The shapes of containers, such as tinned food and drink cartons, are a familiar sight at any supermarket. Believe it or not, the dimensions and shapes of each are meticulously optimised to bring cost savings. Whether that be minimising material cost or ensuring each product fits on a pallet size, each container is its shape for a reason. In this article we will be examining the shapes of these containers, finding out why each is this shape and has the dimensions they do.
Material Cost vs Practicality
Different products come in a variety of different sized containers. An interesting example is the food can. This cylindrical shape is not used to pack to most volume or to minimise the cost of materials. If wanting to maximise the volume of food stored for the smallest amount of materials, the containers would be in the shape of a sphere. Spheres have the smallest surface area to volume ratio of any shape, and so would be the most cost-effective. However, they would not be practical at all. They would be hard to open, hard to store on shelves and difficult to handle in general.
On the other hand, if we wanted to optimise packing efficiency or to calculate a pallet size, cuboids would be the best shape. To minimise wasted space these can be stacked together in boxes. However, when it comes to creating an airtight seal, cuboids are not the best shape. The corners of these objects are stress points; areas in an object where stress caused by different forces conglomerates. Although some food containers such as corned beef are in the shapes of cuboids, they have round edges. These are easy to manufacture and reduce stress concentrations.
Cylinders are the shape of choice as they are easy to manufacture, have a small surface area to volume ratio and they minimise stress concentration. As their cross-section is cylindrical, they have no corners and so stress is minimised when the can is under pressure. This makes them great for storing fizzy drinks. They are also easy to handle; easily fitting in your hand and staying put when on shelf. They pack in boxes much better than spheres too.
Transportation and Pallet Size
By doing a little maths, it can be worked out that the optimal dimensions for a can in terms of minimising surface area to volume ratio is when the height and the width of a can are equal. However, in practice, this is almost always never the case. For instance, the height of fizzy drink cans can be twice their width. This is because of usability issues; there is, of course, a maximum width of a can the human hand can hold. The exact dimensions are also dependent on the boxes used or pallet size on which they are to be transported.
This is another major consideration of the shape and size of containers. Although tinned foods are largely contained in a cylinder, other products can be contained in boxes or cuboids. These all need to be transported on pallets to their destinations. In order for the logistics and transportation costs to be at their most efficient, the sizes of the containers and pallet size must match. Containers are designed for the pallet size, and not the other way round. Although there is no internationally recognised pallet size standard, the International Organization for Standardization (ISO Standard 6780) currently has six standard pallet dimensions. Most companies adhere to these. Dimensions of each container are optimised on the shape of the container and the pallet size. They both minimise leftover space and fit as much on the pallet as possible.
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