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Thread: Zero point adjustment off after brown out..

  1. #1
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    Default Zero point adjustment off after brown out..

    Hello, this is my first post so please bear with me. After we had a brown out and battery back-up failed, we lost the machine reference home position on our Mori Seiki SL303 machine. As a result, the (X) zero point adjustment is now off by 0.219. Does anyone have any ideas on how to adjust for the 0.219 difference and still keep the machine X alignment marks in line? Thanks.

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    Here is a procedure that will work on the SL303. Bascially you will Zero return your machine and move it the amount you think you are off and then toggle the bit. Make sure to follow the last step to check that the overtravels.

    Zero Return parameter setting procedure for Fanuc 16/18 and 16i/18i Controls
    Move the axis to where you think zero return should be. If you can't get to the position you would like hold in "P" and "Cancel" on power up to bypass soft overtravels or you could change the soft overtravel limits to temporarily. WARNING- Do not try holding in any other keys except P and Cancel. You could blow out parameters, programs or other data.
    Select "MDI" mode

    Press the function key “OFFSET SETTING”
    Press the soft key “SETTING”.
    Move the cursor to “PARAMETER WRITE” . May need to page up or down to get to the top of the Parameter numbers.
    Turn on PWE (Parameter Write) make it a 1

    Press the function Hard key "SYSTEM"
    Press the softkey "PARAM"
    Type1815 and press "No.Search" . This should bring up parameter 1815.
    Arrow down to whichever axis you want to change X,Y,or Z.

    Change bit 4 (APZ) (make sure you count from the right starting with first space is Zero, Bits are as shown here-76543210). This will delete the current reference zero. Alarm must power down will appear, DO NOT POWER OFF

    Go back to the parameter 1815 and make bit 4 a one

    Power off machine for one minute and power up. New home position will be set.

    Check coordinates of program and see how far you are off if they are not correct repeat steps. Also make sure you handwheel the axises slowly to there overtravels and make sure nothing binds no servo alarms occur or destroys any way covers If you set incorrectly severe damage can occur. Also remember if this is an axis that the pallet changer or Tool changer is dependant on alignment then you must check this also because it is based off of zero return. Do not change 2nd reference position to comp for this. Always change home position.

  3. #3
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    does this work for fanuc fx15n? I also am having this problem after we pulled the limit switch off cause we kept getting overtravels(not my idea) our x axis is off by about an 3/8 of an inch. its a ikegai 6t

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    Petro,

    Your method is similar to the one I've learned, but differs in the power-off/on sequence.

    The way I learned it was to find the "true zero" first, as your method does.

    Next, change the parameter 1815.4 (APZ) to "0", and power the control off completely (following the instruction on the screen display.)

    Power it back up, and change the 1815.4 (APZ) back to "1", then power it down a second time and reboot again. Done.

    If I recall correctly, if you do NOT power down in between setting the 1815.4 from off back to on, it will NOT retain the new zero point. I guess next time I have to go through the procedure, I'll try it your way.

    Mind you, with either method, this needs to be a complete power down, main switch off.

    MIC809, it might be the same on your Ikegai, just find which parameter is labeled APZ.

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    Yep you are correct it will work your way also, the only thing that I am not sure of if it is done your way and its on a vertical axis. The axis will drop a little depending on how quick the axis brake kicks in. Granted the amount depending on the machine can be only a few thousands somtimes if the brake is working properly. Then when you power up will the servos recover this lost postion? If I remember right I think it will stay at where the axis had dropped to. So if you then toggle the bit back to one which sets the new home point you would be off from your original position . Do you know if that is the case or does the axis recover?

    Thanks

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    The axis will NOT recover position if you power down before changing APZ back to 1. At that point it has no established marker on the encoder. I learned the same method of toggling 0,1 and then powering off and back on. In all of the manuals we supplied when I was with Liberty, that was the method we recommended.
    Cody Stamper



    (Note: The opinions expressed in this post are my own and are not necessarily those of cnc-professional-forum.com and its management)

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    There are also some Machine tool builders for example Mori where they have a Zero point set function. That way for example if you change APZ to 0 then set in one of the screens a function labeled " Zero point set". I can not remember exactly but if I am not mistaken this changes somthing that allows you to move the axis where you would like home to be when APZ is a zero. Then you would put the machine in Zero return mode. Press one of the axis jog keys. THe axis then moves slowly and looks for the one revolution pulse and counts the grid shift from there to set your home.

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    My understanding of the "Zero Point Set" on the Mori Seiki machines, is to ignore the soft travel limits until the first successful zero return is completed. This is similar to the P & Cancel on Fanuc controled machines with decel switches.

