The function of the fluidized bed powder barrel is not to "blow the powder as alive as possible", but to reduce the internal friction of the powder layer with a uniform and controlled rising airflow, so that the powder forms a loose state that can be stably absorbed by the powder pump. Insufficient fluidization can cause lumping, bridging, rat holes, and powder suction interruptions; excessive fluidization can cause large bubbles, furrows, powder tumbling, fine powder lifting, coarse and fine powder delamination, and powder suction concentration fluctuations. The permeability uniformity of the microplate determines whether the air flow at the bottom of the powder drum can be evenly distributed: local blockage, damage or edge leakage will form a high and low flow rate zone, which will periodically change the apparent density of the powder near the inlet of the powder pump. The effect on the primary powdering rate is usually indirect - it first affects the amount of powder per unit time, the powder-air ratio and the stability of the powder cloud, and then affects the powder charge-to-mass ratio, the spraying width, the film thickness uniformity, the over-spraying and the quality of the workpiece deposition. The flow rate of fluidized gas, the pressure drop of the microplate, the state of the powder layer, the coefficient of variation of the minute amount of powder and the one-time powdering rate calculated according to the unified boundary should be measured at the same time for selection and debugging, and the pressure gauge reading should not be looked at alone.
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