I’ve been looking into the world of plasma tables
and most companies use gear racks.

I’ve seen some really nice home built tables on here
and some guys use a fixed belt system to move the X/Y.
Now if there’s no give in the belt this looks like the most accurate setup.

Now if you took the plasma torch out of the equation
how accurate is a gear/rack table?

Sir,

Your system accuracy depends on a number of things:
1) Gear rack accuracy around .005"/foot, could be less for more $$
2) Long axis ways straightness - you determine this
3) Cross axis ways straightness, "
4) perpendicularity of X to Y axes, "
5) Z axis perpendicularity to X-Y plane, "
6) Lost motion in each axis bearings to ways

In business, we used rack and pinion for many reasons, practicality, cost, accuracy, longevity, and customer acceptance. You will find MOST commercial machines use R & P.

Regards,
Jack C.

One thing to think about is how the precision of the moves would be affected by belt stretch. As long as the racks stay clean and don't get corroded they should stay consistent.

I use a laser cutting company for all my stuff
for now and their laser machine is BIG.

I know that a laser is in a whole other class than
a plasma but the guys I use can hold +/- .005 so
at very least there table is good.

What are those type of machines using R&P belts ballscrews?

This link has info on belt drives

http://www.cnczone.com/forums/showthread.php?t=59570

Now that's some cool stuff!!!

Thanks for the reply’s keep them coming.

So what do the big laser machines use?