Robot Plastic Material Selection Guide
Most robot part failures trace back to the wrong resin, not bad molding. Pick by continuous temperature, load, moisture, and cost — in that order — and the part lasts.
This guide gives a five-question framework, a full comparison table, and the traps that catch engineers. It ties together the material choices across the robotics & AI hardware content.
Robot plastic selection in brief:
- POM — gears and sliding parts; dimensionally stable, low friction.
- PA (nylon), glass-filled — brackets and housings; stiff and tough, but absorbs moisture.
- PC / PC-ABS — shells and covers; impact strength and finish.
- PPS / PEI / PEEK — hot zones; stability and strength above 150 °C.
Five questions get you 90% there
Walk these in order. The first applicable answer usually points to the right family.
- Continuous temperature? Over 150 °C → PPS, PEI, or PEEK. Over 100 °C → glass-filled PA66, PBT, PC. Under 100 °C → most options open.
- Load type and magnitude? Sustained load needs creep resistance — POM, PPS, PEEK over standard grades.
- Moisture or wet cycling? If yes, avoid unfilled nylon. POM, PPS, PEEK stay stable.
- Friction or wear surface? Gears and slides → POM. Higher heat and wear → PEEK.
- Cost and volume? High volume favors moldable standard grades. Reserve PEEK for where nothing else survives.
Use continuous operating temperature, not peak exposure. A grade rated for a brief spike still fails under steady heat above its limit.
The comparison table
| Resin | Continuous temp | Strength | Watch out for | Best robot use |
|---|---|---|---|---|
| POM (acetal) | ~80–100 °C | 60–70 MPa | Lower impact; brittle in cold shock | Gears, slides, precision linkages |
| PA6 / PA66 | up to ~150 °C | ~80 MPa | Absorbs 2–3% moisture, swells | Brackets, clips, general mechanical |
| Glass-filled PA66 | up to ~150 °C | up to ~180 MPa | Fill affects wear & mating surfaces | Structural brackets, housings, mounts |
| PC | up to ~100 °C | High impact | Solvent stress cracking | Clear or high-impact covers |
| PC-ABS | up to ~100 °C | Tough | Not for high heat | Exterior shells, cosmetic panels |
| ABS | up to ~100 °C | Moderate | Low heat & chemical resistance | Low-cost covers, prototypes |
| PPS | >150 °C | High, stable | More brittle; higher cost | Sensor/power housings, hot zones |
| PEI (Ultem) | >170 °C | High, insulating | High cost | Electrical enclosures, hot electronics |
| PEEK | up to ~250 °C | Very high | ~30× ABS cost | Hot, high-load, chemical, sterilizable |
| LCP | ~240 °C | High, thin-wall | Unforgiving process | High-speed connectors, fine parts |
The moisture trap: nylon’s hidden failure
This is the most common selection mistake in precision robot parts. It deserves its own warning.
Creep: the failure that shows up months later
A part can pass inspection at install and fail a year later. That is creep — slow deformation under sustained load, worse at heat.
A nylon bracket under steady load at 80 °C can sag measurably after 12–18 months. POM resists creep better than PA. PPS and PEEK resist it best at elevated temperature. For any continuous-load structural part, check creep at operating temperature, not ambient.
Semi-crystalline vs amorphous — a useful mental model
| Semi-crystalline (POM, PA, PEEK, PPS) | Amorphous (PC, ABS, PEI) | |
|---|---|---|
| Strengths | Stiffness, wear & chemical resistance | Predictable tolerance, impact, clarity |
| Trade-off | Directional shrink in molding | Lower wear & chemical resistance |
| Use for | Sliding contact, chemical exposure | Precision dimensions, cosmetic parts |
Rule of thumb: semi-crystalline for gears and moving parts, amorphous for precise or cosmetic parts.
Cost reality
Raw resin cost spans two orders of magnitude — from ABS to PEEK. PEEK can run around 30× the price of a commodity grade. That premium only pays off on continuous duty above 150 °C, harsh chemicals, or biocompatibility.
Where each material goes — by part
The rest of this content series covers the parts in depth. Match the material here to the part there.
Gears → POM (Delrin)
Shells, brackets, housings → PC-ABS & glass-filled PA
Hands & grips → PA/POM + TPU/LSR
Connectors → LCP & PPS
Shielded parts → conductive filled grades
Not sure which resin fits your part?
Send the part and its operating conditions — temperature, load, environment, volume. We will recommend the resin, flag the traps, and quote the mold and parts.
Get a material recommendationFrequently asked questions
What is the best all-round plastic for robot parts?
There is no single best. POM suits gears and slides, glass-filled PA66 suits structural brackets and housings, PC-ABS suits shells. Match the resin to temperature, load, moisture, and cost.
POM or nylon for robot gears?
POM for dimensional stability, since nylon absorbs water and swells. Nylon wins on impact and cost. If the part runs above about 70 °C, choose glass-filled PA66 over POM.
When is PEEK worth the cost?
Only on continuous duty above 150 °C, in aggressive chemicals, or where biocompatibility is required. PEEK can cost around 30 times a commodity resin, so avoid over-specifying it.
Why did my nylon part change size after months?
Nylon absorbs 2–3% moisture and swells, which shifts precision dimensions over time. Switch to POM, which absorbs under 0.2%, or design the clearance for the moisture-equilibrium state.
What resin should a robot part above 150 °C use?
PPS, PEI, or PEEK. These high-performance grades hold strength and dimensional stability at elevated temperature where standard grades like PA, PC, and ABS lose integrity.
Bottom line. Resin selection is a sequence: continuous temperature, then load, then moisture, then wear, then cost. Nylon’s moisture swing and long-term creep cause most surprise failures, and over-specifying PEEK wastes money. Get the sequence right and the part performs for years. Send us your part and its operating conditions, and we will recommend the resin and quote it molded.
