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Author Topic: Why did this bad cut happen??  (Read 4984 times)

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Why did this bad cut happen??
« on: June 29, 2008, 06:47:37 PM »
I hate mistakes. 

I was in the middle of cutting this part (see pciture). I noticed a clamp was getting to close to my cutter.
I stopped Mach3 to adust the clamp. When I restarted my machine again, I noticed that it now had a mind of it's own.

Why did it not just keep cutting my circle?  What happened?  Everything else cut just fine.

Jonny
Re: Why did this bad cut happen??
« Reply #1 on: June 29, 2008, 08:45:24 PM »
When you need to pause, use the "Feed Hold",(called "Pause" below) then it will resume as normal.
If you hit "Stop", no telling what you will get when you restart.
Also, if you hit stop while in a rapid move or a fast G1, you really should re-reference the machine for obvious reasons.
RC
Re: Why did this bad cut happen??
« Reply #2 on: June 29, 2008, 09:28:59 PM »
I have always wondered about that.  Usually if I have to use stop I adjust my feed rate to "as low as posible".
I have used stop in the past without any ill effects.  Did it have any reason to do with cutting a circle?

Thanks.
Re: Why did this bad cut happen??
« Reply #3 on: June 29, 2008, 11:36:21 PM »
I think that it is just the fact that it is VERY unpredictable. You would probably get a different result every time.
RC

Offline Hood

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Re: Why did this bad cut happen??
« Reply #4 on: June 30, 2008, 03:12:04 AM »
Stop really shouldnt be used unless its an emergency and then really you should have an E-Stop button for these situations. You should always use the Feed Hold button then if you want to rewind etc you can then press the Stop button.
Hood

Offline jimpinder

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Re: Why did this bad cut happen??
« Reply #5 on: June 30, 2008, 03:52:28 AM »
But then where did you resume from ???

Yes, the fact that you were cutting a circle may have something to do with it. You cannot just resume in the middle of a cut, having just hit Stop, becasue there is no telling what information has been lost.

You need to rewind you GCode at least a line, so that Mach 3 knows where it was at the end of the last line, and then processes the line again to recut it. If, unfortunately this means moving the cutter back manually to where it was at the end of the line, I am afraid that is what you have to do.

I usually lift the cutter with the jogg, then use the MDI line to get the cutter back to the co-ordinates it was at at the end of the last line, then use the MDI line to drop the cutter back down to it's correct depth. Wind the GCode back, make sure the correct line number appears in the window, then run from here and Cycle Start.
Not me driving the engine - I'm better looking.

Offline Hood

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Re: Why did this bad cut happen??
« Reply #6 on: June 30, 2008, 03:58:39 AM »
Another way to go back is use the Run From here option, you just click in the code window and use the Up/Down arrows to get to the line you want then press the Run Friom Here button, when you press Start you will be given a Prep move to agree to, clcik OK if it looks fine then it will move there, press Start again once it gets there and it will continue.
 However saying that if you have stopped by pressing the Stop button rather than the FeedHold you really need to Home your machine again before you resume. Try and get into the habit of pressing the Hold rather than the Stop.
 BTW if you have the Demo version then the Run From Here is not operational.
Hood
Re: Why did this bad cut happen??
« Reply #7 on: June 30, 2008, 08:00:12 AM »
Alright.  Thanks for all the advice.  Feedhold is the button of choice.
 
Still not sure why things would get messed up by pressing stop. I can understand missing steps on my stepper.
But Mach3 is just a number counter.  If you press stop, it should just stop counting.  If you press start, should just resume counting.
I would think it to be no different then a movie or music cd.  When you press stop, the movie stops, when you press start, the movie continues.
Although (you are right) I would press pause in that case.  Laugh

Thanks guys.   Jonny
Re: Why did this bad cut happen??
« Reply #8 on: June 30, 2008, 08:07:23 AM »
Theres more going on than that. Especially if you are in a G2 or 3 move when you hit stop.
Here is a clip from Turn. Same in Mill I believe.
Re: Why did this bad cut happen??
« Reply #9 on: June 30, 2008, 08:21:11 AM »
Another way to look at your CD player.
Compare hitting the PAUSE button to killing the power to the unit.
When powered back up, it will not resume from where it was....it knows what to do to internally to re orient  itself by a programmed sequence.
Machine tools leave that up to you. Too hazardous to let the machine handle that.
The Pause will resume as normal.