Spray Tips: Volumetric Powder Feeders
August 04, 2017
Source: ASM International
Volumetric powder feeders are based on a positive-displacement mechanism that delivers packets of powder. The diagram schematically shows a common volumetric feeder design. Volumetric mechanisms include screws and wheels that are slotted, spoked, or drilled. As a screw turns or a wheel rotates within the bed of powder, the powder is displaced by the screw or picked up by the wheel. Powder is then taken to the carburetor, where it is suspended or fluidized in the carrier gas delivered to the powder port in the gun.
Tampers are sometimes used to assist the packing of non-free-flowing powders into the wheel slots or holes. Vibrators are also used when powders do not flow well. Scalpers or scrapers are sometimes used to scrape excess powder from the tops of the slots/holes, so that a predetermined volume of material is delivered to the carburetor for each wheel revolution. In screw feeders, the end of the screw enters a tube, which serves the same function of controlling the volume per revolution of the screw, keeping excess powder from entering the carburetor.
Volume 5A, Thermal Spray Technology ⇒ Thermal Spray Processes and Coatings ⇒ Process Control and Control Equipment ⇒ Material Feed
Materials Processing and Treatment
Materials Processing and Treatment | Coating
Materials Processing and Treatment | Powder Metallurgy
Materials Processing and Treatment | Thermal Spray Technology