With your shiny new CAD, product design or mechanical engineering qualification – and diligent application of learning – you might be persuaded to think that designing a new product is a straightforward activity. You create your fresh new design. You check that all your component parts fit perfectly together on the CAD screen. And they do.

Sadly, not all manufacturing processes are created equal, and few production processes are 100% perfect. So, you will have to take into account multiple different factors that will affect the fit, form and function of EACH of your components:

• Fit
  •  the way the component interacts with each other to fit as an assembly.
• Function
  •  The way the components fit together and function in a way intended by the designer.
• Form
  • The shape of each component affected by manufacturing processes

Each component will have dimensions to define a shape or a feature, for example a hole, a thread, a groove. Each dimension will have a tolerance. A tolerance is a permissible variation in measurement deriving for the nominal dimension.

Example of a simple manufacturing design problem

Take a very basic example of a tenon and mortise joint. We want to assemble the tenon inside the mortise:

The tenon will have a width and height dimension, to which we have to apply a tolerance. For example 10mm±0.2mm means the tenon can be 9.8mm or 10.2mm and everything in between.

The same applies to the mortise. We want them to fit tightly together to remove movement in all directions. However, you could find an issue where your tenon could be 10.2mm or oversized, but still within tolerance, and the mortise is 9.8mm or undersize, but still within tolerance. The result is that neither can fit together due to the interference between the two features. When this happens on a new product, it is a relatively easy problem to solve. The issue is staring you in the face.

Problem solving function failure – using rule sets

A more complex issue is when all the components fit together but do not function as intended. Quite often, the issue lies somewhere within an assembly and finding out how to fix the problem, especially in a complex assembly, requires some extended problem solving. Problem solving rule sets help.

One way of doing it is using the “5 why”. This technique was invented by the Toyota Motor Company in the 1950’s in Japan. It is easy as it sounds by asking “Why” until you can find the root cause of the issue.

Let’s take a simple example scenario of a car which stop working:

1. Why did the car stop?
   1. The engine overheated causing it to lock.
2. Why did the engine overheat?
   1. There was insufficient lubrication. 
3. Why were there insufficient lubrication?
   1. The oil pump is not circulating enough oil.
4. Why is the pump not circulating enough oil?
   1. Because some debris and dirt block the oil strainer?
5. Why is the oil strainer clogged?
   1. Because the car was not serviced properly, and the filter never been changed.

You get my gist.

Today this method is used in a wide variety of production and manufacturing environments, especially in the automotive industry.

Design Failure Mode and Effect Analysis (DFMEA)

The best way to avoid problem solving your design at the production stage – is to pre-empt possible points of product failure at the earlier design stage. The Design Failure Mode and Effect Analysis (DFMEA) is the perfect tool and is widely used in automotive settings. However, here at Convert Design, we apply it for every component we design, be it an oil and gas pipeline flow measuring device or a simple coffee maker machine.

To find out how we can help you convert your concept to reality, get in touch with our team.