Swapping a machined or die-cast metal part for a molded plastic one can cut weight, cost and assembly steps, and end corrosion problems. It works well when the material and the design are chosen together.
Good reasons to convert
- Weight savings
- Lower part cost at volume (no machining or secondary operations)
- Combining several metal parts into one molding
- Corrosion resistance
- Quieter running gears and parts
Resins most used for metal replacement
| Resin | Why it’s used |
|---|---|
| Glass-filled nylon 66 | The workhorse: strong, stiff, heat resistant, economical. |
| Carbon-fiber nylon | Stiffer and lighter than glass-filled; static-dissipative. Carbon-filled nylon |
| Glass-filled PBT | Better dimensional stability than nylon in humid conditions. |
| PEI | High heat, inherent flame resistance, strength. PEI |
| PEEK | The top tier: heat, chemicals and wear. PEEK |
What to watch
- Stiffness: even filled plastics are far less stiff than steel or aluminum. Ribs and geometry make up the difference.
- Creep: plastics slowly deform under constant load, more so when hot.
- Heat: check long-term use temperature, not just HDT. Heat resistance explained
- Moisture: nylon changes size and stiffness as it absorbs water. Nylon and moisture
- Fiber orientation: filled parts are stronger along the flow than across it.