I am planning to build a 3D printer using rack gear on all 3 axis with a tooth height of 1.5mm and gear with 20 teeth. I will be using 2.2Nm Nema23 Step motors. I would like to get your comments.
Is there a reason for using rack and pinion? It’s not ideal for 3d printing as you are forced to either move the heavy Nemas around with a fixed rack or (with fixed Nemas) you need a printer envelope n*2 the length of each rack for each axis.
Have you considered trapezoidal lead screws as an alternative?
Also, with rack and pinion, your stepper increments may be too much and any rack machining errors will manifest in the print in the same place every time. I suspect backlash would be an issue as well. As well, cost will be an issue for a large build platform as +Tim points out.
@Clint_O_Connor , @Tim_Rastall Thank you for your comments. I thought 1 rail per axis was enough. In the meanwhile I think this approach is not suitable for Z axis. My design for X-Y axis is letter “H”. There will be 1 rack per axis (appr. 400mm per axis). The gear will be directly driven by the stepper.
My initial design included lead screws for all 3 axis. However due to cost issues I thought about other alternatives.
My lead screw design used 20/20 lead screws on X,Y-axis to increase the speed. The motors will be mounted on the axis. Therefore Y-axis motor will move itself (Nema23) + X-axis screw 20/20 + extruder with Nema17 + Nema23 for X-axis drive. I thought Nema23’s 2.2Nm torque would be enough to move all these on a 20/20 lead screw.