A wedge test is a fast, practical method to screen key resin behaviors before committing to final parts. With a single print, you can qualitatively compare peel/separation behavior during printing and estimate flexibility/rigidity and toughness trends between materials.
Wedge screening protocol
- Print a wedge using your selected 3D resin.
- Scale the wedge footprint to reflect the total projected area you expect on the build platform.
- Default: print the wedge directly on the build platform. If removal with the spatula causes breakage due to excessive adhesion, print with supports or orient it sideways to facilitate removal.
- Optional: print the wedge horizontally (without supports) when this orientation is better suited to your printer and workflow.
- Use the printed wedge to screen:
- peeling/separation force behavior (qualitative)
- flexibility vs. rigidity (rigidity threshold vs thickness)
- fracture resistance / toughness (fracture thickness at the tip)
- Measure the rigidity threshold thickness (in mm).
- Place the wedge vertically.
- Apply a gentle but firm side force and determine the thickness at which the wedge does not deform or bend. This thickness indicates the transition to a rigid response. Below this threshold the material behaves as flexible.
- Measure the fracture/toughness response (in mm).
- Place the wedge vertically again.
- Apply a strong, firm side force until the tip breaks, then measure the remaining wedge thickness at the break location. The lower this thickness, the tougher the material (i.e., it resists fracture down to thinner sections).
- Adapt the wedge geometry to improve sensitivity for your use case.
- Thinner and longer wedges are preferred for small parts and for resolving small differences in rigidity and toughness.
- Thicker and shorter wedges are often sufficient for large parts.
- Longer wedges generally enable more precise readings because the deformation and fracture transition can be measured over a larger thickness gradient.
- Based on results, decide whether to evaluate a more rigid or more flexible resin, considering your required flexural strength and elastic modulus.
- For final mechanical validation, print standardized dog bones and bars as needed to comply with ASTM or ISO testing standards.
