Putting the base and stage together we used discarded offcuts. We were not able to use the milling machine so resorted to the rotary saw to cut the parts for our Y axis. Our intention at this point was just to get a rough base together so that we could test out the rack and pinion system.
One of the suggestions we got from our lab manager Martin was to try and make the machine modular in that it could fit the dimensions of various plywood sizes, however we might take this consideration in account once we get the gears, rails and motors working and can actually mill our machine base.
What we found:
The acrylic is actually a perfectly good material to make the rack and pinion. What is missing and we will need to 3D print is support pieces that grip on the other side of the rail and provide pressure on the gear.
Our fist task was to try and test the Jens's rack and pinion design files without changing any of his dimensions. We decided to try lasercut the rail using some left-over 3mm ply and 3D print our pinions. Unfortunately, the only printer available was the Freeform which didn't allow us great resolution, despite using 100% infill. Depending on the outcome and time considerations we may retry this with the RepRap.
The importance of this was to test the original design files, get a feel of the size we want to make our machine and the tolerances to experiment. We also wanted to have something basic to show our lab manager Martin and get some feedback.
What we found:
Our first attempt at 3Dprinting our gears was somewhat frustrating as it took the better half of an afternoon to get them printed, and they didn't really work with our lasercut ply rail. Also PLA printed gears may not be the desired material, even using 100% infill they still appear too brittle for a motor powered gear.
The laser cutter proved far more useful, and we even managed to laser cut the same gears out of some discarded 10mm thick acrylic which is not show below but we used the same files.
Our goal was initially to make the machine modular by creating extendable chamfer rails with linear puzzle joins to extend the work surface area.
What we found was while the joins worked fine in our laser-cut acrylic modules, there was still a notch that inhibited the smooth flow of the rack and pinion on the Y axis. As we had hastily put together the base and Y foundation, this created misalignment, inhibiting smooth movement of the rack and pinion.
We also learned the importance of aligning our 3D printed side block and tighteners. These act as the stabilising counter force to the rack and pinion mechanism and provide more control, limiting unnecessary degrees of freedom.
Also our initial prototype did not include a chamfer motor plate, meaning the side blocks on the X foundation created more counter friction to the rail slide on the Y plate.