1	Projektovanje i CAD/CAM Dr Ahmed Kovačević
2	PROGRAM Inženjerski dizajn (Engineering Design) CAE/CAD/CAM: Uvod, Struktura Hardware i Software Modeli u CAD, IRP, Baze podataka, Interface Pre i Post Procesori CATIA i MDT CFD/CCM - Metoda konačnih volumena FEM - Metoda konačnih elemenata
3	Engineering Design Process Manage the Design ® Be successful Follow the Process ® Be efficient
4	speaking as a designer committed to building better product better = more efficient “a better learning experience” “learning-from-working” “working-to-learn”
5	Useful Reading
6	Design can be artistic or technical
7	Abstract design
8	Aesthetic design
9	Functional design
10	Aesthetic and functional design
11	Engineers - Designers Engineers: Provide ways to meet needs and wants of society Invent or design new products and processes Improve existing products and processes Work in teams throughout the design process Bottom line: ENGINEERS ARE DESIGNERS
12	What is DESIGN in Engineering? Design is: Systematic Process by which solution to the needs of humankind are obtained and communicated Essence of Engineering Structured problem solving activity Engineering Design Process is: Multidisciplinary task which contains: Technological factors Social factors Team iterative work
13	Engineering & Mechanical Design Engineering design process an iterative decision making activity, to produce plans by which resources are converted, preferably optimally with due consideration for environment into systems and devices (products) to meet human needs. (Woodson.T.T ) Mechanical design process is the use of scientific principles and technical information along with innovations, ingenuity or imagination in the definition of a machine, mechanical device or system (product) to perform pre specified functions with maximum economy and efficiency. (Engineering Design Council, UK)
14	Engineering Design Process Design – structured problem solving activity Process – phenomenon of making changes to achieve a required result Design Process – cyclic continuous activity
15	Design Process Timing All projects have time constraints An adequate planning leads to a satisfactory project finish
16	Customer (Examiner) Satisfaction
17	The business process
18	Konkurentni inženjerski dizajn
19	Crtani film - primjer
20	All designs start with sketches
21	Generation of ideas
22	The Engineering Design Process
23	Design Process Overview
24	The Objectives Tree Method The objectives tree method is an approach to transform vague design statements into more specific customer requirements Make vague statements more specific by asking: What is meant by that statement? Other useful questions to ask when expanding and clarifying design objectives: Why? How? What?
25	The Objectives Tree Method (1) Three step procedure: Prepare a list of design objectives Order the list into sets of higher-level and lower-level objectives Draw a tree of objectives, showing hierarchical relationships and interconnections
26	Step 1: Listing the Objectives This can be done by: Talking with (interviewing) customer Thoroughly reading any written design statements and requirements Take vague statements and make them clearer by asking “what is meant by this statement”
27	Step 2: Ordering the List Group the statements into related topics using an affinity diagram
28	Affinity Diagram Copy design objectives to post-it^® notes Place one on a board Compare next objective card to the first If different, begin a new column If similar intent, place under the first column Repeat for all design objective cards Result: Objectives sorted by similar statement Within each column there may be levels of objectives Lower-level objectives answer the question “How?” Higher-level objectives answer the question “Why?”
29	Step 3: Draw the Tree The Objectives Tree diagram looks like an “upside-down” tree The overall objective of the tree is at the top Underneath it, branches break the objective into more detailed objectives Can have many levels and interconnections
30	Step 3: Draw the Tree (1) The objectives tree diagram may alternatively be drawn on its side Example: Car door
31	Try: Bumble Ball As a team, generate a list of objectives for the bumble ball toy Complete the affinity method for ordering the objectives in class Draw an objectives tree for the bumble ball
32	Objectives Tree and Functional Model Objectives are qualities the object should have Clients tend to speak in terms of objectives The Functions are what the product does without considering any particular solution Engineers tend to speak in terms of functions Identifying the basic functions an object does, and then determining solutions for these functions separately, leads to better solutions for the overall problem Two levels of functions: Overall functions and Sub-functions A product function is defined in a block diagram known as a Functional Model
33	Why to create and use Functional Models? It places the emphasis on what has to be accomplished rather than how It makes clear the various sub-systems or functions that need to be solved in order to solve the entire problem Enhances the creativity of the design team by allowing them to focus on one sub-function at a time Sub-functions may be derived from objectives tree (or customer needs)
34	Functional Model Definitions Functional model It is a picture, a graphical representation The overall function of a product is sub-divided into smaller, more elemental (i.e. atomic) sub-functions The sub-functions are connected by the flows on which they operate Sub-functions Simpler expressions of part of the product’s overall function Expressed in verb-object form at a consistent level of detail
35	Visual Functional Mode - Definition
36	Functional Model Basics A functional description is a combination of a function (verb) acting on a flow (object) Function - the operation that the product performs on a flow or a set of flows to transform it from its input state to its output state Flow - a material, energy or signal that is used by or affects the product Think of a flow as anything that is input to the product or an output of the product
37	Functional Model Basics (1) Functional description form: Function (Verb)–Flow (Object) Examples of functional descriptions
38	Functional Modeling Procedure Step 1: Create a “black box” model of the product State overall function of product Use your objective tree high level objectives to help determine the overall function Identify input and output flows Possibly related to lowest level objectives
39	Functional Modeling Procedure Step 2: Break down overall function into sub-functions Follow each input flow through the product and imagine what function the product performs on the flow The Zen approach: BE the flow
