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### Author Topic: tips for getting started with 2 axis plasma cutter  (Read 678 times)

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#### endritcnn

• 11
##### Re: tips for getting started with 2 axis plasma cutter
« Reply #10 on: February 06, 2023, 12:05:32 AM »
"I have found a solution for the voltage with Arduino. However, there is still something unclear to me. How should I set the speed at which the axes move based on the thickness of the material? Is it necessary to go to motor tuning every time for tuning purposes?"

#### joeaverage

• 7,570
##### Re: tips for getting started with 2 axis plasma cutter
« Reply #11 on: February 06, 2023, 12:44:33 AM »
Hi,
you may need to study up some Gcode.

G1 XnnnYmmm Fppp means travel linearly from the current X,Y location to (nnn,mmm)  at a feed rate of ppp units/min.
The speed is included in the Gcode.

Craig
'I enjoy sex at 73.....I live at 71 so its not too far to walk.'

#### endritcnn

• 11
##### Re: tips for getting started with 2 axis plasma cutter
« Reply #12 on: February 06, 2023, 07:42:09 PM »
Hi, thank you very much for your help. I really appreciate it. Now I know how it works.

#### joeaverage

• 7,570
##### Re: tips for getting started with 2 axis plasma cutter
« Reply #13 on: February 06, 2023, 08:13:51 PM »
Hi,
the issue is lets say you want to cut from 0,0 the current location to 150,150 (in mm) through 6mm steel.

Lets ay you also know that you can cut at 1000m/min with 6mm steel. You could cause this to happen by coding:
G1 X150 Y150 F 1000.

The machine cannot go from zero speed to 1000mm/min instantly, it will have to accelerate up to speed. Likewise at the end of the cut the machine
will have to decelerate to a stop. During the acceleration and deceleration the plasma arc voltage will vary. It might be stable at 100V during the majority of the cut
but the 10mm at each end the voltage will increase, and that is where you expect the tip of the torch to go down a little bit to maintain the right, or optimum cutting voltage.
But what happens when it actually stops, the voltage will increase and the THC will try to drive the tip into the material. This is called 'tip dive'. A good THC system
will have strategies to overcome this called 'anti dive'. It will include at look ahead through the Gcode to find places where it might expect the tip to dive and counter it.

I suspect this is where your notion to use an Arduino will fall short. Very simple THC systems often have the problem of tip dive, and they don't accommodate it well.

Another sure-fire test for a THC system is if you go and do a cross cut over the top of a previous cut. Right at the moment that the arc is in the other cut the voltage will spike high
and the tip of the torch will dive into the plate. For this reason its considered poor practice to cut over the top of an existing cut with simple THC. A good THC with good anti-dive
strategies can do it whereas simple ones fail.

Craig
'I enjoy sex at 73.....I live at 71 so its not too far to walk.'

#### endritcnn

• 11
##### Re: tips for getting started with 2 axis plasma cutter
« Reply #14 on: February 19, 2023, 06:45:39 PM »
Hi,
if  you are new and do not yet have a license you should go with Mach4. All development on Mach3 ceased eight years ago, it works but whatever bugs it has it will always have.

https://www.machsupport.com/forum/index.php?topic=42891.msg278176#msg278176

Mach4 all but requires an external motion controller, I'd recommend an Ethernet SmoothStepper (ESS). You need a breakout board to match, and for a simple machine
such as you are contemplating a single port (17 IOs) bidirectional C10 for \$23.00 is good value or a two port (34 IOs) bidirectional C25 for \$29.00 is good value also.
You may have to provide some very simple external circuitry, relays etc, but should be no problems. Or you could make a breakout board, this is one I made, all three ports (51IOs)
developed, all 24V tolerant, differential outputs for the servos (six axis), plus PWM, relay on/off for the spindle and electromagnetic brake output for the Z axis.

You'll soon want Torch Height Control, a plasma table without it is way less than ideal. Yes, I've heard it all before...' I don't need THC....I'll use X or Y or Z, I don't need THC'
and I call BS, every single one of them comes back to implementing THC

Mach4 has a script based software THC feature, very low bandwidth, say 10Hz, but adequate for many THC purposes. Your electronics skills will come in handy if you wish to do that.
The ESS is matched to a THC controller/breakout board in the form of a Warp Runner board, now you have realtime hardware controlled THC with bandwidth of 100Hz or more.

