ATC Crash


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    Default ATC Crash

    The ATC on my 770 has crashed a few times. The spindle comes down and knocks the tool out of the fork breaking the nylon screws, sometimes damaging the tool and/or part. I tweak the alignment, and while it is not perfect neither is it bad. There is always a small amount of wiggle as it comes down over the TTS tool holder. It doesn't seem like a lot, but I don't know what is considered acceptable.

    Another possibility is air pressure. I am running off a portable compressor, the California Air Tools that Tormach sells. Both the ATC and mist coolant run off it and I wonder if it is not keeping up. PSI is set to 110, but can drop to 85 before the compressor kicks in. The mill will detect if the tray doesn't get to the load position, but I wonder if maybe it's just sometimes slow. It gets there, but a bit late and the spindle comes down before it's completely in place.

    Suggestions appreciated.

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    Default Re: ATC Crash

    (Comparing with how I have the ATC setup on the 1100)

    In my case, the tray is in place before the downward travel of Z even begins (when grabbing a tool). If your tray was arriving late due to improperly set solenoid valve, low air pressure, or other, I think you would see it as being quite obvious and I doubt that's the issue.

    More likely tool/spindle alignment. Either the entire ATC (did you install it and go through the basic alignment techniques using a bar mounted in spindle, etc.)? or more probably the slop in the ATC tray. I fought with some crashes for a bit when we first got this machine. There are several threads on the 'zone about this issue - but in a nutshell the tool tray is bolted onto a shaft (driven by the stepper for the ATC) and it uses a small set screw to lock it in place. That set screw can loosen, or wear a bit and become more wobbly.

    Maybe have a read through this thread to see if it helps: http://www.cnczone.com/forums/tormac...machinist.html

    WW



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    My atc was not very reliable but the following has helped its reliability:
    - Take the bottom carriage off and make sure the large threaded bolt is secured properly.
    - use path pilot
    - re-calibrate and level atc after using for a while. See tormach videos.
    - make sure you don't have excessive spindle runout. If you do fix it.
    - verify that each steel fork is 'true'. This step I am almost finished completing but I found that (4) of my steel forks ad slight bends to them. I think it is because they are waterjet cut from plate before machining. This slight bend was causing crashes but I marked and replaced each of the offending forks and this resolved my last crash issues (knock on wood)
    I have a dedicated air compressor for my pdb and atc and would recommend that but that should not be causing your crashes. If you have low air pressure it will just not complete the tool change sine it has an air pressure sensor.

    Good luck!

    Quote Originally Posted by shassel View Post
    The ATC on my 770 has crashed a few times. The spindle comes down and knocks the tool out of the fork breaking the nylon screws, sometimes damaging the tool and/or part. I tweak the alignment, and while it is not perfect neither is it bad. There is always a small amount of wiggle as it comes down over the TTS tool holder. It doesn't seem like a lot, but I don't know what is considered acceptable.

    Another possibility is air pressure. I am running off a portable compressor, the California Air Tools that Tormach sells. Both the ATC and mist coolant run off it and I wonder if it is not keeping up. PSI is set to 110, but can drop to 85 before the compressor kicks in. The mill will detect if the tray doesn't get to the load position, but I wonder if maybe it's just sometimes slow. It gets there, but a bit late and the spindle comes down before it's completely in place.

    Suggestions appreciated.




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    Default Re: ATC Crash

    My mill is an 1100, but crashes like you describe when the tray solenoid valve air adjustment screws become loose.
    They are pictured and described in the ATC manual in section 4, Air Lines.

    to lazy to chase arrows


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    Quote Originally Posted by wildwhl View Post
    (Comparing with how I have the ATC setup on the 1100)

    In my case, the tray is in place before the downward travel of Z even begins (when grabbing a tool). If your tray was arriving late due to improperly set solenoid valve, low air pressure, or other, I think you would see it as being quite obvious and I doubt that's the issue.

    More likely tool/spindle alignment. Either the entire ATC (did you install it and go through the basic alignment techniques using a bar mounted in spindle, etc.)? or more probably the slop in the ATC tray. I fought with some crashes for a bit when we first got this machine. There are several threads on the 'zone about this issue - but in a nutshell the tool tray is bolted onto a shaft (driven by the stepper for the ATC) and it uses a small set screw to lock it in place. That set screw can loosen, or wear a bit and become more wobbly.

    Maybe have a read through this thread to see if it helps: http://www.cnczone.com/forums/tormac...machinist.html

    WW
    Excellent suggestions in that thread. Yes, I did the basic alignment procedures at install, but was never happy with it. Felt I was chasing my tail. Too much play, which some suggest as a feature.

