System and method for state monitoring of linear drives of stretching and/or blow moulding machines

A linear drive for a stretch and/or blow moulding machine, said linear drive including a force sensor for detecting an actual force absorption of the linear drive during operation, a storage device in which data for a desired force absorption of the linear drive during operation are stored, a comparison device for comparing the actual force absorption with the desired force absorption, a signal emitter for outputting a signal if a previously defined deviation between the desired force absorption and actual force absorption is exceeded, and a data processing unit for calculating the data for a desired force absorption of the linear drive during operation from parameters which are selected from a group consisting of a weight force of the moving parts, an inertial force of the moving parts depending upon an underlying movement profile, a pressure prevailing in the container or the preform, pneumatically effective surfaces of the system and a frictional force of the stretching unit, and for calculating a model from the parameters which includes a variable for the frictional force on the stretching unit and for carrying out optimisation process simulations of the desired force absorption of the linear drive including variation of values for the frictional force simulation until a sufficiently good approximation between the simulation of the desired force absorption and the actual force absorption of the linear drive is achieved.