Specifications PuckChuck Receiver: Lite Puck Mechanical Automatic Construction 4140 Steel (~30HRC) Hardened Tool Steel (~57HRC) XY Repeatability ≤0.0002"[0.005mm] ≤0.0002"[0.005mm] ≤0.0002"[0.005mm] Z Repeatability <0.0001"[0.0025mm] Angular Repeatability* ±0.015° Positional Accuracy 0.0005" [0.013mm] 0.00025" [0.0064mm] Clamping Mechanism Single Clamping Screw 2-Sided Clamping Jaw(Screw Driven) (3) Air-Open, Spring-Closed Clamping Jaws Clamping Force 2,000 lb [8.9 kN] 2,000 lb [8.9 kN] 425 lb [8.9 kN] Retention Force 2,700 lb [12.0 kN] (Aluminum Pallet Threads)6,200 lb [27.6 kN] (Steel Pallet Threads) *only relevant for single-receiver use cases with a clocking pin - assuming the 'worst-case' (loosest) fit between clocking slot and pin, this is approx. ±0.0004" [0.01mm] of tram error across a part the same ~3.5" [88mm] diameter as the Puck. Explanation of Specifications Repeatability The repeatability specification is a measure of how consistently a pallet returns to the same location after unclamped, removed, and replaced in the receiver. The angular repeatability is a measure of the clearance between the clocking slot and pin when using a single PuckChuck receiver. Some clearance is necessary for easy installation of the pallet, but also means the pallet can be rotated slightly left or right. Always preloading your pallet (e.g. twisting clockwise) when clamping can reduce the specified repeatability spec, as can turning your own, larger clocking pins (at the sacrifice of ease of assembly). Positional Accuracy The positional accuracy is a measure of how the pallet is positioned relative to the center of the PuckChuck receiver. For example: the Lite Puck uses a single-screw clamping mechanism. This consistently pushes the pullstud in one direction, repeating quite well, but results in a slight deviation between the pullstud centerline and the receiver centerline. Clamping Force The clamping force is the total force imparted to the pullstud by the receiver (either by heavy springs in the case of the Automatic PuckChuck or screw force in the case of the Lite Puck and Mechanical PuckChuck). Retention Force While clamping force is the force that pulls in the fixture, the retention force is the force required to pull out the fixture. Due to friction this force is much higher than the clamping force - so much so that the pallet threads will fail before the receiver unclamps (hence why the specified retention force is based on the pallet material). This same principle dictates why a screw doesn't simply loosen and fall out - the forces at play plus the angle of the threads create frictional forces so high that the screw can't back out on its own. For example: if an Automatic Puckchuck is assembled without clamping springs it will still take a significant amount of force to pull the fixture out of the receiver. As the pullstud is drawn upward, the friction on the clamping jaws increases proportionally - so each pound of upward force produces an increase in the frictional holding force as well.
