Work Preparation; Flexible Nc Programming; Variables - Siemens SINUMERIK 840D sl Programming Manual

Work preparation

3.1

Flexible NC programming

3.1.1

Variables

The use of variables from the system data and user data areas, especially in conjunction with
arithmetic functions and check structures, enables highly flexible NC programs and cycles to
be written.
Material damage and personal injuries caused by changed variables
When using variables in the NC program it must be taken into account that machine operators
or unauthorized persons with corresponding access rights can change the variables and thus
affect the program run. This can result in material damage and personal injuries.
● In order to avoid negative effects on the program run caused by changed variables,
● System data
The system data contains the variables predefined in the system. These variables have a
defined meaning. They are primarily used by the system software. The user can read and
write these variables in NC programs and cycles. Example: Machine data, setting data,
system variables.
Although the meaning of a system data item is fixed, the user can modify its properties within
certain limits by redefinition.
See "Redefinition of system data, user data, and NC commands (REDEF) (Page 402)"
● User data
The user data contains those variables defined by the user with meanings defined
exclusively by the user. They are not evaluated by the system.
The user data is divided into:
– Predefined user variables
– User-defined variables
NC programming
Programming Manual, 12/2019, 6FC5398-2EP40-0BA0
WARNING
appropriate data checks ("input validation") are to be provided in the NC program.
Predefined user variables are variables that have already been defined in the system
and whose number is parameterized in the machine data. The user can change the
properties of these variables.
See "Redefinition of system data, user data, and NC commands (REDEF) (Page 402)".
User-defined variables are variables that are defined by the user and are not created by
the system until runtime. Their number, data type, visibility, and all other properties are
defined exclusively by the user.
See "Definition of user variables (DEF) (Page 397)"
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