Plasma table set, fine tuning a problem

Hi all, Firstly great crowd. Love your work.Ok so I have bult a table. Setup is as follows: 1.2mx1.2m cutting capability. Mesa 7i96 card. THCAD2 THC, Unimig Razorcut45 CNC enabled cutter.X Y, Y1, Z config. I have set the THCAD2 to 1:1 10v High status, and the Unimig at a 30:1 ratio, which should produce a roughly 5V at top end signal. I do not have any resistors in the mix.I have the cutter running but only WITHOUT THC. It cuts, BUT it does not do this nicely and I do not know how to best tune the system. I started on 5mm steel. (probably a little ambitious.). And I dont have enough knowledge on how to set the speeds, heights etc.. to get a clean cut before THC. Then I will need to solve THC. But thought best to get basic answer on settings for the 5mm first then the THC. So settings are as per the images below. I have not performed any other settings other than servo setups and max speeds. Unimig fires off, so Arc on/off work. Arc OK seems to be ok as when has no steel, it shuts off. THC yet to get working. 

 Not sure if you have a cut chart for that machine.  Have a look at this generic cut chart to get a sense of amps to use for a thickness. It will also give you a guide on speeds.  1.5mm cut height and 2.5 to 3mm pierce is pretty standard.  

 


 

Thanks Tommylight.
-Set up the THC, any fine tuning without it is useless when THC is active.
Ok. Will note

-25A for 5mm thick is way to low, roughly 10A/mm is OK
Yes this is already set to 40A in the 5mm profile

-with working THC, you need to fine tune air pressure (exclusively while the air is ON), voltage=cut height, feed rate
Ok. This I have definitely NOT looked at. Will do. Thanks.

-cut quality will vary based on air moisture, material being cut, nozzle type and wear, so use new nozzle for fine tuning and after you have things working properly
I have a three stage Breathing Dryer rig from when painting, + a standard dryer, so dry air should not be a problem. But the rest of it I will need to work through. Thanks.

My main concern was the settings in the Configuration setting, specifically arc voltage setting etc... Any thoughts on this? Do you have some that you may be using?

Hi yes, I have a cut chart for the cutter. BUT it does not specify a variable air pressure chat such as the one you have presented. So I think this could be useful. Thanks.

Separately, I was concerned about the configuration settings: mostly about the arc voltage etc... I read somewhere about a need to set the config of the THCAD2 into the settings of the Software based on a frequency... Cant remember where I saw that but the config setting are my main concern at the moment. The other thickness settings are in line with the cut charts for the machine.

That being said, I have literally never used a cutter, so have zero experience on how this should be set up. I live in Melb, AU. So if anyone local, would put on beers coffee or whatever for some localised help. 

aikiaviator wrote:

I read somewhere about a need to set the config of the THCAD2 into the settings of the Software based on a frequency... Cant remember where I saw that but the config setting are my main concern at the moment. 
 

The thcad is a voltage to frequency converter. It has individual calibration frequencies at 0 volts and max scale volts (10v or 5v) on a sticker on the board. you enter this data into the QTplasmac interface. Read the docs and  it is well explained.

Hi Rod, Thanks. Found the section. Looks like no actual settings defined for the newer and current THCAD2. I guess I can muck my way through it. Looks like the calculator doesn't have it factored either. Thanks for the pointer.

You can still use the calculator. The only difference with a THCAD2 and THCAD10/THCAD5 is that it rolls the 2 earlier devices into one and gives you a way to select the full scale range of 10v (THCAD10) or 5 v (THCAD5). So just use the mode that suits your use. Normally you would use a 10 volt full scale for torch voltage

Hi Rod, Thanks for the feedback. Unfortunately it does not have THCAD5, and this is what I am using. So calculator does not allow me to double check. It does have THCAD10 and THCAD300. So I have set to 10, and the Voltage scale is 1/2. So hopefully this makes sense. The setting I have are now: THCAD2: Low (i.e. Down) 5V, Frequency divider: 1/32. 0V 95.4, 5V 896.0. Gives me the following as set by pnconf: Voltage Scale 0.005996, Voltage Offset 2981.25. Plasma machine: Unimig Razorcut 45 CNC port is set to 30:1 ratio. I set the Plasma to 30:1 ration as a precaution. Do people think this is necessary, or would 20:1 be fine? It is a 45A plasma cutter.

20:1 eg 200 volt full scale is fine and gives a bit more accuracy but I have used 30:1 (300 volt full scale) on one plasma cutter which is also fine..
The thcads are rated for 500 volt over voltage and you will only exceed 200 volts when piercing when the THC is not active. If using halscope you will see that the voltage will flat line at the full scale before dropping back to the 120-130 volt cut voltage before the THC is enabled.