CORDIS - EU research results

Polymer Injection Advanced Moulding

Final Report Summary - PIAM (Polymer injection advanced moulding)

The aim of the Coordination Action PIAM was to gather European specialists involved in polymer physics, experiments, injection moulding technology and modelling from both the academic world and from industry.

The main objectives were the followings:
- to draw the state of the art on existing software packages: description of the physical laws, comparison of results on well defined parts;
- to specify new software packages capabilities according to the demand of the end-users (part and mould designers), and identification of blocking points (either numerical or physical). Test of the new software developments and comparison with the initial ones;
- determination of material data: good practice guide can be established up for some data, but this is more difficult for advanced data. Guides to overcome this difficulty will be given, and advanced data will be provided;
- to identify the issues related to the use of thermoplastic software packages to other polymer systems (blends, composites…);
- to identify the issues related to process data acquisition, which are important for computation validation, and process understanding and control. A set of well defined comparison between experiments and computation will be provided;
- to identify the relation between injection moulding, induced structure (orientation, crystallisation), and final properties;
- to identify non-standard or emerging moulding technologies, and list the needed developments (physical, numerical modelling);
- to obtain an overview of education activities dedicated to injection moulding in Europe, and to organise an advanced course;
- to identify how technology transfer centres link SMEs and research centres (circulation of information in both directions);
- to build research projects and to apply to national or European calls, taking into account the conclusions of the PIAM consortium about the research and technological domains which require further efforts.

Huge progresses have been made in the 3D modelling of the injection moulding process:
- adaptive meshing driven by error estimate;
- code parallelisation which allows to develop now computations with more than one million unknowns;
- space / time finite element methods which decrease significantly computation time.

A series of benchmarks with increasing complexities has been defined and different softwares have been tested. This benchmark will be used for several years to test the consistency of new developments in injection moulding modelling. This is certainly one of the prominent results of this Coordination Action.

Advanced physical investigations of thermoplastic polymers and more complex systems (fibre reinforced, polymer blends) have been performed. Sometimes new experimental devices have been developed, which allow measuring new data:
- crystallisation mechanisms and kinetics under severe conditions (high cooling rates, stress and pressure);
- PVT diagrams under the same severe conditions;
- viscoelastic measurements in the liquid state.

These enriched physical models and data have been progressively introduced in the 3D injection moulding softwares in order to master progressively the whole injection moulding cycle:
- coupling of filling and packing stages;
- introduction of viscoelastic constitutive equations in order to predict both the macromolecule orientation and the stress distribution at freezing time;
- prediction of fibre orientation during filling and packing;
- prediction of polymer crystallisation.

Transparent moulds have been designed, built and tested in order to follow precisely the 'dynamic' of mould filling (more precisely than with the well known short shot approach); specific moulds have been built in order to investigate part warpage.

New injection moulding technologies (gaz assisted, water assisted, micromoulding) have been tested. Specific numerical models are under development.

A one week PIAM winter school has been organised January 2007 in Aussois (France). This was a great success:
- a series of lectures given by specialists;
- practical works both on physical instruments (optical microscopy, differential scanning calorimetry, rheology) and computers;
- open exchanges on the current problems in injection moulding;
- more than fifty people from industry and university were attending this winter school.

The potential impacts are numerous:
- good practice in injection moulding: what are the relevant parameters governing the process regularity and the part quality?
- the important material parameters and how to measure them in physical conditions near the process conditions;
- dissemination of softwares;
- development of new injection moulding processes.