This book by JGA Corp. is a virtual catalog of ideas for inspired retail design. It features work that is international in scope in innovative in content. These 1,000 touchpoints of brand identity include ...
By Lynn Manning
Kicking the container around with simulation
And it’s quite a range of disciplines. The group began with top loading and vacuum pressure simulations. They moved on to drop-testing, blow molding, conveyance, denting, and leaning. They are currently working on pasteurization and retort (heating during sterilization) simulations. And they're even starting in on ergonomics, to simulate the effects of a human hand putting pressure on a container. “Being able to simulate multiple load conditions at the same time is very important to us,” says Krishnan. “You have to take into account a number of parameters simultaneously, such as fluid-structure interaction, temperature, pressure, and material strain rate.”
With their FEA results in hand, the Advanced Engineering Services group has a clear vocabulary for discussing the viability of a design with the industrial designers. Using multiple iterations between CATIA and Abaqus, the parties can collaborate to arrive at the best solution that validates the appearance, performance and functionality of a particular container. Such improved communication pays off: “One of our performance metric targets was to reduce the number of design revisions we made by 20% in a year,” says Krishnan. “Right now we are well ahead of that goal.”
The benefits from virtual testing can extend beyond the testing laboratory all the way to manufacturing, Krishan says. When they achieve an optimum top load value via simulation, they can use that data to provide actual section weights to the process engineers in the plant, so the engineers can more easily produce the container that gives the desired performance.
PET plastic behavior is complex
The PET material itself brings unique challenges to this whole process. PET is highly nonlinear, with biaxial properties that vary with the amount of stretching it undergoes. A semi-crystalline thermoplastic, PET softens at a “glass transition temperature” of approximately 170° F (76° C). Above that, it becomes elastic and can be formed, a property effectively utilized in the stretch blow molding process.
But when PET containers are filled with a hot liquid, they are susceptible to shrinkage back towards their “remembered” previous shape (the preform), a characteristic that has to be taken into account when designing the initial container configuration. The bottles also collapse slightly due to vacuum pressure resulting from cool-down after hot-filling. So the design for a hot-fill PET bottle includes “vacuum” panels for designed collapse. “We can now easily model these kinds of physics-based characteristics with Abaqus FEA, using a customized script for hydrostatic fluid elements that enables us to accurately simulate the behavior,” says Krishnan.
The contents of every type of PET container must also be taken into account in Amcor’s simulations, from adjustments in the density and viscosity values of liquids (from pure water to sticky paint) to the internal pressure fluctuations inherent to carbonated soft drinks.
Amcor continues working on advanced material properties for their models. While PET is 100% recyclable, containers made from recycled PET (RPET) may have slightly different material properties than the originals. Initiatives also are underway in the industry to develop biodegradable PET using ethanol. “Although we are not simulating either of these materials at the time, this is certainly a consideration for the future,” says Krishnan.
Managing all that data
It all adds up to a vast amount of simulation data. Amcor keeps track of everything the Advanced Engineering Services group generates by using Dassault Systèmes’ ENOVIA solution for collaborative product development, which facilitates the organization and easy retrieval of all CATIA and Abaqus data for each container design while managing all processes to keep them in synch.
“Whoever in our organization—from the Advanced Engineering Services group of 14 engineers all the way to our manufacturing plants—needs information about a specific project, they can pull up the report in ENOVIA and find the latest version, completely standardized, which is very helpful,” says Krishnan. “ENOVIA automatically saves the history of every previous iteration as well, allowing for easy reference, tracking and communication among our project teams.”
The growth of Amcor’s physics-based simulation capabilities has been the driving force behind the company’s lightweighting initiative. Krishnan cites one example where a 63-gram container design was reduced to 43. “We used realistic simulation to validate performance while trying out various Amcor-developed technologies and eventually met all performance requirements with the lighter design,” he said. “Simulation helped us try many more options than we normally would and compare multiple designs with one another.”
Although Amcor still validates their virtual tests with physical testing, the ever-increasing accuracy and refinement of their computer predictions has allowed them to decrease physical prototyping dramatically. “We see a close match between the curves that Abaqus provides and the test results so we’ve got a lot of confidence in simulation now,” says Krishnan. “We’ve cut our design cycle down to nine months from 12 to 18, which has significantly reduced our product development costs. And we’ve gained a lot of management buy-in to our methodology.”
Another area in which the use of CAE has proved of value for Amcor is when proposing new ideas to clients, Krishnan says. “We include animations of our Abaqus simulations in all our presentations. We can demonstrate how we create a design, perform FEA on it, and try out as many options as we want.” Any industrial design proposal can be quickly simulated; if a customer puts in a request in the morning, animations can ready by that evening. “It really frees the designers to explore whatever ideas they have,” says Krishnan. “It’s a fast-changing business and the next new design is just around the corner. Somebody else is always looking to capture that design so we have to be really fast—and with CAE in our arsenal, we are.”
