Rapman assembly part 7

I've been in a Red Queens Race with this damn thing for the past few days (running as fast as possible just to stay in the same place) and it's only now that I have some true progress to show off.

I spent a lot of time on the extruder; it looks the same but it runs much more smoothly now. The gears that were slipping are much improved, and I learned a considerable amount about how to fine-tune the spring-loaded bearing. When you tighten the spring bolts too far it acts like they aren't tightened enough, but the real solution is to back them off. I originally had them done right up, which did nothing but grind the reaction washer on the other side of the extruder and eventually force it out of place. After replacing the washer (backwards, as one side is now badly gouged) and releasing the spring bolts it came good.

I was forced to remove the top frame from the cartesian bot and disassemble it a few days ago, so I spent a long time getting everything perfectly aligned before trying to reassemble it. I made a measuring jig out of a long strip of acrylic with rod-sized holes at the appropriate distances, and it's been far more accurate for getting the frames perfectly sized than the original sizing bars that came with the kit. Once I reassembled the full frame and put another couple of holes in the jig it made setting the diagonal tie bars effortless.

Unfortunately I discovered after the top frame was on that one of the opto-endstops was on the wrong bar! There was a short panic as I contemplated disassembling the top frame AGAIN - the only way to move the endstop - but thankfully it was possible to rearrange things so that it's only slightly different to the instructions, but all the endstops can still do their job. A big sigh of relief there, I must say!


Tonight Buzz and Andrew were also at the hackerspace, and Buzz decided to MacGyver a stepper-driven extruder from a large stepper he had in his bag, along with a bunch of scrap acrylic from my rapman kit. It works amazingly well for something thrown together in a couple of hours! It's a bit large and ungainly to fit on my rapman, but a bit more work and it'll plonk straight onto his repstrap. It was also a good test of my stepper drivers, as we watched a piece of ABS filament go back and forth, and back and forth, and back and forth...