Fanuc 6M-B 4th axis reference woes


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Thread: Fanuc 6M-B 4th axis reference woes

  1. #1
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    Default Fanuc 6M-B 4th axis reference woes

    Howdy all, I've been looking for a couple weeks and can't seem to find a fix.

    So my boss has tasked me solving a problem they've been having with the 4th axis on a LeBlonde-Makino FNC-128 A30R. I don't know the entire history of this machine, but from what I've seen in the electrical cabinet and drawings it looks like the company bought a Tsudakoma RNCN-400R and probably had a local repair expert install it to avoid buying the option from the MTB. There's a few things that tipped me off to this, mostly that I have not found an M-Code which wants to clamp the rotary table, despite M10 and M11 being in the programming manual for the machine as the M-Codes to clamp and unclamp the axis. I did find an odd toggle switch inside the control cabinet that looks like it might have been tied into the circuit controlling the clamp and unclamp solenoid in the rotary table.

    Now to describe the problem. When performing a reference return of the rotary table, the reference point typically varies .500 degrees, and sometimes as much as 2 degrees. It's very inconsistent and I've made an adjustment of the reference dog and switch and am satisfied that it engages and disengages at the same points in rotation. I can't detect any binding with the plunger at any rotation speed.

    When I started digging into it, when I began a reference return in the positive direction it would hit the dog, decelerate, roll over the dog and grid shift however many pulses were in parameter 85 (GRDS4). Then I tired to reference it in the negative direction and when it hit the dog, rotation reversed to the positive direction, it decelerated and rotated the grid shift amount. I noticed when referenced in the negative direction the reference return point was very consistent, all within .003 degrees.

    I changed parameter 12 bit 3 (ZM4) and that had the effect I was looking for; to change initial reference direction. It behaves exactly the opposite while referencing. Unfortunately that half to 2 degree randomness is still there, but in the negative direction now.

    So now is where it really gets frustrating for me. Thinking I had the problem nailed, I turned it over to production and we ran it. Everything was fine until the e-stop was pressed for whatever reason. After this machine comes out of an e-stop, none of the axis are referenced, i.e. a G28 move will make them decel at the reference dog and grid shift into position, whereas a G28 move in a previously referenced configuration will go exactly to home. This isn't a huge problem because the tool change program makes a G28 move to Z tool change position and is only several tenths off, same with X and Y, and the origin points are still valid. But the 4th axis will roll over the dog in a G28 move and I'm back to square one with being a half to 2 degrees off.

    Sorry for the book, and hope I was able explain well enough, but "I tried nothin' and I'm all out of ideas". Yes we'll be able to work around this, but ultimately I just want it to work consistently.

    I've looked into some other parameters like those listed in table 5.3.2(3) (Reference point return function) in my manual, and tried to see if parameter 305 bit 3 (G604) made any difference (it didn't).

    I saw something else yesterday that I'll have to look for, something about how the machine behaves in e-stop.

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  2. #2
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    Default Re: Fanuc 6M-B 4th axis reference woes

    So I found parameter 308 #3 (RSTB)

    "1: On resetting by an emergency stop, external reset, or reset & rewind, no resetting signal is issued during the reset

    0: On resetting by an emergency stop, external reset, or reset & wind, a resetting signal is issued"

    Currently it is set to '0'

    This machine has a reset button not part Fanuc's MDI panel used to reset the separate PMC, wonder if that's the "external reset"



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Fanuc 6M-B 4th axis reference woes

Fanuc 6M-B 4th axis reference woes