Your post is lack of information. 

1st , let know what are you doing? who instruct you to disable 1st measuring system to make backlash --it is not true!

2nd MD30240 value =2 it is "reserved" means it is NOT used , cannot set to 2

3rd, to switch from 1st measuring system to the 2nd one, normally it is by PLC interface

DB3y.DBX 1.5 or DBX1.6, here DB3y y=axis number 1st axis y=1 and so on,

DBX1.5="1" -- 1st measuring system, DBX1.6="1" 2nd one. they cannot be "1" at the same time. 

If possible post machine builders name and machine type number--(such as INDEX B200, made in Germany)

please post NC MD page including MD30200 and MD30240 

Samantha1255

Hello, I need to disable the first measuring system of a CNC lathe (Sinumerik 840) to do the correct backlash measure. in this machine theres tow measure systems, a linear encoder(first) and a motor encoder(second). We used to put the P30240 in 0 but when we do that the reference position its lost. Theres another way to disable the first system without that happen?

I looked for and realized that in the parameter 30240 when its set to 2 its "reserved", but i didnt tried yet. Does anyone know how can i disable the first system measure without lose the reference position? 

I appreciate any help.

Samantha1255

Hello, I need to disable the first measuring system of a CNC lathe (Sinumerik 840) to do the correct backlash measure. in this machine theres tow measure systems, a linear encoder(first) and a motor encoder(second). We used to put the P30240 in 0 but when we do that the reference position its lost. Theres another way to disable the first system without that happen?

I looked for and realized that in the parameter 30240 when its set to 2 its "reserved", but i didnt tried yet. Does anyone know how can i disable the first system measure without lose the reference position? 

I appreciate any help.

Hello Samantha1255,

Please follow below steps.

1. If axis active measurement system is no 2 i.e. external encoder, you need to change it to 1 i.e. motor encoder. To do so, change axis MD 30200 = 1. Do not change any other encoder related parameter.

2. Check axis MD 32450 value, set it to 0, if not 0.

3. Please check your PLC logic, for active reference signal. Check DB3x.DBX1.5 should be active i.e. motor encoder measuring must be active. If your machine has incremental referencing system, you need to modify your PLC logic so that motor encoder referencing will become active.

After checking & modifying above values, carry out referencing & check axis backlash.

Hope this helps.