Newb here, just a few starting off questions..

[SlimJimmy]

Well ive done a bit of reading and searching and I have a few questions. Excuse my ignorance, I dont know alot about CNC....yet. I want to build my own CNC plasma table to build some flat 3/16" steel parts for a company im starting up involving air suspension for vehicles. I would like to keep the table as simple as possible, and dont need it very big. A 4x4 table would be perfect. I have read a few things about 'Z-axis' and needing a voltage monitor height adjustment or something? Why is this needed? Could I make the table simply x & y axis's and have the Z axis as a mechanical adjustment for when I want to cut a different thickness material? As for the parts im cutting, they dont need that high of precision, it would just be nicer for cutting circle plates etc on a CNC rather than doing them by hand. Also, the electronics side of this project (servos, motors, computer boards, etc etc etc) is REALLY intimidating me. I dont know alot about the programming side of computers besides html work (which, lets face it, is fairly simple compared to this stuff haha). As for the table...I shouldnt have too big of a problem doing the physical side of the table. I can grind, drill, weld, and all that with no problems. Can someone give me a link of someone who has built a very basic table? Also, what should I expect this to cost me (not including the plasma i choose)? One last question, what is the most common method of triggering the hand held plasma torch. Id like to be able to not have to rewire it as I will be removing it at times to use by hand. Again, excuse any ignorances I have, the veteran's of the site are probably laughing at my stupidity...lol. Anyway, Thanks!

[Weldtutor]

Originally Posted by SlimJimmy Could I make the table simply x & y axis's and have the Z axis as a mechanical adjustment table. Can someone give me a link of someone who has built a very basic table? Also, what should I expect this to cost me (not including the plasma i choose)? One last question, what is the most common method of triggering the hand held plasma torch. Id like to be able to not have to rewire

Welcome to CNC Zone.

This link will take you to a build log for my CNC plasma table.

http://www.cnczone.com/forums/showth...4&page=1&pp=15

A lot of your questions are answered there. The cutting area is slightly over 4' X 5'.

A torch height control (THC) helps to control the "stand-off" distance when surface irregularities are encountered due to warpage or other factors, & the resulting cut quality & cleanliness. It also increases the life of torch consumables by minimizing damage caused to them, especially when piercing materials.
Manual adjustment is possible, but much more difficult to control.

Triggering the plasma is usually done with a relay controlled by the software.
Depending upon your plasma machine some simple modifications may need to be done to allow for CNC, as well as manual operation.

Construction cost has many variables such as your labour, software, PC features, table design chosen, hardware used, component quality, to name a few things.

My system requires only some minor wiring to complete, & make it operational.
The table construction costs, electronic controls, and computer represent an investment of approximately $3200 Canadian, plasma machine not included. (NO SHIPPING!)

[paulC]

Weldtutor may know for sure, but I remember seeing a z axis that had a spring to hold the torch down and a set of ball rollers positioned around the torch to keep the distance from the work constant. This way the z only needed to be roughly set then the spring and rollers took care of the rest. There are sure to be both pros and cons to this approach.
Paul

[massajamesb]

I sent you a private message. Let me know if you need any more help. Although you can build a small table for under 1000. including software.

[SlimJimmy]

Okay, so ive been reading a bit more... I was told to check out xylotex.com. They seem to have a good package set up. for 300 some dollars I can get 3 stepper motors, a drive circuit, power supply, and a fan. So can I basically buy this, buy some software, figure out what method I want the stepper motors to move the axis's, weld it all up, and i should be good to go? Can I put a gear on the stepper motors and use a roller chain to move the axis's? How do I know what size gear to use so that it doesnt conflict with the driver/software. Also, if I dont care about the z-axis and I will be babysitting the CNC everytime I make a cut anyway, can I just ditch the 3rd stepper motor? I was checking out Super-Tech's plasma table and it looks very similiar to what I want to build and does not seem too complicated. What is the advantages of their rack and pinion set up?

[massajamesb]

you will probably be happier using that third motor to dual drive the y axis { the one coming/going, not the side/side}. You don't have to automate your Z axis right away, but it does need to be moveable manually. You just lose a little tip life from piercing, and cutting sheetmetal is a little harder. As far as gearing, a lot of people will gear down their steppers, so they will not spin as fast, but produce more torque. With a gantry like Super-Tech, weight really is not an issue. He has some sample cuts shown, so you can see the resolution of his cuts. Rack and pinion is nice, and very easy to set up, but will cost in the 200-300 dollar {American} range, if you dont gear them down with pulleys or gearboxes. Your software has a section in it for the step angle, and distance the stepper motor will move for every step. Go to artofcnc. com, and try a free download of mach 3. You won't be able to do much with it, and it might seem confusing at first, but look under HELP, and between that and if you register it, their are a lot of tutorials availabe, plus this site. What I did was find as many freebie CAD programs as I could, started drawing parts, and then trying to load them into the freebie Mach 3 program, so I could get some ideas. So, in the end, you need.
1.xylotex.com or hobbycnc.com three axis kit
2. mach 3
3. I highly recommend Sheetcam {sheetcam.com} for what you are doing. Plus, if you get Mach 3 and Sheetcam together at their site, you get a package deal
4. rack and pinion, chain and sprocket, timing belt and pulley, acme thread, what ever you want to move the table with
5. relay for firing torch
6. properly designed table and gantry
7. roller bearings {vxb.com has a special on some. 1.99 for 8}
8. torch height controller {optional}
9. gear boxes for stepper motors {optional}
10. machine torch {optional}
11.beer {neccesity}

[massajamesb]

By the way, what thickness metal are you mainly cutting? I would guess 1/4. What sizeand manufacture is your plasma? The xylotex kit or hobbycnc kit will probably be more than fast enough for you if you have a 30-40 amp plasma. Well, since I am still a bit of a newbie as well, is there anything else anyone would like to add to help this chap?

[SlimJimmy]

Nice, Im starting to understand this stuff . Still got more questions tho...of course! Yea, I havent bought my plasma yet, but it will be under 40 amps and I will be using it to cut mostly 3/16 and 1/4. Maybe some sheetmetal here and there. I think for now im gonna go without the automated z-axis. As for motion, I think im gonna make something similiar to super-tech except I think i will put the stepper underneath the rail and horizontal like the torchmate 3. So the software will automatically know how far the distance is for each step, I just need to input the specs from whatever rack and pinion I buy like number of teeth, etc? How would I go about syncing two steppers to work together, just reverse the wiring on one, and wire them both to the same 'port' or whatever on the driver board? Im gonna go download some of those programs and start looking into that area of things. Wheres a good place to get a rack and pinion set that will match up with the steppers that xylotex offers?

[massajamesb]

well, there are ways of figuring out the steps per inch. For me it is more trial and error. I have basic geometric shapes that I insert in cad, put through the process, then see how accurate the table draws them out. Probably more work than it needs to be, but that has been the best way I have thought of. There is probably a better way, but I am unsure. Carr-mcmaster have all the parts you need, if you download the assembly instructions at Super-Tech on the robotorch, there is a parts list at the end. I am unsure if his design is copyrighted, so you may want to make some modifications to prevent a lawsuit. As far as dual drive, you just use a rack, pinion, and stepper on both sides. I believe the xylotex driver will support both motors, you might email them for more info, they know their product better than I do. Any pros out there want to help him with his step/distance/speed questions, or have I confused him enough already?

[massajamesb]

Oh, and by the way, I am not trying to run this thread, nor make any kind of sale for any one particular vendor. BUT, if you need a plasma machine, send me a private message, I can probably help you out,Slim.