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Case Study: 'Redesigning' the CD Case

Introducing the case study

This case study demonstrates a typical student exercise or lecture component in which CES EduPack is used to identify alternative materials for the manufacturing of an everyday object, in this case a CD ‘jewel’ case. In this exercise, the student will consider not just the mechanical properties of the material, but also their processing, economic, and environmental properties. In so doing, they will use both the MaterialUniverse and ProcessUniverse databases within CES EduPack.

The materials selection problem

First, we identify design requirements for the CD case. Such cases are currently made from crystal polystyrene. We wish to consider possible replacements for this material, which scratches easily and is brittle, meaning that it cracks easily and the hinges break. So we can define our design requirements as:

• The material must be optically clear, so that the label can be read
• Its fracture toughness must be greater than polystyrene, making it less prone to cracking and breakage
• We must be able to recycle the material at the end of life, making the case less environmentally damaging
• We must be able to injection mould the material, allowing large numbers of the case to be made cheaply

We take the last issue – processing – first.

Exploring the world of processes

CES EduPack’s ProcessUniverse database helps students to explore the world of materials processing and to gain a deeper understanding of the processes, as well as to conduct materials and process selection exercises. Below is an image of the record for injection molding, which provides a description of the process, an image illustrating it, and detailed information about the parameters that define the process (e.g., the shapes that can be formed, physical attributes of the process, economic properties, and design guidelines).

For more on the contents of the ProcessUniverse, view the case study recording...

Selecting based on links between materials and processes

One useful feature of CES EduPack is the way in which the ProcessUniverse is linked to records in the MaterialUniverse, the corresponding database of materials and their properties. Every process is linked to the materials to which can be applied. Conversely, every material is linked to the processes that can be applied to it. And these links can be used in making selections. So the student can, for example, quickly select only those materials that can be injection molded and plot their fracture toughness (below).

For more detail, and to see all of the selection stages, view the case study recording...

Completing the selection - economic and environmental properties

To complete the selection exercise, the student can use the graph above to choose only those materials with a fracture toughness greater than or equal to polystyrene, and then use other selection features in CES EduPack to identify the subset that are optically clear and recyclable. A useful additional component in this exercise, which relates it nicely to real industrial selection processes, is to ask the student to consider price. They can simply extend the plot of fracture toughness for the remaining four materials to include price on the x axis (below) and draw conclusions about which materials (if any) might be used as polystyrene substitutes.

For more detail on case study conclusions, view the recorded presentation...

Benefits of the case study

This simple case study shows how CES EduPack can be used to:

• Explore the interrelation between materials and processes
• Consider processing requirements in material selection
• Identify replacement materials
• Examine the commercial aspects of material selection and processes