3Dresyns® Structured Mechanical Screening Protocol (SMSP)

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 our Engineering Resin Selection Tool and our structured selection pathway by adding a fast empirical confirmation step: No instruments. Minimal setup. High signal.

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 (low-load bending response)
• Toughness vs brittleness (fracture under high flexural load)
• Peeling / separation behaviour (qualitative)
• Large-area stability when printed at large footprint (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 (no supports)
• Scale to cover a representative build-plate area (optional)
• Use for: adhesion stability, peel behaviour, exposure uniformity across the vat

SMSP-B: Vertical mode (cantilever mechanical fingerprint)

Use vertical mode to obtain a cleaner flexural readout (rigidity threshold and break thickness) with a cantilever-type loading behaviour.

• Print the wedge in vertical orientation (no supports)
• Use for: rigidity vs flexibility, 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 (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 (mm) at the fracture point.

Rule: lower break thickness (fracture closer to the tip) typically indicates higher practical toughness under flexion. Higher break thickness indicates more brittle behaviour.

Graphical interpretation (described, no sketches)

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 (rigidity threshold). 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 (thin section)
• Balanced: break occurs at an intermediate thickness
• Brittle: break occurs far from the tip (thicker section)

Toughness readout: record the thickness at fracture (break thickness). 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

Integration into the 3Dresyns® workflow

• Define requirements
• Select by engineering criteria (property targets & structural behaviour)
• Confirm with SMSP (empirical, printer-native readout)

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.