Re: [CAD_CAM_EDM_DRO] Re: Is my SMALL plasma table idea nuts?

Hi Will;

I see no reason why a cheap plasma machine can't be made. There are
many on the market today that are very cheap indeed. I do have issue
with the description of attaching it to the sheet. I suspect that that
will be problematic.

The issue with sheet attachment would be thermal growth and
distortion. There are other issues such as the control of sparks and
other airborne hot stuff. Lastly the stiffness of the sheet itself
might be an issue.

That is the thermal issues, I do see some other issues, some due to
considering a small machine myself. The first thing to realize is that
once you build a small machine it doesn't take much to discover the need
for a larger even though you don't foresee that at the moment. Of
course this has to be balanced against the limited space we often have
to deal with. The other issue with machine this size is the extra cost
incurred in having sheets reduced in size this much. That is the
costs of sheering and sourcing 2x3 sheets is non zero.

So considering those issues I'd reccomend a machine that can at least
handle a standard sheets width. It doesn't have to handle the length
but ideally would be open ended. Even if you opt to continue to
purchase small sheets, after all they are light and easy to handle, I'd
still go for a machine handling a standard sheets width. The big
problem here is "what is a standards sheets width". The answer I
would imagine is to contact your local supplier and see what material he
normally stocks in the size you want. Some materials are available in
36" 48" and 60" widths last I knew. Note too we are talking about a
more conventional plasma table type machine. Designed for you
original sheet size of 2x3 would be very doable, it might take moving
the axises around to handle a sheet longer than 2 feet but would not be
an hugely extra expense in materials.

Another option I was thinking about was to make one axis a tractor.
That is a plasma robot where one axis is clamped or grips an edge.
Sort of like the OA torches often used for cutting sheets, but with a
bit more intelligence. There are problems with this and I'm not sure
if you idea is actually one in the same (sort of missed the beginning of
the thread). I can see where one could be had that would produce good
results, I just can't see it as being as cheap and durable as a table
top model. In any event don't let my thinking stop you.

Dave


William Meincer wrote:

> I never really was concentrating on only mounting the table on the
> sheet, even though that's what I said in my original post. The main
> idea is that because of my limited space I wondered about the
> viability of partially plasma cutting a design and then moving the
> sheet sheet relative to the table and continuing to cut the same
> design with another subset of matching g-code (actually I only plan on
> needing designs larger than the proposed table size of 2' X 3' rarely
> anyway). I can work out the actual mechanics of attaching the table to
> the sheet or the cutting table after I try it.
>
> I have already experimented with an engraver design using MDF, drawer
> slides, standard threaded rod, etc. and the accuracy and lack of
> backlash is rather amazing. Considering that the kerf width of my
> plasma cutter is MUCH bigger than the error of my engraver design it
> seems to me that a cheap (but strong) plasma table design should
> satisfy my needs (which aren't exceedingly demanding) as long as it
> fits my working space....... so here goes!
>
>