Building a washout unit

I’m interested in building a photopolymer washout unit.

Can anyone detail how the orbital washout mechanism works?

I imagine an eccentric gear mounted to a rigid shaft with bearings between the platen would work.

From what I’ve seen, it looks like they’re given support from four “legs” which rotate in holes appropriately sized to accomodate the orbital travel of the square platen. Is that true?

Also, has anyone tried a rotary brush that traverses across the plate surface? It seems like that could work just as well as the flat brushes, but I’m not sure.

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We have a copperplate washer/polisher that uses a transverse rotary brush that travels across the plate. At the same time, the plate sits on a turntable that rotates….. sort of like the turntable in a microwave oven. The combination of the two motions very thoroughly cleans the plates.

A similar construction would also work for a PP washout machine, I’d guess.

What I have seen has two eccentrics driven by chain (and reversal of motion). Some have motor above platen, others have motor in base, and platen hinged and suspended above brush. For letterpress use the flat brushes cover the entire area of plate motion. There are different designs for flexo and other uses (stamps, signage, ?) using rotary brushes, spray washout, etc.

Spray washout! That’s a good idea! Much experimentation must be done, but I feel that may work just as well as a brush, with significantly lower cost and maintenance issues. I will keep this thread updated as I progress.

When we started to use photopolymer plates (mid 1980s), we converted a paddle-type metal etching (Master Corp.) machine to spray by dismantling the paddle system and putting two spray bars with multiple spray heads under the orbiting platform on which the plates were mounted.

That machine is now gone and I have a conventional processor with flat brush, but many plates were washed using spray only. I can’t remember how long the washout time was with that unit, but it probably took longer than a brush system to totally clean out the unexposed polymer.

To get the spray pressure, it required a pump in-line with the spray heads, similar to a high pressure system used to clean buildings and driveways.

I think I got the idea from a system I saw at a newspaper which had an in-line processor/dryer for their photopolymer plates. If your spray heads were not completely effective, you could open up the machine and do a bit of brush work by hand to finish out the processing.

I was at one time considering taking a matchprint 3250 tabletop developing machine and seeing if it could be adjusted for PPP. It has in it a rubber conveyor, a couple of spray bars and two rotary brushes. I believe I abandoned the idea because the general consensus was that the speed of rotary brushes was to harsh and unidirectional for a good washout.