I don't quit understand you. answer me:

You are making testing on the test bench (even on the machine) or you want to fix the problem on the running machine (not including you are design machine, such as you are doing re-building a used machine with Siemens 840D)--What are you doing

#2--If the running machine, --are you really check there are 2 measuring system , and who made PLC program , who made NCMD setting.

 I suggest you make new topic --talking to your Siemens 840D issue you think.

do you have any alarm regarding 2 measuring system, such as " measuring system switch no possible" or 2 measuring system showing large diffrency"  

SABALANKOOH

HI

Our machine is carousel that made by BLANSKO  company from czech  about 20 years old .

After Q.C. reject workpiece , we zoom on problem and observed that conditions  I described !

SABALANKOOH

Hi to all experts

For some testing I need to delete 2nd measuring or switch to another measuring , so I tried , on 840d sinumerik for linear axis , and I observed following :

- MD 30200 = 2 but  both MD30242 ENC IS INDEPENDENT[0] = 0  [1]=0

- DB31.DBx1.5 = 1 & DB31.DBx1.6 = 0

I could to change any MD but DB31.DBx1.5 was fixed ! and DB31.DBx1.6 possible to change .

Is normal above conditions ?

My main problem : after any commands to axis in both directions  axis go to setpoint position but after approximately 4 seconds axis have some replacing on minus direction about 0.05 mm !

[snip]

Hello SABALANKOOH, 

Set MD 30200 = 1 30242[0] =  0 DB31.DBX1.5 = 1 User cannot modify this. Please check values in 36000, 36010 & modify 36030 = 0.020. Check this setting & report what error or fault you get.

 Can you make it Clare --why you want to switch to 2nd encoder, do you know your machine has really 2nd encoder for all axis or for specific axis. ?

Do you have PC/PG with SIMATIC Manager to online check PLC program in 840D, to see how DB31.DBX1.5=1 being programmed 

Hi 

I couldn't access to my account so I late ! And I try with another device (my cell phone).

Machine problem solved by readjusting mechanical wedges on vertical axis. 

But switching to 2nd encoder or deleting that not possible!

Have everybody any document for that's procedure?

Thanks 

 I checked your zip file and see at least  your X axis has 2 measuring system (2 encoders) , seem 1st one active in your picture. I think you are experienced member here, and you should know the basic?

However I will guess what you want and try to answer your doubts.

1st) --from basic and how to test this on the test bench or test control system:

#1--2 measuring system can only have one active (another one passive)

#2--DB3x.1.5 or 1.6 to select 1st or 2nd encoder active for test you can make PLC program like this: such as for X axis 

A   I 44.0 

= DB31.DBX1.5

AN I 44.0

=DB31.DBX1.6

#3-- Switch from one encoder to another , there are some conditions, I remember one of these is the 2 measuring systems current values difference  MUST  be less than MD36500. or you will have alarm 

2nd) How switchover works in real machine. I use DMG machine as an example. OEM making PLC program , when machine start up, using 1st encoder (normally motor encoder) and after Axis referenced , they using PLC interface signal to switch from 1st to 2nd encoder (normally linear scale) 

You have SIMATIC Manager in your PC, so you can read OEM PLC program to find out how can they made switch happen and if possible make your own PLC program like I show your the sample to practice  

    Detail Documentation check 840D FB1 Chapter G2   

SABALANKOOH

Hi dear nulizhang  

plz refer to attached  .(both backup nc and plc .)

I have another question for cerate a full complete backup of nc which options must be enabled ?

because when I checked some parameters didn't wrote on new archive !

thanks alot of all experts ( best wishes for you )