In episode zero I told the story of twenty-five years of spray booth. This is the new part: the water-curtain cascade.
The idea
A fan with a filter does its job, until the filter clogs with paint and the fan starts pulling less. Water doesn’t clog: a sheet of water running down the back wall captures the overspray, the paint ends up in the tank and not in the filters, nor in the workshop air. Together with extraction moved to the top, the idea is to exploit the Bernoulli effect: the extracted air and the moving water work together, instead of against each other.
The prototype, made by hand
Before opening FreeCAD the rule is always the same: check that the idea actually works. So I built the first prototype entirely by hand, without printing anything. Clear hinged panels on the front to close the booth when needed, a light at the top, the back wall where the water runs and, at the bottom, the drip teeth: they break the curtain into lots of small, even rivulets, instead of letting it dribble wherever it likes.
The first run is never the final one, but that wasn’t the point: the point was to find out whether the principle holds. It does. The curtain forms, flows and ends up where it should.
What now?
A hand-made prototype proves the idea works, but it’s hard to replicate and to improve: every change means redoing everything. That’s why the next step was redesigning the cascade in 3D, part by part, to print it. That’s episode 2.