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    Petro,

    The method you're describing sounds to me like it would be used with incremental encoders and an external home switch.
    Cody Stamper



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    Actually I am sure I have used on switchless machines a few times just to try it. Since I prefer using the toggle bit method I may have got somthing wrong with how I explained it. The benefit in the way that I had explained is that if there is a crash or loss of batteries and the mechanical linkage does not slip You could start the procedure above within a .5 inch of zero return. The procedure would then find the Marker pulse and count the gridshift and the position would be exactly were it was before. If you were to far one way or the other it would still find the marker pulse but would be off one full revolution of the ballscrew. All the 3 digit Mori seiki machines (SV500,SL300,ect) have this capability if it is a switchless machine and is the recommended way from the factory. But the thing is either way you still must check all your measurements anyway and it is just easier just to toggle the bit. The times when this is more useful is when a customer runs so many parts and they are rough castings that vary so much that its hard to determine the actual place it was before. Unless you set it exactly to factory specs. Which is the right thing to do but in many cases the customer does not want to change all the NC programs.

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    I guess I am a little confused as to how it would find a marker on the encoder with APZ set to 0 without an external input. My understandind of the APZ bit is that when it is set to 0 the markers become unestablished until it is set back to a 1. I guess that it could still count pulses, but in that case if it's only looking at 1 rev of the encoder wouldn't it be possible to enable it from anywhere on the axis and be a lot farther from "0" than .500/in.? It wouldn't be able to look at software position switches, since they are established off of the axis setting. It would be interesting to see how the logic is handling it to set the "0" position.
    Cody Stamper



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    That is correct. On the mori's that are switchless machines they have 2 arrows that when aligned should be at factory zero or real close. So you would then move back about .25-.50 inch and perform it. If APZ is zero, then yes there is no home position established. I believe if you make APZ zero then power up the axis will not move at all. So when you flip the "Zero point set" to valid this will allow you to move the axis. Probably because its like RRL said, since there is no home position set it does not know where the soft limits are. So by setting this bit it will bypass them temporarily to move the axis to set zero.

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    That makes sense. I think I would still have some type of gauge bar so I could set a true zero. That would be too hit and miss for the micron tolerances we hold around here.
    Cody Stamper



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    I'm quite familiar with those braked-axis that drop a wee bit with a power-down. My method was pretty good, though it does take two or more tries to nail it.

    What I do is find the zero, perform the APZ procedure, and power it down. Then after reboot, zero it again and see how much it dropped. Raise it that much ABOVE the true zero, do it all again. Usually, it's within a couple of tenths on the 2nd try.

  15. #15
    Swarf Bin Guest

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    Quote Originally Posted by Petro
    That is correct. On the mori's that are switchless machines they have 2 arrows that when aligned should be at factory zero or real close. So you would then move back about .25-.50 inch and perform it. If APZ is zero, then yes there is no home position established. I believe if you make APZ zero then power up the axis will not move at all. So when you flip the "Zero point set" to valid this will allow you to move the axis. Probably because its like RRL said, since there is no home position set it does not know where the soft limits are. So by setting this bit it will bypass them temporarily to move the axis to set zero.
    This procedure is correct and is not a "hit and miss" as it picks up the reference position within the arrows. This reference position will only have moved if someone has altered the gridshift. When it establishes the zero psition. Mount a boring bar holder which you know id true in the turret and fix a DTI to the chuck. Come down to the X0 position and check the centerline with the dti inside the boring bat holder. The clock should read Zero Zero. If not then a small gridshift is required.

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    When I have the capability to zero from anywhere in vicinity of the axis alignment marks, I would call it hit and miss. I like to have a gauge bar from a true location back to Zero, so that no programming adjustments or grid shifts are required.
    Cody Stamper



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  17. #17
    Swarf Bin Guest

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    Quote Originally Posted by codyst
    When I have the capability to zero from anywhere in vicinity of the axis alignment marks, I would call it hit and miss. I like to have a gauge bar from a true location back to Zero, so that no programming adjustments or grid shifts are required.
    You don't have the capability to zero from anywhere. You can only establish a zero when the control registers a marker pulse from the encoder. If you are less than one revolution of the ballscrew away from the arrow then you will zero in the correct position. Granted it's possible to pick up on any marker pulse along the axis travel but then the arrows will not align and you know you haven't picked up on the correct marker pulse. To start again you simply make 1815 bit 4 a zero again and retry.

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    Quote Originally Posted by Swarf Bin
    You don't have the capability to zero from anywhere. You can only establish a zero when the control registers a marker pulse from the encoder. If you are less than one revolution of the ballscrew away from the arrow then you will zero in the correct position. Granted it's possible to pick up on any marker pulse along the axis travel but then the arrows will not align and you know you haven't picked up on the correct marker pulse. To start again you simply make 1815 bit 4 a zero again and retry.
    If it's possible to pick up any marker pulse, then I do have the capability to zero from anywhere. I understand the procedure, I just personally feel that it is inaccurate. I can't eyeball plus or minus a few tenths just looking at the arrows.
    Cody Stamper



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  19. #19
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    You clearly don't know the procedure. Mori Seiki pride themselves on accuracy. I don't imagine they would have a zero set procedure which included "eyeballing a few thenths". The procedure always repeats to the marker pulse not plus or minus a few tenths away from it. If it is going to be out it will be out by 10mm, 20mm, 30mm etc which are increments of the pitch of the ballscrew. The arrows are an indication that you have selected the correct marker pulse, not an indication of the correct zero position, that has already been set by the grid shift.

