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Thread: Do all fanuc based machines over travel?

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    Default Do all fanuc based machines over travel?

    Hey everyone, ive been working fulltime in a machine shop for about 8 months now, started from pushing a button to programming and setting up lathes and mills and am learning a swiss lathe at the moment which basically led me to my question.

    We have 2 miyano bnc lathes, and a leadwell which are all fanuc based and will overtravel. We also have an older matsurra but it is based on a yasnac control and overtravels as well; which led me to the assumption that because they are all older 10-20 year old machines that the technology (im not even sure what this is) to prevent over travelling didnt exist.

    Our other machines include a milltronics mill, a haas vf3 and a citizen l20, all of which are not fanuc based and are fairly "new"; the millttronics and citizen are less than 5 years old and the haas is about 10 years, so my previous theory seemed to work out, until..

    ..We got ourselves a citizen K16 which is fanuc based.. (this one is kind of "mine", ive learned most of my swiss knowledge and programming from our L20, but since im new my boss is letting me be the one to learn the machine). I found out today that it does indeed overtravel, when our L20 does not. I figured being a swiss lathe of the calibre it is and its age that overtravel would not be a headache to deal with but I was wrong.

    So my theory of older machines overtravelling and new ones not was thrown out the window.

    Aside from the yasnac, fanuc control and servos/motors seems to be the only common denominator.

    So why? What exactly is the reason for this?

    Im not so weathered on the maintenance and true mechanical properties of the machines, but my basic knowledge includes a ballscrew attached to the servo which moves the axis around.. our machines that dont overtravel are designed this same way, so what gives, surely if other manufacturers have worked around this, then fanuc could right?

    Sorry for the long drawn out post :P

    Thanks!

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    Community Moderator Al_The_Man's Avatar
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    Most systems, Fanuc included have software (parameter) limits as well as hardware limits to prevent overtraveling causing damage.
    In ,many cases, the software limit is either not set up correctly, if at all.
    The idea of the software limit is to prevent ever reaching the physical overtravel limit.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design (Skype Avail).

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


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    Software limits are provided because it is desirable not to reach hardware limits. A hardware limit causes emergency stop, and you need to start again (at least this happens on my machine). A software limit does cause alarm, but you can manually move the tool to the permitted zone, reset the control, and alarm goes away.
    In some cases, software limit has to be used. For example, you may have a hardware limit for a chuck of a particular size (so that the tool does not hit the chuck). Now, if you replace the chuck with a chuck of a different size, the position of hardware limit switch would become incorrect. It may or may not be possible to shift the hardware limit switch on the machine (fixing holes may not be at the right place). But, you can define any position as software limit.



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    Registered christinandavid's Avatar
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    Default Limit Switch

    Hi,

    Having gone from Heidenhain to Fanuc, I too find it annoying that machine will happily travel to the software limit and then alarm out, requiring the aforementioned jog and reset to continue. It would be nice if the control could inhibit further axis movement without bringing up an alarm and when in cycle mode, as on Heidenhain, predict the occurrance before performing the movement.

    DP



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    I have to add that if you purchase a new machine, the MTB may not have put the hardware as well as software limits at the right place. I realised this only after the tool actually hit the chuck due to a programming mistake on my machine. So, on a new machine, before you start working, move the tool manually to check if it enters dangerous area.



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    is very simple theory

    every machine ,but every machine, has a soft limit that u can adjust as u wish.
    after that limit that is write down in parameters depending on what type of fanuc u have,is a limit switch for emergency limit.
    many of machines from nowdays has also a mechanical stop that is a round rubber on ballscrew at the end or somewhere else .
    if machine pass the soft limit and the limit switch is not working will go more and will hit everything because u have some more space on ball screw .

    so they put a round rubber to stop machine slowly and not to be IRON CRASH IRON so will prevent damaging

    i think in u case all parameters for soft limits are lokk like 9999999,-999999
    so u have to put the corect ones



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    Well I understand that there are soft limits and hard limits, and when it overtravels its usually a soft stop unless of course you rapid past hte stop.. then things can get hairy.

    But on our machines that dont over travel, I can jog and all the way to the end of the axis and the machine just stops at that point, no matter how fast I seem to turn the jog handle, the machine just stops and is happy to continue doing its thing



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    hi

    from what u say i am not exactly able to understand u problem
    if u can give us an example of what u want to do with the axes and what machine do real.

    u say is overtravel before to reach the limit?
    give me an example how u do and what is happening

    i think i can help u

    cu m8



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    Registered dcoupar's Avatar
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    If it makes your life easier, most newer Fanuc controls have a parameter that automatically clears the alarm when you jog the offending axis off the "stop" (no RESET necessary).

    There may even be a parameter that controls whether the alarm is issued at all, but I haven't found it yet.



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    now i understand u
    should be like a warning or some of operator alarms that don't stop the proces just it say for information

    say what type of fanuc u have and i will look for the parameter

    ps:i know that new fanuc have that option.



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    Quote Originally Posted by zavateandu View Post
    now i understand u
    should be like a warning or some of operator alarms that don't stop the proces just it say for information

    say what type of fanuc u have and i will look for the parameter

    ps:i know that new fanuc have that option.
    Sorry... I was replying to glenthemann



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    im not having any problem, im not looking for any parameters to have it automatically clear the alarm once the axis is moved off of its stop. I am wondering why it is that OTHER manufacturers machines do NOT overtravel. Soft or hard limits or not, these machines just dont overtravel. They stop right at their limit no matter how much more you move your jog handle. There are no alarms or overtravels, the machine just simply stops. Ie. if I move x towards its return position x0 then the machine will stop at x0 whereas it seems the fanuc will just happily move past that point and then send you a message saying you overtravelled.

    I just dont understand how other companies get aorund this silly overtravel business and yet fanuc which as far as I know is one of the oldest and top NC/servo/motor companies around, hasnt ever worked this out?



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