PLA, PETG or ABS: which filament to choose for 3D printing

In short: choose PLA for decorative objects, figures, prototypes and tests, because it is the easiest to print. Choose PETG for parts that must withstand knocks, water and sun, even outdoors. Choose ABS only for technical parts that must handle more heat: it warps easily while printing, wants an enclosed printer and gives off fumes, so you need a well-ventilated room.

Before you start

• Read what your printer's manufacturer says: not every printer handles every material well. Open-frame printers, for example, struggle with ABS.
• Use the slicer's ready-made profiles for your filament: temperatures and speeds are already set. Prusa advises always starting from those.
• Check the print sheet: some materials stick too well to certain sheets and can damage them (see PETG below).
• Keep your filament dry: all filaments absorb moisture from the air, some more than others.

PLA: the easiest

What for: detailed models, figures, prototypes, toys that take little stress, vases, desk objects.

Pros, according to the Prusa Knowledge Base:

• it is one of the easiest materials to print, suitable for beginners;
• it prints at low temperatures and doesn't strictly need a heated bed;
• it warps little while printing;
• it gives good detail and also works for large objects.

Cons:

• it is brittle: it breaks along the layers or shatters if knocked;
• it doesn't like heat: it softens and deforms above roughly 60 °C;
• it degrades in sunlight (UV rays);
• it isn't suitable for technical or outdoor use.

Moisture: the Bambu Lab Wiki says basic PLA absorbs little moisture and can usually be printed straight out of the bag; some special PLAs (silk, wood, transparent) are best dried first.

PETG: the most versatile

What for: mechanical parts, mounts, brackets, clips, parts that go outdoors or come into contact with water. Prusa uses it for the parts of its own printers.

Pros, according to the Prusa Knowledge Base and the Bambu Lab Wiki:

• easy to print, almost like PLA;
• more impact resistant than PLA, slightly flexible, so it breaks less;
• good adhesion between layers;
• handles heat better: fine indoors and outdoors, below roughly 80 °C;
• resists water and moisture;
• warps little and doesn't have the odor problems of ABS.

Cons:

• it tends to leave strings (stringing) between parts;
• bridges and overhangs come out worse;
• it isn't ideal for fine detail;
• supports are harder to remove;
• it sticks too well to some sheets. Prusa advises against printing it on the smooth PEI sheet, which can get damaged: a textured or satin sheet is better, or glue stick as a separating layer.

Moisture: PETG absorbs moisture from the air. The Bambu Lab Wiki explains that damp filament causes bubbles, strings, holes and rough surfaces, and says to dry it before printing if you don't know how it was stored.

ABS: for technical parts, with a few precautions

What for: tough, heat-resistant technical parts, or parts to be smoothed with acetone vapor.

Pros, according to the Prusa Knowledge Base:

• tough and impact resistant;
• handles high temperatures well;
• can be sanded and smoothed with acetone.

Cons:

• it warps a lot while printing: corners lift off the sheet;
• it needs an enclosed printer (with a chamber) and a very hot bed;
• it gives off potentially harmful fumes (styrene): print in a well-ventilated room, but with no drafts near the printer;
• outdoors it yellows and becomes more brittle over time;
• it shrinks slightly as it cools, about 1–2%: dimensions may come out a little smaller.

How to choose, in practice

• It only needs to be looked at or handled (ornament, scale model, prototype): PLA.
• It must withstand knocks, water or sun (a garden bracket, a spare part for an appliance that doesn't get hot): PETG.
• It must withstand high heat and you have an enclosed printer in a ventilated room: ABS.
• You are learning: start with PLA, which forgives mistakes more; move to PETG when you need a tougher part.

For comparison, UltiMaker also rates PLA as the easiest to print, PETG as a middle ground and ABS as the hardest because of warping.

To find things to print, see where to download free 3D models. If the part comes off the sheet, read the first layer doesn't stick to the bed.

If it still doesn't work

• PETG full of strings: the filament may be damp. Dry it following the manufacturer's instructions, then try the profile's retraction settings.
• ABS that comes loose or cracks: enclose the printer, eliminate drafts and use a brim. Without an enclosed printer, Prusa suggests PrusaSlicer's "draft shield", a wall as tall as the part that keeps it warmer.
• A PLA part that deforms in the sun or in the car: the material isn't suitable. Reprint it in PETG or ABS.
• A part that breaks along the layers: increase the number of perimeters. Prusa recommends this for stronger parts, rather than just increasing the infill.
• Need a part that does real work (a spare part, a mount under load): the choice of material and print orientation matter as much as the design. A technician can help you choose them and prepare the file.