What about a rack and pinion Z axis?

[waynec]

I'm still trying to rebuild my PR Shopbot, and I'm stuck on the Z axis right now. Its a sad tale, but the short of it is that I bought a lemon actuator with a badly galled ball screw on Ebay. It will cost more to fix the ball screw than I can spend, so I now need to figure out another Z axis.

The new gantry is extruded aluminum with Bishop Wisecarver rails for the Y car. Its very much like the new Shopbot PRS gantry.

So, I'm wondering if a Z axis with rack and pinion drive would provide accuracy and reliability in line with the PRS machine.

I can use the steel rails and bearings from my defunct Ebay actuator, and get things back on track. I dont' want to sacrifice accuracy- I need enough to get good results with inlay and fine 3d work.

Is rack and pinion Z axis viable?

Wayne from White Salmon
Ebay Idiot


My thinking (read my budget) is to make a

[thewoodcrafter]

Wayne,
I have a PR I have been working on (in my mind) to upgrade. I sure would like to see some pictures of the gantry.
Have you ever visited a forum for building a machine by the name of Mechmate?
http://www.mechmate.com/forums/index.php
It is an off shoot of ShopBot and uses a rack for the Z. Seems like a well engineered machine.

[stevem]

I have been using these on a home built machine for several years and will be converting my PRT Z axis shortly. Cost of the screw is approx. $1.00 per inch and the nut was approx. $20.00. The ends will require machining and you will have to make or buy bearing mounts. http://www.roton.com/Mating_Components.aspx?family=7059321

[waynec]

Steve M THANK YOU!

The easiest and best way for me to get going (I think) will be to replace the ball screw. I don't even mind if the specs drop a bit as long as it travels smoothly and has low backlash.

This site looks like just the thing, and at prices I can use.

Thanks so much for the tip.

I have several pics. I'll post them or at least some links to them in the next day or so.

W

Wayne C