PETpla.net Insider 03 / 2016

INSPECTION 26 PET planet insider Vol. 17 No. 03/16 www.petpla.net Optimising material distribution and material orientation Bottle control One of the biggest challenges for a process engineer in the production of PET bottles is to control the blowing pro- cess by managing the stretching process in such a way that material orientation (strain induced crystallinity) is optimised without negatively affecting bottle material distribution. The degree of orientation and its optimisation directly affect per- formance in the areas of burst pressure, volume expansion, top load, impact strength, dimensional stability, permeability and environmental stress crack resistance, and is therefore critical to producing consistently high performance bottles. Producing bottles that have accu- rate material distribution on a consist- ent basis is a challenge. The Pro- cess Pilot blowmoulder management system from Agr International, Butler, PA, USA conquers this dilemma. Installed within the blow moulder, the Process Pilot system utilises infra- red technology to precisely meas- ure material distribution, and any changes thereof, on every bottle produced. Continuous data on mate- rial distribution, trends and changes are captured and work as feedback for blowmoulder management. Using this information, the Process Pilot system automatically adjusts the blowmoulder oven and mould control parameters based on the location of material to minimise overall process variation. Unlike operator adjust- ments, the Process Pilot system can adjust one or all of the blowmoulder controls simultaneously to achieve the best possible material distribu- tion. of pearlescence by detecting the very edge of where the process gets too cold and pearlescence begins to form. How it works The CrystalView measurement system is an optical device that works in conjunction with the Process Pilot blowmoulder management system. It incorporates a set of discrete vision components that are mounted inside a reheat stretch blowmoulder. As bot- tles exit the mould, the CrystalView system scans every bottle for the onset of pearlescence. When viewed by the CrystalView system, the onset of pearlescence can be detected well before the human eye. Sophisticated control algorithms incorporated into the system actively monitor the levels of pearlescence. When evaluating possible solu- tions for material optimisation, Agr engineers determined early on that managing orientation while maintain- ing thickness would be quite a balanc- ing act. More often than not, changes made to optimise one would adversely affect the other. The CrystalView tech- nology is said to have the capability of monitoring pearlescence with high precision. The Process Pilot system on the other hand can manage mul- tiple blowmoulder controls simulta- neously while maintaining material distribution at a specified thickness to within ~0.0025mm. Processing temperature and lightweighting In the cold mould process, typi- cally higher than necessary process- ing temperatures are used in order to safely manage process and blow- moulder variability. As a rule, colder is better when optimising orientation. However, without proper feedback it is difficult to determine appropriate tem- perature limits. With the CrystalView system, the point in which orientation is optimal, just at the “edge” of the transition state where pearlescence becomes visible, is defined precisely. The CrystalView technology makes it Optimising material orientation Maintaining appropriate mate- rial distribution, and at the same time optimising material orientation, requires great skills. In a continuation of its work to fine tune and simplify the management of the blowmould- ing process, Agr has announced the pending introduction of its CrystalView system to address the needs of bottle manufacturers using the chilled mould process. The CrystalView system is designed to optimise material orien- tation. In the cold-mould process, pearlescence results from overstretch- ing or running the process too cold. Under these conditions, the material is stretched beyond the point for optimal orientation and molecules are broken, creating reduction in performance and clarity. The CrystalView measurement system offers a simple, reliable and hands-free means to optimise material orientation while avoiding the creation Material optimisation using a colder process can result in improved PET bottle performance. The CrystalView technology facilitates blowmoulder operation at the coldest possible temperature in which orienta- tion is optimal for maximising bottle performance. I NSPECT I ON S P E C I A L