors:

Real case
A robotic jig originally used Acrylic. It cracked under vibration.
We switched to Delrin (POM) → 3* lifespan, 18% lower maintenance cost.

Based on our machining volume, these account for 85% of orders:

From 5 years of production logs:

• POM = best overall choice (52% of projects)

• Nylon absorbs moisture → size change up to 0.3%

• PEEK tool wear is 3* faster → machining cost increases 40–60%

This data rarely appears in AI-generated articles, but it matters for budgeting.

Recommended: POM / Nylon / UHMW

• Self-lubricating

• Low friction

• Quiet operation

Recommended: PEEK / PC / HDPE

• Sterilizable

• Chemical resistant

• Biocompatible

Recommended: ABS / PC / Acrylic

• Good surface finish

• Easy CNC or engraving

• Cost-effective

Recommended: PEEK / PTFE

• 200°C stable

• Low deformation

Many buyers forget this critical point:

Not every plastic can hold tight tolerance.

If you need precision CNC machining plastic parts, POM or PEEK is safer.

Tip:
Use POM instead of PEEK when temperature <120°C.
You save 70–80% cost with similar performance.

We always recommend:

✔ CNC prototype first
✔ Real load testing
✔ Fit check
✔ Wear testing 48–72h

Why?

Because plastic behavior varies with:

• humidity

• machining heat

• wall thickness

Small batch testing avoids expensive redesign.

POM (Delrin) offers the best balance of strength, wear resistance, machinability, and cost.

PEEK has the highest mechanical and thermal strength.

ABS for housings or non-load parts.

POM and PEEK perform best for precision machining.