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IndustryArena Forum > MetalWorking Machines > Okuma > Wrong home reference VMC MB-46VA +OVERFLOW Position
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  1. #1
    Join Date
    Aug 2015
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    36

    Wrong home reference VMC MB-46VA +OVERFLOW Position

    Hello,

    In newbie to Okumas, and here we have a VMC MB-46VA equipped with OSP-E100L control that has lost home. The initial position was showing big numbers in the three axis, the Z axis was 16187.0mm even the pot was almost touching the table (attached pictures of the screen). The situation was similar for X and Y axis.

    Our approach to solve this situation was remove the encoders and plug out the power of each servomotor to recover the position in the control just turning by hand the encoders to get closer to zero position. But when we went near to zero and reach negative positions the control shows +OVERFLOW position and get alarm "1153-01 MCS CON APA deviation X-AXIS" (different number corresponding to proper axis), so we can´t go in negative direction by hand. In the parameter position screen the N TRAVEL LIMIT was +OVERFLOW for the three axis, I changed this values to zero.

    Here is our trouble, we have returned the position of the Z axis to home by hand and now if we indicate in MDI G30P1 the control starts to look for home in negative direction until -OVERFLOW position (in MDI the movement in negative direction to reach home is possible), we don´t know how far the position is going to be set. One alternative we have talked is plug out the servomotors again and let them run free until the -OVERFLOW is reached, from there observe if we can move the axis in handle mode.

    I would like to hear your comments based on your experience.

    Thank you in advance.

  2. #2
    Join Date
    Apr 2009
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    1262

    Re: Wrong home reference VMC MB-46VA +OVERFLOW Position

    When you get the overflow, the encoder has exceeded its range and you need to add/ sub a value to the MC Zero Offset Parameter until you get rid of the overflow error. At that time, you will have an actual coordinated displayed. Compare this number to your actual position and shift the MC Zero Offset to correct the deviation.

    I’m afraid It’s a bit of a hunt to find the magic range. At least I’ve never been able to get the info out of Okuma on how they do it.

    Best regards,
    Experience is what you get just after you needed it.

  3. #3
    Join Date
    Jun 2015
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    4131

    Re: Wrong home reference VMC MB-46VA +OVERFLOW Position

    hy catalyst there should be a io safety switch inside the electrical cabinet; this allows to move the axis only by using the hand wheel; like this, you move all axis until you hit the hard limit in both directions, by looking at the limitators when they are nearly to be pushed : this requires to have a visual of the limitators, and also, i am afraid that in this mode ( io switch position <> default ), you won't be receiving the over travel alarm A, and it may be dangerous; even if the alarm occurs, then there is a chance for a fail if a hard limit is faulty, so maybe this method should be postponed until it is understood how it works; however, once mastered, it allows defining the soft limits pretty accurate

    an alternative, would be to inspect the parameters of soft limit travels, but i don't know where they are located for your machine / osp generation ... i may guess, but i may get it wrong if you know where those parameters are, you simply inspect the limits and adjust the encoders base to be between them, but not anyhow : if i remember correct, X & Y base 0 is at travel/2, while Z base 0 is <> travel/2 ( regarding the relative position of the base 0 and the soft limits, maybe you can check the management data card, that maybe is inside the electrical cabinet, somewhere down or in a pocket on the door inside : if it has written the original bases and soft limits, you may figure it out if positive and negative travels are equal or different; even so, it should be possible to re-calibrate the axis, by puting the base 0 anywhre you wish between soft+ & soft-) ; however, as long as base 0 is between soft+ & soft-, even if it is not where it should be, then an alarm A over travel should occur if a hard limit is reached; again, you may get into trouble if a hard limit switch is faulty, so once again i recomand having a visual of these hard limit switches, so to stop feeding the axis when you are near them, and also to check if alarm A occurs as it should

    another thing, is that once you have rotated the encoders by hand, it may be possible that their new position is not updated inside the controller, or, if it was updated, then the soft limits are still as before

