Do it yourself CNC Plasma recipe' **Post up**

[carbidecraters]

The purpose of this thread is to enable a crafty person/s the knowledge to make a CNC plasma table

Ok so as far as I know you need

1. A sliding X and Y table with a rack and pinion
2. A Z on some sort of stepper or servo
3. A set of steppers or servos
4. Some type of controller for the steppers or servos
5. Software

Am I missing something?

Who, what where why and how do you get the steppers? Servos? Controller interface? Software?

This thread is so we can dumb it down a little and make it easier for me and folks like myself to understand exactly what it takes.

[vacpress]

there is a rather nice-seeming set of free plans out there somewhere in the file bases. it is sort of awkward to view though, being arc c or d size pages, all in 1 dxf file...

still, alot of work someone did... check that out.

[vacpress]

also, you are probably missing alot...

1. a plasma gun appropriate for automation
2. power to run this thing
3. some sort of 'torch height' adjustment circuit & supporting software
4. there is more, i just cant remember, not myself being particularly interested in plasma at this point.. however, the term 'charge pump' comes to mind.. that could be the same as torch height though...

most people seem to use welded steel to make the frame, with a sort of honeytcomb pattern for the cutting bed... it seems like many plasma setups are appropriate, and mach 3, as well as some other windows, diy-type cnc software will work.. because a plasma torch is much lighter and has no contact, the whole machine can have slightly different priorities than a wood router...

speed is important, as opposed to raw ridgidity.. of course it also must be plenty ridgid to withstand its own forces created by moving a 40(ish?)lb gantry at speed..

really. there is lots of info on this in the forums. lots. full machine builds, free plan sets, in depth discussion of torch height control.. links to good web resources and sources for bits of equipment and software...

FORUMS!

[carbidecraters]

I have read the other threads on plasma table building and have downloaded the plans. I really couldnt read the plans well at all and they showed zero dimensions. I have seen the tables members have built but every thread is missing valuable information. I did include the Z axis in my first post however

[vacpress]

well. the Z needs some sort of automatic height adjustment circuit to be built.. i beleive it adjusts the distance between torch and workpiece depending on the current draw of your torch... something like that...

i will stop replying now. i dont know enough about this topic.

i do know that it would take you weeks to read everything about it in the forums...

[carbidecraters]

Yup been reading for months now. Yes a voltage height controller can be bought for roughly 2400.00 from torchmate and this would control the Z axis for plasma and you would need a eye for a router head.

[vacpress]

what is the 'eye' ?

also, ive seen DIY circuits for torch height.. i beleive that it is totally doable on a DIY basis.. and would likely cost more like $100.00 to 200.00

[Torchhead]

Or you can buy one that is assembled and will work directly with MACH3 from Campbell Designs for $350.00. A stand-alone THC for 200.00 would be a miracle even if you didn't count the 100 or so man-hours in software programming. It's more than just measuring the voltage and moving the head up and down.

I actually posted a DIY THC schematic a couple of years ago. A grand total of three people I know of actually built it. Two of them wanted me to help them troubleshoot it and then teach them how to interface it and use it....I removed the post.

I still am wondering about the "eye" concept. Not sure how that has anything to do with routing where you need precision (.001) depth control and the ability to do multiple passes all perfectly aligned...but hey, I haven't seen everything yet!

[carbidecraters]

You use a tool eye when your engraving

[carbidecraters]

So basically after the table is built I need a drive board for each axis with a power supply? A program to interface with the driveboards and a decent cad-cam (which we already have)?

[Torchhead]

The generally accepted set of components that most builders end up using are:

Steppers or Servos with a drive for each motor that will take step and direction control signals. The Servo drives most used are made to close the servo loop at the drive and the software controller "thinks" it is talking to a Step & Dir (which it is) drive. The most popular for larger motors is the Gecko units. Smaller steppers can use the Xylotex or HobbyCNC multi-axis drives.

A power supply rated to provide the voltage and current for your motors. Average current for the chopper type drives like the Gecko or Xylotex is roughly 50% of the total current ratings of the motors. Voltage is ususally limited by the Drive module ratings. Gecko's top out at 80VDC while Xylotex is around 30VDC. Steppers are current devices and you pop them with higher voltage to get the coils to charge faster so a value of 10 to 20 times the nameplate number is common. Servos are voltage devices and you should not run them above their rated voltage.

Some form of breakout and interface card for the PC paralell port. While some units like the Xylotex do not need the buffering from the parallel port they do need the isolation provided by opto-isolated inputs back into the port. It's more about noise and ground loops in that case> Other drives like the Gecko need more signal than the average parallel port can supply thus the need for a buffered breakout for the Step and Dir signals.

Controller software that runs on the PC to send the Step & Dir. The most popular for Windows is MACH. TurboCNC is avaialble for DOS and EMC for Linux. MACH3 has a lot of features that make it very functional for all kinds of cutting.

A form of CAM that will take a line drawing and let you define how you want the machine to cut it: What tool to use, How many passes, direction of cut, offsets, lead-in's, special corner cutting, etc,etc. Some CAD/CAM packages have botht he drawing and CAM part but it has been my experience that one or the other is ususally a compromise. I like the flexibility to change one aspect of the equation without having to throw it all away. I use SheetCAM as my CAM since it offers features (especially for plasma cutting) I can't get in the combo packages.

There are other pieces as well. Sometimes over-simplification can cause problems. In each and every part of a CNC table there are technical issues that if ignored will cause problems later in the operation. There are a lot of things to have to get your arms around on a project of this magnitude. The availability of others on this list and on the other lists like CCED (9000+ members) is a rich source of information. While even that can get confusing since you have to sort through lots of opinions and arguments about the number-of-angels-that-can-dance-on-a-pin at least there is the wealth of information out there.

The good news is that a lot of the software has demo versions that you can try before you buy. All you need is a PC and some time.

[mlaws1172]

I just happened to run across this thread and one post said there were no dims on the plasma plans. If you look at "FREE PLASMA TABLE PLANS" on this site, they have full dimensions, a cut list, and step by step instructions.
There are quite a few that have used them as a starting point.
The plans are zipped and then in dfx. If you do not have cad, you can download A9Cad from A9Tech.com. The program is free.
This plans along with CandCNC boards, Gecko drivers, Sheetcam and Mach3 CNC software will make a pretty nice plasma machine.
And it is hard to beat the price.
Mike