Materials
Choose materials from stiffness, impact, wear, manufacturing, and repair requirements rather than strength claims alone.
Material selection matches a part's loads and environment to a material and manufacturing process. The best choice also fits the team's tools, time, , and replacement plan.
Material properties
controls elastic deflection. limits loads before yielding or failure. Toughness describes resistance to fracture while absorbing energy. Hardness concerns local indentation or wear. These properties are related but are not interchangeable.
Geometry matters too. A deeper section can resist bending more efficiently than extra material near its center. For a simple rectangular section bending about its thickness direction, the second moment of area is . Doubling thickness multiplies this geometric quantity by eight while doubling mass, assuming the other and material remain unchanged. Holes, joints, load direction, and local failure still need checking.
Material selection
| Material | Common useful role | Limitation to investigate |
|---|---|---|
| Aluminum alloy | Frames, plates, brackets, and structural members | Alloy and temper, joint stiffness, bendability, fatigue |
| Steel | , wear surfaces, and compact highly loaded parts | Mass, corrosion, machinability, and exact grade |
| Polycarbonate | Impact-tolerant guards and shaped guides | Flex, scratching, , and fabrication method |
| Acetal or HDPE | Low-friction guides, spacers, and machined plastic parts | Stiffness, creep, retention, and dimensional change |
| Printed thermoplastic | Custom guides, fixtures, adapters, and cable relief | Layer direction, temperature, fit, and repeatability |
| Flexible TPU | Compliant fingers, rollers, and contact surfaces | Grip, wear, deformation, and printing setup |
| Carbon-fiber composite | Selected lightweight structural parts | Directional properties, edge damage, joining, and dust handling |
Use supplier data for numerical properties; generic material names do not specify a rated part.
Stock specifications
"Aluminum" is incomplete purchasing information. Record alloy, temper, thickness, form, and where relevant. A bendable sheet alloy and a heat-treated structural plate can behave differently during forming even if both look similar.
Use supplier data to decide a drawing's material specification. Do not transfer a property table from one alloy or temper to another.
For polymers, distinguish solid stock from a printed part. A filament supplier's material properties do not establish the strength of your layer orientation, infill, holes, and screw joints. Test the manufactured part under the load direction it will experience.
Mass reduction
Removing material from a plate can reduce mass, but every cutout changes stiffness and stress distribution. Preserve support around , , and high-load interfaces. Avoid sharp internal corners and narrow bridges unless their load has been assessed.
A decorative pattern is not evidence of an optimized structure. Compare loaded deflection and failure behavior before and after a mass .
Part testing
Make a representative sample with the actual process and joints. Check fit first, then introduce a safe load gradually. Test repeated , impact where relevant, and time under load when creep matters. Keep people clear and contain a possible failure.
Record stock or filament identity, dimensions, revision, process, load, and result. New teams can begin with established kit members and use custom materials for small low-risk interfaces. Experienced teams should retain a known working replacement until a new material has passed equivalent tests.