    regarding these limits, it may be possible that some parameters self update, if other parameters are changed, so it would be ok to have the values written before begining to edit them; stuff may escalade quickly if some parameters will self update, without being aware that also they need to be checked

    in the end, if all goes ok, you should check and update :
    ... home position 1 & 2 : so to avoid crashing during a tool change sequence, since those homes may be used as a reference during tool changing
    ... pivot distance : in case a 4th 5th axis is used, and the ' pivot ' parameters is used during coding; even if you don't use it, it should be where it was before, just in case a rotary is added and the person that will setup it is not aware; this is not so critical, if a rotary is adjusted later, by someone who knows what he is doings
    ... there may be also other parameters


    my god, you are so lost i am afraid that you need someone near you ( like a trustfull pet ), or at least to have teamviewer on your machine / kindly
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  4. #4
    Join Date
    Apr 2009
    Posts
    1262

    Re: Wrong home reference VMC MB-46VA +OVERFLOW Position

    Okuma’s have absolute position encoders so they will know where they are at even if rotated by hand. It is much like the odometer on a car so you are not going to reteach it without using the MC Zero Offset that I referred to. The switch kitty refers to is only for overtravel and is not for overflow. Completely different. Once re-taught you will not need to adjust stroke end limits or variable limits. They will fall back into place with original recorded numbers from your Management Data card in the back of the machine.

    I’ve done this many times. Every time you upgrade to .1micron control you will need to go through this procedure. It’s not that hard to get rid of the overflow. Try going up by 1000 at a time until you get real numbers to appear instead of overflow. Once you have numbers it’s easy to adjust for difference from target.

    Best regards,
    Experience is what you get just after you needed it.

  5. #5
    Join Date
    Jun 2015
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    4131

    Re: Wrong home reference VMC MB-46VA +OVERFLOW Position

    maybe he did not encountered the real overtravel case, but i believe that after encoders were removed, rotated and puted back, effect is pretty similar to overtravel

    after rotation, it may be possible that encoder got out of -9999..99 +9999..99

    if, and only if, after enconders were put back, their position is the same as before ( or rotated 360*1 *2 *3 etc ), and also the nut & screwball are the same, thus if everything is like there was not dissamble, then the data from the management card will work; otherwise, if original zeros are restored, but axis are shifted, then a grid shift is required ... or a crash may occur, especially if a hard limit is faulty, or maybe during a tool change

    The initial position was showing big numbers in the three axis, the Z axis was 16187.0mm even the pot was almost touching the table (attached pictures of the screen). The situation was similar for X and Y axis.
    i still wonder what have caused this ... let's hope that it will be fixed by restoring the zeros

    maybe there was activated a wrong wcs, or something happened with wcs [1] ?

    Try going up by 1000 at a time until you get real numbers to appear instead of overflow
    after real numbers are displayed, i would add a few more 1000's, so to get a bit away from the limit, then use ' cal '

    Every time you upgrade to .1micron control you will need to go through this procedure
    do you use such precision ? why ? maybe you should try a cnc grinder ... kindly
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  6. #6
    Join Date
    Apr 2009
    Posts
    1262

    Re: Wrong home reference VMC MB-46VA +OVERFLOW Position

    The MC Zero Offset is how you accomplish the “grid shift” for the absolute encoders. Once done properly NO data needs to be adjusted for Zero Set, Variable limits, Stroke End limits, etc. It’s change the 1 and done!

    Precision? I was holding a +\- .0001” bore on a lathe with a boring bar and was cutting less than .00004” taper while doing it.

    Check out some precision:

    https://youtu.be/ULEJatGhcks

    Best regards,
    Experience is what you get just after you needed it.

