THC config that works.

Hi, so I did not wrap the wire in Al foil, but I did add a shielded cable, not sure whether it helped, may have installed it wrong. What I did do is debounce the float switch electrically with a 100nF across the switch, I went one step further however and installed and opto-coupler. I also rewired the switch to be normally open.

There is a new problem however. For some reason now, as soon as the arc establishes, and motion begins, the machine moves extremely slow and I have no idea why. Everything works fine, even my own implementation of THC, and normal motion is at the correct speed, but when I issue the M3 command, the motion is extremely slow.

Attached is my thc_toma.ini file

Any ideas???

Regards
Jacob

groblerjf@gmail.com wrote: There is a new problem however. For some reason now, as soon as the arc establishes, and motion begins, the machine moves extremely slow and I have no idea why. Everything works fine, even my own implementation of THC, and normal motion is at the correct speed, but when I issue the M3 command, the motion is extremely slow.

It is slightly hard to work out what is happening without the HAL file, but I notice that you enable adaptive feed in the INI, so my assumption would be that you need to calibrate the input to the adaptive feed pin.

The slow motion is a result of the ARCOK signal going on and off . Set the voltage on the THC correctly and try cutting a thicker metal part so the voltage at the torch is stable for longer periods of time.
What type of THC are you using?
The normal voltage on most of the machines i have and use while cutting 3-6mm thick plates is 113-128 V.
Tom

Ok, so the THC that I am using is my own that I built with an Arduino. Locally I cannot buy a THC so the next best thing was a micro-controller.

According to the Hypertherm manual, I need an arc voltage of approx 112V for a 1.6 mm plate. As far as I can tell, the THC is working correctly, because I can see that LinuxCNC receives the move up or move down signals.

O, so I sort of understand why I should rather cut thicker metals, but I want/need to cut the thinner material.

Regards
Jacob

Hi Tom ; Andy,

I finally got my build to work properly. I do not know whether my solution is the correct method, but it works. I debounced the Arc OK signal with a 100nF cap and that seems to do the trick.

However, I will definitely be ordering a Proma THC or other, because the little Arduino seems to be too problematic and the analog inputs is susceptible to interference from each other.

Regards
Jacob

groblerjf@gmail.com wrote: the analog inputs is susceptible to interference from each other.

The problem you are seeing might be due to the capacitance of the multiplexer. It might help to tie all unused analogue inputs to 0V.

glad you made it work.
Tom

Hi Andy,

So I did tie up all the unused inputs to zero, and there was definitely an improvement. Another guy I talked too also suggested that I install a first order low pass filter on the arc voltage input from the plasma cutter, so I will try that as well to see if I can get and improvement.

---

Thanks to all for helping me.

Hi all,

I am back. I have been having some trouble with the THC user interface that shows the ARK OK, UP DOWN etc. signals. With the input values, such as the switch travel, travel height and gap width. When I change the standard values, it seems that the program does not recognizes the changes. Thus far I have manipulated the torch pierce height and switch travel values with the torch holder, but I have build a new torch holder which does not allow for such manipulation.

Any suggestions.

Regards

I have tested and used those functions for a very long time and on a lot of machines and they do work properly all the time.
Can you explain exactly what is working and what not? It would help a lot at troubleshooting.
Regards,
Tom