So many many successes since the last update. I've gotten my extruder reliability up pretty high, and I have had hours of successful printing (even joining two seperate ABS filament sections using a lighter, instead of having to stop to reload).
First things first, I went ahead and replaced the ball chain on my x and y axis. The difference is huge. My ball chain was slowly stretching and the chain was no longer meshing well with the laser cut gears that it originally fit. I wasn't able to print smaller items as the movement wasn't smooth and occasionally I could even have an axis jump an entire tooth. I ruined a long print this way and so I decided to go ahead and tear down that part of the machine and rebuild it around a "ladder" style cable. Don't know the official name for it, but it works great. No more stretch, it meshes well, and my prints are hugely improved. No more waviness between layers and the constancy of motion is great, especially visible in the evenly spaced rafts. The only huge trouble with it is that I didn't originally have gears for it (and couldn't print accurate small parts before I installed it. chicken vs egg scenario). I ended up actually "carving" my own out of larger laser-cut acrylic cylinders. I didn't have to drill the hole, and centering was fairly easy, but I did have to form the teeth & spacing. Took a while since I had to make three just using simple files, but they are now working very well.
I also went ahead and exchanged my thin acrylic base for one a quarter inch thick. My build surface stays consistently flat now; the older 1/8th sheet was getting wavy even though it was bolted down.
This kaizen approach is how I envision my work to continue for a while. At least until I've managed to print an entire mendel. I have a decent list going as to what aspects of my darwin I need to upgrade before I start printing in ernest and most of the improvements will actually carry over to the next gen machine pretty well. I've already printed a new pinch wheel extruder which should decrease my print times by quite a bit. I'd like to run that through the bowden cable configuration that some people are implementing so that I can at least lower the inertial issues that my top heavy machine already has. Hopefully I'll hit up against the upper limit of my head travel speed. also, before I can attempt some of the larger mendel pieces I need to deal with the warping that occurs, as my extruder body and large spur gear showed some level of it, and it would only be worse as the parts I attempt get bigger.
I'd like to design a heated bed that would cover up to 50% of my current print area, but easily removable so that I could throw it on to print a single large piece (such as the mendel x-carriage), but still be able to print an entire bed of smaller (more warp tolerant) parts.
I'm excited at the rate this is all picking up. I've printed sucessful parts and now a sucessful mechanism. next step is to integrate it into a sucessful system. Eventually I'll transfer to an entirely self made printer (and improve it further from there.)