  7. #7
    Join Date
    Jun 2015
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    4131

    Re: Wrong home reference VMC MB-46VA +OVERFLOW Position

    a while ago i needed to change the z- soft limit, so to allow a tool to reach it's final depth; i simply enlarged the maximum z travel, by shifting the soft- limit, but still knowing how far i was from the hard limit

    also, i like to calibrate axis zero's, so program_zero = distance_from_table, and z_offset = distance_from_spindle_face

    when i have done such things, it did not worked everything only with a single edit

    on lathes, i know that editing some encoders zero will also shift the soft limits, but this does not happen to all origins

    i don't remember exactly which axis needs extra-caution, since i do such calibrations pretty rarely last one was more then an year ago ...

    Once done properly NO data needs to be adjusted for Zero Set, Variable limits, Stroke End limits, etc. It’s change the 1 and done!
    stuff 2 do after editing encoder zero :
    ... cas origins need to be re-defined
    ... after a clutch slip, is needed to re-adjust the soft limits

    Precision? I was holding a +\- .0001” bore on a lathe with a boring bar and was cutting less than .00004” taper while doing it
    once i was holding a +\- .00009” bore on a lathe with a boring bar and was cutting less than .000039” taper while doing it; just kidding / kindly
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  8. #8
    Join Date
    Aug 2015
    Posts
    36

    Re: Wrong home reference VMC MB-46VA +OVERFLOW Position

    Quote Originally Posted by OkumaWiz View Post
    When you get the overflow, the encoder has exceeded its range and you need to add/ sub a value to the MC Zero Offset Parameter until you get rid of the overflow error. At that time, you will have an actual coordinated displayed. Compare this number to your actual position and shift the MC Zero Offset to correct the deviation.

    I’m afraid It’s a bit of a hunt to find the magic range. At least I’ve never been able to get the info out of Okuma on how they do it.

    Best regards,
    Wiz,

    Thank you for the advice. Well there are times it turns out to be such a hunt. Mine starts tomorrow.

    I see in the parameters screen N TRAVEL LIMIT and P TRAVEL LIMIT must have the same amount (with the different sign ) and these limits are the axis travel, now this machine has different amounts in both limits. Then we´ll start looking to find the magic range to the zero offset.

    Thanks again, I´ll post the progress later.

    Ari

  9. #9
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    Jun 2015
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    4131

    Re: Wrong home reference VMC MB-46VA +OVERFLOW Position

    hy catalist, is not critical to have positive travel = negative travel, thus is not a must to set those ranges equal

    also, it takes more time to make those equal; in other words, is faster to set the machine without caring if positive and negative travels are equal, unless you wish to calibrate the encoders zero : calibration means that encoder 0 will no longer mean a random position, but a phisical absolute position for the axis; even if a machine does not have the zeros calibrated, this does not mean that it does not work; you may wish for calibration, for example, when you have an external tool setter, and external fixture preparation, and you wish to avoid measuring the tools and fixture inside the machine; also, even if you don't use an external setter, a calibrated cnc allows declaring program zero and tools zero much faster; calibration, if required, is done on a machine that works nice, only if the parameters inside the machine allows to shift the zeros, and okuma osp does that

    i attached some images from a newer osp, and maybe some parameters are also on your machine ( i highlighted the interest ones ) :
    ... 01 limits shown are in respect to wcs
    ... 02a machine limits, not relative to wcs; x&y travels, + & -, are equal, but z travel is not simetrical; " zero offset machine " is the encoder zero; check also the in-position, so to be close to those values
    ... 02b pivot & encoder offset
    ... 02c more in-pos settings
    ... 03a home positions for the tool change sequence
    ... 03b movement order for 03a
    ... 04 i have no clue about those ones

    Then we´ll start looking to find the magic range to the zero offset
    carefull; a faulty hard limit switch will ruin your day / kindly
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  10. #10
    Join Date
    Aug 2015
    Posts
    36

