It is not possible to give a uniform ± percent away from the specific system. Pressure regulating valves, stepper valves and proportional valves in the powder delivery system, which mainly control the compressed air pressure, air flow or valve opening; they themselves do not directly measure the powder mass flow. The actual amount of powder per minute also depends on bucket fluidization, venturi powder pumps or other powder feeding devices, powder tube length and bending, powder particle size and moisture content, fresh/recovered powder ratio, air source stability, nozzle resistance, back pressure, valve hysteresis, controller resolution and feedback sensors. In the absence of specific model, powder conditions and long test data, uniform accuracy should not be promised.
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