The near-linear cumulative weight-loss curve demonstrates that the G4 feeder’s mechanical metering system delivers this fine WC-based powder at a highly stable average rate, within the resolution and sampling bandwidth of the measurement. This level of mechanical feed stability is essential for producing uniform coating thickness, since fluctuations in powder delivery can result in local variations in deposition rate. However, this test characterizes the powder discharge from the feeder only. It does not necessarily prove that the instantaneous powder flow exiting the spray gun is completely free of pulsation. Flow irregularities may be introduced downstream of the feeder as the powder is transported through the carrier-gas line. Possible causes of downstream powder pulsation include: - improper powder-hose diameter for the selected powder feed rate and carrier-gas flow; - excessive hose length, vertical lift, sagging sections, loops, sharp bends, or kinks; - abrupt changes in internal diameter at hose connections, reducers, unions, compression nuts, or other fittings; - internal steps, cavities, protrusions, or dead volumes inside adapters and connectors where powder can accumulate and then be released in batches; - powder accumulation in low points, elbows, fittings, or the gun injector, resulting in intermittent slugging; - insufficient, excessive, or unstable carrier-gas flow; carrier-gas pressure fluctuations caused by regulators, valves, mass-flow controllers, or the gas supply; - inadequate or varying pressure differential between the feeder and the gun; - changing backpressure from the gun, injector, combustion chamber, or nozzle; - leaks, loose fittings, or unintended gas ingress into the powder line; - partial restriction, contamination, wear, or improper geometry of the powder injector; - electrostatic charging of the powder or hose, particularly with very fine powders; - powder agglomeration caused by moisture, cohesion, or interaction with the hose wall; - incomplete feeder pressurization or unstable conditions during startup and shutdown. Therefore, the graph confirms the excellent mechanical performance of the G4 metering system, while the stability of the powder stream at the gun outlet also depends on the correct design and operating conditions of the entire powder-transport path—from the feeder outlet through the hose, fittings, and injector to the gun nozzle.