THC config that works.

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16 Feb 2015 20:09 #56003 by groblerjf@gmail.com
Hi, I am also trying this config, and so far it seems to be working, but I am encountering something weird.

Every time I execute the M3 command, the system finds the work piece and sends the Torch on signal, but as soon as the plasma sends the Arc OK signal the Estop is triggered for some unknown reason.

I do not know if it could be that I inverted my Arc OK signal and I now need to invert something else.


Thanks
Jacob

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16 Feb 2015 20:26 #56004 by andypugh
Replied by andypugh on topic THC config that works.

groblerjf@gmail.com wrote: Every time I execute the M3 command, the system finds the work piece and sends the Torch on signal, but as soon as the plasma sends the Arc OK signal the Estop is triggered for some unknown reason.


Is there any error message, such as a limit-switch trip?

It might well be electrical noise.

Could you attach your current HAL file so we can see if there are any inputs that might be picking up noise to cause this?

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16 Feb 2015 20:49 #56007 by groblerjf@gmail.com
There are no error messages that pop up.

Other than changing the pins, and inverting some of the signals nothing else was changed from the files I downloaded.

I did try it again, same result. However I may been wrong in describing that the Estop is triggered, because the Estop button on the interface is not depressed. To allow motion however, I have to press the Power button.

Thanks

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16 Feb 2015 21:06 #56008 by andypugh
Replied by andypugh on topic THC config that works.
OK., that is quite a config isn't it?

I would guess there is something funny going on with the inputs to estop-latch.

Perhaps it would help to get a graphical view of the HAL wiring?

wiki.linuxcnc.org/cgi-bin/wiki.pl?Rockhopper_Web_Server

(I have never used that, but I have heard it can help)
The following user(s) said Thank You: groblerjf@gmail.com

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16 Feb 2015 23:13 #56014 by tommylight
Replied by tommylight on topic THC config that works.
Hi

The problem you describe is exlusively related to High Voltage/High Frequency start systems in plasma cutters, so Andy was right regarding the electrical problem.

There are solutions for this as noted below:

Cabling
the torch and ground cable from plasma should not be parallel with other cabling -NEVER EVER- exept when using high quaity RF shielded cabling.

The limit switch used for finding the work piece
it has to be configured and connected as NC or normaly closed. This for a simple reason: it stays always connected to ground exept when triggered by touching the work piece so when the torch starts it is at ground potencial and way less prone to RF interference.

Plasma cutter
as far as posible from everything else. This is limited by the length of the torch cable, but having the computer and electronics on one side of the machine and the plasma cutter on the other helps a lot.

BOB
This is more complicated to fix and requires some soldering skills and 5 220 - 330 ohm resistors. The resistors have to be soldered to 5 inputs on the BOB and to +5V so it keps them pulled up all the time until there is a signal on the inputs.

That is it.

I have done this several times ( over 15 ) on a wide range of CNC plasma cutters and this is the exact procedure that i use and it always works, always.
There are also High Voltage start plasma cutters and they cause much less troubles, and scratch start, but the latter is not usable for cnc.

regards
Tom

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17 Feb 2015 01:10 - 17 Feb 2015 01:10 #56016 by groblerjf@gmail.com
Ok, so the system I am running is a Powermax 45 with machine torch.

So I implemented the solution you suggested Tom.

- I rewired the limit switch so that it is normally closed. I installed a pull up resistor on the 5 inputs.
- The plasma cutter is as far as possible fom the PC.
- The cutting torch cable and the ground cable of the plasma cutter is on the opposite side of the control cables as well.
- The only cable that runs next to the other cables is the pc interface cable that is connected to the plasma power supply.


I have not yet tried the online diagnostics tool as Andy suggested as my PC is not connected to the internet. I did however discover that it is indeed the float switch that is causing the problem. I used a standard mill config and just arced the torch. If a z limit is defined during configuration then an Estop is triggered, but when that same pin is set as unused, then the system arc's and I can cut further.

Any suggestion on how to fix this.

My z float is just two wires dangling next to the machine torch, should I perhaps just install shielded wire and see if that does not fix the problem.




Thanks
Jacob
Last edit: 17 Feb 2015 01:10 by groblerjf@gmail.com.

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17 Feb 2015 01:46 #56019 by tommylight
Replied by tommylight on topic THC config that works.
It is absolutely necesary to use shielded cables in your case, you can use even RG 58 or RG59 tv antena or video camera or audio cable with one wire in the midle and one as a shield. Just connect the shield to the ground on your bob and the midle wire to the input.

I also forgot to mention one of the common errors i have seen around : stop grounding everything at the same point. That is o.k. for other machines, but it can be fatal on plasma cutters. I have explained that in this forum and some others so i won't repeat myself, just to prove a point : almost all power supplyes have ground connected to minus terminal internaly as it is supoesed to be but the plasma cutter clamp that is usualy clamped to the material or the ribs on the cnc is the positive.
Tom

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17 Feb 2015 01:50 #56020 by tommylight
Replied by tommylight on topic THC config that works.
Do a test an wrap the limit switch with alu foil properly, afetr you change the wire. If the switch is close to the torch that will help a lot.

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17 Feb 2015 01:59 #56022 by groblerjf@gmail.com
Thanks, will do it in the morning.

Regards
Jacob

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17 Feb 2015 03:00 #56024 by PCW
Replied by PCW on topic THC config that works.
Another thing that can help is debouncing the input signals with the hal debounce component

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