Messages

2311

General Mach Discussion / Re: 1st pierce is longer...

« on: September 09, 2014, 04:30:48 AM »

Ok, I think I see it now, nothing happens until we get arcok.

Now, looking at the issue then, what could cause the variation?

There definitely IS a variation and the only difference is the post-flow air being on or off.

The response is the difference between getting a solid pulse of the torch OR not getting enough signal to even trigger the torch.

Hang on a minute, looking at that last sentence, i was not even getting an arc on the latter part of that test as mach was not triggering the relays long enough to do it - straight M03-M05 is too fast UNLESS its the first trigger is with air OFF.

Now i'm really confused

2312

General Mach Discussion / Re: 1st pierce is longer...

« on: September 08, 2014, 02:25:48 PM »

None of this would matter if you base your timings on arcok. I know I'm sounding like a scratched record but there it is.

Yes possibly but what if the arcok is delayed on the first pierce but arrives faster when the post-flow air is on?

Surely the result would be as it is now - were waiting for a signal that arrives at varying time periods??

No real way to tell without some serious measuring equipment I think.

But I do now know that Mach IS consistent and that the pierces WILL vary if post flow is on.

Without a method of triggering the air earlier I doubt there's much can be done, but at least I have a reason now.

Thanks for all the discussion.

2313

General Mach Discussion / Re: 1st pierce is longer...

« on: September 08, 2014, 07:34:57 AM »

My conclusion only applies to using the torch as a drill though, where there is no movement code following the M03, for normal cutting it will not fail to fire but it wll give a longer pierce dwell on the first cut providing the cuts are close enough together to be started with post-flow still running.

2314

General Mach Discussion / Re: 1st pierce is longer...

« on: September 08, 2014, 06:59:33 AM »

Results are in.

made a job that was just 4 pierces in a row, first test was no pierce delay
This set the code to a straight M03/Mo5 and I get one good mark and three where there was not enough loop time to actually fire the torch.

second test i set a 0.5s delay between each M03/M05
This time I got one deeper mark and three good ones

reduced to 0.4s delay
Result was slightly less depth than the previous test.

Then i realised the there was another factor at play - after the first pierce the torch air was still on its post-flow stage

The next test i made each pierce one at a time, allowing the air flow to stop between each firing
result - 4 perfectly equal marks.

Conclusion - there is a cumulative loop delay required of about 0.4s to get a reliable arc start on the torch PLUS if the air is still flowing then  the pierces WILL be quicker.

Summary - Not a lot i can do about that really, there is no way to stop the post-flow and no way to pre-trigger the air flow so the 1st pierce will always be longer.

Damn interesting test though and thanks for all the help.

2315

General Mach Discussion / Re: 1st pierce is longer...

« on: September 07, 2014, 02:22:19 PM »

Thanks, just re-read that thread again.

So, if I were to set a realistic delay (longer than the electromechanical delays in the system combined) say 1sec then I would likely see stable timings in the G4 but because my zero delay request is far shorter than the inherent delays (allied with the mach bug)  then I am seeing seemingly random timings possibly caused by the arc ok arriving later for the first fire or some other micro variable delay?

I think that makes sense.?

I see you had some vb code for the M3 that might help but, as you said then, it could cause cause an infinite loop if the arc never arrives which is possible so I think I will leave that alone for the present.

I'll have a play as soon as I get some quiet time.

2316

General Mach Discussion / Re: 1st pierce is longer...

« on: September 07, 2014, 12:33:53 PM »

Very interesting stuff, so without an arcok system, a straight M03-M05 should be so fast as to not give any action at all? Probably just make a relay quiver somewhere.

Ok, so we switch on, wait for arcok, then switch off, is that the correct internal sequence?
Inside Mach there is a loop following the M03 that waits to see an arcok signal BEFORE processing the next command which in my case is M05, but I guess could just as easily be a move etc?

If that is so, then yes there is a long loop involved in getting that signal, in my THC it's created from a Hall effect trigger on the plasma ground lead so the current has to build to trigger point before it's sent, and as you said there are gas valves, relays, even the blowback start cartridge in the torch.

This all explains why a zero pierce delay is never really zero I guess.

Thanks for all this by the way, it's much appreciated.

2317

General Mach Discussion / Re: round circle with perfect backlash on straight moves

« on: September 07, 2014, 11:35:37 AM »

Could this be something as simple as a pulley or gear working loose on a shaft - this can create backlash which would cause oval circles.

The area to look at is the axis that shows the issue - if the circles are correct in the x-x direction but short in the y-y direction then look at the components for the y axis drive. A loose pulley can be a bugger to find until it falls off

2318

General Mach Discussion / Re: 1st pierce is longer...

« on: September 07, 2014, 11:29:09 AM »

Arcok, who's that?   

Ok, I'm hoping to get some time tomorrow to pull that code apart and do some tests.

If it went
M03
M05

I guess that is the absolute shortest bite it can give?

Is there a delay in going from pilot to main arc?
I mean, if the metal is clean, the torch is at pierce height and then fired, surely the delay is microscopic and of little relevance. Does it not move to main arc as soon as the pilot arc touches the sheet and current starts to flow?

If the cycle time is so short, does it even get a chance to transfer to main arc?

Will do some tests on this.

Thanks

2319

General Mach Discussion / Re: 1st pierce is longer...

« on: September 07, 2014, 09:18:24 AM »

Is it the F1000 at the end of the line between the m3 & m05 ??

I guessed that was just setting a feed rate but as there was no feed, it did nothing?

If it's not that then what?

2320

General Mach Discussion / Re: 1st pierce is longer...

« on: September 07, 2014, 07:53:13 AM »

D'oh!, what an idiot

Yes I had coffee, maybe not enough;)

Anyways, I still don't see what arc ok can do if the torch just fires and stops, I thought arc ok would only be relevant before a torch move?

This new system is a proper current monitoring arc ok signal so should be accurate, it's passed all the tests recommended by CandCNC anyway.

If there is some test I can do to narrow things down I will do it, but the delay seems to be the same if I'm doing a series of quick bursts or a series of long cuts, the first activation is longer.

Thanks