Re: Is my SMALL plasma table idea nuts?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "William Meincer"
<bmeincer@...> wrote:

>
> Since I have limited space I am considering making a small plasma
> table that sits ON the metal sheet to be cut. I already have a small
> cutting table and ventilation system for my Powermax 600 and thought a
> small (maybe 2' X 3') table might be fine for my art. If I wanted to
> cut larger pieces I would cut the graphic into pieces in the cad
> program, make piece-meal g-code and move the table around the sheet of
> metal. Since it would be small the alignment issues and cost would be
> reduced significantly too.
>
> Is this idea nuts?
>

How are you going to deal with the flame and sparks that need to fall
out the underside? You will need a grid below the metal to hold it.
If you are going to build a grid big enough to handle the cut area
then you will have to index the material rather than the cutting
mechanism. (Grid needs to match up under the cutting area)

Next problem is going to not be holding it down to the material, but
rather to keep it from sliding sideways. For thin material you need
some pretty aggressive cutting speeds (200 - 300 IPM) and with those
speeds you need good acceleration to keep corners sharp. With heavy
acceleration you have opposite forces on the table. The size of the
table dosn't matter much as to the forces involved except with less
mass you get more movement. Even with a fairly light head and Z drive
your gantry will have enough mass so that acceleartion and
deacceleration from 0 to 300 IPM at 1200 IPM/sec will setup some
interesting vibrations and flexing.

I think when you look at the costs you will have 90 to 100% of the
cost of a 4 X 4 stationary table and you don't have to buy your
material in odd sized pieces.

I saw a Chinese design the other day that was a conroller with a long
arm that hung over the material and ran up and down a tracks on one
side. It was totally portable but any mass but just the torch (had no
THC or lifter) would be too much.

I don't want to squash ideas but this one comes with a set of problems
that may prove to be more complex than you first think.


I would think a robotic arm approach might be better so it would tuck
into a corner but unless you have a source of surplus robots (you may
soon be able to buy some from Ford (:-o)) the cost might give you pause.