Building a plasma table, need advice.

[Lee Roberts]

This is a copy of your original post:

I would like to build a cnc plasma table but I don't have the time to sit in front of the computer for hours to research everything, so if you guys can help pointme in the right direction that would help save me allot of time :-)

Ideally want to build a 2.5m X 1.25m work area, I would like it to have quality rails, ideally servo motors, and proper software etc

ideally would like to aim for £5k on the build but can go above that if needed, already have the plasma.

any help I can get will be greatly appreciated.

I'm still reading the other posts, for now...

.Me

[Robin Hewitt]

I would like to build a cnc plasma table but I don't have the time to sit in front of the computer for hours to research everything, so if you guys can help pointme in the right direction that would help save me allot of time :-)

I went through this. I went to cnczone and noticed that everyone made the same mistakes. Have they changed?
They weld up enormous constructs in steel, find the tool does not fly in the way they expected then try and fix it with THC.
The torch Z axis is invariably driven by an enormous stepper motor because stepper motors seem to come in packs of 3 and they cannot see any other way to do pierce and cut height. The THC then has to convert analogue to digital so everything becomes tortuously complicated controlling stepper coil current when all the cables are next to a plasma arc.
Apparently the only possible plasma unit is the Hypertherm because it has a very nice head for cutting thin stuff. Being Americans they cannot possibly buy a matching low power tool it has to cut 2" armour plate or nothing.
Mostly they will cut plates about 1 to 2 feet across but they make huge water tables and pump tons of polluted water because they can.
I nearly overcame all this, but at the last moment I discovered that the 5M pitch pulleys I had based it around had enormous backlash. I got disheartened after all that work,it got put on a back burner and is still waiting.
Anyway, there are a few snags you might want to think about, assuming you are still here

[superclarkey]

I'm still here, thanks for the advice :-)

i dont want to build anything over kill, seems pointless when I see the most important factor being control and precision, it's not driving any force so I fail to see why stepper motors are the choice for so many plasma tables when they draw so much current regardless of work done, closed loop servo seems the way to go and I don't think they need to be very big.

be interested to know if people run servos direct drive or step them down with ratio to give more accuracy, I would like to reduce it to so that I have no backlash in the drive.

is there a go to liner rail with screw drive already built in for the X and y?

That was a question i wanted to know, why can you not pump the water down the drain?

And yes guys take it on board I pissed you all off, sorry :-)

[Robin Hewitt]

You are worrying about all the wrong things. Maybe you have to build the plasma table in your head and get it out of the way first.

The water is polluted by the green guck you put in it to stop the bed slats from rusting.

[Boyan Silyavski]

I'm still here, thanks for the advice :-)

i dont want to build anything over kill, seems pointless when I see the most important factor being control and precision, it's not driving any force so I fail to see why stepper motors are the choice for so many plasma tables when they draw so much current regardless of work done, closed loop servo seems the way to go and I don't think they need to be very big.

be interested to know if people run servos direct drive or step them down with ratio to give more accuracy, I would like to reduce it to so that I have no backlash in the drive.

is there a go to liner rail with screw drive already built in for the X and y?

That was a question i wanted to know, why can you not pump the water down the drain?

And yes guys take it on board I pissed you all off, sorry :-)

OK. if you are serious from now on, you will be helped.

Lets start from the beginning:

-How big you will like the plasma table to be? working area
-Z travel?
-do you plan to cut square tubes? Round tubes? if yes how long?
-aluminum , welded steel, mixture or aluminum profile structure?
-only dedicated plasma machine or you will try to do other stuff also?



Some answers:

-Hiwin 20 rails is best, same price as 15 size but easier to mount and overall engineer. There is one other rail i like better but is more rare- MGW Hiwin, though its ideal if you use only one rail on Z and X. Which you could do with the HGR also

-1605 ball screw for Z, 1610 for X. Nope, better design them yourself and order them from China. later we will point you from where. Y? still not clear until you say what length will be your longest axis. If you want to cut 2500mm long - rotating ball screw nut both sides is best
So yes, if you dont go bigger than 2500mm on one axis it could be all ball screw machine which simply put is much better than any other option.


