Re: Build CNC Plasma cutting Table

Deborah,

I built a plasma table with XY travel to cut specific 11ga and 16ga
production parts. I built the carriage such that I could trace
patterns on an adjacent table, with the plasma trigger being
activated by a pull solenoid activated by a foot pedal. The plan was
to add leadscrews/CNC later.

I used heavy steel floor grating (24"x24" sections) in the cutting
area (bought one to check it out, found it was very flat, so I got
more) and got them all leveled to the carriage axii, and was able to
bolt risers in fixed locations where the cut path wouldn't hit them,
since I would always be cutting the same parts.

The problem I ran into was gap control... no problem making the torch
travel in a flat plane of course, and no problem establishing a flat
table plane. The steel being cut is the problem. Even assuming it
is flat to start with (I got a lot that wasn't, and was useless), it
doesn't stay that way long when you start cutting... edges of cut
sections pop up, catching on the torch tip, moving the part or
stopping progress. I know some costly systems use sensors that
manipulate torch height with a servo... I tried to come up with a
mechanical version that rode the surface. I know people have plasma
tables that work, so I'm not discouraging you from your project...
just warning that, with HEAT involved, things don't always go the way
you envision. To avoid headaches and heartbreak, investigate the
marketed systems thouroughly and ask lots of questions first and talk
to people who use them; see how they handle the heat warp problems.
The feed control that CNC allows vs. my manual path tracing (hard to
maintain a steady path following a pattern, fighting carriage
inertia, etc.) may go a ways toward reducing the heat induced into
the sheet.

In my case, after delaying my business startup for three months while
I messed with building and fighting the plasma table, the overhead
(while making no product) was killing me so I went outside for laser
quotes. Laser shops seemed to fall into two distint groups; those
who treat the ROI on their laser like any other machine (i.e. a large
machining center representing the same investment) and those whoe
think a laser is something special and price their work 2-3 times
higher. The first group, I found, supplies my beautifully laser CUT
parts (accurate to .001" on everything I've checked) at a LOWER cost
than I could even buy the steel sheets (they buy great volumes of
steel). I thought plasma cutting was a neat, "little-guy-enabling"
technology until my experience with it... now I'm not a fan.


--- In CAD_CAM_EDM_DRO@yahoogroups.com, "cordero_deborah"
<cordero_deborah@y...> wrote:

> Hi,
>
> I'm new at this.
> Can anyone give me an idea how to go about building a (good) CNc
> Plasma Cutting table.
> I've seen lot's of site on the web and these tables are very
> expensive.
>
>
> Thanks
> Deborah