What plasma machine do you have?. Any HF start plasma is far from ideal for a Plasma table, the electrical noise is very hard to accommodate, contact start like Hypertherm is much preferred.
Even contact start plasmas are electrically noisy and so USB connected motion controllers are not recommended. Transformer coupled USB is better but still has more latency
and less noise immunity than Ethernet.

Craig

Hi,
I have considered your suggestion for ESS and WarpRunner, and I have decided to go with ESS and Warp. However, I have a question: would it be more effective to use a stepper motor instead of a servo motor, considering the cost difference? Apologies for my delayed response. And will use a plasma with ignition contact or pilot arc.

Thank you.

#### joeaverage

• 7,570
##### Re: tips for getting started with 2 axis plasma cutter
« Reply #15 on: February 19, 2023, 07:20:07 PM »
Hi,
depending on the material you are cutting and the output current of your plasma you may require very high cutting speeds.

I had a customer, some years ago now, whom had a 65A plasma but would on occasion cut 1.5mm sheet. The cut speed was in excess of 8m/min
to maintain a good cut profile. The steppers kept blowing up....they really struggle to go that fast. We fitted servos to X an Y (two required), and problem
solved. Those same servos are still working after 8 years.....and this outfit uses the plasma table almost continuously 8 hours a day, 5 days a week.

If you require high cut speeds then servos are probably the only realistic choice. If however you have a plasma of low output and are cutting 3mm sheet or
more then you may not need high speeds and therefore steppers will be adequate.

Note that while you can dial down a plasma the torch usually has an optimum current below which the cut quality drops off a cliff.

HF start plasmas are exceptionally electrically noisy and ALL electronics are going to struggle. Contact ignition like Hypertherm is less noisy and therefore much preferred.
Plasma is by definition a 'contained continuous lightning strike' and is still electrically noisy....so take any advantage you can get.

Craig
'I enjoy sex at 73.....I live at 71 so its not too far to walk.'

#### endritcnn

• 11
##### Re: tips for getting started with 2 axis plasma cutter
« Reply #16 on: February 21, 2023, 08:15:08 PM »
Hi,I'm having difficulty buying ESS and WarpRunner because of the high shipping fees due to Kosovo not being readily available nearby. Can I ask for your opinion on an alternative product called PoScope? It also has breakout features and THC, and it's easier to purchase from me.

https://www.poscope.com/product/pokeys57cnc/

Thankss

#### joeaverage

• 7,570
##### Re: tips for getting started with 2 axis plasma cutter
« Reply #17 on: February 21, 2023, 08:38:15 PM »
Hi,
I don't have any experience with PoKeys products, but they are well regarded. I'm not at all sure that PoKeys boards support THC in Mach4, Mach3 I would say is
a almost certainty, but I'm not sure about Mach4.

Those boards which do support THC tend to use something like a Proma THC unit which produces an UP/DOWN signal only, that is to say that there is no anti-dive
strategy or anything of that description. The WarpRunner is quite a sophisticated product, in fact to my knowledge is the most sophisticated THC unit for ANY of the Mach4 ready controllers.
The only other controller that I've seen enough discussion on to suggest that its a worthy contender is Vital Systems Hicon and Proma 150. The problem is that the Hicon is expensive in itself but is
also a US made product and likely to suffer the same shipping costs as ESS/Warprunner.

Craig
'I enjoy sex at 73.....I live at 71 so its not too far to walk.'

#### endritcnn

• 11
##### Re: tips for getting started with 2 axis plasma cutter
« Reply #18 on: February 21, 2023, 08:48:19 PM »
Thank you so much for all the info you've given me. I am very grateful for your help.

Sincerely,
Endrit.

#### joeaverage

• 7,570
##### Re: tips for getting started with 2 axis plasma cutter
« Reply #19 on: February 21, 2023, 08:53:26 PM »
Hi,
another possiblity is CNCDrive. They manufacture both software, UCCNC, and hardware control boards like the UC300. Their control boards work with both their
own software AND Mach3 and Mach4. I don't believe that CNCDrive products have ever supported THC, but I could be mistaken. CNCDrive is a Hungarian company
so would be a much easier proposition to get genuine products than stuff from the UAS.

Craig
'I enjoy sex at 73.....I live at 71 so its not too far to walk.'