A crushing defeat…

Crush ribs, an inventive way to overcome design constraints or a cost cutting step too far?

I recently bought a large plastic modular storage unit for the office from a well-respected storage supplier. Upon receipt I eagerly tore the boxes open and began the task of constructing the unit, keen to see what the final result would be. Overall, exactly what was expected and very good value for money compared to its metal alternatives.

I then came to attach the wheels which was one of the appealing features this design had to offer. The castors / wheels were to be fitted at the bottom of the unit using crush rib interference, the designer within me was very impressed to see that such a rarely used feature had been put on such an industrial type of fitting. Upon fitting the wheels I was quickly reminded why this design feature was rarely used in this way. I was soon picking the wheels up from underneath the collapsed unit and starting again. With a bit of brute strength and a team effort the wheels were soon in place and now we have a well-positioned storage unit.

The following days have given me time to think about it a little more and I have been left with a nagging question. Were the crush ribs a well thought out way to reduce costs or simply destined to fail when used in this way?

My experience of interference fits has told me that they are often challenging to achieve, with everything other than very shallow features needing at least a little draft to overcome moulding issues. Of course this then results in a sloppy interference fit which is far from ideal.

In these instances are crush ribs a viable option for heavy duty operations or are they a cost cutting step too far? Do you have different ways of approaching the same issue or have you a more positive experience of a great heavy duty crush rib. An interesting topic that we would be keen to discuss more. Please feel free to drop us a line on technical@plastribution.co.uk with your thoughts.