    The crashes I was carefully watching -- funny how it rarely crashes when you're trying to replicate it -- SEEMED to be due to inadequate x-axis travel. The spindle clipped the tool on the left. That's why I suspected pressure as a possible cause, but most people rule that out. I may be completely wrong about this as it was hard to watch. I should have filmed it. Anyway, I lubricated the rails and tweaked the x-stop nut. Haven't had a problem since, but am quite nervous on changes.



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    Default Re: ATC Crash

    I have several tool holders that have be tool changed enough that the corner between the 3/4" TTS body and the end chamfer have been worn into a radius. I run my draw bar fairly tight and noticed that these holders rarely experienced an "event" as compared to new ones. I now break that corner with a radius and it either seems to help or at least fools me in to thinking it helps.


    I still go through a couple of screws a week. The worst culprit seems to be loosening screws. I think it is the nature of the nylon screws to stretch and loosen. If I check the screw after running for 10 or 12 hours they will be slightly loose (our most used program averages 45-50 tool changes per hour). I snug them up a couple times a day and it seems to help. When they loosen, the tool tilts slightly and the open collet hangs on the corner of the TTS holder pushing it down and breaking the finger bolts. This is a real PITA event but it only takes a minute to replace the two screws and be back in business. The worst scenario is for this to happen when you are not there to catch it. The results after the next tool change can be really bad.

    gary



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    Default Re: ATC Crash

    Gary -

    I may have mentioned this elsewhere - but the fix for loosening nylon bolts is to switch to longer version (+10mm or so) and add a nylon nut. I don't tighten them much at all, and the benefit is 2 fold. First - they no longer have to be tightened on a regular basis. Second, when there is an event, most of the time the tool finger(s) break the bolt closest to the spindle and the bolt behind it stays intact, keeping everything (often the tool too) from falling. I expect if I played with this arrangement a bit more and dialed in the ATC just a hair tighter than it is (pretty sloppy at the moment) I would no longer have any events at all. As is now - maybe once/twice a month at most.

    WW



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    Default

    Cool
    Which McMaster part numbers for the bolt/nuts you are using
    Thanks


    QUOTE=wildwhl;2078538]Gary -

    I may have mentioned this elsewhere - but the fix for loosening nylon bolts is to switch to longer version (+10mm or so) and add a nylon nut. I don't tighten them much at all, and the benefit is 2 fold. First - they no longer have to be tightened on a regular basis. Second, when there is an event, most of the time the tool finger(s) break the bolt closest to the spindle and the bolt behind it stays intact, keeping everything (often the tool too) from falling. I expect if I played with this arrangement a bit more and dialed in the ATC just a hair tighter than it is (pretty sloppy at the moment) I would no longer have any events at all. As is now - maybe once/twice a month at most.

    WW[/QUOTE]



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    Default Re: ATC Crash

    Nylon absorbs moisture doesn't it? Perhaps that is causing a large enough dimensional change in the screws so as to affect performance.



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    Default Re: ATC Crash

    Quote Originally Posted by CadRhino View Post
    Cool
    Which McMaster part numbers for the bolt/nuts you are using
    Thanks

    The bolts are 6x1mm - and I selected 30mm long. https://www.mcmaster.com/#94175A535
    (25mm would possibly work as well)
    The matching Nylon nuts are #https://www.mcmaster.com/#93800A600



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    Default

    Thanks


    QUOTE=wildwhl;2078728]The bolts are 6x1mm - and I selected 30mm long. https://www.mcmaster.com/#94175A535
    (25mm would possibly work as well)
    The matching Nylon nuts are #https://www.mcmaster.com/#93800A600[/QUOTE]



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    Default Re: ATC Crash

    A friend of mine found the solution that he implemented on his ATC's (he has 2 1100's), and he also helped me implement it on mine.

    We took the entire ATC hub assembly apart, and drilled and tapped a hole for a larger set screws to lock the hub to the shaft. I have not had a single problem with the ATC, and it doesn't go off center anymore either. The setscrew they include with it by default is too small, and moves around in the keyway on the shaft too much.

    Haven't had an ATC crash since implementing this fix.

    Wade



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    Default Re: ATC Crash

    Quote Originally Posted by wwendorf View Post
    A friend of mine found the solution that he implemented on his ATC's (he has 2 1100's), and he also helped me implement it on mine.

    We took the entire ATC hub assembly apart, and drilled and tapped a hole for a larger set screws to lock the hub to the shaft. I have not had a single problem with the ATC, and it doesn't go off center anymore either. The setscrew they include with it by default is too small, and moves around in the keyway on the shaft too much.

    Haven't had an ATC crash since implementing this fix.

    Wade
    This is important - and what Wade speaks of I highly recommend. I made some mods there as well, though I'd like to tighten it all up a bit more. Given the mill was just moved I think now is the time.

    WW



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