Hi everyone, we are having issues with commissioning a vertical lathe machine with double column and would like to probe some of your experience and knowledge.

Axis are as follows: one column being X,Z (HEAD1) and the other U,W (HEAD2). There is a rotation axis C and a crossrail Y. PMC & NC name is Fanuc F16 RB3.

The double columns axis X, U (horizontal) and Z, W (vertical) are identical. Horizontal axis X, U are mirrored with negative (-) movement toward the center of the lathe. Position is monitored via linear incremental scale heidenhain LB 326, scanning unit AE LB-326. Drivers (a06b 6078 h106) and motors are of the same type (for X,U). Incremental scale is used with the two vertical axis Z,W but don’t know the precise model or scanning unit. Drivers and motors are of the same type for Z,W. So basically this four column axis could be interchangeable between them.

To my knowledge we have connected everything correctly and ofc rechecked multiple times. When we started with the testing of the lathe at first there were no alarms – both heads X,Z and U,W axis were working as intended. After some time the error “416 SERVO ALARM : U AXIS DISCONNECT” started to sporadically show up on U axis movement and now it has progressed so that on any movement of the U axis the same error occurs.

There is one more error on HEAD2 (U,W axis) “414 SERVO ALARM : W AXIS DETECT ERR” which still shows up sporadically with no particular order. The error sometimes shows even if whole system is just ON and resting for some time. But I would like to first debug the 416 U axis disconnect error which occurs only when there is movement in U.
I am mentioning this error on W axis because both (and only) errors are on HEAD2 (U&W). HEAD1 works with no problems.

So browsing the internet and forums we have tried some suggestions but with no success.

First we instructed the system to ignore the scale completely by setting 1815 register and others. With scale off the U axis worked with no errors.
So we figured that it has sth to do with scale itself or connection. We swapped scanning unit with that of X axis from HEAD1, the error stull persists on U, HEAD2.
We have replaced the cable but no change.
We have interchanged signal inputs from U and X (connectors JV1, ENC1, SCALE1) on the central unit so that U was represented (connected) as X in the system but the axis disconnect error remains (this should mean that the unit inputs are OK, no cold joints or bad boards).

Is there anything else we can try to get to the root of the problem?

On interesting thing is that if we use cable for scale from U on X the direction of X scale switches – previously positive movement is now incremented as negative on X and thus we get excess error. Is there any parameter to set the scale increment/decrement direction?
How is that done on fanuc system?

Any help appreciated!
Thank you for your time!