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Tips & Tricks no. 3 - The Venturi principle, or how does the powder injector work?
The diagram below shows a cross section through a WAGNER
The functional principle
Good to know: The powder particles must be delivered at a speed of around 12 m/sec in order to achieve a uniform powder delivery and a soft cloud.
The secret of the air flows
The feed air is responsible for the powder quantity. In order to influence the powder velocity, dosage air is also required.
The air flow rate which you set on the controller consists partly of feed air and partly of dosage air. The ratio of dosage air to feed air has a great influence on the amount of powder delivered:
feed air high / dosage air low = large flow of powder
The sum of both air flows, i.e. the total air, and the powder velocity in the tube remain the same.
In order to maintain the desired powder output the experienced
powder coater increases the feed air at this point. Normally, this measure works
until the collector nozzle is completely worn and must be replaced.
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