Editor's Note: CR4 would like thank PJ Sikorsky of GEA Consulting for contributing this blog entry.

In my last blog post I described 5 repetitive problems I have observed in material selection. I said I'd come back in subsequent posts to discuss each of those problems in greater detail. This week I'll start with problem #1. Material Selection after the part/component is 'designed'.

Since material cost is typically the primary driver in piece part cost, it seems logical that materials should be selected early in the design process. Yet, more often than not, materials are chosen after the part is 'designed'. When this happens, the part design winds up dictating the material selection, rather than vice versa and not only do we lose control over one of the most effective levers we have to control piece part cost, we also lose some control over manufacturability and reliability.

In order to move material selection 'up' in the design process, I think it is useful to start to think of the material as another dimension of the part, just like the dimensions that describe its size and shape. In order to optimize part design we need to think of all of its dimensions as interrelated. We need to start asking materials questions early on:

1. What material properties are critical - strength, toughness, fatigue resistance, thermal conductivity, corrosion…..?

2. What physical characteristics matter - density, magnetism, color….?

As we start to narrow the list of candidate materials, we can start to define the physical dimensions of the part and then we can start to ask second level questions:

1. What are the limitations of the candidate materials - do we sacrifice toughness for strength, wear resistance for corrosion resistance……?

2. What are our manufacturing options - are the materials weldable, machinable, castable…..?

3. What about cost and availability?

By asking these questions early in the design process we can make rational choices and optimize part design. We select materials with the characteristics we believe are important and utilize those characteristics to help shape a part that is functional, reliable and cost effective.

In our next post we'll discuss the second problem - Material Selections not reviewed over time.

- PJ Sikorsky