Quick Selection Test – The Wedge Method
The 3Dresyns® Structured Mechanical Screening Protocol (SMSP) is a structured, printer-native methodology to obtain a practical mechanical fingerprint of a photopolymer system on your own equipment.
It translates mechanical behaviour into two simple, reproducible readouts: how much the wedge bends (rigidity vs flexibility) and where it breaks (toughness vs brittleness under flexion).
SMSP complements the Engineering Resin Selection Tool by adding a fast empirical confirmation step: no instruments, minimal setup and high practical signal.
For broader calibration, troubleshooting and engineering documentation, use the consolidated 3Dresyns® Photopolymer Engineering System and Resources.
Download the STL
- The Wedge (STL): Download
If you need the full calibration pack, including CRT-related files, email info@3dresyns.com.
What SMSP screens
- Rigidity vs flexibility through low-load bending response.
- Toughness vs brittleness through fracture under high flexural load.
- Peeling / separation behaviour as a qualitative process-stability indicator.
- Large-area stability when printed at large footprint, including levelling and light power distribution effects.
Two complementary print modes
SMSP-A: Flat mode (large-area / process stability)
Use flat mode when your target parts cover large cross-sections or when you want to screen levelling, adhesion uniformity and vat-wide exposure consistency.
- Print flat on the build platform, without supports.
- Scale to cover a representative build-plate area when relevant.
- Use for adhesion stability, peel behaviour and exposure uniformity across the vat.
SMSP-B: Vertical mode (cantilever mechanical fingerprint)
Use vertical mode to obtain a cleaner flexural readout, including rigidity threshold and break thickness, with a cantilever-type loading behaviour.
- Print the wedge in vertical orientation, without supports.
- Use for rigidity vs flexibility and toughness vs brittleness under flexion.
Printing instructions (standardised starting point)
- Bottom adhesion layers: 2 layers. Use your established bottom exposure approach.
- Standard layers: start with the exposure time needed to cure 1.5 layers.
- If available: record printer light power at 405 nm in mW/cm² for improved reproducibility.
If removal is difficult or the wedge cracks during removal, do not force it. Print flat (SMSP-A) and/or reduce bottom exposure. Excessive adhesion typically indicates bottom overexposure rather than superior mechanical strength.
SMSP readouts
Readout 1: Rigidity threshold (low-load bending)
- Hold the wedge vertically.
- Apply gentle lateral force at the tip.
- Identify the thickness in mm at which bending becomes negligible.
Rigidity threshold is the practical transition from compliant to rigid behaviour for the selected geometry and print state.
Readout 2: Break thickness (high-load fracture)
- Apply stronger lateral force until fracture occurs.
- Measure the thickness in mm at the fracture point.
Rule: lower break thickness, meaning fracture closer to the tip, typically indicates higher practical toughness under flexion. Higher break thickness indicates more brittle behaviour.
Graphical interpretation
A) Low-load bending: rigidity vs flexibility
Apply a gentle, controlled lateral force at the tip. Compare the wedge shape after bending. More curvature indicates higher flexibility at thin sections.
- Rigid: minimal curvature; bending concentrates only at the very tip.
- Rigid but brittle: appears rigid at low load but tends to fracture early under high load.
- Semi-rigid: curvature initiates near the upper region.
- Flexible: curvature initiates around mid-height.
- Elastic: curvature initiates low, near the base, and shows high recovery after unloading.
Rigidity readout: record the thickness at which bending becomes negligible. Lower rigidity threshold typically indicates more rigid behaviour for a given geometry.
B) High-load fracture: toughness vs brittleness
Apply stronger lateral force until fracture occurs. Tough resins typically break only at very thin sections, near the tip. Brittle resins break at thicker sections, further from the tip.
- Tough: break occurs very close to the tip, in a thin section.
- Balanced: break occurs at an intermediate thickness.
- Brittle: break occurs far from the tip, in a thicker section.
Toughness readout: record the thickness at fracture. Lower break thickness typically indicates tougher behaviour under flexion.
Mechanical interpretation matrix
| Rigidity threshold | Break thickness | Practical behaviour | Selection direction |
|---|---|---|---|
| Low | High | Rigid but brittle | Select tougher family |
| High | High | Flexible but weak | Select tougher / stronger family |
| Low | Low | Rigid and tough | Structural candidate |
| High | Low | Flexible and tough | Compliant / impact-tolerant candidate |
Mobile: scroll horizontally to view all columns. The first column remains visible while scrolling.
Integration into the 3Dresyns® workflow
- Define requirements: application, geometry, load mode, target behaviour and workflow constraints.
- Select by engineering criteria: property targets, structural behaviour and material family.
- Control curing: use CRT and calibration logic where dimensional or mechanical reproducibility matters.
- Confirm with SMSP: empirical, printer-native readout of real printed behaviour.
- Validate application performance: final qualification must be performed under application-specific conditions.
If you share your rigidity threshold and break thickness measurements, along with printer model and layer height, we can recommend a suitable resin family. Contact info@3dresyns.com.
