Final Hardness
Final hardness is the rigidity of a Plastiform impression after it has fully cured. It determines whether you can extract the impression from a complex shape without tearing it, and which measuring instruments you can use on the replica.
All Plastiform products fall into one of three hardness categories measured on the Shore A scale.
Shore A is an international standard for elastomers that runs from 0 (very soft) to 100 (very hard).
Flexible: 0 to 40 Shore A
Flexible impressions that bend, stretch, and compress easily.
This lets you extract them from threaded holes, grooves, or any shape with any type of removal constraint. The impression deforms on the way out, then returns to exact geometry as soon as the stress is not applied on it anymore.
Because they are soft, flexible impressions cannot be inspected using contact pressure from calipers or CMM probes. Measure them with non contact instruments only: profile projectors, scans, vision systems, or optical microscopes.
Typical products: F20, F30 Visual, F30 Max, F40, P25, P35, M25
Use Flexible when:
- The shape has undercuts, threads, or grooves
- You have a non contact measuring system
- You do not need to slice the impression for profile analysis
Medium: 40 to 80 Shore A
Medium hardness works for most applications. The impression is resistant enough to extract from simple shapes, and enough rigidity to handle a transversal cut.
Medium impressions can be sliced with the Double Blade Cutter to produce a thin cross section for profile projection or vision system analysis. This makes them the most versatile category for dimensional control.
Products near the upper end of this range (around 65 Shore A and above) can tolerate light contact measurement, but non contact methods remain the safer choice for precision.
Typical products: F50, F65, M60, M70
Use Medium when:
- You want to slice the impression with the Double Blade Cutter
- The shape has a low to moderate extraction constraint
- You need a balance between ease of removal and measurement adaptability
Rigid: 80 to 100 Shore A
Rigid impressions barely deform.
They feel solid, almost like plastic. This makes them ideal for simple shapes with zero extraction constraint where the impression slides straight out.
In exchange for the lack of flexibility, you gain the ability to measure with contact instruments: calipers, micrometers, CMM probes, and roughness testers.
If you use a rigid product on a shape with any undercut or thread, the impression will lock in place. Forcing it out will break it.
Typical products: F85, P80 Ra, P51 SD, M80 LP, M90
Use Rigid when:
- The shape is simple and straight with no undercuts
- You need to measure with a contact instrument
Shore A vs Stretchability
Shore A measures rigidity, not stretchability. Two products with the same Shore A can behave very differently during extraction.
F30 Max and F30 Visual both sit at 30 Shore A. Both are Flexible. But F30 Max stretches far more without tearing, making it suitable for shapes with severe undercuts. F30 Visual stretches less but its glossy black surface makes it ideal for visual inspection.
For extraction constraints, check the product’s removal constraint percentage, not just Shore A.
See Removal Constraint for further information about this topic.
