Voice of the Engineer VOE Function Trees Fall

Voice of the Engineer (VOE) Function Trees Fall 2012 -1 Mechanical Engineering Department

Functions (VERB NOUN pairs) • Start with ranked groups of needs • Create a list of functions that need to be accomplished to meet those needs • VERB NOUN pair (support load, apply torque, store data, etc. ) – Does it need: • Power • Information • User interface • Supports • Enclosures Mechanical Engineering Department

Step 1: Formulate – Identify Core Functions Shopping carts That leaves us with… 1. Function 1: Handle Products 2. Function 2: Transport Products Mechanical Engineering Department

Step 2: Assume – Identify the subfunctions which Each Primary function must achieve Next, identify the further details or subfunctions that the shopping cart needs to provide. Focus on WHAT the shopping cart needs to do, in order to provide the functionality of each primary function. Mechanical Engineering Department

Step 2: Assume – Identify the subfunctions which Each Primary function must achieve 1. Function 1: Handle Products a) Support Products b) Contain Products c) Protect Products 2. Function 2: Transport Products 1. Translate products 2. Stop moving 3. Rotate products Mechanical Engineering Department

Step 3: Chart - Function Tree in Graphical Form Describe HOW you plan to meet your shopper’s need: Design a device to enable a customer to collect products and easily move them through the store. Handle Products. Support Products Contain Products Transport the Products Protect Products Translate products Stop moving Rotate products Mechanical Engineering Department

Step 4: Execute – Fill in the details of the function tree, and articulate the interface specifications Design a shopping cart. Handle Products. Support Product s Mass of product (kg) Contain Products Max volume of product (m 3) Min volume of product (m 3) Max surface area of product (m 2) Min surface area of product (m 2) Transport the Products Protect Product s Translat e products Stop moving Transpo rt products without damage ? (Y/N) Force to initiate motion to # speed (N) Force to stop moving from # speed in # sec (N) Rotate products Turning radius (rad) Force to change direction (N) Mechanical Engineering Department

Constraints There might be other things that have to be met that are not functions -cost limits -production methods These constraints can be listed alongside the functions Mechanical Engineering Department

Functions interrelate • Flow of power (mechanical, electrical) • Flow of information (signals, sensors, actuators) • Flow of material (water, widgets) Mechanical Engineering Department

Example Mechanical Engineering Department

Functions (focus of brainstorming) • Brainstorming focuses on ways to achieve the functions Mechanical Engineering Department

Brainstorm on – Shopping cart handle Mechanical Engineering Department

Brainstorm on – Obtain direction information from user Mechanical Engineering Department

Specifications • Objective • Can be measured – Practical (test costing $10, 000 won’t work) – Need to be measured • Complete - Relate to the customer needs Mechanical Engineering Department

Needs vs. Metrics • Metrics translate needs into objective things that can be measured. • “I need it to be light” • Product and battery but not charger must have a mass <= 1. 5 kg • This allows you to objectively see if a design meets the customer needs • One metric may meet more than a single need • House of Quality Mechanical Engineering Department

Specifications cover all needs • “House of Quality” • Some needs are covered by more than one metric • Some metrics cover more than one need Mechanical Engineering Department

House of Quality bicycle shock From Ulrich and Eppinger Mechanical Engineering Department

Metrics also can protect you • What if the customer is unhappy with the thing you produce which meets all the specifications (list of metrics) Mechanical Engineering Department

Non-standard metrics • “The system needs 3 different diameter wheels” – Yes/no – Spread in diameters • “The product must instill pride in the user” – Subjective – Focus groups/ surveys Mechanical Engineering Department

Caution! • Try not to spec. your project so that: – – – It is impossible (no solutions) It requires costly exotic materials (unless needed) There is only a single solution It requires too much time to analyze or build It requires fabrication processes that we don’t have access to – It is exceedingly dangerous or risky – It is not challenge at all • It’s ok to have 1 or 2 “reach” specs but not all of them • Specifications can drastically change the outcome Mechanical Engineering Department

Simple initial hand calculations • It’s very easy to set up an “impossible” set of metrics to be met • Weight: < 0. 01 g • Volume: > 10 m^3 • Load carrying capacity: > 10 k. N • Engineering analysis will help you determine a reasonable set of specifications Mechanical Engineering Department

Exercise • Mass of shopping cart: < 2 kg – Is this a reasonable spec? Mechanical Engineering Department

Shopping cart initial analysis • • Load bearing capacity Mass of cart Frictional losses Power consumption Refueling times Cost Can you come up with a design that you can show will meet the specifications you list? Mechanical Engineering Department

Negotiation • What if you agree to meet an impossible specification? • How do you deal with creeping elegance? • What is creeping elegance? • Types of customers that you may have to manage. Mechanical Engineering Department

Next week • Continue specifications Mechanical Engineering Department