Which filament should you choose: PLA, PETG, ASA, ABS or TPU?

Diameter first: 1.75 or 2.85 mm

Almost all home printers use 1.75 mm filament, like Creality Hyper PLA and Polymaker Polyterra PLA. Some printers, such as many UltiMaker models, use 2.85 mm. That strand does not fit a 1.75 mm printer, and the other way around. The diameter is on the spool and in your printer's manual.

A spool usually weighs 1 kg. There are also 500 gram spools, handy for a colour you rarely use, and large spools of 3 kg or more for people who print a lot. How many metres of filament are on a spool? shows roughly how many metres a spool holds.

PLA: where to start

PLA melts at a low temperature and hardly warps. Prusa lists 210 to 215 °C for the nozzle and 60 °C for the bed. It gives clean prints and comes in many colours and finishes: matte, silk like Polymaker Panchroma Silk, or with wood or stone mixed in.

The drawback: PLA does not handle heat well. According to Prusa it softens and deforms above about 60 °C. A print on a car dashboard in the sun or next to a radiator can bend. For figures, decoration, prototypes, holders and toys indoors, PLA is the obvious choice.

PETG: tougher and more resistant to moisture

PETG is the next step. Prusa calls it tough and slightly flexible, with little warping and good layer adhesion. It resists water and humidity and, according to Prusa, temperatures up to about 80 °C. That makes it a good fit for parts under load, boxes, brackets and things for the kitchen or garden.

PETG prints hotter than PLA: Prusa lists 230 to 240 °C for the nozzle and 85 to 90 °C for the bed. It strings more easily, leaving thin threads between parts of your print, which your slicer settings help with. Examples are Sunlu PETG, Anycubic PETG and Raise3D Premium PETG.

ASA and ABS: for outdoors and heat

ASA and ABS cope with more heat than PLA and PETG. Prusa calls ASA suitable for outdoor use because it resists UV light and heat, up to about 93 °C. Prusa sees ASA as the successor to ABS: it is more UV resistant, warps less and smells less.

Both materials do warp as they cool. For ASA Prusa advises an enclosure to keep the heat around the print, a nozzle of about 260 °C and a bed of 105 to 110 °C. They give off fumes while printing, so put the printer in a ventilated room. With an open printer PETG is often the easier choice. Examples are Sunlu ASA, Anycubic ASA, Spectrum smart ABS and Elegoo ABS.

TPU: flexible

TPU is rubbery and bends. You use it for cases, feet, gaskets and tyres. The hardness is on the spool in Shore, for example 95A. Prusa lists 60A to 90A as typical for flexible filament and says the softer it is, the harder it is to print.

Flexible filament prints slowly. Prusa mentions a speed of about 20 mm per second, a nozzle of 230 to 245 °C and a bed of 60 to 75 °C. The strand has to be fed gently, so it is easiest on a printer with direct drive. An example is Anycubic TPU.

Filled filaments

There is also filament with short fibres mixed in, like PLA with carbon fibre. It looks matte and is stiffer, like Creality Hyper PLA-CF and Polymaker PolyLite PLA-CF. Those fibres are abrasive. They wear a brass nozzle quickly, so print them with a hardened steel nozzle.

Keep it dry

Filament absorbs moisture from the air. Prusa writes that most materials do, and that nylon and flexible filament need drying more often than PLA. According to Prusa, damp filament gives a rougher surface, bubbles and weaker layer adhesion. Store open spools in a sealed box with desiccant, or use a dryer like the Polymaker PolyDryer or the Kingroon dry box.