    Re: Wrong home reference VMC MB-46VA +OVERFLOW Position

    Quote Originally Posted by deadlykitten View Post
    hy catalyst there should be a io safety switch inside the electrical cabinet; this allows to move the axis only by using the hand wheel; like this, you move all axis until you hit the hard limit in both directions, by looking at the limitators when they are nearly to be pushed : this requires to have a visual of the limitators, and also, i am afraid that in this mode ( io switch position <> default ), you won't be receiving the over travel alarm A, and it may be dangerous; even if the alarm occurs, then there is a chance for a fail if a hard limit is faulty, so maybe this method should be postponed until it is understood how it works; however, once mastered, it allows defining the soft limits pretty accurate

    an alternative, would be to inspect the parameters of soft limit travels, but i don't know where they are located for your machine / osp generation ... i may guess, but i may get it wrong if you know where those parameters are, you simply inspect the limits and adjust the encoders base to be between them, but not anyhow : if i remember correct, X & Y base 0 is at travel/2, while Z base 0 is <> travel/2 ( regarding the relative position of the base 0 and the soft limits, maybe you can check the management data card, that maybe is inside the electrical cabinet, somewhere down or in a pocket on the door inside : if it has written the original bases and soft limits, you may figure it out if positive and negative travels are equal or different; even so, it should be possible to re-calibrate the axis, by puting the base 0 anywhre you wish between soft+ & soft-) ; however, as long as base 0 is between soft+ & soft-, even if it is not where it should be, then an alarm A over travel should occur if a hard limit is reached; again, you may get into trouble if a hard limit switch is faulty, so once again i recomand having a visual of these hard limit switches, so to stop feeding the axis when you are near them, and also to check if alarm A occurs as it should

    another thing, is that once you have rotated the encoders by hand, it may be possible that their new position is not updated inside the controller, or, if it was updated, then the soft limits are still as before

    regarding these limits, it may be possible that some parameters self update, if other parameters are changed, so it would be ok to have the values written before begining to edit them; stuff may escalade quickly if some parameters will self update, without being aware that also they need to be checked

    in the end, if all goes ok, you should check and update :
    ... home position 1 & 2 : so to avoid crashing during a tool change sequence, since those homes may be used as a reference during tool changing
    ... pivot distance : in case a 4th 5th axis is used, and the ' pivot ' parameters is used during coding; even if you don't use it, it should be where it was before, just in case a rotary is added and the person that will setup it is not aware; this is not so critical, if a rotary is adjusted later, by someone who knows what he is doings
    ... there may be also other parameters


    my god, you are so lost i am afraid that you need someone near you ( like a trustfull pet ), or at least to have teamviewer on your machine / kindly
    Hello Kitten

    Once the encoders were rotated the new position was updated and the limits seems to be the same as before. We have checked the parameters, beside the ones we changed, they are still the same. We have the original 3.5" diskette with the parameters, but we are not able to read in old PC´s, this just doesn´t boot up.

    First the MC Zero Offset Parameter was updated and then the home position 1 was updated to avoid overtravel when zero return was commanded.

    Until here everything ok.

    PS I´m lucky to have my pokemons always with me :3 :wee:

    Greetings

  11. #11
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    Aug 2015
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    36

    Re: Wrong home reference VMC MB-46VA +OVERFLOW Position

    Hello Wiz,

    You were right, there´s no just a number, it could be a variety depending on the current postion of the encoder, so if somebody is found in such situation they will have to start hunting.

    Greetings

  12. #12
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    Aug 2015
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    36

    Re: Wrong home reference VMC MB-46VA +OVERFLOW Position

    Oh partners, there´s a new situation. We have set the home position, now we´re running the first program test. Everything ok until a linear interpolation is commanded with G1, no matter what axis, the machine doesn´t move to the designated position even it is pointed as target In the Block Data Screen, I see the feed per revolution Fr shows +OVERFLOW. At this point I literally have no idea how to approach this.

    Again, I would appreciate a lot some hint to help me solve this new problem.
    Greetings.


    .



