Dr Gary Menary
Research Group Leader at Queen's University Belfast / CTO at Blow Moulding Technologies
Dr Gary Menary leads a research group focusing on stretch blow moulding at Queen’s University and is Chief Technical Officer of Blow Moulding Technologies. He has been researching stretch blow moulding for the past 20 years. The main focus of the research is to reduce material and energy usage in ISBM by developing a fundamental understanding of the manufacturing process using skills in simulation, material modelling and characterization, experimental mechanics and instrumentation.
Simulation driven design of preforms in stretch blow moulding
The work presents a new methodology for preform design based on material characterization, material modelling and process simulation to evaluate the influence of processing conditions on bottle properties and thus enable optimized preform designs. A case study is presented where a new preform was designed for an experimental PET material. The experimental material was initially characterized using a combination of specialist biaxial stretching equipment and a unique state of the art free blow device alongside traditional testing techniques of DMTA and uniaxial tensile testing. The combination of these test methods provided data that enabled an understanding of the how the natural draw ratio of the experimental material shifted with respect to processing history, how this differed to virgin PET and the influence of processing on final mechanical properties. The key material data (i.e. the stress strain curves) at the different process conditions were used to calibrate a nonlinear viscoelastic model of the material behavior which was subsequently embedded within a simulation of the stretch blow molding process using the commercial FEA package Abaqus. The simulation was initially validated against an existing prototype bottle.. Following validation, the simulation was used to redesign the preform to ensure that the material reached the critical areas of the container to prevent failure. The new design not only met the in-service performance requirements of the container but also had a 10% reduction in weight. The new lighter preform design was subsequently manufactured with the experimental PET and used to manufacture a container which passed all in-service performance requirements. The work highlights the power and potential savings of using a simulation driven design approach to preform design in stretch blow molding.
Disclaimer: Any opinions or scientific interpretations expressed in this presentation are those of the author and do not necessarily reflect the position or policy of PepsiCo, Inc.