-dedicated THC is a must, i dont know whats new this year, but last year Neuron was best here in EU. It controls directly your Z axis and has all the necessary functions, like pause at corners and so on. I have one but not the time to make the plasma table. Avoid cheap THC which are not dedicated/ can not control axis directly/

-even cheap servos with 2500 encoders have enough resolution at 1:1 at one revolution 1610 screw will move 10mm so 2500/10=250 ppr so 1mm/250=0.004mm resolution at speeds 30m/min, which is really fast
depends on design probably 200W or 400W servos for the machine. I will point you from where to buy cheapest in internet.

- I don't like water bed machines. Too much hassle if not a heavy production . When i make my plasma cutter it will be air, sucked and vented into the table

Most importantly- don't rush buying until you have completed the design. If you are lazy or don't have time to design, search for designs to buy, then show us so we could help you choose. I do also bespoke designs these days. Post a job request in relevant forum section . Dean and maybe others make custom machines.


So as you see, there are options. I for once was very busy today and just sat down to respond you but was amazed at the development of your thread. So lets take life easy and see what we can do here.


If machine is meant small size, there are other options. Thats why you were pointed to read build logs. There are modular designs with elements from china, that are quite suitable for 1x1m machine.


Hope that helps

[JAZZCNC]

-1605 ball screw for Z, 1610 for X. Nope, better design them yourself and order them from China. later we will point you from where. Y? still not clear until you say what length will be your longest axis. If you want to cut 2500mm long - rotating ball screw nut both sides is best
So yes, if you dont go bigger than 2500mm on one axis it could be all ball screw machine which simply put is much better than any other option.

Did you miss the word PLASMA.!! . . . .Ballscrews with rotating nuts.???????????????????????

[Boyan Silyavski]

Did you miss the word PLASMA.!! . . . .Ballscrews with rotating nuts.???????????????????????

I did not. what do you suggest for 4x8 table? belts or RP? Same price. So why not ball screws?

That's why i asked him what length. Did you check recently prices for *belts and pulleys* or *RP+pulleys and belts* . Exactly same as for ball screws. Until we don't know what exactly he intends to use the machine for it irrelevant to discuss further.


I personally say for Z belt, for X ball screw and for Y -RP, but that will confuse him and others who read further. There are many ways to make a plasma machine. Did i tell you that the big commercial plasmas use Ballscrew on all and RP on Y, and mind that - 2 motors with brushes on each side of gantry, so they brush rails for dust not to damage Hiwin seals

[JAZZCNC]

Boyan we know exactly the use it's in the title "PLASMA TABLE". Also have you seen the crap that comes off plasma machine.? What do you think that will do to ballnut rotating at high speeds along static rod effectively covered in grinding paste.???

You'll be hard pushed to find many commercial plasma cutters using ballscrews other than on Z axis. 99% will be helical R&P with more than enough resolution and easily achieve high feeds without stressing anything.!

[stirling]

-dedicated THC is a must, ... Avoid cheap THC which are not dedicated/ can not control axis directly

@Boyan - Can you explain please?

[Boyan Silyavski]

@Boyan - Can you explain please?

Hi,
Nothing against cheaper controllers. But you should know the answer to that question better than me, having in mind you are selling THCs. What is the reason that are you asking me? There are more ways than one to skin a cat . This is just my opinion for my future plasma cutting table. As i said i have already bought the controller for myself -the Neuron.

But here is your answer:
I am starting a new trend for myself / or am i stupid or getting wiser / :The more the *hardware way* possible and the more away from * software like windows, linux ,mach3 and plugins* possible, the better. I think i am starting to get industrial

So IMHO now is even the time to try a dedicated hardware controller like the chinese sell for around 400-500euro. I have seen videos of it working. Or the chinese don't know how to cut steel with that industrial revolution there? Of course further investigation is due. But yes, all in one for that money is a no brainer.


I am sorry guys/ EU and USA manufacturers of boards, software and so/ , but if you follow the trends, in a couple of years DIY machines would be chinese from electronics to rails. Who doesn't believe me just remember 5 years ago when nobody had ever heard of "water cooled spindle". And DIY machines had Kress or Dewalt routers . Hey right now i am running 150 euro dedicated offline controller/ from yesterday/ on my i may say almost industrial CNC, which does a better job than a couple of combinations that cost as 10 times as more
Not to speak of the Leadshine and similar drives and motors. Where are the Geckos that we imported from USA 5-7 years ago? Its time to wake up


Anyway Sterling, nothing against you or the board you sell. I say- its even great that you could shed some light on things. I would have bought your board a year ago if i knew that i would want a Hypertherm now. Its never late to be wise. In short I want a Hypertherm and a HAAS for New Year present