  13. #13
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    4131

    Re: Wrong home reference VMC MB-46VA +OVERFLOW Position

    hy catalyst, hand wheel works ? if so, move the z axis up50, then reverse 25; same with xy

    then g91 g00 x10 y10 z10; see what happens
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  14. #14
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    Quote Originally Posted by deadlykitten View Post
    hy catalyst, hand wheel works ? if so, move the z axis up50, then reverse 25; same with xy

    then g91 g00 x10 y10 z10; see what happens
    Hello Kitten,

    The handwheel works, but the jog buttons doesn’t make movements.
    The control admits and executes incremental commands. The commanded block moves all the axis +10.0

    In any instance there’s no trouble with rapid command G00, wheter incremental G91 or absolute G90

    Greetings

    Ari

  15. #15
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    Re: Wrong home reference VMC MB-46VA +OVERFLOW Position

    hy catalist, i don't know ... check the wcs coordinates; put all axis in the middle, then use ' call xyz'; maybe the wcs is wrong ?

    i just checked on the lathe arround here : z_pitch = 12, and encoder range is 0 - 99999.999; maybe you received the overflow, even if you rotated by hand the encoder only a few turns, because, before removing the encoder, it's zero was close to range bounds / kindly

    Quote Originally Posted by OkumaWiz View Post
    The MC Zero Offset is how you accomplish the “grid shift” for the absolute encoders. Once done properly NO data needs to be adjusted for Zero Set, Variable limits, Stroke End limits, etc. It’s change the 1 and done!
    Quote Originally Posted by deadlykitten View Post
    on lathes, i know that editing some encoders zero will also shift the soft limits, but this does not happen to all origins

    i don't remember exactly which axis needs extra-caution, since i do such calibrations pretty rarely last one was more then an year ago ...
    hello mr wizard when adjusting soft limits, there are restrictions if modifications are made in " user parameter ", but restrictions are removed inside " system parameter "

    normally, no one edit's those, because, like you said, a zero edit will shift all, but so far i hit these 2 particular cases ( and possibly others ) :
    ... z clutch slipped
    ... there was a setup using the tailstock pretty close to w- limit, and pushing force ( thrust value ) was high; part flew away ( or chuck was open too soon, etc ), and the tailstock traveled over the w- limit with 0.1 or something small ( for same program_z zero, tailstock clamp position changes, depending on thrust )
    * in such cases, it is required to edit the soft limits / kindly
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  16. #16
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    Re: Wrong home reference VMC MB-46VA +OVERFLOW Position

    Everything ok until a linear interpolation is commanded with G1, no matter what axis, the machine doesn´t move to the designated position even it is pointed as target In the Block Data Screen
    sorry for an obvious tip, but did you started the spindle before g01 ? wcs and tool offset are ok ?
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  17. #17
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    Re: Wrong home reference VMC MB-46VA +OVERFLOW Position

    Yeah. It could be obvious, but sometimes is oka go to the basics. We tried with spindle on and off, no movement with G01 was allowed.

    Later I found in the operation manual the M130 condition to allow the G01 movements go with spindle off. I just add M130 to the program to start making chips.

    Thank you very much, partners. This machine had been out of service for fourteen months.

    Greetings

    Ari

    Enviado desde mi SM-J700M mediante Tapatalk

  18. #18
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    4131

    Re: Wrong home reference VMC MB-46VA +OVERFLOW Position

    I just add M130 to the program to start making chips
    so, now you are able to execute g01 ? but are you also spinning the spindle ?
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  19. #19
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    Re: Wrong home reference VMC MB-46VA +OVERFLOW Position

    Quote Originally Posted by deadlykitten View Post
    so, now you are able to execute g01 ? but are you also spinning the spindle ?
    Yeah, we are running G01 with M130 and the spindle as usual. M131 is active even with the spindle running.

    It seems that the needing to command M130 is a damaged interlock in the ATC door, but I'm not sure about this. What's real is that interlock was causing an overspeed alarm that limits the running of spindle up to 800rpm and a
    magnetic encoder alarm 1170 MCS .

    Enviado desde mi SM-J700M mediante Tapatalk

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