The Framework

"Form" is about  considering how and why specific attributes of components, including shape, dimensions (size), and weight, are important. The BOM is a record that identifies how each of those components is incorporated into a manufactured or produced article that is used in the manufacturing or production process. The components may be documented as raw materials, sub-assemblies, or other parts. 

The handle of a device is, in fact, an extension of the user’s hand; therefore, we must design handles for a particular universe of users, some of whom may have special needs. This fact may impact the  range of acceptable handle lengths that are compatible with a medical device. Because it is part of a system, handle size must be assessed within the context of all reasonable usage conditions. Form and fit are closely intertwined. 

Whereas “Form” is about the specific physical attributes of each component, "Fit" is about considering how those pieces are assembled, mated, or otherwise interconnected.  For example, the form of a medical device focuses on a target handle size, but fit considers how two handle pieces work with each other and how that complete handle subassembly connects with the rest of the instrument. 

The space shuttle Endeavour was mated with a modified 747 airplane for all cross-country travel. The image to the right shows the Shuttle Mate-Demate Device (MDD) NASA used to create that fit. 

There are many tradeoffs during the design and development process. When the demands on a system spike, designers are often left scrambling to implement process changes to accommodate the new throughput target. A very common mistakes in system design occurs when we unknowingly optimize efficiency at the expense of effectiveness, which can result an unreasonable (or even catastrophic) loss in overall "Function."