Hello all

I'm a new owner of a Prusa i3 and new to 3D printing as well but very technically and mechanically minded so hopefully I've got the skills to get this working. After extensive research I decided this would be the most fun and suitable printer to play with. I got it from Greg Colbourne on eMaker. I believe it to be a fairly high end version of the i3 if I've done my research right. The build went well, had it all up and running within about 7 hours, quite impressed how simple it is.

I am however having some teething problems with it. Sorry to dump it all in one post which will likely be a long one, I've been doing a bit of searching online but haven't found anything so far that has helped.

Probably the most annoying one seems to be the Z endstop doesn't seem to stay accurate. I've run through the calibration process on this page and the first print following calibration seems to be pretty good but by the end of it the Z endstop is out of alignment again causing the nozzle to hit the bed on the next print. I've done a handful of prints on the machine now and I've only once been able to do 2 prints in a row without the Z endstop causing issues. It's mounted on tight, calibrated using the thickness of two sheets of standard A4 paper. I'm at a loss now what could be causing these issues, the machine is also on a flat level desk and all nuts/bolts are tight. The endstop is the type with a small microswitch (with lever) mounted on a PCB which is mounted to the vertical smooth rod on a 'candy cane' shaped plastic bracket with a bolt to make it grip on the rod, I'd assume it's standard for these although if I can print a better one I likely will.

The next issue is that with every print, the first layer is misaligned by about 1.5mm on the X axis and just under 0.5mm on the Y axis. The only thing I can think of is a slack belt or loose pulley grub screws but neither of them seem to be the issue, the belts are fairly tight, I've tried loosening them (made all layers sloppy) and making them even tighter (no noticeable difference), grub screws as well are tight. Strangely it's only the first layer though, after that all remaining layers are very straight and aligned well. This seems to happen on all prints no matter what the item is. Out of interest, does anyone recommend those spring tensioners available on ebay, the ones that look like clothes peg springs that clip on the belt? If so, where on the belt could it be mounted? As far as I can tell, wherever along the belt it could be put would cause it to catch on the frame or pulleys during printing.

Also another thing, not sure if it's a design flaw or if it's meant to be this way but the hot end does have some movement where it slots into the extruder, by hand the nozzle end can be moved a good 3-4mm in all directions. The bolts holding the extruder to the bearing plate/X axis are fairly tight to the point where it's deforming/denting the front surface of the extruder when tight. It has been like this since new and slackening/tightening the bolts makes no difference, is this normal? I can't visibly see it moving during prints but it had me a little worried that it shouldn't be like this and may be contributing to other issues.

Another thing that has only happened once, but may be worth a mention. I was printing a 20mm hollow test cube and right at the top just before it did the bridging, all the axis motors went spaz and vibrated at the same time and the extruder pumped out a good amount of filament on the edge of the cube, moved 5mm along the Y axis, and continued to print (so there was a lot of excess filament, and the bridged lid of the cube was hanging over the edge of the cube by 5mm). Not sure what could have caused it, sounded like a motor current issue but that's all been calibrated fine so I'm not sure, either way it's only happened once so far so I'm not too worried.

Any help would be much appreciated. If it matters, I'm printing with 3mm white PLA with hotend at 180C and bed at 60C.