Robust Design: Testing products before they’re manufactured

How do you ensure everything is done correctly from the start of production while keeping control of costs and time?

All product development involves numerous uncertainties, such as: will this work in practice, have we chosen the right thickness of material, will this spring tolerate the number of compressions required by the customer? Uncertainties that depend on uncontrollable factors such as what temperature the product will be used in, humidity and how the user handles the product.

It’s pretty standard to try to avoid uncertainties by reducing the range for the highest and lowest application temperature, opting for more expensive materials and adding certainty factors such as thicker material. But these all lead to making the product more expensive than it actually needs to be.

“There are a lot of examples of a safety margin being added to all of a product’s components,” says Anders Nilsson, a technical physicist and product developer at Nolato Medical’s Technical Design Centre (TDC). “Or where small adjustments are still being made here and there to get the product to work optimally years after the launch of the first version.”

 

Robust design

A significantly better solution is therefore to test the product virtually before it’s manufactured so that a ‘robust design’ can be ensured from the very start.

Robust design is based on optimising the product’s ability to allow for the variations that occur in manufacturing, use and the environment in which the product is used,” says Anders Nilsson.

This method is based on the approach developed in the 1950s and 1960s by Japanese quality management expert Genichi Taguchi. The approach has since been refined and adapted to the possibilities offered by today’s advanced computer simulations.

The first thing we do to achieve a robust design is to identify the requirements of the customer, users and regulatory authorities that the product has to meet. Some of these correlate with each other, so the first stage, and the one that provides the best value for money, is to develop a design that fulfils these requirements,” says Anders Nilsson.

 

Virtual testing is best

Requirements that conflict with each other remain, however, and may be hard to resolve. Anders says there are four ways of managing these:

  1. Ignore conflicting requirements and hope for the best.
  2. Prevent conflict by, for example, setting reduced temperature ranges for use.
  3. Turn the requirements into an advantage by adapting the design.
  4. The same as point 3, but increase the effect by combining a number of factors that generate synergies.

Obviously we aim to work according to these last two methods”, he says. “So in our projects we endeavour to avoid the traditional trial and error method, which can be expensive for the customer. Instead, we carry out virtual testing of all a product’s properties and functions using advanced computer simulations before the product is made. This allows us to test the product before it’s produced, which both reduces development costs and saves time.”

 
Get it right from the start

The challenge is to find smart solutions to resolve conflicting requirements. Developers use simulations at the design stage to identify problems and find good solutions.

So in practice robust design is about being able to do things right from the beginning when the product starts to be manufactured,” says Anders Nilsson. “Before that we can perform virtual tests, make changes and find the best solutions while maintaining control over costs and time.”

A computer image of a dosage device

A simple example of the advantages of testing 
a product before it’s manufactured:
Nolato’s developers are able to use simulations at the design stage to identify, for example, that the spring in this automatic dosage device for subcutaneous medicines can only cope with five injections instead of the required ten. By continuing to conduct virtual testing, they are able to achieve an optimal design so the spring has exactly the right strength. Or perhaps come up with a completely different design that is even more innovative and sustainable.

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