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    With 4 of their mills and 2 of their lathes on the floor, I am very aware of their procedures. I have a way I like to set up my machines so that I know my zero points are 100% accurate all the time. Will the procedure work? Yes. Do I use it? Positively not. I tried it on my machines after Petro mentioned it and I am just not comfortable with it. We have one dedicated project on the lathes, and I zero off of the chuck with my gauge bar, and it's ready to go. I don't like the idea of trying to find a point in space and lining it up to a set of arrows. I don't like the idea of "I missed it that time, lets try again". To me there is no better way to have a true zero position than by having a gauge bar set to a known length and taking it to a zero position off of a fixed location, that way I touch off, zero and I'm done.

    I'm sure a lot of people use it with no problem what so ever, but in MY mind it's not accurate, and not the way I want to set up my machines.
    Cody Stamper



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    Let me see if I can clarify some things a little more for the Mori procedure. Ounce the marker pulse has been established. You would then adjust the grid shift value to bring it in to the smallest resolutioin the machine is capable of. The Mori Seiki manuals comes with specific distances from zero return which you would use to dial in the grid shift value. By adjusting the gridshift you can attain just as much accuracy as toggling the bit. However it will take longer doing it with the grid shift method. The only benefit I can see is if you use the Mori method and adjust gridshift. Is when you pull or loose the pulse coder batteries or replace a drive, you could perform the arrow alignment procedure without the need to get any test bars or indicators out to verify position. As long as no crashes or mechanical linkage has not changed from the last time you established zero return. However since you never know what has happened to the machine you would most likely check with your testbars and indicators anyway, so why not just use the toggle bit method to start with and save some time.

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    Petro,

    That's what I was getting at. Most of the time when we have to rezero it's because someone had an oops at the machine. When we replace a drive/motor/encoder we still use a testbar mainly because I'm finicky about how things are setup and I like to have a visual of exactly where the machine is sitting. I wasn't trying to say that it was a bad procedure, just that for my way of setting things up I prefer a testbar. We've got testbars for pretty much all of our machines after one of our engineers told me his method of "cut one and see where it's at". It only took a few times of running into a part in rapid to see why I felt that way.
    Cody Stamper



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    Cody,

    I AGREE with you totally!
    Though Petro is correct in his statement, there is always the UNKNOWN that is the issue.

    RRL

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    Thats what I had said before, I was just trying to clarify Mori's procedure. I agree with you Codyst completely. I personally have always used the toggle bit method, NOT the Mori way. I was ony referencing other ways manufacturers sometimes recommend and attempt to explain there possible reasoning behind there own procedure verses how most of us currently set zero return on switchless machines.

  25. #25
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    I'm afraid I feel I have to bring this subject back up again as it seems we are talking about two different things.

    We need to seperate whether we are establishing the zero point after a servo battery loss or after a collision.

    If it is after a battery loss then the Mori Procedure of zero point set which involves aligning the arrows will bring you back to where you were before battery loss. There is no need to adjust grid shift or anything. Assuming the procedure has been followed correctly then a DTI to the internal of a boring bar holder will let you know if your centerline is correct - which it will be. I never suggested at any point that you do not check with a DTI or a test bar after setting. That is a given!

    In the case of a collision then either the grid shift or the 1815 toggle will need to be done as it is impossible to reset the turret back exactly to where it was before the crash. The new turret position will have no relation to the marker pulse of the X-Axis encoder.

    We then have the arguement of 1815 toggle against gridshift. I would say that in 95% of cases after a collision I would use the 1815 toggle as it is quicker and does not require calculations. However, Mori Seki always state that the gridshift should be recalculated again. The reason for this is quite difficult to explain but I will try anyway. If the last person to set up the zero position used the 1815 toggle then the gridshift value now has no bearing to the new zero position. If a "tweak" is required later then the new gridshift value would be calculated and either added to or subtracted from the original gridshift value in 1850 which is already wrong. The result of this will be that when you check the centerline with a DTI or testbar after adjustment the new position will be incorrect. Therefore, Mori Seiki's thinking is that everyone should recalculate gridshift so that this does not happen.

    The way I personally get round this problem is to re-enter the same figure in 1850 before I start my calculations. This will mean I don't have to calculate twice when using gridshift.

    I said 95% of cases I would toggle 1815 which is true. The case where I would need to calculate gridshift would be if I was setting up a complicated millturn for example, where turning centerlines need to match milling centerlines and calculations need to be made to "tweak" the centerlines after test cutting and measuring. This is not possible with 1815 toggle.

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    Default Re: Zero point adjustment on Fanuc 6m-A

    I have the same problem how do I fix it on a fanuc 6M-A?
    would it be the same case?

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