Newbie- Nube need advice

[Rhinorider]

Happy New Year everyone. I am a nube here and have been lurking around for a couple weeks. In fact this is my very first posting. I want to build a plasma table, but like I said a nube and green as grass. Trying to decide what type of guides to use on drives, rail, ball screw, rack and pinon, belt? I am so confused! My table will be in the 4 x 8 size range. I am looking for high degree of accuracy. What are the pros and cons of the different guides. I am also thinking of using the Hypertherm 1000 or 1250. These units now come with onboard interface but what does the interface do, is it a full driver like a geko or is it just a plug in pin out to turn the torch and air on and off? I am leaning toward building the frame out of 2 x 4 tubing or 4" channel (already have a bunch of channel). Suggestions folks? I am sure I will be asking a bunch of questions during the coming build.

[matttargett4]

hi,

welcome to the site, ill try to help where possible but i was new not so long ago, hopefully if i make a start it will start a discussion for you.

Firstly you need to decide exactly what you will use your table for, plasma only? plasma / router combo? since this affects how it is designed, n short plasma is light and fast whereas router is heavier, more rigid (to withsatnd cutting forces) and as a result slower.

Also plasma is (relatively) low accuracy, the arc is likely less accurate than a really well built table so in my opinion there is no point in chasing accuracy if you dont need to.

Also i would establish an approximate budget, things are more straight forward if you have a heap of money but if not i think you need to be prepared to do some "engineering"!

Having just finished my build i would also look at used machines in your area, i recently saw a well used machine for less than it cost to make my 10 x 5, maybe i was scrap i dont know but i have to confess to thinking well i wish id seen that before! There i think that underestimates the hours of entertainment the research, design and build has brought me.

In terms of rails, the v groove stuff is really good for plasma since it withstands dust and dirt well, linear rails (hiwin etc) are good but suffer with dirt and are in my opinion needlessly accurate for plasma and so consumes cash that could be better spent. I think the same is true of round rails and unless you use fully supported they are no good for long runs.

as for a drive system for your x axis you cant use a ball screw on 8 feet, so its belts or r and p, i used belts since it worked out cheaper, its a bit more complicated to do but gives a decent result, r and p is cheaper in the us so it may be different for you.

You could use a ball screw on the y but again i wouldnt bother, quite a bit of weight and serious cost for good quality, z axis on the other handi think is a good place for it, short screws can be picked up from ebay worth the money, i used a trapezoidal screw with a delrin anti backlash nut sice i felt the accuracy is not so imperative especially if you use a torch height control system.

In terms of motors i would use a dual drive x axis with a slave axis in mach 3 (One axis mirrors another) and a pair of decent nema 34 motors, i used 1600 oz in but i think smaller would do the job.

Another single 34 for the y axis and then a 23 for the z, depending on where you get them from etc.

for drives if i was i the us i think id use geckos, the idea of the g203v is good, pay a little more to buy a good drive which you cant kill rather than have to change one if you make a mistake with the wiring.

Then use mach 3 to control them, seems to me the only reason you would want to use another system is if you didnt use windows as an operating system, felxibility, support and functionality are great in my opinion.

You will also need a cam program unless you want to spend a lot of time offsetting lines and adding lead ins in your drawing package, i use sheetcam and it works well for me but it depends what you are looking to do, if you have another system already etc etc.

And to the cutter, i have a hypertherm cutter without the cnc interface, if i bought a new machine i would spec the intrface, this provides you with a plug to connect to from which you can read the tip volts (for torch height control) read the arc good signal (this is a signal whichgoes high when the cutter has pierced the material and is ok to move, mach waits for this signal after piercing and before moving and will stop again if you loose the signal) and you can switch the cutter on and off remotely (works the button on the torch) so no this doesnt do anything to control your machine only makes it easier to connect up your plasma tot he system, saves having to take the cover off and find the correct wires to connect up to.

Finally to the table, i would design your table so that the material your rails bolt to, or cold rolled flat bolt to, or rollers run on etc for your axes is not welded at all, no matter how carefull you are it will bend, alll ove the place and no rail, hiwin, v groove, cold rolled flat or other is strong enough to remain flat if you bolt it to a bent base. After that make it out of what you like, if you want to cut on water to reduce smoke and dust and reduce material warping 4 inches is deep enough so 4 inch rhs or channel will do fine for that , weld a bottom on it, put some slats in the top and bingo youve got a table. For the gantry i would urge you to look at t slot alu extrusions, i found them to to be light, easy to assemble and as cheap as steel without the hassle of bending it if you weld it.

Hope some of my rabling helps you, if you have any questions about what ive said or if someone else wants to abuse me feel free.

matt

[Rhinorider]

Thanks Matt, good stuff there, you gave some good ideas. I had originally planned on just a plasma machine however you brought up a good point, if I make it for router also I could have a dual purpose machine.

If I build plasma only I will probably go the V grove route for rails, if I go dual purpose I probably go the linear route.

Drives for X axis I'll probably go with rack and pinion. Y, either rack and pinion or screw depending if I do the router build. Z, I am thinking of rack and pinion, Hypertherms machine torch comes with a rack already attached.

I think I have decided on Hypertherm 1000 cutter. What you said about the built in interface is what I suspected, pin outs that make hook up easier, plus just unplug data line and machine torch, plug in hand torch and have plasma will travel.

I will research the gantry alu you metioned as well as the motor sizes. Mach 3, and Gekos are for sure. I don't know anything about the sheet cam you mentioned I'll have to research it, any other cam software I should compare with it?

I think I will use the 4" channel I have on hand for the table, I've been thinking on size and 5 X 10 is what I have decided on. that way I can load a full 4 x 8 sheet. Yes on the water table, can't stand a messy shop.

I am building a large trailer right now in the shop, it is almost finished and ready for paint. As soon as I get it done, and make some room in the shop the table is going to be my next build.

[matttargett4]

sounds like your well on the way, i wish you success!