Evaluating Viscoelastic Creep and Tactile Probe Indentation during Elastomer Metrology
Tactile metrology of elastomers requires sub-0.02 N trigger forces and zero-load extrapolation to prevent viscoelastic creep from corrupting part dimensions.
Touch Trigger Force
Meaning
Threshold parameters define the minimum contact load required to register a coordinate point during automated tactile inspection. Mechanical probe heads rely on a calibrated touch trigger force to signal the coordinate measuring machine when contact occurs. The parameter determines the sensitivity of the sensor and prevents accidental triggers from high-speed movements or vibrations.
Trigger Mechanism
Mechanical switches inside the sensor body open when the probe makes contact with the part surface. The electrical circuit is interrupted once the contact force exceeds the pre-tension of the internal spring. This interruption generates a signal that captures the current machine coordinates.
This mechanism must be highly repeatable to ensure measurement accuracy.
Calibration Value
Preset values must remain high enough to prevent false triggers from high-speed acceleration or vibrations on the shop floor. If the force is set too low, the probe may trigger while moving through open air, which halts the cycle. A high trigger force, on the other hand, can deform the part or cause the stylus tip to slip along the surface.
Technicians use a master sphere to calibrate the deflection behavior of the stylus under the chosen trigger load. This calibration compensates for the pre-travel variation that occurs before the switch registers the contact.
Operational Limit
Precision manufacturing relies on low trigger forces to prevent workpiece deflection and surface scoring. Delicate or polished components must be inspected with minimum force to protect their finish. This restriction ensures that the inspection process does not damage the product.