This week I've spent my evenings getting the printer to run. The problem is that I want to print above all other stuff that needs to be done before you should be printing. Things like getting the homing to work (no end switches), a heated bed (we don't have a heated bed), leveling the bottom with respect to the x-y movement. The way to quick results is done in buurman-en-buurman style.
Yesterday I tried to use a big round mirror because I though the multiplex base was not level enough. Also with the mirror I could not get the settings right. When moving in the x-y plane the height from the nozzle should stay at the same height. I measured a difference of 3 mm between the middle (0,0) and the end of the working area... Hmmmmmm... I even thought that the mirror was not level. So I went to the hardware store to get some 15x15 cm mirror tiles... They are level. No doubt about that. But the error was still there. (then I double checked the round mirror, and lo and behold. It's as straight as an arrow).
After some measuring and searching I found that the dimensions of the machine that are needed for making the calculations were off. We used a slightly wrong dimension. After updating the firmware a 7 cm movement of the machine was actually 7cm. Further more all was (reasonable) level. Below some visual proof of the result:
Printing an internal spur gear in layers of 0.10 mm
A movie of the printer in progress. The ticking you hear is the filament coil bouncing against a column: