W. Durfee, Sept 1999

(bring: slides, foam models, snow machine models, Toro BDS, ken model, index cards, catalogs)

(For each exercise, call on 3-4 groups to respond. By end of class should have cycled through all groups.)

Spend 1 minute writing down definition in your notebook or on an index card.

Discuss as a class.

"OK, you are all correct".

Prototype: "Anything that approximates the final product" (U&E text definition)

Many forms of prototype: loose sketch to pre-production beta release of product.

Each company you work for will have its own definition. For example, here are two used by Toro:

Important to get all stakeholders to agree on what your meaning is.

Because you wish you had the final product to do something with, but you are not there yet.

Goal: reduce risk, increase probability of success

Prototypes cost time and money.....consider carefully.

Knee-jerk reaction is, "Oh, let's prototype". Watch out, might get you stuck in the "hardware swamp" and really slow down your design process.

1. Define the purpose(s) [WHY]

2. Establish what is to be approximated (and what is not) [WHAT]

3. Determine form of prototype [HOW]

4. Set design/construction plan, establish cost. [WHEN]

5. Determine tests, data to be gathered. [OUTPUT]

On a piece of paper, write three reasons why you want to prototype at this phase of your project. (Or why not.)

Discuss with your team.

Open discussion in class.

You can sort "purpose" into two categories:

Convincing the team that it works. Required for new technology (e.g., you are using composite leaf springs to save weight). Essential for complex phenomena that cannot be clarified through intuition, experience or modeling. (e.g. heat flow in a novel radiator)

Typically done for a specific subsystem via an "engineering bench model" or a "works-like" model.

Prototype the subsystem you have the least confidence in (strength, wear, quality.....)

Convincing outside stakeholders that you have a good idea and that it works.

- customers

- management

- investors

- trade show

In the case of customers, may be prototyping to get customer reaction to concept via market research.

For tradeshows, may be convincing a skeptical public (or distributers or OEM's) that your product actually works.

Often a ‘looks-like’ model

Many (most?) viewers won’t care about technological niftiness.

Example: snow machine at the design show

Purpose defines what.

Example: For cordless power tool, may be interested in balance to establish trigger, battery, motor location. --> need prototype with proper shape and weight. Does not have to work.

Examp: May be interested in battery life --> need motor, transmission, load.....but not proper balance.

Examples: marker rendering, computer model and simulation, isolated mechanism, working hand-held preliminary product, foam mockup, wood carving.

[Show any toys you brought.]

Be careful that concept not obscured by inappropriate look and feel. (particularly important if purpose is to get customer reaction to concept since reaction can be influenced by "quality" of prototype)

Tools of the Trade for constructing prototypes:

Virtual prototyping increasingly the norm (Chrysler crash test example)

Exercise (optional)

Jot down your thoughts on what form your prototype will take.

Discuss with your team.

Discuss as a class.

----can show slides here...or at the start

Enough said. Make sure its worth it, not because someone told you to do it.

How many to build?

Note that cost of prototype does not equal cost of production product. (Different production volume, materials, mfg methods..) Be sure to make this clear in your design reports where you can provide data on prototype cost (because you would have built it by then) and can estimate final product cost (c.f. lecture on cost and price of products or U&E text chap 9.

Exercise (optional)

As a team, do a quick bill-of-materials (BOM) for your project and assign estimated costs for each. Total. (5-7 minutes)

Discuss as a class. (Give us total, and 2-3 items on the BOM.)

Must use prototype to assess some aspect of product.

E.G. Function, lifetime, customer reaction.....

Have a specific experimental design up front.

- Old style. You would let the machinists do it for you. That is, hand 'em a concept sketch and let them figure out the details. Now, need to be much more careful about prototyping.

- Dual prototypes are common if cannot satisfy multiple purposes with one. Examp: a look/feel prototype and an engineering feasibility prototype.

- All stakeholders (and test customers and design show jury) should have clear picture of what is real in the prototype (e.g. shape, function) and what are approximations (e.g. materials, fatigue life, weight).

- Can prototype one subsystem to test another subsystem. Examp: simulate car for testing real-time engine controller.

- Mathematical models/simulation are flexible and (usually) low cost. Enable rapid iteration. Garbage in, garbage out. Examine assumptions. Usually need hardware prototype to verify. Virtual prototyping

- Some companies (Japanese) bag "customer reaction" prototypes, go straight to small scale production, and evaluate success in the marketplace. Gets you to market fast.

• Can change the scale on a prototype. Examp: Large scale model of mcro-surgical instrument. Examp: Small scale model of a building.

• Prototype early and often è go for simple ones

• Don’t confuse prototype with the final product. Different materials, mfg methods, purpose.

Notes on the slides:

General themes:

- draw/sketch at appropriate level for the objective

- stick to basic machines

- for electronics, wire-wrapping is pretty good

- hardware stores: great source for ideas/parts

- know your catalogs

- plastics are expensive to prototype

- "low-cost" molding is possible

- rubber molding

- RP is not always rapid....and is not cheap

Another note on the Toro RP slide

- "Rapid Prototyping" Fast. From CAD straight to part w/o going through mold stage. Molds are $20k - $200k.

- engine part: 3-4 months, $13K