The Importance Of Weight Reduction

You may have heard the story about how American Airlines saved $40,000 a year by reducing just one olive from each salad they served on their flights. The more interesting thing about this fact is that $40,000 was only the direct saving from reduced expenditure on olives. The airline is said to have indirectly saved thousands of dollars more – up to $500,000 a year, by some estimates – due to factors such as reduced fuel burn thanks to lower weight on board.

The moral is that weight can significantly impact costs – whether it’s with olives on flights, or the parts in your next manufacturing project. Of course there’s the obvious advantage of saving raw material – lighter parts use less material – but there are also other benefits, such as reduced process times and lower shipping / logistics costs. Here are the most important keys to minimising weight with manufactured parts.

Small Savings Add Up

The most important principle behind weight reduction is that even a marginal reduction can translate to huge cost savings over the span of an entire production run or product lifecycle. Unless you’re designing the wings of a 60-foot span sailplane, the material saving you can expect is generally in the range of a couple of grams than kilograms.

Small material savings of even a gram or less can add up to big dollar savings.

In a recent case, a consumer product manufacturer needed a plastic outer body for a new product. The original part weighed 28 grams, but after studying the forecast production volumes, we suggested a revised design that reduced the weight to 26.5 grams by hollowing out certain part features.

On the face of it, this 1.5-gram-saving (5.3%) may not have seemed worth the trouble, especially considering the increased complexity and cost of tooling. Over the 20,000-piece production run though, it added up to enough material to make more than 1,000 additional parts.

Plan and Design for Lightness

Speaking of production runs, accurate projections of production volumes can inform important decisions during the design stage. For instance, with injection moulded parts, it’s often recommended to avoid undercuts in part design wherever possible. While this is sound advice, it may sometimes pay to incorporate weight-saving undercut features in the design even if this adds to tooling cost – as illustrated in the previous example.

Ribs, grooves, honeycomb structures – 80% of part weight depends on design.

The decision on whether to do this hinges on the production volumes. Investing in a more expensive tool to save half a gram each on 1,000 parts may not make sense, but the same choice becomes a no-brainer for a 120,000-part production volume. Other design choices that influence part weight, especially with injection moulded parts, include the use of honeycomb structures (light but strong), support ribs, and thin part walls.

Choose the Right Material

There are over 80,000 grades of plastics commercially available today, and many thousands of grades of metal. A lot of attention is devoted to ensuring that a chosen material fulfills the functional or mechanical requirements for a part, such as tensile strength, chemical resistance, or impact strength. Rightly so. However, even though weight may not be a specially defined functional or physical parameter for a part, it’s good practice to evaluate weight at the time of material selection.

In industries such as automobile and aerospace, weight saving is always a priority and commonly factored during material selection. But other domains, such as toys, or even stationery, can also unlock benefits through good material selection and weight saving.

Engineering Plastics made it possible for a small manufacturer of modular furniture to reduce the part weight of a connector by 52%, by substituting a diecast aluminium part with a design made in polyetherimide (PEI). In addition to the direct savings on material cost, this also allowed drastic savings by reducing manufacturing lead times and shipping costs.

Have a part you’d like to put on a weight-loss diet? Ask us for a free manufacturing assessment, or send us a mail at enquiry[at]engineeringplastics[dot]in.