Tuesday, April 2, 2013

More MendelMax 1.5 reprap improvements....

The original vinyl tubing Z-axis connector was showing it's age- starting to crack and slip. The version of MendelMax 1.5 I built uses a 3/8 inch ACME thread Z-axis threaded rod- so it's not easy to find a drop-in replacement My first try at an improved Z-axis connector was to design and print one. This connector can be found on thingiverse.

Printed 3/8" ACME to 5mm Stepper connector, installed

Printing parts with the new connector
The new connectors didn't work quite as well as the vinyl tubing- and seemed to introduce a good wobble to the Z-axis threaded rods, and thus made the parts print with irregularities in the layer thickness.

Unfortunately nice machined aluminum couplers are not available to join 5mm shafts to 3/8" ACME rod. I was able to find some very inexpensive 5mm to 8mm aluminum flex couplings on e-bay. Then, a friend helped me turn down 0.5" of the shaft end to 8mm to fit the couplings.

3/8 ACME rod with end turned to 8mm
Coupler Installed
I've also been fighting part warping. I thought one way to combat this would be to control airflow, and to keep the air around the printed part still and fairly warm. I found some thin acrylic sheet at the local Lowe's hardware store. It cut very nicely by scoring it with a knife and also with a bandsaw.

Cutting Acrylic Sheet
Material Detail

Draft Guards installed


  1. Andrew, you may want to try some delrin nuts for these acme screws. You can get them for your 3/8 12 screws from dumpstercnc.com, he usually ships them within 48 hours.

    Delrin is very durable and you get anti-backlash included. My trinity labs kit included delrin nuts, which is probably the only quality component I got out of that kit :).


  2. I'm using brass ACME nuts right now. They seem to work pretty well, most of the backlash / slop is between the nut itself and the X-end frames. Do the delrin ACME nuts run smoother? I'll definitely take a look at them.

  3. I have no point of comparison as far as smoothness goes. If it's any indication, I have not put any lube on my acme screws. The Z axis is very smooth going up but there is some noise on the way down due to binding with the X rods I assume. Since I do not lose steps when this happens and considering that it is not a printing move I have not bothered with resolving this issue, many other things to attend to on the MM. I will try and post a video so you can check it out.

    I would say that if you don't have any Z wobble in your prints and you're satisfied with the backlash situation you probably don't need to bother with Delrin for now. Keep that for the next printer ..

    1. I think my next printer will be a belt drive Rostock.... But I'll keep the delrin nuts in mind.