Re: [CAD_CAM_EDM_DRO] New Member to be has interest in home-brewing plasma table...

Short and Sweet Version.............

I Built my First CNC Plasma machine on the cheap because I needed something
quick. I used Cold Rolled Steel for Linear Rails and simple Cam Followers to
slide the carriages on it. Motion was provided by some very small stepper
motors using Belt drive to Rack and Pinion.

Having Built a very qualified CNC Router already with the "more appropriate
components", I was a bit hesitant to use such cheap Linear Motion Techniques.
But, After using it a while, I am not sure that I would do it much different
next time.

Why ? First off, Plasma cutting is one really messy job. The typical grit
involved would for certain, eventually slip past any seals or wipers used by
a recirculating ball type bearing. Once inside, your little ball bearings
would quit turning smoothly in short order. I've considered using Frelon, but
even then I can see eventual buildup scratching any Linear rail to pieces.
Protecting any type of "Real" linear method would be difficult. The only
thing you need to do with the cam followers is to apply some type of
"scraper", (Plastic preferably) to the carriages just to wipe the Cold rolled
as the cam follower comes thru. Sometimes the grit on the rail can make the
carriage bind just a tad.

Additionally, I gave some consideration to the necessary accuracy of a Plasma
Cutter. We're not talking Laser here..... The accuracy of any project you
typically use a plasma cutter for does not come into tight tolerances. I've
made some components for Automotive applications that just simply do not
matter if they are off a few thou. This is true especially if the components
get welded together. If the edge is smooth but off as much as .030 no one
would know. I've never measured anything off that much even with the cold
rolled rails.

Granted, My machine only cuts a 4' X 4' area. so if your building something
much longer you would have to make sure your rails are straight.

I would also use the Rack and Pinion again...... No way any type of screw
could last a long time in this application. As long as the rack is placed on
edge so any Swarf can fall out you are set. Amazingly, I only use some 80oz
motors. She'll run as fast as 400ipm using a 36 volt supply. Obviously, a
little bigger motor couldn't hurt but these amaze me.

Finally, I only have it set up for 2 axis. I can see that next time I would
plan for a 3rd Z axis and some type of software arc control. You do need to
have the material pretty straight and level to get a good job. Sometimes that
isn't so easy.

So, as crude as it sounds, Plasma is one application where doing it the
"cheap" way just might be an excellent way for the hobby low volume user.


My experience in a nutshell......................

Chris L

janrwl wrote:

>
>
>
> Hi, guys. In our local metalworking group which meets monthly, a
> first-timer (aforge@...) asked me if I had info on how to
> go about cobbling a home-brew plasma-cutting table. I have seen that
> topic covered extensively in here, so I am sending him this e-mail,
> too. He will be applying for membership, soon, so, those of you who
> have dealt with such as best linear ways/bearings for a plasma table,
> ACME or ball?, etc., and other caveats, he will want hear directly
> from you.
>
> Thanks! Jan Rowland
>
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