Question about design verification approach of a specific requirement

[seraphim8136]

Hi all,


Would like some advice on the approach to verification for a requirement I had a disagreement about with a co-worker. To generalise the requirement, basically it was " the object shall have a minimum coating thickness of X um".

My understanding of design verification in this particular case is a design review is sufficient here and to just point to the drawing specs that we have defined this thickness but they have argued that it should be a sampling test instead in which we measure the coating thickness of a representative sample of actual units (note we outsource production of these units). This doesn't make sense to me because this just seems like a incoming goods test that verifies the quality of that batch from that specific supplier, not the design itself.

Have I misunderstood? Any feedback is appreciated, thanks.

 

[John Predmore]

A design review is a meeting. What transpires at the meeting is the designer presents answers to managers, on the question, "how do you know the design is good enough?".

Typically, the design process takes design inputs (requirements, collected from real or potential customers and other stakeholders, including internal manufacturing experts and yes, the perspective of the supply chain ) and generates design outputs (which consists of dimensional drawing, specifications, and other details) believed sufficient to fulfill requirements with confidence.

A coating specification is an design output. The corresponding design input(s) may include requirements such as resists corosion (as defined by an established engineering test), resists wear (as defined by a identified engineering test), provides a smooth surface (as quantified by however smoothness will be measaured), or maybe acceptable appearance after X years under Y conditions.

It is possible that your firm has lots of experience with the proposed coating, from similar products under similar in-use conditions. It is possible the design process could answer the question "how do you know?" by citing as justification previous experience, published industry coating standards, or even the proverbial 'engineering judgement'. If these references satisfy the management to answer the question in a design review, then conceivably no testing will be called for. In this scenario, there would be a risk (that something important was bypassed as trivial) and the management will bear the risk of adverse consequences. In this sense, a design review is risk management activity.

Later, in production or pre-production, supplier qualification or incoming inspection of purchased goods may be also used to further confirm that a selected supplier, or the particular batch, is believed capable to fulfill production requirements with confidence. But in most cases, some level of design verification testing is used to gain confidence in advance of production, when any discovered shortcomings can be corrected with minimal interruption and cost.

 

[indubioush]

If this is a critical design requirement, it is acceptable to require your supplier to do process validation to show that their coating process consistently meets the specification even before you do design verification.

 

[Ed Panek]

In the past we've used suppliers that help us meet a design requirement because we don't possess the skill, or knowledge or infrastructure to do so. In this case if the coating is an important feature and not just to make it look "Nicer" I would ping the supplier and ask how they know they are meeting that specification. You could impose that they test it prior to shipping and include it in a lot testing report along with the product itself.

This solves a lot of risk. An expert is testing it, they have the experience, they know what knobs to tutrn to fix it, they can take actiion immediately as opposed to you which will take longer to address.

A good example of this is sterility. Ethylyne Oxide sterilization is a very dangerous process and most companies lack the technical ability to argue with regulators about this.

How do you control this process? During the supplier audit/qualification. You can visit the supplier and ask to see their data regarding this requirement. How is it trending? By visiting the supplier and actually snooping around where the process takes place you can see a lot of things they wont tell you about, but could be a critical issue for your customers.