CNC Plasma Table Motor/Electronics/Interface parts, in 2020? ........

[Smokey]

I'm building a small cnc plasma table of my own design (about 24in x 24in work area) .  The mechanical aspects are mostly finished, and now I need to select the motors, drives, and interface components and integrate those into the system.  I only need 3 axis now, but I may want to add another 2 axis at some point. 

Since this is a plasma table, not a router, there is essentially no cutting force so the motors don't need to be nearly as big.  I'm looking to go as inexpensive as reasonable since this is for my personal garage use, not a 24-7 business type use.  I'm totally willing to do my own integration, but I don't want to reinvent anything I don't need to.  Given the maturity of the tech and widespread use of similar components in lots of systems, there should be lots of good options now that may not have existed at a reasonable price before. 

What do you guys recommend now in 2020? 
What have you used? 
Any luck with cheap import ebay stuff?
Does it make sense to look for a cnc machine stepper package or part out the motors, drives, and interface separately? 

Thanks!

[Smokey]

I also need a Torch Height Controller.  I have a Hypertherm Powermax30 that has no THC support at the moment, so I would need a universal controller.  If I had to I could upgrade but that would suck.

[rvalente]

IN the DIY field you've pretty much all possibilities, there is also the good and the better.

First things firsts, what would be your CNC controller? Mach3/4?

These usually runs with controller boards, usually ethernet is better (smoothie board) + stepper drivers, I would say for you the cheap toshibas based are just fine.

Recently, ethercat has been leading the way, check leadshine drivers, there is no interface board, just a daisy chain ethernet cable.

As for the torch height, sorry, never made a plasma cutter before

[Smokey]

Getting ready to post a dump of the research and options I've been finding for stepper kits for plasma tables. 

I've been in automation for a while now, and if I was going high end build for a real production type machine I would totally put together a brushless servo system and I agree that especially for something like this, EtherCat would be really nice.  Problem with that option is the cost vs performance.  I feel like, especially with a plasma table, the motion requirements are so low that the advantages of a servo over stepper are really small and the size of the machine and number of axis I'm talking about won't make quite the rats nest of wiring that makes Ethercat really attractive.
I have this conversation with one of my friends periodically.  When he wants a new piece of equipment he just goes and buys the low end pro gear and gets working, but I spend a considerable amount of time getting to the bottom of all the options to find the most cost effective solution even if that means making large parts of it and spending more time getting it working.  I try to justify it by saying I'm learning more along the way, but he's probably the smarter one in the end.

[Smokey]

Kits with motors and drivers:
They are not all equivalent.  The motors are different and some have components the others don't, like controllers and interfaces and more axis.  This is more of an overview of options than a direct comparison.
I also haven't used any of this stuff yet, so I can't attest to the quality or functionality. 
From Higher to Lower Cost:

1) CandCNC BladeRunner Dragon Cut 300-4 (Bundle) = https://www.candcnc.net/store-home/bladerunner-dragon-cut-300-4-bundle/
$2,525.00


2) CNCRouterParts 4-Drive DIY NEMA 23 Electronics Kit = https://www.cncrouterparts.com/4-drive-diy-nema-23-electronics-kit-p-75.html
$765.00


3) Probotix 3-Axis Monster Hybrid Stepper Motor Driver Kit = https://www.probotix.com/CNC-CONTROL-SYSTEMS/CNC-CONTROLLER/3-Axis-Monster-Hybrid-Stepper-Motor-Driver-Kit
$499.95


4) BuildYourOwnCNC 3 Axis Electronics Combo = https://buildyourcnc.com/item/electronicsAndMotors-3axis-425-elcombo
$390.00


5) HobbyCNC HobbyCNC Combo Kit = https://hobbycnc.com/product/combo-kit/
$310


6) OMC-StepperOnline 3 Axis CNC Router Kit 3.0Nm(425oz.in) Nema 23 Stepper Motor & Driver = https://www.omc-stepperonline.com/3-axis-cnc-kit/3-axis-cnc-router-kit-30nm425ozin-nema-23-stepper-motor-and-driver-3-dm542t-23hs45.html?mfp=16o-ship-from%5B59%5D
$188.42

[Smokey]

Controllers and Interface Cards:
1) GeckoDrive G540 4-Axis Digital Step Drive (Drives + Parallel Interface)
$269


2) Warp9 Ethernet SmoothStepper (ESS) Controller = https://warp9td.com/index.php/products
$180


3) CNCdrive UC400ETH ethernet motion controller = https://www.cncdrive.com/UC400ETH.html
$130


