Re: plasma setup-leadscrew vs. rack & pinio n + software

-- In CAD_CAM_EDM_DRO@yahoogroups.com, Miroslav Pejic <peja@n...>
wrote:

> Hello, Ballendo,
> I saw once on this forum, roller chain is NOT enough linear for CNC
> machines.
> So, you recommend it again ?
>
> And, I can't find an email address of Plasmacam, Inc on

plasmacam.com. Do

> you have it?
> Peja
>

<snip>


Laser, water, milling, router, drill, all have very defined cutting
paths and cuting tolerances. The CNC movement needs to be 4 times
more accurate than the precison needed of the part. just a fact of
the math.

eg: if you need to be +/- one inch, and one step=1 inch, you can
predict you are either up one inch, right on or down one inch.
if you are +/- 1/4 inche, you are up 1/4, down 1/4 or right on for
the 1/2 inch spread with no movement, no slippage, no other
tolerances of any sort. Servo's must move on the encoder to know it
if off and needs to be re-posistioned. imagine going off one count,
then moving one count to make up for the movement.

That said, plasma cutting is like a machinegun. it sprays the stuff,
so step accuracies typically needed for routers and mills is wasted
on these machines.

also, being a non-contact device, MUCH less energy is needed to move
the tables. That said, belts, gears, chains, etc will offer good
accuracy as forces are low. Roller chain can be and is used for
linear movement in many applications. Lubrication and wear are
concerns of all contact devices and the chain will break in like
belts do, and will wear like gears, the time and extent may change,
but the monitoring of wear is just more frequent.

Dave