Injection blow molding machine II

Source: CAN Newsletter September 2004

Ossberger, manufacturer of injection blow molding machines such as the SB2/60, uses CANopen for networking their blow molder. Ossberger use the IQT705 human machine interface with touch screen for controlling the blow molding machine. With it the machine operator is able to switch motors and heating zones on and off, select a different operating mode or a particular function. Similarly, all process values as well as texts can be entered via the screen at the touch of a finger.

For further processing, these data are transmitted to the various slave devices via CANopen. Using the CANopen closed-loop controller with its sub-layered control units as slave devices, great importance was attached to the special control algorithms for electro-hydraulic drives. The speed controllers for the individual axes work with a pre-defined rate time, and the acceleration and braking functions are displacement-dependent. The devices used for these purposes implement various characteristics such as linear, sinusoidal or profiles operation mode. Several position, pressure, and speed controllers are used. A combined pressure and speed controller with bumpless switchover is active during the initial production phase. In addition, a master/slave synchronization controller for several axes ensures a precise parison profile. Temperatures are maintained accurately by means of two-point and three-point stepping controllers. Together, all these control functions result in a high and reproducible product quality.

The automatic optimization of screw speed and profiling speed (100 segments) simplify the manual adjustment of mutually independent process sequences. For example, if a speed profile is changed, any other dependent speed profile is adapted automatically.

Additional monitoring and control functions such as the automatic weighing of the finished components on a precision scale are an important contribution towards reject detection, and therefore overall quality assurance.