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PLA, PETG, ASA or nylon: how to choose a material for a replacement part
By the ReplacementParts.app editors, The Spool List · Published October 12, 2026
The short answer
Choose by where the part lives. PLA is for indoor, cosmetic parts and test fits: Prusa says it softens above 60 °C. PETG suits most clips and brackets indoors and out below 80 °C. ASA is the outdoor choice, with UV resistance up to 93 °C. Nylon is for gears, hinges and other parts that rub or wear.
The same clip can last for years in one material and fail in a week in another. The deciding question is not how strong the plastic is, but where the part lives: how hot it gets, whether it sees sunlight, whether it rubs against something and whether it gets wet.
What the manufacturer says about each material
The quotes below come from the Prusa Knowledge Base, the filament guidance of a large 3D-printer maker. The temperatures are its practical guidance for finished parts, not laboratory heat-deflection results, and they are not the temperatures the printer uses to melt the plastic.
| Material | In the manufacturer's words | Typical replacement parts |
|---|---|---|
| PLA | "gets soft and deforms at temperatures over 60 °C"; "degrades under UV light"; "not suitable for technical and outdoor use" [1] | Test fits, indoor cosmetic caps and covers |
| PETG | "especially suitable for mechanical parts for both indoor and outdoor use", "with temperatures below 80 °C" [2] | Clips, brackets, covers, garden parts |
| ASA | "UV and temperature resistance (up to 93 °C)"; "suitable for outdoor use" [3] | Exterior trim, garden, marine and caravan parts |
| Nylon (PA) | "extremely resilient material, resistant to abrasion"; absorbs water "up to 10% of filament weight" if stored badly [4] | Gears, bushings, hinges, wear parts |
| Polycarbonate (PC) | "great tenacity, tensile strength, and heat resistance"; "extremely hygroscopic" [5] | Tough housings, parts near moderate heat |
Manufacturers use the same families for their own parts. Mercedes-Benz Classic, for example, makes 3D-printed sliding-sunroof rollers in PA12, a nylon, for older models whose original tools no longer exist [6].
Steps
- Rule out safety-critical parts. If the part carries a person, holds back gas, water pressure or mains electricity, or is part of a vehicle's brakes, steering or suspension, no material choice makes it suitable. See parts you should never 3D print.
- Check the heat. If the part sits near an oven, a heater, a motor, or inside a car in summer, PLA is out. Below 80 °C, PETG; up to 93 °C, ASA; PC is the manufacturer's heat-resistant option [5].
- Check the sunlight. For anything outdoors (garden, car exterior, boat, caravan), choose ASA, which the manufacturer calls "suitable for outdoor use" [3]. PLA "degrades under UV light" [1].
- Check for wear. If the part rubs, turns or slides (a gear, a bushing, a hinge pin), nylon is the usual answer because it resists abrasion [4].
- Check for water. PETG is described as water resistant [2]. Nylon and PC absorb moisture, which a maker manages by drying the filament; mention constant wetness in your post.
- Check for flex. Snap-fits and clips need some give. The manufacturer describes nylon as an "extremely resilient material" [4] and PETG as suited to mechanical parts [2]. Tell the maker which parts flex.
- Tell the maker, then let them advise. Write down the conditions you found and suggest a material. A maker may propose another, or a different process such as machining the part in metal.
Food contact and children
Printed plastics have layer lines where residue can collect, and many filaments and colourants are not certified for food contact. Treat parts that touch food, and parts used by young children, with caution and ask the maker what they can certify. Nothing here replaces the material's own data sheet.
Why the printing matters as much as the plastic
A UK government study of 3D-printed spare parts lists porosity, weak bonding between layers, and the effects of moisture, UV and ageing among the risks of printed parts [7]. Orientation, wall count and infill change how strong a part is in each direction. That is why a good maker asks how the part is loaded, not only what it is made of.
Get this part made
Post your part free on The Spool List with your photos and measurements. Makers who print, machine or cut parts send quotes with a price and a lead time, and you choose.
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Sources
- Prusa Knowledge Base: PLA (accessed October 12, 2026)
- Prusa Knowledge Base: PETG (accessed October 12, 2026)
- Prusa Knowledge Base: ASA (accessed October 12, 2026)
- Prusa Knowledge Base: Polyamide (Nylon) (accessed October 12, 2026)
- Prusa Knowledge Base: Polycarbonate (PC) (accessed October 12, 2026)
- Mercedes-Benz Classic: genuine replacement parts from the 3D printer (press release via Automotive World, 22 November 2018) (published November 22, 2018)
- UK BEIS/OPSS Research Paper 2020/039: 3D printing of spare parts for consumer appliances (September 2020) (published September 2020)
Figures are quoted as the sources state them, checked October 12, 2026. Rules and schemes change, so check the source before relying on a figure.
Drafted with AI assistance and checked against the sources above by the ReplacementParts.app editors. ReplacementParts.app is a guide published by The Spool List Ltd. Its buttons lead to The Spool List, our marketplace, which earns a commission from makers on completed orders. We don't sell parts ourselves, and no maker pays to appear in these guides. ReplacementParts.app is not affiliated with or endorsed by any manufacturer named on this page.