I spent a few hours with the maching yesterday and found "possible solutions" to my issues. I ran a large fan blowing on the controller.
First I started with an attempt to print the calibration cube with the clear PLA. It got through the hole job, though it seemed a bit more porous in some layers than others. but it did complete. The next attempt resulted in obvious under-extruding and it had a pronounced layer shift about 70% through the job. The first layer shift (a step, not the tilting as previously observed) was forward (y-axis) about 1/16". the overall footprint was ok, but it overhung the previous layers. It did this for about a dozen layers (0.1mm/layer). then it suddenly shifted toward the back and overhung the rear by 1/8"/. Again, the footprint was the same as all other layers. One final attempt of the cube.
this last attempt was absolutely pitiful. It was very under-extruded and completed only about 25% of the job before it began to extrude forward (Y-axis) by about a half inch. I just sat watching it as it extruded less and less material until it was just going through the x-y-z motions.
Stubborn as always, I swapped the PLA for ABS and was curious what would happen with the fan mount model. It extruded the first layer by sometimes extruding material and other times just not pushing anything out of the nozzle. It did the same thing on layer two, and then it shifted badly. Again the Y-axis was affected only. It put down the second layer about 5/8" to the rear of layer one. But I heard an odd sound. I cannot even begin to describe it, but I knew there was something amiss with the y-axis. I removed the motors, checked the set screws and they were fine. There was no way the gears were spinning on the shaft. I then re-installed the motors, tightened the belts, and jogged the machine around. Once or twice it "bound up" along the Y-axis. I loosended the little screws on the carriages and noticed the same thing.
I checked the voltages on the drivers and they were all ok. So I swapped the x and y axis drivers, re-checked & slightly adjusted the drivers, and attempted another cube print: layer shifting and under-extruding. The layer shifting leads me to think that the bearing in the Y-axix carriages or binding.
I will either have to take the carriage blocks off the rails, clean up the balls, re-lube and re-install.....or better yet, get a good set of carriages to replace these. That should (knock on wooden head) take care of the shifting. So which linear guide blocks to get?
Then there's the under extruding which progressively got worse. I debuged the extrusion issue today and found that by slightly pulling up on the lever the filament is grabbed by the feeder gear, and the extruded length is nearly spot on. (just about 100mm extruded as commanded.) The moment I release the lever, the filament is sporadically fed--only about 25mm of the 100mm command. So the filament is slipping inside the extruder. The spring is obviously not forcing the pressure wheel foward enough to the sprocket and the filament just slips. I disassembled the extruder (thoght not filled, the teeth had PLA material within them) but there is no adjustment to be made here. A stronger spring may be needed; orperhaps a small washer under it to slightly increase the effective length. Or better yet get a new extruder/hot end (Titan Aero) before having an opportunity to play with the stock unit. Unfortunately, I'm in a Catch-22: I cannot print a mount unless I get this one to work.
I was hoping to get the machine working this weekend and begin to work on organizing the build pictures; however, "one thing led to another...and the directions got all fouled up and...." (Dewey Oxburger).