PLA, PETG and TPU — choosing the right one

The short version

• PETG — most tough functional parts. Brackets, housings, mounts, guards, anything handled roughly or left outdoors. If you are not sure, this is usually the answer.
• PLA — parts that need to hold their shape accurately and are not under sustained load. Prototypes, fixtures, jigs, gauges, anything where crisp detail matters more than toughness.
• Flexible TPU — anything that has to bend, grip, damp or seal. Gaskets, soft jaws, grommets, bumpers, strain reliefs, non-marking pads.

You do not have to choose. Describe what the part does and where it lives, and the material gets chosen for you as part of the quote. That sentence is genuinely the most useful thing in an enquiry.

PETG, and why it is usually the default

PETG is the workhorse. It is tougher than PLA and far less brittle, which matters for the things that actually happen to parts — being dropped, over-tightened, knocked, levered against. Where PLA tends to snap, PETG tends to bend and survive. It also holds up considerably better outdoors and against sunlight, so anything that lives outside or in a vehicle should generally be PETG.

The trade is a slightly softer surface and marginally less crisp fine detail than PLA. For a functional part that is almost never the deciding factor.

PLA, and what it is actually for

PLA has a reputation as the beginner's material, which undersells it. It prints accurately with excellent detail and dimensional stability, which makes it genuinely the better choice for a part whose job is to be exactly the right shape — a gauge, a drill guide, an alignment fixture, a prototype being checked for fit. The planetary gear set was printed fine-layer for precisely this reason: on a gear tooth, how closely the printed flank follows the intended curve is what decides whether it meshes smoothly.

Its limits are real, though. PLA is comparatively brittle, so it fails suddenly rather than bending. It softens at modest temperatures — a part left in a car in an Australian summer is a genuine risk, not a theoretical one. And it degrades outdoors over time. For anything living in heat, sunlight or rough handling, PETG is the better call.

TPU, and when flexibility is the point

Flexible TPU is a different kind of material rather than a softer version of the others. It bends and returns, absorbs impact, grips rather than slides, and it is tough in a way rigid plastics are not — it tears far less readily than its softness suggests.

Use it where flexibility is the function: a gasket that has to compress, a jaw face that has to hold a part without marking it, a bumper that has to absorb a knock, a strain relief that has to flex repeatedly without cracking.

Where stiffness is the function, PETG or PLA takes over — TPU is chosen precisely for the parts that have to give. It prints more slowly and favours bolder detail, which is priced into the quote.

Matching the material to the duty

The choice is made from what the part actually has to survive, and it is made at the quote so you never find out afterwards.

Outdoors, sunlight or rough handling → PETG. It takes knocks and daylight considerably better than PLA, which is why anything living on a machine or in a vehicle is normally printed in it.

Accuracy and crisp detail, light duty → PLA. Gauges, guides, alignment fixtures, prototypes being checked for fit.

Compression, grip, damping or sealing → flexible TPU. Gaskets, soft jaws, bumpers, strain reliefs, non-marking pads.

Holding liquid → PETG with thicker walls, and designed around a bought seal or gasket, which is how a printed part is made properly watertight.

A wear surface → usually PETG, treated as consumable. A part that costs little and reprints from a kept model on a day's notice is often the better arrangement, particularly where it is protecting something expensive.

Every quote includes an assessment of the duty. Where a part will run near sustained heat, carry heavy structural load, contact food or drinking water, or do a job where failure would be dangerous, we say so at the quote and recommend the right process — which is usually machining or a metal part. Getting that answer before you commit is the point of asking somebody who works with these materials every day.

Layer height, and where the detail comes from

Material is only half of it. How finely a part is printed is chosen per job, from 0.1 mm where detail and surface matter to 0.3 mm where speed and bulk matter more. It is a real trade rather than a setting left on a default: a fine layer height follows a curve more closely and gives a better surface, and it takes considerably longer to print.

On some parts it decides whether the thing works at all. The planetary gear set was printed fine for exactly that reason — on a gear tooth, layer height is what determines how closely the printed flank follows the intended profile, and a coarse setting turns a smooth curve into a staircase that meshes roughly and wears quickly. On a bracket that nobody will look at twice, the same setting would be wasted money.

You do not need to specify it. Say what the part does and it gets chosen, along with the material and the print orientation, as part of the quote.

Why three materials, used well

Three materials printed constantly means the settings are known, the behaviour is familiar, and the advice on this page comes from parts that have actually been in service rather than from a datasheet. Depth in three beats breadth across fifteen.

It also means you get the useful answer early. Knowing at the enquiry which material suits your part, and what to do if the answer is a different process entirely, costs you a day — and saves you a part, a machine and a fortnight.

Frequently asked questions

Which material should I pick?

Leave it to us. Describe what the part does, what it touches, where it lives and what it is exposed to, and the material, wall thickness and print orientation are chosen from that as part of the quote. If you have a preference, say so and we will confirm how it suits the job.

Can you print in a specific colour?

Within the range of filament stocked and available, usually yes. Colour is matched as closely as available filament allows — expect close, and say if an exact match matters so it can be planned for.

Is PETG waterproof?

It is made watertight by design rather than by default. A part that has to hold liquid gets thicker walls and is designed around a bought seal or gasket — which is also what keeps it serviceable when that seal eventually wants replacing.

Can you print a part that goes in a dishwasher or near a heater?

Sustained heat is where these materials stop being the right choice, so for a part near a heating element, an oven or an exhaust we will recommend the right process at the quote. Tell us what it sits next to and how hot it gets, and you will have a clear answer before anything is made.

Do you print higher-temperature or fibre-filled materials?

The workshop runs PLA, PETG and flexible TPU, printed every day, which is what makes the settings and the advice reliable. Where a part genuinely wants something else, we will tell you what it needs and point you to the right supplier — that answer is worth having early.