Cetus Z axis clamp

thingiverse

Improved design see: https://www.thingiverse.com/thing:3586841 Works much better than the original Cetus part. This clamp design incorporates more degrees of freedom to compensate for printer manufacturing tolerances, resulting in a more consistent clamping force. Equally important, this approach makes two threaded stepper holes available for a Z axis brace. The Z axis shakes whenever the extruder stepper motor is accelerated, and these vibrations are frozen into the print surface. PLA makes a poor braking surface because friction causes heating, which then turns the PLA into a lubricant, leading to the Z axis crashing into the print bed. A strip of shim brass isolates minor PLA viscosity changes. Then, the compression spring compensates for any minor PLA shifting from a layer hill to a layer valley. Print on fine with a 0.1mm layer thickness. Use a 0.4mm nozzle but choose a 0.3mm extrusion line width. The PLA is thin, 0.6mm around the sprag clutch bearing, which distributes the clamping force more uniformly over the bearing surface. You need a stiff spring with about 2 lbs of force when compressed, a 4-40 or M2.4 nut and bolt, and a small strip of metal. I used 0.005 thick shim brass cut with scissors. I folded the end to double the thickness then poked a hole with a nail for the bolt to pass through, preventing the brass from shifting or rotating in the final assembly. In the photo, the steel bracket firmly connects the Z stepper motor face to the printer base. Measuring deflection with a Dial indicator shows that the top of the Z axis deflection is now 0.003" over the travel limits of the shifting extruder motor weight. The bracket also makes tramming the printer possible (making the three-axis perpendicular to each other) if you're so inclined. -Peter