Machine coordinate system off by .0591 in Z on siemens 840d
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  1. #1
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    Default Machine coordinate system off by .0591 in Z on siemens 840d

    Been making parts with my recently acquired DMG DMC103V with 840D control for a month or so. All is well except for one last problem. Z in G54 is exactly .0591" off.

    In other words, if I setup a part and "scratch" to set the work coordinate system to 0 in Z at top of part, then run the part, after the program calls up G54 at beginning of program, the Z offset changes to exactly .0591 less.

    If the program is paused, in the position window, the Z reading is correct. But if I reset/stop the program, the value indicated is exactly .0591 less than it should be. Ive been getting around this by touching off the part, then moving off the part and adding .0591 to the Z WCS. All the tools run at the correct height.

    With the Z axis all the way against the upper limit the display reads guess?? .0591". I tried setting the password access to the highest level, "System" and resetting the base zero in Z at that position but that didnt change anything. Not a big deal but Id kinda like to fix it. Any suggestions?
    Attached Thumbnails Attached Thumbnails offset1.jpg   offset2.jpg   offset3.jpg  

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    On a Fanuc there is a "Shift" (G53) register usually located on the same screen as G54 and is used to apply global adjustments to all work coordinates on the machine at the same time and by the same amount. Do you have something like that on your control? A global shift register? Does this happen only when using G54, or when using any other or all work coordinate registers? (G54-G59 etc.)

    You might scan through your parameters for the numbers that represent machine home positions or max machine travel. Stuff like that. Likely listed in metric. It wouldn't surprise me that the previous owner did some kind of adjustment by the wrong methods to fix a potential Z height problem relating to the tool change position. I had something like that once where someone had changed a number in parameters to suit the X coordinate of a pallet change position instead of adjusting the pallet station like would be the correct thing to do.

    Look for something like that.

    Just an idea.

    Dave

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    G53 is called base zero in siemens speak. I reset that to be zero at .0591 below the Z upper limit (the tool change initial Z position with no tool offset loaded "T0"). I also tried going to parameter page/G53 and G54/ changing Z offset/ saving, and the Z offset numbers can be changed but no effect on the G54 offset when running a program.

    DMG service didnt know or wouldnt tell me how to reset the .0591 difference. They said it would require a DMG service technician visit. Parameters cant be accessed like you can on some 840d controls due to DMGs implementation.

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    hey mark when the machine starts does it do a cold move to hit a ref switch? not sure how dmg
    set the machine up. If it did try startup->set password "SUNRISE", then parameters MD, machine data
    ,axis specific, I think right vertical softkeys +/- to z, then go down to 34100 [0] and not sure which way to go, but add or subtract what your off by, set md active and power boot, save the original so you can go back if needed. and if its off by 2x the amount go the other way.

    but wondering if that going mess up the tool change position? that may be another md setting that would need to be adjusted.
    Last edited by pcasanova; 01-15-2020 at 10:58 AM. Reason: thinking about it

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    I needed to move -.0591 away from where the Z 0 was set in "base" zero (g53). I was trying to move +.0591 towards the Z limit. I guess you can only set the G53 away from the limit switches. I had reset the base zero about 12" off by mistake when I was reviving the machine from its 16 year slumber. I thought I had reset it correctly but it was .0591 too short of the correct position. Now G54 and G53 positions are aligned.

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    Well - if this has been down for 16 yrs, then this aint no 5X machine, so why does this value matter in any way?

    What are you dooing with regards to Machine Z0 anyway?


    -----------------

    Think Snow Eh!
    Ox

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    [QUOTE=Ox;3475056]Well - if this has been down for 16 yrs, then this aint no 5X machine, so why does this value matter in any way?

    What are you dooing with regards to Machine Z0 anyway?

    Not actually down , just not used By the original owner after 180hrs, long story. Correct it’s a four axis machine (once I put the fourth axis on the table!). I just needed to synchronize the machine coordinate system with the work coordinate system. On this machine it looks at the machine coordinate system and references the work coordinate system to that setting. I just needed to figure out how to get them to both be the same.


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