A DC electromagnetic brake that pulls in weakly usually points to an electrical supply or air-gap issue. On overhead crane and gantry crane motor brakes, the most common causes are undervoltage, incorrect rectifier selection, excessive voltage drop due to long cables, loose terminals, or an incorrect coil rating (110V vs 220V). A failing power supply box/rectifier can also create high ripple DC, causing buzzing and reduced magnetic force.
Mechanical factors can amplify electrical weakness. If the air gap is too large due to wear or misadjustment, the coil may not develop enough force to fully release or fully attract the armature. Dirt, corrosion, or warped armature surfaces can also prevent full contact. The fix is to measure coil voltage at the brake terminals under load, confirm rectifier specs, check coil resistance, and reset the air gap to OEM limits. Reliable electrical power is essential for consistent brake release and safe operation.