You might be forgiven for thinking I was going to ramble on about being busy again, but you would be mistaken. Yes, of course I am often in a position where I am stretched to my limits in terms of my mechanical engineering output, but I want to focus here more on the injection moulding materials that I am involved in working with, at least five days a week.
As time has moved on and margins for bringing a new product to market, have been further squeezed, us design engineers are being asked to be even more creative, when designing a product or component. This pressure to produce something more efficiently than what has gone before can be quite trying and puts the expectation on needing more from the plastic materials used in the moulding process. This can be further exasperated when designing a medical device where regulations can stipulate the exact type of material to be used.
At the back of every good design engineer’s mind is to consider the flexibility of the finished injection moulded product or component. It is at the CAD design stage where particular focus is given on the part which needs to be flexed. Every material has an elastic limit and without getting too technical, we have to ensure that the right balance is reached between the function required of the product and that of the limitations of the plastic used to make it.
Plastic limit vs. elastic limit. If we push it too much, i.e. exert too much stress or pressure on the material then this can invoke plastic deformation and subsequently prevent it from being able to return to its original shape. The behaviour of plastic is fundamentally a product of the structure’s design and the degree of flexibility required in the finished injection moulded component needs to be carefully considered at the design stage. So you see, there is a very fine line indeed between getting the most from a material and stretching it beyond the limit to which its physical properties can endure.
