The blow valves used in a stretch blow molder can wear differently. This means that the bottles blown with them change over the service life of the stretch blow molder depending on the station. In the production process, this can lead to deviations in material distribution and thus to varying bottle wall thicknesses. Previously, parameters could only be adjusted for the entire machine and not for the individual stations. With the new digital control system Unit Mold Control, manufacturers can optimize their blow moulding process by making individual settings for each station. "This enables more precise control of the material distribution per station and thus minimizes variations in wall thickness from mold to mold by more than 30 percent," explains Frank Haesendonckx, Head of Technology at KHS Corpoplast.

The inspection technology of the Mold Control unit continuously measures the material distribution of each bottle and adjusts the settings for optimization fully automatically. "The system identifies deviations at the individual molding station. Using an algorithm, the variability is reduced without operator intervention and possible incorrect settings are avoided," says Haesendonckx. In addition, the data collected from the individual forming stations provides valuable information for the condition-based maintenance of valves, stretching systems or mold carriers, for example.

Unit Mold Control offers further advantages, particularly with regard to the growing proportion of recycled PET bottles. "Process accuracy reaches its limits with these containers," explains Haesendonckx. "As the material quality fluctuates when using recycled PET, the bottle becomes increasingly unstable as the preform weight decreases, or manufacturers have to use heavier preforms to ensure stability." With the new system, weight reduction and bottle stability can be reconciled, says Haesendonckx. "The Mold Control unit effectively compensates for deviations by detecting unwanted material displacements during wall thickness measurement and automatically counteracting them."