Hi, 

Thank you for replying.  

Control system is siemens 840D.

Yes y axis is referenced in 2 times,  first run for y1 and second run for Y(G). 

And sure would like to get help from your experience.. 

Regards 

nulizhang

I don't find what kind of Siemens CNC system you used. for 15 years ? it is possible 840D or 840C.

I have a little experiences for customer service "Gantry" --But I remember. normally you need 2 time referencing.

1St set Y1 axis ref. then 2nd time set YG axis ref. after that 'Gantry" jointing to Y axis 

If you only making "one time ref." possible your machine builder Programmed in PLC to do 2 ref. internally.

And I am not sure your situation will affect to using. If it is effect,

you have Siemens Manual for Function Description --Part 2 I think (FB2) , I did not read in detail,

but can you check if ref. point shift possible? to settle you issue

Busy today If you like We can discuss later

  

PISCEAN 2010

Have you checked points mentioned in my reply in this topic.?

 Yes I have checked the mechanical assembly.  

Brake release is ok. 

Reference cam &  limit switch operation & repeatability is also perfect. 

Ball screw and ball nut are also checked. Both are securely attached.  And also there is no back lash or axial play/looseness. 

Actually problem is y axis repeatability is OK untill it is referenced.  Once the y axis is referenced level of gantry axis changes. 

Hi,

Picean mentions reference point shift to fix the issue but the difference is not consistant. Do both axes show the same position after referencing and sychronization?.

If the error is greater than 0.2 mm then it should request confirmation before making the adjustment.

I would be tempted to break the link in machine data and make an error of 0.5mm provided it will not damage the machine, reconnect the link and reference again to see if the system tries to synchronise.

Pee