Formation of a self-supporting powder or particle arch above a hopper outlet that obstructs discharge.
Also called: arching; hopper bridge; powder bridge.
Why can powder stop feeding while the hopper is full?
A bridge is an obstruction spanning above an outlet. It can involve mechanical interlocking of particles or a cohesive arch, unlike the open flow channel of a rathole. Powder visible in the hopper does not establish that material is reaching the feeder.
For a capsule line, separate the upstream supply observation from the downstream dose result. Record where flow stopped, the material condition and whether the interruption appeared after a hold or refill. A fluctuating capsule fill weight is evidence of an outcome; by itself it does not identify an arch inside the hopper.
A screw-speed setting describes the discharge device, not whether the hopper supplies it continuously. Review the hopper and feeder as an interface before attributing starvation to an inadequate dosing setting. An apparent shortfall while material remains above the outlet calls for a flow investigation rather than a universal increase in speed.
Evaluate hopper geometry and any proposed flow aid with the actual powder condition. Controlled activation in one arrangement does not establish that additional vibration is suitable for another.