Start with the part, not the plastic
Most material questions answer themselves once you describe the finished object. Where will it live, what has to survive contact with it, and what happens if it deforms? A desk model, a bracket inside a warm enclosure and a weather-exposed mount are three different problems, and the plastic follows from the answer rather than the other way round.
The four families below cover most everyday printing. They are starting points, not specifications. Two spools labelled PETG from different manufacturers can behave differently, which is why the individual technical data sheet matters more than the family name.
PLA: the default for parts that stay indoors
PLA is the easiest of the four to print. It runs cool, needs little or no enclosure, and holds fine detail well, which is why it is the usual starting point for display models, prototypes and jigs that live on a bench.
Its limitation is heat. PLA softens at comparatively low temperatures, so a part left in a parked car, mounted near a heat source or exposed to direct summer sun can distort. It is also relatively stiff rather than tough, meaning it resists bending but can crack rather than deform under a sharp impact.
Variants complicate this. Matte, silk, high-speed and reinforced grades, and the many products sold as PLA+, are not interchangeable with a basic PLA. Treat each as its own material and read its data sheet.
PETG: functional parts that need to take a knock
PETG is often chosen where PLA is not tough enough. It tolerates more heat, absorbs impact better rather than cracking, and holds up against moisture and many household chemicals, which makes it a common pick for enclosures, brackets and parts that get handled.
The tradeoff is printability. PETG is more prone to stringing and oozing, and it tends to adhere strongly to build surfaces. Strong adhesion sounds like a benefit until removal damages the plate or the part, so check the manufacturer's build-surface guidance and consider whether a release layer is needed.
PETG also benefits from drying more than PLA does. See our guide on drying and storage.
ASA: the outdoor option, with conditions
ASA is chosen mainly for outdoor use. It resists ultraviolet light and weathering better than PLA or PETG, so it is a candidate for mounts, housings and fixtures that live outside.
It asks more of the printer. ASA runs hot, shrinks as it cools and is prone to warping and layer splitting without a stable, enclosed thermal environment. Printing it also produces stronger fumes than PLA, so ventilation matters. If your printer is open-frame and sits in a living space, ASA is the family most likely to disappoint.
ASA and ABS are related and often discussed together, but they are not the same material and their guidance is not interchangeable.
TPU: flexible, and slower than you expect
TPU is the flexible family. It is specified by shore hardness rather than by a single name, and the difference between grades is large: a 95A is firm and springy, while softer grades behave more like rubber.
Flexible filament is demanding to feed. A direct-drive extruder handles it far more reliably than a bowden setup, printing speeds are typically much lower, and retraction settings that work for rigid materials tend to cause problems. Automatic material systems are a separate question again, and a printer that supports TPU through an external spool holder may exclude it from its automatic feeder.
Comparing them side by side
| Family | Typical use | Main strength | Main constraint |
|---|---|---|---|
| PLA | Display models, prototypes, indoor parts | Easiest to print, good detail | Low heat tolerance |
| PETG | Functional parts, enclosures, brackets | Tougher, more chemical and moisture resistant | Stringing, strong plate adhesion |
| ASA | Outdoor mounts and housings | Ultraviolet and weather resistance | Warping, needs an enclosure and ventilation |
| TPU | Gaskets, grips, flexible covers | Flexibility and impact absorption | Slow, needs a compatible feed path |
Read this as a shortlist, not a verdict. Stiffness, toughness and heat resistance are different properties and are not interchangeable: a rigid part can still be brittle, and a tough plastic can still soften when warm.
Where family names stop being useful
Composite filaments, where a base polymer is filled with carbon fibre, glass or wood, take the base material's name but do not inherit its behaviour. Many are abrasive enough to require a hardened nozzle, and a standard brass nozzle will wear measurably.
The same caution applies to any decorative or high-performance grade. If a property genuinely matters to your part, find the number for it on the specific product's data sheet rather than reasoning from the family name.