4) CNCdrive UC100 USB motion controller = http://cncdrive.com/UC100.html
$95


5) [Generic] Parallel Port 5 Axis CNC Breakout Board Interface = https://www.omc-stepperonline.com/5-axis-cnc-breakout-board-interface-mach3-cnc-router-kit-st-v2.html
$10

[Smokey]

Torch Height Controllers:

1) Built into CandCNC full system.  See Above in Kits.
$2525+

2) TMC3in1 + SmoothStepper ESS = https://warp9td.com/index.php/faq/faq-mach4#HeightControlTMC3in1
ESS + TMC3in1 = $180 + $399 = $579


3) NeutonCNC THC = https://neuroncnc.com/products/003
$469


4) Proma THCSD Up/Down = https://www.eagleplasma.com/proma-thc-sd.html
$350




...

CandCNC  Universal Plasma Connection Kit (For machine without CNC port) = https://www.candcnc.net/store-home/universal-plasma-connection-kit/
$142

[0db]

According to LinuxCNC, the parallel port is the best

But read here

3. Why isn't there support for <interface>
LinuxCNC supports two different styles of realtime, kernel-space realtime with RTAI and user-space realtime with PREEMPT-RT (called "uspace"). In RTAI, Linux hardware drivers cannot be used from the realtime context, so it is not possible to reuse them. "uspace" is new in LinuxCNC 2.7. For this reason, almost all hal hardware drivers have been written in the lowest possible terms: inb(), outb() and the like.

• 3.1. Ethernet
  Several people have had positive experience with "uspace" realtime and UDP ethernet communication. However, realtime ethernet performance depends on the Linux network driver itself having good realtime performance.
  In principle, the RTAI realtime kernel has a network interface, RTnet. However, no one has ever submitted a driver that uses RTnet. It is not clear whether RTnet as written will work with HAL's timing model.
  
  (Note: A working ethernet HAL driver using RTNet is currently being developed, see rt-8p8c.)
• 3.2. USB
  In principle, there is an RTAI project to add USB support, rt-usb. However, no one has ever submitted a driver that uses rt-usb. It is not clear whether USB can meet HAL's timing model.
  With "uspace" realtime and the hm2_7i90 driver, USB ethernet dongles fail to work reliably at a 1ms servo cycle time.
• 3.3. RS232 Serial
  Many PCs have a common, easy-to-program chip for RS232 serial interfaces, the 16550 FIFO. However, the top speed is 115200 baud. In 200us, only 16 usable bits can be transmitted in each direction (10 bit times per character, 2 characters = 173uS), which is not enough to send DAC commands and retrieve position feedback for multiple axes.

4. Why not use a micro controller over USB as a step generator
Short answer:
because it breaks the idea of the project - LinuxCNC as a machine controller.

Long answer:
If you wished to do rigid tapping with your USB-based controller - you would have to add the tapping code to your microcontroller.
USB will not allow reliable communication between the motion controller (LinuxCNC) and the motor controller (your micro).
Multiply that by other options and now you have basically made your micro controller into a motion controller.
This has been done in a fork of LinuxCNC - USB to a mesa 7i43 card in the araisrobo project (now uses machinekit AFAIK).
Now if someone added some cool option to LinuxCNC's motion controller you wouldn't be able to use it until you added it to your motion controller.
It also doesn't allow LinuxCNC's built-in scope and meters access to the micro controller's internal test points.

Dumb hardware
By using relatively 'dumb' hardware, we avoid that scenario - whatever LinuxCNC can do it can do with all hardware that supports the basic requirements.
You can even run an analog servo using the parallel port - just the performance would be low. So is it a waste of time for simple I/O stuff? Yes, I guess you could say that - but when you look at the bigger picture it makes sense - LinuxCNC does a lot more than just simple step driven mills.

We prefer that the motion controller is in one place - LinuxCNC.

Now if you could figure out how to get USB3 to be low latency relatime...now you are talking!

[0db]

5) [Generic] Parallel Port 5 Axis CNC Breakout Board Interface = https://www.omc-stepperonline.com/5-axis-cnc-breakout-board-interface-mach3-cnc-router-kit-st-v2.html
$10

is there any schematic that internally describes this board?

[Smokey]

This is a different board without the relay, but I think it's essentially the same otherwise.  Just some optos and a power supply.
https://www.electronics-lab.com/project/parallel-port-breakout-board-with-buffer-for-cnc-routers/

[rstofer]

Don't forget to include the mass of the product when figuring the required  motor torque.  I would be cautious about small motors.  Look around and see what the commercial equivalents are using.

