J. A. W. M. Groot

A Computer Simulation Model for the Stretch Blow Moulding Process of Polymer Containers

Stretch blow moulding is a widely used technique e.g. for the production of PET bottles. In a stretch blow moulding process a hot preform of polymer is simultaneously stretched and blown into a mould shape. The process takes place at a fast rate and is characterised by large deformations and temperature gradients. In this paper the computer simulation model presented in is applied to the stretch blow process for the production of PET bottles. The model was previously developed by the authors for the simulation of 2D axial-symmetrical blow processes for the production of glass containers. The model is based on finite element methods and uses a level set method to track the interfaces between air and the material. The simulation model is modified in order to correctly describe the material behaviour of PET, take into account the stretch process and substitute the process parameters for stretch blow moulding. Furthermore, it is verified that the PET behaviour can be modelled as a non-newtonian, isothermal fluid flow, based on a viscoplastic material model. An application presented is the stretch blow moulding of a realistic PET water bottle.Copyright

Modelling Preform and Mould Shapes in Blow Moulding

Blow moulding is an essential stage of manufacturing glass and polymer containers, i.e. bottles or jars. A preform is brought into a mould and subsequently blown into the mould shape to produce the container. Two different problems regarding blow moulding are considered: the forward problem, which consists of determining the mould shape from the preform shape, and the inverse problem, which consists of determining the optimal preform shape corresponding to the designed container shape. This paper is concerned with the constraints on the mould surface and sensitivity to perturbations in the shape for both problems.

A Numerical Shape Optimisation Method for Blowing Glass Bottles

Industrial glass blowing is an essential stage of manufacturing hollow glass containers, e.g. bottles, jars. A glass preform is brought into a mould and inflated with compressed air until it reaches the mould shape. A simulation model for blowing glass containers based on finite element methods, which adopts a level set method to track the glass-air interfaces, has previously been developed [1–3]. A considerable challenge in glass blowing is the inverse problem: to determine an optimal preform from the desired container shape. In previous work of the authors [4, 5] a numerical method was introduced for optimising the shape of the preform. The optimisation method described the shape of the preform by parametric curves, e.g. Bezier-curves or splines, and employed a modified Levenberg-Marquardt algorithm to find the optimal positions of the control points of the curves. A combined finite difference and Broyden method was used to compute the Jacobian of the residual with respect to changes in the positions of the control points. The objective of this paper is to perform an error analysis of the optimisation method previously introduced and to improve its accuracy and performance. The improved optimisation method is applied to modelled containers of industrial relevance, which shows its usefulness for practical applications.© 2011 ASME

Numerical Optimisation of Blowing Glass Parison Shapes

Industrial glass blowing is an essential stage of manufacturing glass containers, i.e. bottles or jars. An initial glass preform is brought into a mould and subsequently blown into the mould shape. Over the last few decades, a wide range of numerical models for forward glass blow process simulation have been developed. A considerable challenge is the inverse problem: to determine an optimal preform from the desired container shape. A simulation model for blowing glass containers based on finite element methods has previously been developed [1, 2]. This model uses level set methods to track the glass-air interfaces. In previous work of the authors [3] a numerical method was introduced for optimising the shape of the preform. The optimisation method aims at minimising the error in the level set representing the inner container surface. The objective of this paper is to analyse the inverse problem by means of an analytical approximation of the flow problem and to improve the performance of the optimisation method previously introduced. In particular an initial guess of the preform for the iterative optimisation algorithm is constructed from the approximate solution of the inverse problem. The main goals of this work are the analysis of the inverse problem and the development of the optimisation method in consideration of the application to containers of industrial relevance.Copyright

Development of a Numerical Optimisation Method for Blowing Glass Parison Shapes

Industrial glass blowing is an essential stage of manufacturing glass containers, i.e. bottles or jars. An initial glass preform is brought into a mould and subsequently blown into the mould shape. Over the last few decades, a wide range of numerical models for forward glass blow process simulation have been developed. A considerable challenge is the inverse problem: to determine an optimal preform from the desired container shape. A simulation model for blowing glass containers based on finite element methods has previously been developed [14,15]. This model uses level set methods to track the glass-air interfaces. The model described in a previous paper of the authors showed how to perform the forward computation of a final bottle from the given initial preform without using optimisation. This paper introduces a method to optimise the shape of the preform combined with the existing simulation model. In particular, the new optimisation method presented aims at minimising the error in the level set representing the glass-air interfaces of the desired container. The number of parameters used for the optimisation is restricted to a number of control points for describing the interfaces of the preform by parametric curves, from which the preform level set function can be reconstructed. Numerical applications used for the preform optimisation method presented are the blowing of an axi-symmetrical ellipsoidal container and an axi-symmetrical jar.