Re: [CAD_CAM_EDM_DRO] Long X axis Method of travel.

dex367 wrote:

>I am in the preliminary process of designing a 4 axis machine using
>open loop stepper motors and a PC. It will be used to route wood. The
>X axis needs to be 96 inches long. That about 2.4 meters.
>
>What would be a good method to drive this long lenght?
>
>1. Tooth Belt Drive
>2. Rack and Pinion
>3. Lead Screw
>4. Other?
>
>

Lead screw would be atrocious. The only way to make an 8 FOOT long
leadscrew work would be a rotating nut. Even then, the sag on a 7' length
of screw when the gantry is at one end would likely bind the nut!

Rack and pinion has some problems with contamination, and so you should
think of ways the rack could be shielded from sawdust. Also, there
are problems in maintaining alignment on such a large machine.

Toothed belt drive may be your best option. Especially a belt that normally
lays on a flat surface, so it won't flap as the machine moves.

One other possible mechanism that might work is steel aircraft cable
wrapped around a grooved drum. The cable can be kept tensioned very
tightly. If the drum was ~ 3.820" diameter at the cable pitch diameter
it would wind up 8' of cable in only 8 turns. That would allow you to
fix the cable at one point on the drum if you allowed 16 turns of groove.
Or, you could just have 3 or 4 turns of groove and allow the cable to "flow"
through the grooved drum.

Jon