Powermax 45xp lost arc delay (Solved)

phillc54 wrote:

Nick7251 wrote:

The hard thing is that I could get it to work by moving the ground clamp closer to the cutting location for a while then the problem would pop back up. So I'd turn off the cutter and back on and that would sometimes allow it to cut again and sometimes not. Then I'd hit the pulse button and that seemed to get it to cut sometimes and sometimes not.

So I suspect none of those things actually effected anything and it was just intermittent and tricking me. Also the fact it is intermittent makes it hard to duplicate for serious testing and fixing.

Seems a lot similar to:
"It may be of importance to note: When this was all going on, with the SSR, I noticed that if i had the ground clamp near the torch I had a MUCH higher chance (but not always and the length of time the pilot arc was stable varied) of getting a reliable pilot arc. If I took the ground clamp off the table, it would never fire."
From this post

Yes, agreed. I sense a mechanical relay in my future but still want to try some hal scoping to ensure I have proper delay set for the THC.

Also the polarity theory is interesting that Rod just mentioned. I have mine wired like in the attached picture.

Nick7251 wrote:

Also the polarity theory is interesting that Rod just mentioned. I have mine wired like in the attached picture.

Its not a theory. Its fact!

Interesting that you have the polarity marked on your 7i96 but the Plasma cutters are silent on polarity. (probably becasue it does not matter on a mechanical relay which was probably what was widely in use when the docs were written years ago...)

For my Thermal Dynamics A120 plasma cutter
pin 3 = spindle ENA -
pin4 = spindle ENA+

On your diagram you have the polarity reversed. I wonder if all these issues can be traced back to the one circuit diagram as this is not the first time I've seen your schematic?

rodw wrote:

Nick7251 wrote:

Also the polarity theory is interesting that Rod just mentioned. I have mine wired like in the attached picture.

Its not a theory. Its fact!

Interesting that you have the polarity marked on your 7i96 but the Plasma cutters are silent on polarity. (probably becasue it does not matter on a mechanical relay which was probably what was widely in use when the docs were written years ago...)

For my Thermal Dynamics A120 plasma cutter
pin 3 = spindle ENA -
pin4 = spindle ENA+

On your diagram you have the polarity reversed. I wonder if all these issues can be traced back to the one circuit diagram as this is not the first time I've seen your schematic?

Sorry Rod. "Theory" was the wrong word to use.

Maybe that is it then for me too. Polarity backwards. Too bad Hypertherm doesn't list it in their manual like TD does. I'll try swapping the wires before I do anything else. That way we are only testing one variable at a time to ensure we know what exactly fixed it. Hope to get a chance to go freeze tomorrow.

Unless you think that is a bad idea. I read over in another post that switching the polarity will start the torch in the on position.

forum.linuxcnc.org/27-driver-boards/3659...96-and-thcad?start=0

Second post.

snowgoer540 wrote:

Hopefully you get cutting reliably soon! I feel you on the cold thing, been really chilly lately over here in PA as well.

Where's the snowgoer! You of all people complaining about the cold...

Actually, now that Plasmac has a setting to ignore ArcOK, It would be worth doing some tests with ArcOK disabled becasue that would isolate testing to just the torch start.

The torch start and ArcOK are separated by milliseconds and are closely related (eg if you don't get an arcOK, the torch will turn off). The only way you can measure them is to use halscope.

So forgetting about the OP's 7i96 for a moment and focussing on Snowgoer's 7i76 and my 7i76e. give or take an ethernet connection, they are identical.

Both have to use a relay on outputs
I started with a mechanical relay and replaced it with a Mosfet relay a couple of years ago.
Snowgoer started with a Mosfet relay and replaced it with a mechanical relay.

I'm going to assume there is little difference in the triggering of a Hyperthem and Thermal Dynamics machines. After all, they seem to behave the same way if the circuit is active low..

So the question is why does a Mosfet relay work for me and not for Snowgoer on the same circuit.?
The answer has to be the relays are different.

Now robertspark gave us an additional datapoint

robertspark wrote:

I've just stuck my ammeter on the PMX45 and this time I got the current rising to about 15.1mA in a little over a minute.

It would be nice to know what the current draw was at the start of that one minute becasue thats the timeframe I'm hearing.

In the same post, Robert also flagged a possible issue in a cryptic way.

robertspark wrote:

Load current 0.0025...6 A (i.e. 2.5mA minimum current? .... possible issue??))

So Snowgoers relay has a current range of 2.6 mA to 6 amps
My Relay has a range from 1 mA to 0.5 amps.
I think it can be concluded that my relay is more suited to the task and Snowgoer's is close to that pesky minimum current again which is the "possible issue" Robert was alluding to.

So the 7i76/7i76 spindle relay works for me, why wouldn't it work for snowgoer? That point we don't know yet. I think we need to call upon the test pilot to confirm this

Then we have PhillC switching his 30 amp plasma directly with a 7i96 output

Sorry to be continuing this but there is something here we don't yet understand but we are converging on discovering whats going on.

one thing we have proven is that becasue of my experience, is that some MOSFET relays will work! Its just that you need to choose wisely!