what is needed to build a cnc table(plasma)

[Apples]

Hey every one!

I am new to this cnc stuff. Can some one please tell me what is needed to build a cnc table and recomended brands.

example: 1 you need a table
2 linear rails, home made , bought etc
3 stepper or servo motors

and on and on.

I need like a parts list so that i can work out what i need to buy and then i can price up the whole machine/system.

I will be using it as a plasma cutter table and want a cut area of 8'x4', so i can cut a full sized sheet of steel. I have been recommended a ipm speed of up to 350-400. So do i need ballscrew, rack and pinion, gear reduction etc etc. Hopefully anyone else in my situation can learn what to do as well. Because at the moment i read about people using gecko drives xyloto drives steppers servo's turbo cnc etc etc.

So if some one can help me work out what to do that would be absolutley wonderfull.

Cheers Apples, from Australia

[ynneb]

The purpose of this forum is for each of us to share what we are doing so that others can then make those descisions from what they have learnt. If you dont want to design your own machine then you can always buy professional plans from a cnc designer company.

I will say that Rutex is an Australian company and makes great servo drive cards for any CNC machine.
I see that they also offer flame cutting software too. You might also want to consider using Mach 2 to drive your cards.

Good luck on your journey.

[Hobbiest]

You need the raw materials for the frame, steel or aluminum. You also need your linear ways, and actuators (lead screw, or rack and pinion), and then the stepper, or servos, and corosponding drivers. Go to www.mcmaster-carr.com, and type in linear motion, and you will get a lot of results for these items. There are many other websites as well, but this is the only on I can remember the name of! The problem you are likely to face, is that you are down under, when most of the stuff comes from up over! Go to Google, etc, and type in homemade CNC, and such searches to get examples of what peaople have done for low budget. The most important things that you need are perseverence, dedication, and drive.

[balsaman]

To go 300 IPM count on at least $1000.00 to $1500.00 for the drive. You need to go rack and pinion. Home made linear system is a posiblity because of the low forces involved and reletively low tolerances.

It's a monumental task for a first try...

Eric

[Apples]

Thanks for that input. Well i am prepared to pay around $8000-$10,000 for a complete plasma cutting system. That is including the plasma cutter, ie. all i need is some sheet steel to start cutting.

How do i know what size stepper motors to use. will NEMA 34's be okay or somthing bigger?

Apples

[balsaman]

Nema 34 comes in all configurations and torques, so they will be ok if you get the right ones. I might be tempted to get a servo setup.

That being said, the motors and such is the easy part. I would concentrate on the mechanical design and build first. Once you are 60% built, then go out and get your self a drive system. Probably gecko or similar. Way too many people buy the drive first. Some months later you see the drive on ebay, or as a freind of mine calls it, e-dumpster.

Eric

[Costas]

Im interested in building one as well, Ive recieved sales documentation from a few companies,
(plasmacam, torchmate etc...) but some of my applications require cutting areas of up to 5' x 10'.


The only ones that have a plasma cutting area that is large enough are out of my current budget range. (max 7k) and the ones that fall into the budget have a smaller cutting area (around 4' x 4')

[Apples]

Hi Costas, what are you going to cut out that is 5'by10'? I would be interested to know. Also instead of using costly thk rails or similar. i got prices today $486 per meter of rail then about $217 per each carrage. so thats a lot of cash. i am going to use stainless steel pipe 50mm(2") and use normal roller bearings spaced at 120 degrees apart ie in a triangle. 25mm bearings withe 10mm internal diameter are only $6 each. all up linear setup should cost only $200-300. should be accurate enough as dad says that this setup has been used for ages.

so i think that i might make a table with a cut area of 3m by say 1.4m because sheets of steel 4-5mm thick are only sold in 3m lenghts nothing smaller. so if i am using this for a plasma cutting service i think that i should make it as big as possible in case a customer wants a large piece cut.

Anyway i await your reply Costas

Cheers Apples

[traveler]

I am currently useing a linear guide but soon will be changing back to just a shaft ( or tube) with ball bearings mounted on the top and sides of a carriage to guide my bridge. The plasma generates a lot of dust and dirt that keep me cleaning the linear rails and bearings often. When I don't clean the rails the dirt accumulates in the linear bearings and causes enough drag that the stepper motors slip and I then lose accuracy in the cut. The simple bearings didn't give any trouble but I thought linear would be better, I was wrong,Oh welllllll live and learn. Besides you can save some big bucks with the ball bearing/shaft method as opposed to the linears

[traveler]

More thoughts on this, I used ball bearings only on the top and sides of the guide rail because gravity works so well here that I don't need to hold my carriage down. Also I made my table 10 feet long so I can move my carriage to the far end out of danger of bumping it when loading sheet stock. I sometimes cut 1" plate with oxy/acet machine torch and it is heavy enough that it would do real damage to my carriage or bridge if it were to get even a light tap.

[Apples]

how accurate is the pipe and bearings setup?

What is the cut quality like when cutting with oxy, have you got some photo's you can email me?

megballard@bigpond.com

Cheers,

Apples

[traveler]

I used 1-1/4" cold rolled shaft for the guide side and made a bearing mount that incorperated excentrics so I could not only adjust the fit of the bearings to shaft, but also square the bridge (gantry). The accuracy of cut is dependent on how straight your shaft is. One good reason for a fairly large diameter shaft is that it deflects less. I have cut a 4' X 8' sheet length ways, cleaned the dross, then fliped one side over to use a factory edge as a straightedge. Feeler gauges showed a maximum drift or runout with this setup was less that .010, well within my range for tolerances for the things I build. By the way a technique I use to prevent rust on the CR steel and keep the shaft clean is to wax it with auto wax, no rust, no problem.

Remember we don't have "tricks" of the trade, we have techniques to solve challenges
Remember also my motto"never set a pace you can't maintain"
Have fun at whatever you do
Traveler