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Torch head diving down when cutting

Posted: Thu Sep 21, 2017 3:09 pm
by Scratch
I have an old Practical CNC table with a new TD Cutmaster 82. I'm using WinCNC and have no THC. (I just use a pendant for THC) When I start the cutpath, as soon as the torch starts, the Z drives down super fast into the metal, and I can't stop it, I can slow it down with the up button on the pendant, but it still wants to go down.
If I disconnect the machine torch and just plug in the hand torch, then start the cutpath... I can control the Z completely as normal up and down, but as soon as I hit the torch start button on the hand torch... it dives down again fast.

I "think" this happened to me a long time ago and somehow I must have fixed it, but I can't remember what I did... It could have been a dream though for all I know...

One thing I did change was I used to have a TD Cutmaster 151 but it went bad on me almost a year ago. I replaced it with the 82 and now I have this problem. I did wait almost a year to replace it though and my table sat, unused, for that length of time. The problem wasn't there when the 151 went bad.


Any ideas on what it could be?

Re: Torch head diving down when cutting

Posted: Thu Sep 21, 2017 4:21 pm
by WyoGreen
It sounds like your Torch Height Control is sensing the voltage spike from the torch starting, and is trying to lower the torch to lower the voltage to what you have the cut voltage set at. There should be a setting for THC delay, which keeps the THC off for a set period of time until the voltage settles down after the cut start. Generally .5 sec or so, depending on the material thickness. My THC delay is set in my Sheetcam tool table.

My best guess, Steve

Re: Torch head diving down when cutting

Posted: Thu Sep 21, 2017 6:11 pm
by Scratch
Nope...
No torch height control on this bad boy... Strictly pendant control. Practical's THC was junk so I returned it soon after I got the table. Been using an up and a down button ever since.

Pity me.

Re: Torch head diving down when cutting

Posted: Thu Sep 21, 2017 7:13 pm
by Scratch
Edited first post with more details I forgot to add...

Re: Torch head diving down when cutting

Posted: Thu Sep 21, 2017 11:28 pm
by tcaudle
Didn't the old PCNC have a "pendant " for jogging? Is that what you are using for the Z up and down?

Re: Torch head diving down when cutting

Posted: Fri Sep 22, 2017 7:55 am
by Scratch
tcaudle wrote:Didn't the old PCNC have a "pendant " for jogging? Is that what you are using for the Z up and down?

Yes, that's what I'm using. It works perfectly fine and one of the buttons isn't shorted out or anything, but as soon as the torch starts, the Z drives down like twice as fast as I can control it. Never up, only down.

Even if I'm not running a cutpath, If I have Win CNC open and just start the torch it does it.

Re: Torch head diving down when cutting

Posted: Sat Sep 23, 2017 3:23 pm
by tcaudle
Well the manua jog probably has some kind if pulse generator and direction sense. Is the pendant switch or a jogstick (with proportional jog speeds based on deflection)? WINCNC is still around but as you know PCNC went belly up years ago.

Re: Torch head diving down when cutting

Posted: Sat Sep 23, 2017 4:26 pm
by Scratch
tcaudle wrote:Well the manua jog probably has some kind if pulse generator and direction sense. Is the pendant switch or a jogstick (with proportional jog speeds based on deflection)? WINCNC is still around but as you know PCNC went belly up years ago.

It's a simple box with two momentary buttons on it. One for up, one for down. Nothing else.