Establishing Product Functions Reverse Engineering Establishing Product Functions

Learning Objectives Understand the concept of functional analysis and its role in the design process Use a “Subtract and Operate” procedure to develop a function tree for ….. Use the function tree to develop a Function Structure diagram for ……

Reading Required Reading Suggested reading Chapter 9 Establishing Product Functions handout Suggested reading Appendix A - Function Structure Definitions handout Subtract & Operate handout

Functional Modeling and Analysis Problem definition Clarification Customer requirements Distinguish constraints Generate functions tree Compare with customers requirements Create alternative function structures Identify product architecture and assemblies Functional analysis is an integral part of product design and re-design: A way of structuring your thinking about the problem A way of aiding Product Design Specifications development Can also aid in concept generation

Generating Concepts Define Customer Requirements Product Function(s) Model and Analyze Function Brainstorming / Directed Search / Inventive Problem Solving Identify Functional Solutions + + + + F1 F2 F3 F4 F5 6 Formulate Candidate System Solutions OR OR S1 S2 S3

Verify Functions Against Needs

Functional Analysis... Identifies important system components and their functions. Describes how these components functionally interact with each other and super- and sub-systems. Clarifies the best problem to solve.

Functional Analysis/Modeling There are several methods for Functional Analysis Product Function (Top-Down) --- Dissection FAST (Functional Analysis System Technique) (Top-Down) Subtract and Operate Procedure (Bottom-Up) --- Dissection Functional Analysis aids in organizing the design team, it also allows you to have an abstraction level between need and form. In the past, we looked at what the customer needed and then selected forms (objects, subsystem) based on our experience. The Functional Analysis proposed emphasizes going from the customer needs - functions necessary to fulfill those needs. Then forms for generating the functions are considered.

Functional Modeling Basics Product Function – What the product does. A statement of relationship between available input and desired output, independent of any particular form. (Overall Function) Chop Beans Transport People Accept Human Chopper Vehicle Door System

Functional Modeling Basics Product Sub-function – A component of product function. The combined effect of two or more product sub-functions is product function. Example: Hold Liquid Contains liquid Insulates liquid Insulates hand Supports liquid Accepts pour Interfaces hand Pours out

A System... Is an entity that is connected to its environment by means of inputs and outputs defined on its boundary, It can be defined in terms of mechanical construction (form) or by function, and It can be decomposed into Sub-systems connected to each other by means of inputs and outputs defined on their respective boundaries. Inputs System Outputs Input 1 Output 1 Input 2 Output 2 Input 3 Output 3

Typical function expression: “active verb – noun” Functions Functions should be expressed in terms of measurable effects Typical function expression: “active verb – noun” “increase pressure” “transfer torque” “store energy” “cool liquid”

Some functions that products/parts perform Refer to Appendix A - Function Structure Definitions handout for detailed description of functions.

Function & Flows Function Energy Material Signal State 1 State 2 All product activities involve changing the state of three basic quantities: energy, material and signal. We call this change of state a “flow”.

Form  Function  Flow Electric Current R Electric Current Form Water Heater Hot Water Cold Water Function Electric Current R Flow Cold Water Hot Water Heats Water Electric Current

Is “Low Price” a function? No – it is probably a goal; systems engineering calls it a feature

Functions vs. Goals vs. Constraints Functions represent what the product does to satisfy the customer need. Some customer needs are satisfied by how the product is implemented in form. These are attributes or features of the product. Criteria can be attributes on one product but functions on another. Example: Storage compactness Attribute : Small size Functional Solution: Make it fold up When in doubt: If the criteria is met by an identifiable sub-system doing something, then it is a function; otherwise, it is an attribute.

Subtract and Operate Procedure Disassemble (subtract) one component of the assembly. Operate the system through its full range. Analyze the effect. Deduce the subfunction of the missing component. Replace the component and repeat n times where n is the number of components in the assembly. Translate the collection of subfunctions into a function tree. Assumes that the product already exist. The subtraction need not be done literally. It can be imagined. I actually do a combination of the two approaches. I try to start with the overall process and then I am forced to go to the bottom up because that is the way that I think.

Example: Coffee Grinder Chamber Slicing blade Seal Energy System Explain that you put in coffee beans, put on the lid, plug it in, turn it on, and the grinder turns it into coffee dust? What do you call this? I have drawn a rough domain diagram, but it doesn’t specify the functions, it just indicates where interactions might occurr Operator Grinder Ground Coffee Coffee Beans

Elements for Subtraction with Results Chamber Seal Slicing Blade Shaft Armature No defined way of holding content No protection against contents splattering Contents won’t be chopped Slicing blade won’t be attached Shaft doesn’t spin No measurable volume No protection against spinning blade No resistance to torque Contents will not be chopped Electricity is not transformed into mechanical energy No body to measure contents Chamber can’t be closed No body to contain contents Impact noise will not be enclosed No body to hold apparatus Might not be able to turn on if safety feature Looks bad Difficult to clean undefined body Pour out contents

Function Tree Insert solution from book The Subtract and Operate procedure helps us determine the critical functions and subfunctions of our device. These can be mapped to a function tree similar to figure 5.6 from Otto and Wood.

Steps in Creating a Function Structure Identify the overall function. In our case, this is the top block in the function tree. Identify the basic individual functions that are required to accomplish this task. We have already done this in the first row of functions of the Function Tree. Identify more precise functions from the basic functions determined in the previous step. Note that these two steps will be iterative. These more precise functions are the second level of blocks in the Function Tree. Arrange the function blocks in the order that they must occur to accomplish the desired overall function. This is a flow chart of functions in which order is important. The easiest way for us to do this is to take the 3x5 cards we used to make the function tree and place them in position until the group is satisfied. Add the energy, material, and signal flows between the function blocks as appropriate. Double check to make sure you haven’t missed a function block or flow line. Reproduce the function diagram electronically.

Function Structure Thick arrows: material flow Thin arrows: energy flow

Where to go from here? SOP for flash light Generate SOP table Generate function tree Generate function structure All of this is due next Monday

Apply SOP on flashlight / spot light you have Activity for Today Apply SOP on flashlight / spot light you have

1. Case - A very thin spring or strip of metal (usually copper or brass) that is located throughout the flashlight, making the electrical connection between the various parts – the batteries, the lamp and the switch. These parts conduct electricity and “hook everything up”, completing the circuit. 2. Contacts - Deeper grooves for easier hold. 3. Switch - The flow of electricity is activated when you push the switch into the ON position, giving you light. The flow of electricity is broken when the switch is pushed into the OFF position, thus turning off the light. 4. Reflector - A plastic part, coated with a shiny aluminum layer that rests around the lamp (bulb, LED) and redirects the light rays from the lamp to allow a steady light beam, which is the light you see emitting from the flashlight. 5. Lamp - The light source in a flashlight. In most flashlights, the lamp is either a tungsten filament (incandescent bulb) or a light emitting diode (solid state bulb), also known as an LED. The lamp glows when electricity flows through it, thus producing visible light. Incandescent bulb must be replaced when the tungsten filament breaks. An LED contains a very small semiconductor (diode) that is encapsulated in epoxy. LEDs in flashlights are widely considered “unbreakable” – a lifetime lamp. 6. Lens- Clear, plastic part you see on the front of the flashlight that protects the lamp. 7. Batteries- When activated, batteries are the power source for your flashlight. http://www.energizer.eu/eu/ee/site/how-flashlights-work.html

Case Contacts Switch Batteries Reflector Lamp / LED Lens