On how simulation software thinned the PET bottle
10-04-2017 | Posted by Principia
Many of us remember the first 2-litre PET bottles that appeared in the mid 80’s: thick, not very transparent, and requiring a plastic support for vertical stability.
Besides their poor ergonomics and stability, the weight was 72 g; they have now thinned to about 45 g, a reduction of 38%, with considerable improvements in performance, both functional and aesthetic.
This evolution, known in the sector as lightweighting, entails an important reduction in the cost of raw materials, since we are talking about billions of units in which a few grams have been eliminated, adding up to savings of millions of euros.
But this is not enough. Consumers demand an increasing variety of PET bottles, more innovative, better adapted, and cheaper.
How can this demand be met by the manufacturers? The number of design cycles and prototypes must decrease, and the time to market must be reduced. And all this, while offering high-performance products that are competitive and reduce costs all along the supply chain.
Making a PET bottle may seem simple, but answering all these demands requires a robust life-cycle management system, from the design stage to general availability.
For example, the 2-litre bottle mentioned earlier must be designed to each customer’s specifications. It must keep its shape during filling, hot or cold, carbonation, encapsulation, packaging and distribution.
To be competitive in the design and production of these bottles, one must use a simulation software that, in the design phase, is able to reproduce and verify the loads that will be applied in all phases. Thus, starting from a sketch agreed with the customer, the designers can build a model with CATIA, parameterising critical characteristics like volume, weight and surface, to be able to modify the design easily as required.
To carry out simulations of the virtual tests of the container behaviour, the 3D model becomes a finite element mesh. Abaqus is then the best tool for performing those simulations: it has the necessary functionalities to validate any scenario that the container could experience, like handling loads, vacuum, distortions during moulding, filling pressures, etc.
Once those results are available, the process engineering and industrial design teams can review the initial proposal and work together to adopt the best option, taking into account function, strength and aesthetics.
The use of realistic simulations allows selecting the lightest design that satisfies the requirements. And it allows reducing drastically the number of prototypes needed to validate a given design, with the associated cost and time savings.