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PLA, PETG or ABS: which 3D printer filament should you use?

The same part printed in different filaments behaves very differently. A hook that is perfect in a kitchen can droop inside a car in summer. Choose the filament for where the part will live, not for the room you print it in.

The common filaments compared

• PLA (nozzle 190–220 °C, bed 50–60 °C): the easiest to print, stiff, with good detail and little smell. It softens at about 55–60 °C and is brittle under shock, so it is not for cars or outdoors.
• PETG (nozzle 230–250 °C, bed 70–85 °C): tough and slightly flexible, handles heat to about 75–80 °C and does well outdoors. It strings easily and absorbs moisture.
• TPU (nozzle 210–235 °C, bed 40–60 °C): rubbery, grips and absorbs shock. Print it slowly.
• ABS (nozzle 230–260 °C, bed 90–110 °C): handles heat to about 95–100 °C and sands and glues well. It warps, needs an enclosure and gives off stronger fumes.
• ASA (nozzle 240–260 °C, bed 90–110 °C): like ABS, but it resists sunlight and weather.

Always start from the temperatures printed on the spool. They differ between brands and colours.

Where beginners should start

Start with PLA. Move to PETG when a part needs more toughness or heat resistance, and to TPU when it must flex. Leave ABS and ASA until you have an enclosure and good ventilation.

Heat, sun and load in South Africa

Every plastic softens and sags above a certain temperature. A closed car in the sun, a dashboard, a caravan wall or a braai area can easily pass 60 °C, and a PLA part there will slowly bend or loosen.

Sunlight also makes most plastics brittle and faded over months. ASA resists it best, PETG is reasonable, and PLA and ABS do poorly outdoors.

A steady load makes plastic "creep": a printed hook carrying a heavy bag slowly bends, even at room temperature. Make hooks and brackets generously thick, and test them.

Fumes and ventilation

Hot plastic gives off ultrafine particles and gases. PLA gives off the least, PETG and TPU a little more, and ABS and ASA the most.

• Print in a ventilated room, not a bedroom or a small closed room where people sit for hours.
• Use an enclosure for ABS and ASA, ideally vented outside or filtered.
• Keep printing away from babies, young children, pregnant women and people with asthma.
• Never heat filament above its stated range.

Wet filament

Many filaments absorb water from the air: PETG and TPU quickly, PLA more slowly. In a humid place such as Durban, an open spool can be wet within weeks. Wet filament pops or hisses at the nozzle, strings badly and leaves a rough, weak print.

• Dry it in a filament dryer at the temperature on the spool's sheet (often about 45–50 °C for PLA and 60–65 °C for PETG, for four to six hours).
• Never dry filament in an oven that you use for food.
• Store each spool in an airtight box or bag with silica gel, out of the sun.

If a spool that printed well before starts popping and stringing, suspect wet filament before you blame the printer.

Buying filament

Most printers take 1.75 mm filament on 1 kg spools; check yours. Good filament has a steady diameter and arrives vacuum-sealed with a desiccant packet. Glow-in-the-dark and metal-filled filaments wear a brass nozzle quickly, so use a hardened steel nozzle for them.

This guide is based on Chapter 3 of 3D Printing and Making at Home, which also covers waste, recycling and worked examples.