Low and High Fidelity Prototypes

Prototyping can make or break a project.  Often when we think of prototypes, we imagine a fully operational machine, or something close to it.  As discussed in a previous post, not all prototypes are fully functional or even look like the final product. In particular, the aerospace industry is a good example of this.  Early in its history, aerospace companies won contracts by building and demonstrating fully functional planes.  With time; however, building planes, rockets, and satellites became so expensive that designing a new product often cost more than half the company worth.  That means if the company didn't get the contract, it would go out of business!  The aerospace industry has shifted to less costly low-fidelity prototypes of all types to win contracts which reduce the risk of bankruptcy.  There are many other benefits associated with this approach, as we will discuss below.

A hi and low fidelity prototypes are distinguished by how close a prototype comes to the final product.  A 1:100 scale model of a plane will demonstrate the shape and perhaps some function (such as aerodynamic lift), but it is a very low-fidelity prototype since it does not include the millions of other details that must included in the final prototype.

On the other hand, when Boeing designs new planes, they create cabin mock-ups that demonstrate concept cabin arrangements, such as where bins and seats are located, the actual mechanisms, head room, and so on.  These mock ups are built so executives who come to visit them actually feel like they are in the cabin of a plane.  The electronics work, the seats are real seats that are really upholstered, and really recline.  The windows come up and down, and so on.  This kind of prototype demonstrates all sorts of details that a low-fidelity prototype cannot, yet it is not the whole plane.  It's just the cabin.  Likewise in consumer products or student projects, prototypes can reflect various levels of detail.

In general, the two ends of this scale have different advantages:

Low-fidelity

• Are low cost
• Are fast to make
• Avoid design fixation

Hi-fidelity

• Make it easy to study system interactions
• Prevent rework (by establishing design decisions)
• Give a sense of progress to team, reviewers, and customers

A couple of notes here.  Early in the design process, fixation should be avoided at all costs.  However, as time goes on, it is necessary to stop working on a particular design question and move on.  At that point, higher-fidelity prototypes help establish what decisions have already been made.  In that sense, they prevent rework.  If your team were working on a racing tricycle, a CAD model helps solidify the team's decision to use a tadpole configuration (two wheels in the front), or a traditional configuration.  If a high-fidelity prototype, such as a CAD model, were not created, team members may still question if that decision had been made, and promote more discussion.  This can be problematic when the group is trying to move on with a design.

When prototyping, one mistake that student groups commonly make is trying to make a high-fidelity prototype too early, or a low-fidelity prototype to late.  The general rule of thumb is simple: the fidelity should match the design stage.

This is especially true in the early stages of design.  For idea generation, prototypes should not include higher-fidelity ones like CAD.  If you are taking more than 20 minutes on your prototypes at this stage, you are taking far too long.  For idea generation, the ideal is a new idea every minute, but most students seem to perform around a new idea for every 5 minutes.  That includes sketches, writing ideas down, or discussing a single idea.

Well, that's it for now, but let me know if you have any questions.  I'd be happy to answer them!