Any experience with cnc plasma tables?

[jason0012]

I have been toying with the idea of a cnc plasma table. It sounds cool to be able to zip out flower petals, leaves, spoon/shovel blanks ect. I have a plasma cutter I have not yet used and some of these tables are getting pretty affordable. I am not planning to make it the center of my business, and dont intend to have loads of plate lying around. Looking at the options I am baffled. Some units with the same apparent features can vary widely in price, and i am not really 100% sure what to look for. The ESAB crossbow is $12000+ and a pretty decent looking and compact machine, but there is a similar made in china version on amazon for $1800 (?). I dont have a huge budget so $12k is kind of out of reach. Looking at machines with tables there are even wider swings in prices, and advice i have gotten from welding forums is both confusing and unhelpful. Any of you with such a set up that can help point me in the right direction?

[Kozzy]

Can of worms kind of question.  Yes, one can get a chinese version...and have the hassles of trying to find replacement parts when something fails.  That might be possible or it might mean throwing part of the control away and starting from scratch.  It's a crap-shoot.

The other issue is underpowered steppers or servos.  Underpowered doesn't just mean the motors here:  It means motors, amps and power supply.  The power supply feeds the amps which control the motor movement via pulses from the controller (computer) and that whole train varies wildly.

Additionally, physical structure of the frame and gantry vary wildly--from good sturdy designs to total junk that will collapse if you lean against it too hard.  The material support grid on cheap units (a consumable item that will need regular replacement) is often inadequate for cutting anything small.

Here are some generalities to look for:

If you can get one that uses standard Gecko drives/amps in the system, you will be FAR better off if something goes wrong.  Gecko brand stuff is well supported and documented and pretty easy to work with.  They even made one that's referred to as the "vampire drive" because you can't kill it--they put in a ton of internal protection so it doesn't die without some serious bad stuff going on.  Barring geckos, just make sure it uses brand name stuff and not something unrecognizable.

Servo vs stepper.  Most of the low end tables..and many of the high end...use simple stepper motors.  With those, the computer tells it step and direction but never knows if the motor actually made those steps.  Sometimes steppers can get lost (lose steps or worse) because of this lack of feedback to the computer.  Servo drives in general have an encoder on the motor that tells the motor's position.  That way, if the motor isn't doing what the computer tells it to the computer has the feedback to either self correct or shut down if it can't figure out what to do.  

It gets a bit into the weeds but a servo motor can technically be a standard stepper motor to which an encoder is added...but in fancier systems is more complex in the motor configuration that actually positions the armature rather than steps it from one pole to the next (or half/quarter steps to get into even more weeds).

You want torch height adjustment to be automatic.  That costs a little more than the cheapie systems.  Plasma cutters need a pretty specific gap above the material they cut in order to get the cleanest edge possible--and auto torch height makes sure that can happen.

Water table can make a HUGE difference in ability to have such a thing in your shop.  Plasma cutting is extremely messy and usually quite smokey.  Water table cuts that down by 90%.

Most makers really push their own software.  Some is good, some not so good.  Be sure and test drive the software to see if it works well for you.  Mach III (or IV) software is available pretty cheap for these machines and is extremely reliable and easy to use and with a good fan base.  Some makers opt for this as their standard just because it is such a reliable standard.  In any case, make sure the software fits you like a glove and isn't like wrestling an angry badger to use.

Dual vs single motors on the gantry travel (length, not cross travel...Y axis on most machines):  There is some debate on the subject but the gantry will generally stay a lot straighter when it either has dual motors (one on each side) or a system that drives both sides via a cross shaft.  The cheap tables drive only one side and that allows the gantry to skew across the width..making parts un-square or causing binding (and binding/drag causes lost steps on stepper motors).

Support:  You want a place that gives excellent support..for instance lots of good training videos and the ability to talk to a real person if you get into trouble spots.

One could go on for pages with the minutia of details but the above is kind of the rough highlights.  

Without violating the TOU with advertising links, I suggest you poke around the site of a CNC plasma table maker in Bend Oregon.  Might be a bit above your budget but there is some good info there.  

 

[BIGGUNDOCTOR]

Or find a good used unit. I bought a Koike Aronson 5'x10" at an auction. It was used for one government job, then stored. It was $27,000 new, I bought it for $2,700. Now I need a place to set it up.....