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How To Build The PWDR Piston
This is where the Square Nuts go
This version of Pwdr is held together by square nuts and cylinder head bolts. Of course you can use hex nuts as well, but they will not fit too well into the cutouts and turn. Grab six M4 square nuts and have them ready to into the slots in the botton and sides.
Square Nuts in the Hole
The nuts firt somewhat loosely into the cutout (this may change in the next version). Slide them in after putting the parts together and lock them with the 16mm bolt. Now for the bolts, there are two strategies. The correct wya would be to use washers on this soft wood. The easier and almost as effective way is to simply tighten the bolts a bit more than usual until the pull themselves into the wood for a millimeter or so.
Connecting Bottom and Sides
Both Sides Mounted
As you see in the picture, the sides are not truely parallel. The reason is simple: the laser beam is focused through a lens and has a single point of focus. Below the point of focus, the laser beam is conical, and so is the cut that is created. As a result, the cut sides of the bottom part are at a slight angle.
Sinking The Bolt Heads Into The Piston Floor
The piston platform must be flat. For countersunk head bolts in wod, we just tighten the enough. In acrylic material, or with cylinder head screws, we need to manually countersink the holes. There are perfect tools for that. I just used a screw driver.
First Piston Assembled
After assembling the hoppers, the platform need to be sanded down at the edges to create a tight, but non-blocking fit.
Since we will be using wet binder, I decided to cover the pistons and the insde of the hopper in spar varnish. As a last step, we have to glue sand paper (100 or 60 grit) onto the top of the platform. When spreading a new layer of powder, the sand paper wil keep the previous layers from sliding.
(c) 2012-15 Matthias Melcher