Choosing a material
Start from what the part has to survive, not from what sounds strongest.
The short answer
| If the part is… | Use |
|---|---|
| A shape you want to look at | PLA |
| A functional part, indoors, room temperature | PETG |
| Going in a hot car, or outdoors in summer | ASA or ABS |
| Taking real abuse: impacts, threads, hinges | Nylon |
| Meant to bend or grip | TPU |
| A fine detailed model or miniature | Resin |
The longer answer
PLA is the cheapest, easiest and most widely stocked. It prints sharp, doesn't warp, comes in every colour. It also softens around 55 °C, which is a summer car dashboard, and it's brittle: it snaps rather than bends. Great for prototypes, models, jigs, anything decorative. Bad for anything that gets hot or takes a knock.
PETG is the sensible default for parts that have a job. Tougher than PLA, softens closer to 80 °C, survives being dropped. Slightly less crisp on fine detail. If you're not sure and the part matters, pick this.
ABS and ASA handle heat and UV. ASA is ABS that doesn't yellow outdoors. Both need an enclosed printer, so fewer makers stock them and they cost more. Choose these for outdoor mounts, engine-bay brackets, anything living in the sun.
Nylon (PA) is the tough one: impact resistance, low friction, threads that hold. It also absorbs moisture from the air, needs drying before printing, and warps. Expensive, and not every maker has it. Worth it for gears, hinges, living clips and parts that get abused.
TPU is flexible: a rubbery filament that comes out anywhere from soft to fairly firm depending on the shore rating. Grips, gaskets, phone cases, feet. It prints slowly, so it costs more per gram than the material price suggests.
Resin (SLA/MSLA) is a different process entirely: a vat of liquid cured by light. Detail nothing else matches, which is why miniatures and dental models use it. Also brittle, degrades in sunlight, and costs more. Use it for looks, not for load.
Carbon-fibre and other filled versions
Filled filaments (PLA-CF, PETG-CF, Nylon-CF) add stiffness and a matte finish, and they warp less. They don't make a part stronger in the sense most people mean: they make it stiffer and more brittle. They also chew through nozzles, so fewer makers stock them.
Colour
Colour doesn't affect strength in any way you'd notice. It affects availability: black, white and grey are always around; a specific Pantone is not. Pick "no preference" if colour doesn't matter and you'll get more quotes.
Ask instead of guessing
Put what the part does in the notes on your request. "This clips onto a 12 mm rod and lives on a bike" tells a maker more than any material choice you could make, and they'll tell you what they'd actually use.