[Doug Smith]

We have a plasma burn table with has an optical eye to trace plans. I would like to retrofit for a minimal cost to run from the cad system. Any ideas on the best way to get this done.

All sugestions would be great. I am growing very tired of taping 30" plotter paper together to get the 48 " sheet size.

[Al_The_Man]

These tables can usually be converted fairly easily because you usually have the servo system already in place, but it depends on what make of optical trace system was on there, some of the really old ones like the older Linde tables with westinghouse trace system, you would need to replace the motors and drives. You will find a few companies listed in the CNC zone, Torchmate being one company that offers kits, but If you have a large table, I would recommend going with servo's as opposed to steppers.
Al

[Ries]

I guess it depends on what kind of work you do, and how much money, or time, or both, you have.
The commercial retrofits are neither cheap or easy- the smallest, dumbest, Burny controller costs over 10 grand. Without software. So that leaves you with the torchmate style PC controllers. Which are kind of wonky, but ok for short run use.

But I wonder why you need to?

I dont buy plotter paper- I buy a 500 foot roll of 48" wide white butcher paper from my cardboard box supplier, for about 80 bucks, and it lasts me years. I routinely cut 4'x8' patterns with the stuff. Works fine with my optical trace. I just use a sharpie fine point. I have cut things as big as 5'x9' this way, indexing the paper and steel a couple of times.

For my work, I find optical trace is much better than full blown CNC, for a variety of reasons. First, its much quicker for me to generate a pattern. Now granted, I have been drawing and drafting for over 30 years, so I am quick at it. But I also feel that its easier to draw stuff full scale- you can see the small details so much easier, and tell if things look wrong. You can trace a real part, which makes matching a lot easier.
I do a lot of changing radius curves, and the computer programs always make a mess of these. But when I draw em, I can get em right. And after I cut the first one, if there is something I dont like, I have a little jar of whiteout and a sharpie right at the machine, and I can fix it in a minute.

I recently had a batch of stuff waterjet cut in stainless steel, because I needed the sharp edge quality, and there were lots of interior lines that are just 1/16" wide- which my plasma wont do.
They came back with the familiar "Autocad Munch"- where autocad reduced nice curves into a series of straight lines or machine generated arcs, with distinct points of connection. I have to go in and hand blend those little points every time- and I have had a lot of stuff cut over the years by a variety of vendors, and this always happens. No matter what the software guys say, those digitising programs only really work on straight lines and sections of circles. Anything else throws em into a tizzy.
So for me, with relatively small part runs- say up to 100 pieces, but mostly 5 to 10 in a run, with lots of different, complicated shapes, like human figures, optical trace is quicker and better than full CNC.
Also cheaper, more reliable, and easier to train employees to use.
CNC has its uses, but it costs more initially, and then it costs more all along the way, so you have to make sure it will be justified financially, and its not just the whizz bang factor that has got you wanting.
For big part runs, every day, of the same few simple parts, yes CNC is the way to go.