Before you choose
- Stiffness describes deformation under load.
- Strength, impact behavior and elongation answer different questions.
- Methods, orientation and conditioning belong beside every comparison.
Ask what failure looks like
A locator can fail by bending too far while remaining unbroken. A dropped housing can crack from impact. A clip can survive a single bend yet lose its fit after repeated use. These situations call for different evidence, so begin with the part’s unacceptable behavior.
Read the property in context
Tensile strength describes stress in a specified tensile test. Modulus describes the relationship between stress and strain in a defined range. Elongation describes extension before a defined endpoint; it is not a repeated-flex life rating. Impact tests add their own notch, specimen and test-method conditions.
| Buyer concern | Useful evidence | Missing context to request |
|---|---|---|
| Too much movement | Modulus and part deflection | Load, geometry, temperature and duration |
| Breakage under a pull | Tensile test result | Orientation, preparation and method |
| Damage from a drop | Relevant impact/part drop test | Notched/unnotched method and conditions |
| Repeated flexing | Cycle testing of the feature | Strain, cycle count and environment |
Consider the printed structure
Layer direction, wall count, voids and support placement can affect a printed part. Filled material may improve one property and change another. Keep molded values separate from printed values and record whether the specimen was dry, conditioned, annealed or post-cured.
Translate the datasheet into a part trial
Choose one or two critical checks for the application and define a measurable pass result. Include dimensions before and after the test. A shared test method improves comparison, while a representative part trial checks the actual design.
A meaningful acceptance statement is “the locating face stays within the agreed deflection under the defined clamping load and dwell,” with the test setup recorded.
Questions buyers ask
Is carbon-filled material always tougher?
Reinforcement can improve stiffness while changing elongation, impact response and layer behavior. Compare the exact grade and test condition.
Can I compare MPa values from different test methods directly?
Check specimen preparation, test method and conditioning first. Identical units do not guarantee a like-for-like test.
Sources
- Formlabs — material selection and mechanical properties
How stiffness, elongation and other properties relate to the part's job.
- Formlabs — jigs, fixtures and manufacturing aids
Design, loading, inspection and service conditions for manufacturing aids.