Optimizing Mechanical Restraint Forces in Non-Rigid Polymer Metrology under ISO 5459 Guidelines
Balancing restraint forces under ISO 5459 ensures accurate datum seating without distorting non-rigid polymer part features during coordinate metrology.
Support Pins
Meaning
Threaded or fixed mechanical rods positioned within a holding fixture provide localized resistance against bending and deflection during machining or assembly operations. Support pins are strategically located beneath thin-walled or unsupported regions of a moulded thermoplastic component to counteract pneumatic or ultrasonic welding forces. They ensure that the holding force applied by the clamping mechanism does not buckle or warp the warm polymer.
If these pins are missing or poorly adjusted, the part will flex under load, resulting in dimensional inaccuracy, stress whitening, or structural failure.
Mechanical Support
Sufficient resistance to external assembly forces is essential to maintain part integrity during fast-cycle production. When support pins are correctly positioned, they absorb the mechanical energy from welding or drilling heads, protecting the plastic part from localized deflection. This prevents the part from sagging or shifting out of its programmed alignment.
The pin height must be set precisely to match the part’s nominal design surface.
Part Protection
Surface marring and cosmetic defects can occur if the steel tip of a pin makes direct contact with a soft polymer. To prevent this, support pins are often tipped with polyurethane, brass, or other soft materials that match the polymer hardness. This soft contact interface protects the cosmetic surface of the part from scratches and dimpling.
This is especially important for high-gloss automotive parts where any microscopic mark leads to immediate rejection.
Process Flexibility
Adjustable pin arrays allow a single fixture to be reconfigured for different part geometries. By changing the height or location of the support pins, moulders can adapt the tooling to run different models of the same component family. This adaptability minimizes the need for dedicated, high-cost fixtures.