Filament types decoded: when to use PLA, PETG, ABS, ASA, TPU
PLA is right 80% of the time. The honest decision tree by application: outdoor, mechanical, flexible, food-safe.
Filament selection is one of those topics where forum advice oscillates between "ABS is the only real material" and "PLA does everything." Both are wrong. Each material has specific strengths, specific failure modes, and specific use cases.
Here's the honest decision tree.
PLA — the default for almost everything
Use it for: Display models, organizers, tools that aren't load-bearing, prototyping, anything indoor at normal temperatures, anything you'll throw out within a few years.
Don't use it for: Anything that'll see temperatures above 140°F (a car dashboard in summer, dishwasher, near a stove), anything that'll see UV for years, anything that needs to flex.
PLA is easy to print, smells like waffles, biodegradable in industrial composters, available in 200+ colors and finishes. The downsides: brittle at edge cases, deforms in heat, not dimensionally stable long-term outdoors.
Best brands: Polymaker PolyTerra, Sunlu PLA+, Bambu PLA Basic. Cost: $18-25 per kg.
PETG — when PLA's heat or UV limits matter
Use it for: Outdoor parts, dishwasher-safe items, water-resistant prints, items that need slight flex without breaking.
Don't use it for: Tight-tolerance fits (it strings more than PLA), high-detail surfaces, very large prints (PETG warps slightly more than PLA).
PETG handles up to 175°F. UV stable for 1-2 years outdoors. Slightly tougher than PLA — drops without breaking. Dishwasher-safe (so it's used for kitchen tool prints, but NOT for food contact — see below).
Best brands: Polymaker PolyMax, Overture, Sunlu. Cost: $20-28 per kg. Slightly more annoying to print than PLA (more stringing, careful temp tuning required).
ABS — for engineering use
Use it for: Mechanical parts that need impact resistance, automotive prints (interior, not exterior), parts that need to be solvent-glued together, items in the 175-220°F use range.
Don't use it for: First filament, anything where surface finish matters, indoor printing without ventilation.
ABS prints require an enclosed printer to avoid warping. ABS emits styrene during printing — toxic in poor ventilation. Sand-able, paint-able, acetone-smoothable. The classic LEGO material.
If you don't have an enclosed printer, skip ABS for ASA (see below) which is similar and easier to print.
ASA — the modern ABS replacement
Use it for: Outdoor parts that need to last 5+ years, automotive exterior parts, garden equipment, mailbox repairs.
ASA is acrylonitrile styrene acrylate — chemically similar to ABS but with UV stability that lasts a decade outdoors instead of yellowing in months. Best for any print that'll spend significant time in sunlight.
Prints similarly to ABS — needs enclosure for big parts, ventilation always. About 25-30% more expensive than ABS but worth it for outdoor applications.
TPU — when you need flex
Use it for: Phone cases, gaskets, vibration dampers, watch straps, anti-slip pads, prosthetic liners.
Don't use it for: Anything load-bearing in a structural sense.
TPU comes in shore hardnesses from 85A (very soft, gummy) to 98A (firm rubber). 95A is the most versatile starting point. Requires a direct-drive extruder — Bowden setups can't push it through reliably.
Print slow (20-30mm/s) and dry the filament before use. TPU absorbs moisture from the air more than any other common filament.
The materials decision tree
| Use case | Recommended |
|---|---|
| Display model, prototype, organizer | PLA |
| Outdoor part, sun exposure under 1 year | PETG |
| Outdoor part, long-term | ASA |
| Automotive interior | ABS |
| Automotive exterior or mailbox | ASA |
| Phone case, soft gasket | TPU (95A) |
| Dishwasher-safe organizer | PETG |
| Functional load-bearing part | ABS or PETG (depending on stiffness needs) |
| Cosmetic part needing painting | ABS (acetone smoothing) or PLA (sand and prime) |
Food-safe printing
The honest answer: no FDM 3D-printed item is truly food-safe. Even if the filament itself is food-safe, the printing process leaves microscopic gaps in the surface where bacteria grow. Food-contact 3D prints need a food-safe epoxy seal coat.
If you need food-safe items, buy them.
Engineering materials (skip for first year)
Past PLA/PETG/ABS/ASA/TPU, you enter engineering filaments: PC (polycarbonate), PA (nylon), PA-CF (carbon fiber-filled nylon), PEEK. These materials are amazing — and require enclosed printers with ~300°C nozzles, dry storage, and specific printing knowledge. Wait until you have a specific reason.
