The important things to consider when looking at a cnc plasma table:
1. Size. It really does not cost twice as much for a 4 x 4 machine vs a 2 x 4. The cost is in the cnc control, the software, the drives and the linear motion hardware. Get a machine large enough to cover your future needs.
2. Torch height control, full featured. As a 34 year Hypertherm guy....I will tell you that cut quality, consumable life, and productivity will not be had unless your machine has full torch height control capability. This means; a. the ability to accurately find the surface of the plate before each individual cut, b. the ability to accurately retract to the torch manufacturers recommended pierce height, c. The ability to index down from pierce height to cut height rapidly as soon as the pierce is complete, and before the torch gets off the programmed lead -in., d. The ability to track height during steady state cutting (most use arc voltage feedback) accurate to within about .010" of the torch manufacturers suggested cut height. There are many machines sold with no auto torch height....or with THC's that only have initial pierce height functions. Height affects cut edge angularity, cut edge dross, plate warpage, and consumable life (can be the difference between 10 starts on a set of consumables and 2000 starts)
3. The right plasma system. They are not all created equaly....do your homework, consult users, consult experts. As with the table....do not buy too small. A plasma should be specified to work in the middle of its piercing capability range most of the time.
4. There are air plasma systems....which most people think about on entry level machines. The good ones cut very well and have great reliability as well as consumable life (low cost per foot of cut). There also are industrial plasma systems that are as much as 10x more costly compared to air plasma....produce better parts at faster speeds with lower cost per foot.
As far as entry level machines...I consider them as machines that can be up and running (fume control, plasma, shop cnc computer, all necessary software) for under $20k. Equipped with height control they start at about $6k. Torchmate and PlasmaCam are by far the biggest sellers, do it yourself machines using electronics from
www.CandCNC.com are also very popular....there are a half dozen other branded machines as well...most are stepper based using Mach 3 software.....can be good if built and supported well!
Steppers or servos. Most entry level machines use steppers...PlasmaCam is probably the biggest exception. Most industrial machines use servos.
For most applications under about 150 inches per minute cut speed.....steppers and servos will cut essentially the same part in most cases. Servos do have a wider speed/torque curve (properly applied to the machine they are on) and provide better ability to get to (and maintain) higher cut speeds. Servos cost more and are more complex as they require a feedback loop for accurate positioning.
I have both a PlasmaCam and a Torchmate in my home shop...each has their advantages, both have full featured height controls. I'd be happy to show pics of cuts with each machine an offer comparisons.....I will not say one is better than the other. Each has its advantages and disadvantages. I also have worked with the manufacturers of high end (read expensive) industrial cnc plasmas for over 30 years. These machines differe quite a bit from entry level machines....mostly in size and construction.....they are built to run 3 shifts 365 days, for 20 years in a tough environment.
Jim Colt Hypertherm
I hope I'm not blaspheming with the budget part, but that really is what will work best with our business model. We've been looking at Torchmate products (
Torchmate CNC plasma cutters, CNC cutting systems, CNC plasma tables, and CNC Routers.), and a local guy (
Riggen Industries - CNC Cutting Tables) quoted us ~$5000 for a 5'x2' (gantry on the long axis so we can slide a full sheet through). For that price we'd be looking at the torchmate 2x2.
The local guy has only been in business ~5 months, though, so we have worries about dependability as his design hasn't had much time for testing. He uses steppers instead of servos (he claims improved performance due to servos being susceptible to interference from HF plasma arc.) He also has a full Z axis which can be used with arc voltage to compensate for non-flat sheets, and includes computer, Mach 3 control system, some CAD software and Sheetcam.
Any suggestions for other manufacturers out there? Our largest part currently is a 24" disk with tabs I can arrange diagonally to fit in a 24" box, but we'd love to be able to slide a 4' sheet through without having to cut it up first (actually metric sheets, so 1250mm (49.2")).