[Doctorandus_P]

I've bought around 6 Nema23 motors with drivers and 2 Nema34 motors with drivers from Ali, and they all work.
The "closed loop steppers" are significantly quieter in operation, and well worth the price difference.

In the bigger CO2 lasers there is often a small timing belt on the motor to an intermediate axle, and then a cut open timing belt to move the gantry, and it usually adds a extra gear reducion of 1:3. These intermediate axles can be bought as spare parts for reasonable prices. I'm not sure if plastic or rubber timing belts are the best option for a plasma cutter. You may want to consider a regular bycicle chain, but don't make the sprockets too small, or you will get into trouble because those sprockets are polygons (with each teeth) and not "circles".

It's probably a good idea to use these.
Stepper motors loose torque at High RPM, (This gets serious above 600RPM, depending on power supply voltage) but with the 1:3 reduction you need less torque from the motor. Result is higher resolution, and more freedom in choosing the diameter of the pulley's.

If you want to go LinuxCNC. I guggest to add a MESA FPGA card. I think they cost around EUR150, but the extra reliability is probably well worth it.

If you want to go cheap...
I've burned a Grbl clone for an STM32 into a "Blue Pill" and added some good old 74LS line driver chips to drive the opto couplers in the stepper motor drivers. Soldered it all on Matrix board.

I use bCNC for driving Grbl. It's a simple program (for today's standards) but it does get the job done, and it has some nice features for post processing your CAD files. It can add stuff as tool offsets, lead in and out.
It also has special features for cutting plotters, which add "swirls" in tight corners.
I do not know of special features for plasma cutters in bCNC. Would any be needed?
bCNC is also written in Python, and there are some 20+ plugins such as spirograph generators, puzzle pieces and such. You can study those to write your own plugins for special functions if needed.

bCNC also has a Z-height "probe" function built in.
Original function for this is for PCB milling, to take of the copper, and leave the glass alone, but the same feature can also be used for your probe height compensation of course.

[beanflying]

Bit of a necro post but interested if you got your table finished @Smokey?

I picked up a cheap and virtually unused Chinese 6090 router a few months ago and I brought a 45Amp Plasma around a year ago and a new compressor to go with it 6 months earlier (preemptive purchase  ).

I have done a fair bit of looking around at options for making al the bits fit together for a small table but likely when space allows a larger 1/2 sheet one. THC is a bit of a must and Proma offer a few standalone options or the all in one version I opted for as I am currently fairly time poor to want to fuss around with a more ad hock system.

Tried the software out that is available with it and no fuss if that is all you want and with a generic Plasma post processor it looks like it will work fine with code produced out of Fusion 360 (simulation mode worked fine) or just with dxf's generated by it or any other CAD package then using the built in CAM part of it.

Part of the benifit of this system is you can feed it (non HF) raw arc voltage and the interface has really good separation back to the controller and PC. Cracked it open and yep 2-3kV without doing any numbers.

Manual and software here https://proma-elektronika.com/ and there is some ok videos on YouTube from him and others on it as a solution and also farcebook  support groups.

Ordered the steel for the water table so things being well a month or two until I make some cuts.

[coppercone2]

I thought AVE was working on this a while back?

[Smokey]

Bit of a necro post but interested if you got your table finished @Smokey?
...

Like so many things, this one got put on hold for something more important.  Then I changed the design.  Then I put that design on hold for something more important

Some day.

[coppercone2]

I need to refill O2 and N2 tank to see if I can hook up my gas mixer to the plasma cutter to get nicer cuts with a slightly tuned gas mixture

[beanflying]

Bit of a necro post but interested if you got your table finished @Smokey?
...

Like so many things, this one got put on hold for something more important.  Then I changed the design.  Then I put that design on hold for something more important

Some day.

A little Inspiration to keep on going with yours.  I will make a new thread for the whole project but this is a small step to tick off.

My Dumb Cigweld (Esab in Oz) 45A Plasma is going RS485 smart. Proma also make separate THC modules and Isolated Voltage dividers but this all in one makes fitting it inside the box easy. All the switching bits are on the other side of an Aluminium sheet and as it is a non HF Plasma this should work out well rather than doing the same horrible things I have seen others wire up and use double sided tape or cable ties strapped outside the Plasma or wood screwed onto a wall ....

[nctnico]

While you are at it, replace the small pressure regulator with a bigger one. Those small regulators have a large pressure drop and are quite inaccurate. I retrofitted an AW3000-02 (from Aliexpress) regulator on my plasma cutter to get a more even pressure. The original one dropped nearly 1 bar while cutting.