Friday, July 22, 2011

RepRap Milestone - Fame and XYZ

The "Hains" Prusa Mendel RepRap in progress.

Updates on this project have slowed, but it's been in favor of getting work done. But the project reached a significant milestone yesterday that deserved an update. The frame, X, Y, and Z axis and print platform are complete. This constitutes the main body of the machine and most of its mechanical parts. All that's left is to build and mount the extruder, then the electronics.

While I will go back and continue to blog the build process, step-by-step, I want to take this opportunity to give you a few highlights and insights from the work so far. The project has not been without challenges and opportunities for discovery. Filming has added an extra dimension, and I've realized that I tend to drift off in the middle of a sentence while I'm working, so I need to speak THEN do.

The quality of the printed parts matters a great deal, more than I would have thought. Last week I broke a coupler, the part that connects the 5mm motor shafts with the drive bars for the Z axis.

One coupler was well made, the other one wasn't. It's 5/16" end was too big, which made it necessary to route out material between the clamps, and by the time I got it to grip on the drive shaft it flexed too far for the plastic to take. 

I tried a few ideas for building new, DIY couplers. The IRC #reprap channel gave me the idea for the rubber tubing version. I made a couple wooden variations of couplers that are commercially available.

I couldn't machine the wood so that the drive shaft would align with the motor well enough to use, so I wound up going with the tubing.

Besides that, it was a big challenge to get the Y axis smooth rod to line up. That one almost broke me. I think that one was related to the quality of the parts as well, since it seems the variation in the width of the bar clamps affected the measurements for getting the bars parallel. In fact, the hardest parts of this build have been the parts that need a lot of fine adjustment, like the parallel Y axis smooth rod, the parallel Z axis smooth rod, and the level print platform. I was surprised by how much attention these processes would need and failed to appreciate how minute changes can dramatically affect the performance of the machine.

Fasteners have been a problem. It could be the parts list, my ability to shop, or the sales person at Fastenal not being able to understand me, but the parts I got were not universally the parts I needed. It will be fairly important to detail exactly what I got and what I should have bought in this blog, because I have had to cut some screws, use the wrong size screws, and otherwise make do in not just a few cases. Some parts remain completely unused.

But regardless, I've made it through and now I'm on the back nine and feeling good. The next steps are to build the mechanical part of the extruder, then the hot end, and then finally the electronics. Those few steps accomplished it will just be a matter of getting computers to talk to the machine to turn plastic filament into stuff.

Today I film the build of the extruder (the test run pictured above,) and I'll start the hot end. Since I've already given it a try to work out its issues, today's event should go off without a hitch. Tomorrow I'll try to finish the hot end and maybe start to set up the test of the electronics. If I get a test by tomorrow night (not likely) then next Wednesday I'll try to mount the electronics and start to dial it in. If that goes perfectly then I'll maybe try printing something next Thursday. If that happens I'll put up a UStream live video stream of the maiden voyage/calibration print. That's the soonest I could print something. I'll be going to GenCon the first week of August, so that's going to knock a week and a half long hole in my calendar and printing will most likely start the weekend of the 12th of August or the weekend after that. At least I have a decent estimate now, though. 

1 comment:

Shady Mohsen said...

Greate work. Nice ideas for the couplers. I am working on a CNC router with amost standard parts with reduced shop works in Egypt.

your bro Shady.