Why Do Bubbles Occur in Robot Motor Stator Potting? Complete Troubleshooting From Material, Winding to Vacuum Process

Bubbles or internal voids after potting of robot frameless torque motor stators are usually not simply caused by poor‑quality adhesives. Frequent root causes include air entrapment during A‑B mixing, mismatch between material viscosity and winding gaps, excessively high slot fill factor, improper potting direction, lack of air escape channels, inappropriate vacuum process settings, and residual gas expansion during curing. Robot Joint Motor Potting For robot joint motors, the greatest concern is not several small visible surface bubbles, but hidden voids deep inside windings. Stator potting not only fixes copper wires, but also builds a continuous thermal conduction path from windings to iron core and then to the housing. Potting for frameless torque motor stators requires comprehensive consideration of thermal conductivity, CTE, Tg and curing process. Quick‑judgment Table: Where Do Bubbles Likely Come From? Bubble / Void Location Common Causes Priority Inspection Actions Not Recommended as First Step Large number of fine bubbles on adhesive surface Air entrapment from mixing, overly fast stirring Mixing & degassing Directly change adhesive grade Voids deep inside copper wires Poor wetting, no air escape outlets Viscosity, slot fill factor, flow channel Only inspect surface appearance Gas trapped at stator bottom Improper potting direction Placement angle, vent path Simply increase vacuum level Voids at mold corners Locally enclosed zones Mold & flow channel Fill up rapidly in one shot Bubbles only with automatic dispensing Air entrainment from equipment Pump, pipeline, mixing tube Suspect material batch at first Voids formed after curing Residual gas / curing‑related variation Curing profile Blindly raise curing temperature Why Does Higher Slot Fill Factor Make Potting Harder? Robot Joint Motor Potting To miniaturize size and boost torque density, robot joints adopt compact copper‑wire arrangements. Invisible micro‑gaps between coils serve two opposite purposes: allowing adhesive inflow and air outflow. If adhesive flows in…