How does PAUSE work

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Re: How does PAUSE work

Postby Rando » Fri Jan 26, 2018 1:11 pm

Oh...and we also talked about using GCodeShim, which I posted about a while back at:

viewtopic.php?f=4&t=5308&hilit=+gcodeshim

If Roger and I decide it's worthwhile, I'm considering adding a command to scale an axis by percent/decimal fraction kind of thing. This can sometimes be helpful when the finished dimensions are just a little out of whack, and it's easier to just make the part a little longer. Honestly, I suspect it will be a nightmare, since the arc radii will be weird/wrong. But hey, I'll try anything (in hacking GCode) once!

Cheers!

Thom
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Re: How does PAUSE work

Postby Devlin » Fri Jan 26, 2018 5:11 pm

My wife has a Bernina embroidery machine. If the needle or thread breaks I can stop and fix the problem. Then I can reset the position back to where the problem occurred and continue the job. When I asked tech support about this with the shark they said it was on their todo list!!!
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Re: How does PAUSE work

Postby AZRoger » Sun Jan 28, 2018 7:30 pm

Thom,

Thanks for the code chunk. This does let me inspect the work and resume from where it left off.
By inserting the Null Tool Change, I am interrupting the toolpath between g-code commands.
It creates a clean break in the process that lets me continue to a known position. Perfect.
I have attached a metric example.
This example has added comments to your original - in Green - that explain each command.

The toolpaths I need to inspect are very sensitive to the Z0 setting.
They are REST toolpaths and have to carve the finer detail at the right depth.
It turns out that while the execution is paused, waiting for the tool change,
I cannot JOG or use the SET commands to make fine adjustments.
So, if I need to make an adjustment, I need to e-stop out of the g-code program,
make the adjustment, and start at the beginning.
But if all is well, I can just continue. Perfect for my needs.

Thanks again,
Roger
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Metric Example
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Re: How does PAUSE work

Postby Rando » Sun Jan 28, 2018 11:05 pm

Roger:

And now you're seeing why I use the GCodeShim program. Because the ONLY operational method allowed is to fully stop and exit the running program, I shim the toolpath up or down a few thousandths at a time until it does what I want for that piece of material. I don't bother trying to convince the machine the bit is 0.001" longer than it thinks it is, or re-zero; I move the data :D. I can even sometimes measure the incorrect offset and adjust by exactly that amount. Yes, it means "re-processing" the toolpath, or that part. But, it does NOT mean going back into Vectric, nor does it mean you have to re-zero the bit...you change the toolpath, abort, measure, shim, reload, try again. In the times I've had to use it, it proved exactly the need for those few parts I wanted peeeerfect.

The "real" reason why this works is that the exact touch-off point for a bit depends on not only the actual length, but the geometry of the cutting tool's end. So even when I use a solid block of 6061 to touch off, it's still sometimes off by a few thousandths. So if the cut really has to be nuts-on precise, I let the system believe it knows where it is, and I move the cutting path to where it really needs to be to come out right. I'm after proper parts; I don't honestly care what the machine thinks it's doing, as long as it's doing what **I** tell it to :D.

And to be clear, were this "me", I'd add an alignment-verification cut feature into the waste area of the project, or even a tied-down other piece of wood. Use THOSE cuts to determine the cut accuracy, and then adjust the toolpath. That way, you run the test cut, a pause, then the real cut. If the test cut doesn't measure correctly, you kill it at the pause, fix it, and run again. That way you can get your accuracy, but not at the expense of the shipping piece of material. When the initial verification cut runs perfect, you let it continue at the pause, and smile smugly at the now-obedient machine.

Regards,

Thom
Last edited by Rando on Sun Jan 28, 2018 11:36 pm, edited 1 time in total.
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ThomR.com Creative tools and photographic art
A proud member of the Pacific Northwest CNC Club (now on Facebook)
Rando
 
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Location: Hoquiam, WA

Re: How does PAUSE work

Postby Rando » Sun Jan 28, 2018 11:28 pm

AZRoger wrote:Thom,

Thanks for the code chunk. This does let me inspect the work and resume from where it left off.
By inserting the Null Tool Change, I am interrupting the toolpath between g-code commands.
It creates a clean break in the process that lets me continue to a known position. Perfect.
I have attached a metric example.
This example has added comments to your original - in Green - that explain each command.

The toolpaths I need to inspect are very sensitive to the Z0 setting.
They are REST toolpaths and have to carve the finer detail at the right depth.
It turns out that while the execution is paused, waiting for the tool change,
I cannot JOG or use the SET commands to make fine adjustments.
So, if I need to make an adjustment, I need to e-stop out of the g-code program,
make the adjustment, and start at the beginning.
But if all is well, I can just continue. Perfect for my needs.

Thanks again,
Roger


The only thing I'd change is that I'd be more fastidious about adding feedrates onto the G01s. It's important to NOT plunge the sharks up or down at the same as the horizontal rates. The pause code here doesn't do that, which means it's going to be using the same horizontal feedrate it comes into the pause with. It's possible that at the very end of the pause, when it re-inserts itself into the work, that momentum could cause it to sag deeper than the Z-2.000 you want. This isn't conjecture, it really does this. Also, that bit won't be "vertical" in the traditional sense when it bottoms out from the momentum. Small bits can break. Similarly, going up can lose steps if run too fast, say at 80ipm or similar like you might cut in wood. And we all know what bad things happen when steps are lost! :oops:

Other than that, looks good; glad it worked for you!

Thom
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ThomR.com Creative tools and photographic art
A proud member of the Pacific Northwest CNC Club (now on Facebook)
Rando
 
Posts: 583
Joined: Tue Jan 06, 2015 3:24 pm
Location: Hoquiam, WA

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