Here is an update on the filter setters project.
Our first problem was that of alignment. This is something that we struggle with in designing appropriate technology pressing equipment. Finding a cheap and simple mechanism to keep the two halves of the mold aligned
throughout the pressing cycle.
In the case of the filter setter press, the pressures are not extreme, I wish we could figure out how to calculate the pressure curve in solidworks, anyone? facebook
In this case the difficulty of finding 2 pieces of pipe that fit together closely, caused us to try and make the outer pipe to spec. with concrete. We used a piece of 200mm green sewer pipe (expensive at $80) for the main structure. It was wrapped with 4 layers of 6 mil plastic sheet but not taped to the pipe, so the pipe could slide freely. Then placed the parts into a 12″ sonotube and cast quickrete around it.
We also cut holes into the top to fit a branch of maple for the handle.
The inner pipe slid out easily (rotated just as the concrete had hardened green), and then the plastic.
We cut a bottom part of the green pipe now for the female mold.
For the male mold, after trying various other methods, we had it machined from aluminum at Armstrong Machine
This way it could thread directly onto the end of the 5/8″ threaded rod. The cutter is being made now, 1/2″ flat bar and a piece of pipe welded onto some 3mm steel plate. Can I borrow a MIG in Vernon? facebook
This will be cast into quickrete or plaster (running out of quickrete) inside the top part of the green pipe.
Making the female mold was a bit more complicated. We figured out after many tries to cut a profile out of arborite (countertop material $4 for offcuts at homehardware (coated fiberglass)) and to cut a master on a plaster lathe. We used hydrocal here because the pottery plaster from winrock was dead and I didnt want to drive back to Kelowna to return it. It turns out Hydrocal might be better anyway.
Since doing this last time we figured out a better way to cast the female mold. As you can see from the photos the mold is unnecessarily in 3 parts since the level was off on the pouring of the second half (tape blowout, oops). It took quite a bit of time to get it to slide in and out of a whole pipe section easily but tightly.
It was scraped with the edge of a fresh Olfa blade.
The green pipe was a bit warped so it doesnt spin around in the concrete casting as well as hoped. about
100deg but not all the way around. Should still work.
Here are all the photos together on gplus: http://tinyurl.com/qg2cdlc