drive method, ball/lead or R&P

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Originally Posted by JamesKain View Post

thanks for the info!
What dose everyone think of rack and pinon for this? I'm only cutting wood and other soft materials.
I'm thinking fixed gantry but I know with a mobile gantry I will get more cutting surface.

Rack and pinon would be easier on the wallet from what I've read. Is this correct?

Rack and pinion would have even worse precision than roton Lead/ballscrews and also have more backlash. You're best bet would to be ask this question in the DIY Wood Router CNC forum.

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part of what i posted in the DYI forum.

If your axis is relatively small say under 3', a ballscrew or leadscrew assembly might be easier to implement. With a longer axis, it might be better {for a DIYer] to use rack and pinion. While ballscrews can be far more accurae than rack and pinion, longer lengths tend to necessitate larger diameter screws to overcome sag and whip, and the costs increase since you need larger drive motors and the larger screws, well, cost more. A rotating nut is possible, but then that would be more complicated, which usually means added cost.

Rack and pinion however will usually necessitate gearing down the drive motir to "gain" satisfactory resolution and power. With steppes, great speed can be obtained at the cost of resolution. While backlash can be virtually eliminated simply (though not always easily) with ballscrews, it can be more complicated with rack and pinion. Most any form of gearing would also introduce some form of backlash or position error..

If you decide on rack and pinion, most use the components from CNC Router Parts, which makes for a pretty simple installation.
I'd say if your axis is 4ft or less, go with either 1/2-10 5 start acme, or chinese 1610 ballscrews. Over 4ft, rack and pinion is probably a better choice.

Well I ordered 1/2-10 lead screws. Now I need the pillow blocks that go with them. Should I wait to get them before I order them?
Thanks guys!

there are the rolling ballnuts.. does mean screw is static and nuts are rolling

well.. they are already costly...
im really big fan for screws, because no maintenance on them... no adjusting..

the 25/10 lead can drive with 200 ipm to cutting..
on 7 feet i dont have real whipping or wobbling..

true i use always around 100 ipm max.. rarely when need just make flat something i set 5-6000 mm per min...