First, kudos to JP for all that he’s managed to do for the world. I just finished to built a printer that bought in parts from China. It was a weird experience: It was sometimes a nightmare and sometimes exciting when few advances were reached. Quitting was not an option. Finally, after many weeks of hard work and insomnia the assembling is now done and also the printer is “calibrated”. I used Josef’s calculator and without knowing too much of threaded rods, I tried the values 4000 and 3200 and the motors get stuck. Value 2560 worked fine and helped me to make very nice printings with an eventual little noise of a fraction of second on the Z axis motors. I tried the value 2267.71 and it runs very smoothly. The only problem is that the printed pieces with both values come out smaller than the intended size. The calibration model 0.5mm found in Rep rap wiki that is supposed to be 10 mm height, comes with only 6 mm height. Also other pieces that I have printed come smaller. I tried all the possible calibrations with Slic3r – Pronterface and the results are the same. I even changed the size of my hot end from 0.4 to 0.5 and nothing new happens except that the walls come out thicker. My threaded rods have 36 thread lines for inch, (I counted them myself) my extruder is a MK8 J shaped and the filament is PLA 1.75, my motors are nema 17. I HOPE that someone here can give me some ideas. Any help would be greatly appreciated. Sincerely, Victor.