When a part has an actual job to do, filament choice stops being a preference and starts being an engineering decision. PETG, ABS, and ASA are the three materials we reach for most often when someone needs a functional part rather than a display piece, and they get confused with each other constantly. Here is how we actually choose between them.

The short version

Property	PETG	ABS	ASA
Stiffness	Medium	Medium-high	Medium-high
Impact resistance	High	High	High
Heat resistance	Around 70 C	Around 95 C	Around 95 C
UV and weather resistance	Fair	Poor	Excellent
Ease of printing	Easy	Demanding	Demanding
Surface finish	Slightly glossy	Matte, can be smoothed	Matte

Those numbers are approximate because every manufacturer’s blend differs, but the relationships between the three hold.

PETG: the default for indoor functional parts

PETG is what we quote most often for functional work, and there is nothing glamorous about the reason. It is tough, it has a little flex before it breaks instead of shattering, it holds up to water and most household chemicals, and it prints reliably at production scale. When a bracket, an enclosure, a clip, or a fixture lives indoors and does not sit against anything hot, PETG usually does the job at the best price.

Its weaknesses are real but narrow. It scratches more easily than ABS or ASA, it starts to soften in the 70 C range, which rules out some automotive interiors and anything near heat sources, and long outdoor exposure will slowly dull and weaken it.

ABS: heat resistance with a catch

ABS takes more heat than PETG and machines nicely after printing. You can drill it, tap it, and vapor smooth it with acetone into a glossy, layer-free surface, which no other material on this list offers. Plenty of legacy products specify ABS because injection molded versions used it, and matching the material keeps properties consistent.

The catch is ultraviolet light. ABS yellows and gets brittle outdoors faster than most people expect, so we treat it as an indoor material full stop. It also demands a heated, enclosed printing environment to avoid warping, which our fleet provides, but it remains the fussiest of the three to run.

We recommend ABS when the part needs its specific combination of heat resistance and post-processing, and the part lives inside.

ASA: the outdoor answer

ASA was developed as an ultraviolet-stable alternative to ABS, and that is exactly how we use it. It keeps roughly the same mechanical and thermal behaviour while shrugging off sun exposure that would destroy ABS and slowly degrade PETG. Fixtures on equipment, exterior brackets, signage hardware, agricultural and marine parts, anything that lives outside in Okanagan summers gets quoted in ASA by default.

The trade is cost and printability. ASA costs more than PETG and shares ABS’s need for a controlled printing environment. For a part that never sees daylight, that premium buys nothing, which is why ASA is not our universal answer either.

How we actually decide

Three questions settle most cases. Where does the part live, indoors or out? What temperature does it see, room temperature or something hotter? And does it need post-processing like smoothing or machining? Outdoor points to ASA. Heat without sun points to ABS or ASA. Everything else usually points to PETG, and if stiffness is the limiting factor, that is when we start talking about carbon fiber reinforced filaments instead, which raise rigidity well beyond any of these three.

There are edge cases. Parts that flex repeatedly might belong in TPU. Parts with fine cosmetic detail might belong in resin. A prototype printed in the final material is the cheapest way to find out whether the choice on paper survives contact with reality, and we always suggest testing in the production material rather than prototyping in PLA and hoping.

Where PLA fits, and why it is not in this comparison

People sometimes ask why PLA, the most printed material on earth, is missing from a functional parts comparison. PLA is stiff, cheap, accurate, and easy to print, which makes it excellent for concept prototypes, cosmetic pieces, and indoor products that never see stress or heat. But it softens near 60 C, a parked car in summer will deform it, and it gets brittle with age under load. For anything we would call a working part, one of the three materials above almost always serves better, and the price difference is small enough that saving it rarely justifies the downgrade.

All three of these materials also come in carbon fiber reinforced versions, which stiffen the base plastic considerably and improve dimensional stability. When a PETG part is right in every way except rigidity, carbon fiber PETG is often the answer that avoids jumping to a more demanding material family.

What this means for your quote

When you send us a project, name the environment and the job the part does, even if you already have a material in mind. Sometimes the material someone requests and the material the part needs are different, and it is far cheaper to have that conversation before production than after a batch fails in the sun. We will quote the material that fits, explain why, and quote an alternative alongside it if the choice is genuinely close.