Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: tjd10684 on March 17, 2012, 12:24:08 AM
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I have posted a g code for several parts out of plate the total line count is 500000+ I came down to check on the progress and luckely i saw my cutter break (1/8" em) on line 243165 i hit the stop button and took note of the line number I then changed out the cutter and re zeroed my z height. no problem so far right? wrong i found the line number that the cutter broke on and hit the run from here button and i have been waiting ~20 min for it to go through the code to get to the line in question before it will start the prep move. is there any why that i can speed up this process in the future?
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Try turning off the tool path display. I done a litho this
week with lots of lines. Took my Dell optiplex a long time
to load. I also had a hickup when moving to the center to
do a pocket and have never had a single machine problem before.
I turned off the tool path display (on diagnostic screen bottom left
hand side) and it ran flawlessly for two days non stop.
Hope this helps!!
olf20 / Bob
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In large code it may be better to use Set Next Line rather than Run From Here. With Set Next Line it will assume you have all modal states set correctly and start without running through to check them.
BTW if axis are in motion you should feedhold and wait for the axis to stop before pressing the Stop button, not doing so risks losing position.
Hood
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Thanks for the tip Hood, I've never tried Set Next Line, always just waited for Run From Here to run through it all.
I've never seemed to lose position by hitting Stop (esc), been doing that for 3 years, but good to know it's a potential risk.
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If your axis are light and dont have much momentum then it may be you wont lose position too much. How much is too much will depend on the type of work you do and the accuracy needed. If for example it is a wood working machine then a few hundredths of a mm or thousands of an inch will likely not matter, on a metal cutting machine such as a lathe it may well be enough to scrap your part.
Hood
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Ahh that makes sense. I've got Chinese machines, a G0602 lathe and an X2 G8689 mill, so relatively light. I only cut metal on them so tolerances are very important. Then again, maybe I've never attributed my lost tolerances to this issue! I always push escape to cancel, or trip the limit switch on my lathe. Humm, maybe it does lose a few thou, be a fun test one day, especially during rapids.
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If your axis are light and dont have much momentum then it may be you wont lose position too much. How much is too much will depend on the type of work you do and the accuracy needed. If for example it is a wood working machine then a few hundredths of a mm or thousands of an inch will likely not matter, on a metal cutting machine such as a lathe it may well be enough to scrap your part.
Hood
Also helps to have servos. If you're moving slowly enough that the axis coasts to a stop before you exceed the max following error, there will be no position loss, and the servo will bring it back to where Mach3 wants it to be.
Regards,
Ray L.
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You must have pretty slack following error Ray, mine is set to 20 counts max so at 8000 per 5mm that equates to 0.0125mm or just under 0.0005inch.
Hood
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You must have pretty slack following error Ray, mine is set to 20 counts max so at 8000 per 5mm that equates to 0.0125mm or just under 0.0005inch.
Hood
Hood,
I'm running Geckos, which allow up to 128 counts, which is 0.0064". Doesn't help if you're in a rapid....
Regards,
Ray L.
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Servos only allow for that tiny amount error? Wow that's not much at all!! Here I was thinking it could compensate for all kinds of error.
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Geckos as Ray says are set to 128 counts so how much that is will depend on your encoder count, any reduction and pitch of screws. The drives I use can be set to any following error I wish. The thing is you want to get it as tight as you can as that means your machine is where its meant to be, no point in having the machine capable of being off when machining as you will end up with scrap.
Hood
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BTW - Mine typically run less than 20 counts error (0.001") on all axes in actual use.
Regards,
Ray L.
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That makes sense. With my steppers if they ever stall they usually stall by a lot, so I keep things conservative. It's usually because of junk on the ballscrew, hitting the limit without limit switches, rapids that are too fast, or just cutting too hard (happens on Z all the time while drilling). I sort of assumed that servos would be able to read this error, even if it's like 1/2", and correct for it. Good to know!
John
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Servos don't "correct" errors. They can simply make you aware of them. But a properly designed and operated stepper system should never be off-position. This is not an inherent characteristic of steppers, but rather an indicator that the stepper system (motors, drivers, power supplies) were either poorly matched to the requirements, or are being operated outside their capabilities. Under those conditions, servos will fare no better. How would you "correct" for a 1/2" position error anyway? The part is long since scrap by the time that happens.
Regards,
Ray L.
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Yeah the part would be scrap but at least you wouldn't have to re-zero, I make lots of identical parts on fixtures. Thanks for clearing it up for me guys!
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Yeah the part would be scrap but at least you wouldn't have to re-zero, I make lots of identical parts on fixtures. Thanks for clearing it up for me guys!
That's where accurate home switches and fixture offsets come in handy. If you lose position, you simply toss the part, re-home the machine, and get back to work, losing only a few seconds. If you don't have home switches, then I suggest using probing to zero the machine - also takes just a few seconds per axis. You just have to make sure you always have appropriate reference surfaces, on the part, fixture, or vice, to zero to, even if the part has been partially machined.
Regards,
Ray L.