Saturday, May 12, 2007


More Progress on Acorn

Having a Saturday afternoon to kill, I got back to work on my RepStrap machine. First I reinforced the glue/nail assembly with some screws. Then, I decided that the bottom needed a re-inforcement board. I attached those, and then cut and drilled the holes on the Z axis structure boards. I all went pretty smoothly, and everything looks to be in good shape.

After I finished the construction of the structure, I went about installing the Y axis drive rods. I used a skate bearing on each end to allow the rod to rotate freely while also being anchored to one spot. It went pretty well. The rods rotated very easily, and the assembly was very easy. It also used standard parts: skate bearing, nuts, and washers. The rod was 5/16" (3 foot lengths), the nuts matched, and the washers were a bit oversized to catch the lip of the skate bearing.

Once I had it setup, it became obvious that some way of making the nut stay in place is needed. either using two nuts on each end, or a lock washer of some sort would do the trick nicely. After getting the rod assembled, I used some bolt cutters (a hacksaw works too) to cut the rod to length. Now, I just need to build some motor mounts and then I should be ready to rock!

I ordered some pulleys from McMaster, and I already have the belts, so this week I should be able to assemble the axes and test them out. My goal is to have the machine assembled by the end of this week! If things go well, then hopefully next week I can have the boards and computer all hooked up and ready to go. I'm playing with the idea of attaching the computer i bought to the machine and just having everything right there in one unit.

Also, I put caster wheels on the bottom to make it easier to wheel around the shop =)

More Photos on Flickr..

How tightly does the threaded rod fit into the skate bearing? I would assume that you'd want as little slop as possible.
i shopped around when i was at the hardware store, and the 5/16" rod is the best fit without being too big. it is still a bit loose.

however, what keeps the rod attached to the bearing and rotating with it are the nuts on each end. when they are tightened down, it forces the bearings together. eventually the wood stops them and then the rod will just freely rotate.
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