Coordinate Measuring Machine Restraint Fixture Calibration for Thermoplastic Assemblies
Calibrate CMM restraint fixtures by matching datum locators to nominal CAD and regulating clamping forces to eliminate non-rigid part deflection.
Locator Pin
Meaning
Mechanical alignment device ensures the repeatable positioning of a workpiece within a tool or fixture. Use of a locator pin is standard in both injection moulding and secondary assembly operations to maintain tight dimensional tolerances. These components are usually manufactured from hardened steel to provide a durable and precise reference point.
Part Seating
Engagement between the pin and a corresponding hole or slot in the part provides a physical constraint. When a locator pin is correctly sized, it prevents lateral movement while allowing the part to be easily loaded. The clearance between the pin and the hole must be carefully controlled to balance ease of use with positioning accuracy.
High precision pins are ground to within microns of their nominal diameter.
Fixture Design
Layout of the pins determines how many degrees of freedom are restricted during the process. Because a locator pin is a fixed point, it often functions as a primary or secondary datum in an inspection plan. Combining round and diamond pins allows for the control of both position and rotation.
The height of the pins must be sufficient to guide the part into place but not so tall that it interferes with the clamping mechanism. Automated systems rely on these pins to ensure that the robot can place and pick parts with high reliability. Every pin is a critical link in the quality chain.
Production Efficiency
Rapid loading and unloading of parts is made possible by well designed alignment features. A locator pin reduces the risk of operator error during manual assembly. Quality is built into the process through mechanical certainty.