Views: 4 Author: Site Editor Publish Time: 2026-08-27 Origin: Site
The right material is the one that passes the test you actually need to run - structural load, heat, or just how the part looks in a demo. Pick before you brief a shop, because material drives machinability, mold flow and price. This guide groups the common choices with property data and a selection matrix.
Table of Contents
Start from the failure mode. Load-bearing parts need stiffness and yield strength; thermal parts need a high continuous-use temperature; demo parts need surface and color. Everything else is a cost or machinability trade-off against that first requirement. Specify the test and the material chooses itself.
Typical values from published data sheets; your batch may vary slightly. Strength in MPa, temperature in deg C.
Material | Type | Tensile (MPa) | Key temp / HDT | Best test |
ABS | Plastic | 40-50 | HDT ~90 | Fit-and-function, cheap |
PC | Plastic | 60-70 | HDT ~125, transparent | Impact, clarity |
PEEK | Plastic | 90-100 | Use ~250 | Heat, chemical |
Nylon PA66 | Plastic | 70-85 | HDT ~70 | Wear, gears |
POM (acetal) | Plastic | 60-70 | HDT ~110 | Low friction, stable |
Al 6061-T6 | Metal | 276 | Use ~150 | Load, light |
Al 7075-T6 | Metal | 572 | Use ~120 | High stiffness |
SS 304 | Metal | 505 | Use ~400 | Corrosion |
SS 316L | Metal | 485 | Use ~400 | Marine, medical |
Brass C360 | Metal | 300-460 | Use ~200 | Fittings, cosmetic |
Ti Gr.5 | Metal | 950 | Use ~400 | Strength/weight |
PU (RIM) | Polymer | 20-50 (rigid) | Use ~80 | Large lightweight |
Machined specifics for plastics are in our CNC plastic prototyping guide and for metals in our metal prototyping page.
· ABS - cheap, easy to machine, good for fit-and-function enclosures; ~40-50 MPa tensile.
· PC - higher impact and heat resistance, transparent where needed; ~60-70 MPa, HDT ~125 C.
· PEEK - high temperature and chemical resistance for demanding tests; ~90-100 MPa, use to ~250 C.
· Nylon (PA) - wear-resistant for gears and brackets, but absorbs moisture and shifts dimension.
· POM (acetal) - low friction and tight dimensional stability for bushings and clips.
· Aluminum 6061/7075 - light, machinable, the default for brackets and enclosures; 276/572 MPa.
· Stainless 304/316L - corrosion resistant, medical and food contact; ~485-505 MPa.
· Brass - easy machining for fittings and cosmetic metal; ~300-460 MPa.
· Titanium - aerospace and high strength-to-weight; ~950 MPa at 4.43 g/cm3.
When the part moves to molded volume, the same plastics are covered in our injection molding guide.
For large, lightweight enclosures, liquid polyurethane systems cure in a soft tool and span rigid to soft-touch. This is the RIM family - covered in our RIM services guide. It is the polymer route of choice when size rules out a steel mold. (Note: vacuum casting urethanes are covered elsewhere on the site and intentionally not duplicated here.)
If the test is... | Start with | Avoid |
Fit, function, low cost | ABS | PEEK (over-spec) |
Impact or see-through | PC | ABS (too weak) |
Heat or chemical | PEEK | ABS, nylon |
Load or thermal | Al 6061, then steel/Ti | Any plastic |
Wear / moving part | Nylon, POM | ABS |
Large lightweight shell | PU (RIM) | Steel mold (cost) |
A few traps from the floor: PEEK machines slowly and costs more, so reserve it for the test that needs it; nylon absorbs moisture and shifts dimension, so control storage and re-measure before assembly; thin aluminum walls dent in handling; and polyurethane can creep under sustained load, so do not spec it for structural members. These are the calls that separate a passing prototype from a misleading one.
Send the test the part must pass and the shop will recommend the cheapest material that still passes. If cost is the open question, our cost and quoting guide shows how material choice moves the price.
Q: Which plastic for a functional prototype?
A: ABS for general fit-and-function (~40-50 MPa), PC where impact or transparency matters (~60-70 MPa, HDT ~125 C), PEEK for heat or chemical (use to ~250 C). Pick against the test, not the price.
Q: Which metal for a bracket?
A: Aluminum 6061-T6 is the default - 276 MPa, light, cheap to machine. Use 7075 where stiffness matters (572 MPa) and stainless where corrosion resistance is required.
Q: What is polyurethane used for?
A: Large, lightweight enclosures via RIM - rigid to soft-touch. It is the polymer route when size rules out a steel mold, not a structural-metal substitute.
Q: Does material affect cost much?
A: Yes - PEEK and titanium cost far more than ABS or aluminum, and some plastics machine slowly. Match the material to the test so you are not paying for margin you do not need.
Q: Can the shop recommend a material?
A: Yes. Send the test the part must pass and a good shop will name the cheapest material that still passes it.