40	Functional Modeling Procedure For the flow of electrical energy, what is its associated sub-functions?
41	Functional Modeling Procedure Flow of the user mechanical energy, what are associated sub-functions?
42	Functional Modeling Procedure Step 3: Connect the sub-function chains together This may require additional sub-functions or connecting flows
43	Functional Modeling Procedure Step 3: Connect the sub-function chains together This may require additional sub-functions or connecting flows
44	Functional Modeling Procedure Step 3: Connect the sub-function chains together This may require additional sub-functions or connecting flows
45	Functional Modeling Procedure Step 4: Define the system boundary This ensures that only product sub-functions are considered for future design work
46	Functional Modeling Procedure Step 5: Identify appropriate components to perform sub-functions and their interactions
47	Functional Modeling Summary What’s the difference between objectives and functions? Objectives tell us what the final product will “be”, what qualities it will have Functions tell us what the object will “do”, without regard to any particular form Functions will always relate input to output Functions capture the transformation that takes place between input and output Though the difference may seem subtle, it is a very important distinction
48	Why to follow a design process?
49	Setting Requirements The Performance Specification Method
50	Setting Requirements After the objectives of what the product must do are set, its performance has to be specified It is formulating Engineering Specifications Engineering Specifications: Specify a target range for performance Define required performance, not the solution Provide a way to evaluate proposed solutions
51	Expressing Specifications Three ways to formalize what the user wants in terms more suitable for engineering design and analysis Prescriptive specifications (or constraints) Specify values for attributes of the designed product/process Ex.: The ladder step length can not exceed 20 in. Procedural specifications Identify specific procedures for calculating attributes or behavior Ex.: Maximum bending stress on a step is computed from s_max = Mc/I and the step is safe if s_max does not exceed s_allow Performance specifications Identify performance levels that signify the desired functional behavior has been achieved Ex.: A step on a ladder is safe if it supports an 200 kg load
52	The Performance Specification Method Step 1: Compile specifications Use the functional model as a starting point For each sub-function, write an associated specification (independent of any particular solution) For example:
53	The Performance Specification Method Support for Step 1: Standard categories for searching for specifications
54	The Performance Specification Method Step 2: Sort the engineering specifications by type Prescriptive (constraints) Procedural Performance Step 3: Quantify each engineering specification Engineering specifications should be quantified Express specifications as a range with limits or specific values (in the case of constraints) Quantifying may lead to more detailed specifications For example:
55	The Performance Specification Method Step 4: Determine testing/verification approaches Identify what procedure your team will use to check that each specification is met State when the test or verification will occur in project timeline Examples (from disc launcher):
56	The Performance Specification Method Step 5: Compile elements of engineering specification into a single document
57	The Performance Specification Method Step 6: Evaluate and update specifications as needed throughout the design project Make sure identified constraints are not too restrictive as to eliminate a better solution If specifications are updated, indicate so in the date column of the sheet
58	Establish Design Matrix The Quality Function Deployment Method or Design Matrix or House of Quality
59	The Quality Function Deployment method After the Function is analysed, designer has to define Engineering characteristics of a product. Designer defines ® ® ® ® Physical properties Physical properties determine® Engineering characteristics Characteristics determine ® ® Product attributes Product attributes satisfy ® ® Customer needs and requirements Marketing people require Þ desirable attributes Designers and engineers Þ engineering speak in terms of characteristics
60	Steps in QFD Method QFD has background in Japanese design science. Concerned with the translation of customer requirements into engineering characteristics. Identify customer requirements in terms of product attributes, Determine the relative importance of attributes, Evaluate the attributes of competing products, Draw a matrix of product attributes against engineering characteristics, Identify the relationship between engineering characteristics and product attributes, Identify relevant interactions between engineering characteristics, Set target figures to be achieved for the engineering characteristics.
61	Steps in QFD Method (1) Identify customer requirements in terms of product attributes Customer requirements should not be re-interpreted but only described in terms of product requirements. Determine the relative importance of attributes, Rank-ordering methods can be used to help determine the relative weights of each attribute. To do that systematically compare pair of objectives, one against the other. Objectives A B C D E row total A - 0 0 0 1 1 B 1 - 1 1 1 4 C 1 0 - 1 1 3 D 1 0 0 - 1 2 E 0 0 0 0 - 0 Evaluate the attributes of competing products, Performance scores for competing products and the own product should be listed against the set of customer requirements
62	Steps in QFD Method (2) Set target figures to be achieved for the engineering characteristics. These information are obtained from the comparison with competitor products or from trials with customers. These can be set comparative to competitors.
63	House of Quality Design Matrix
64	Objectives, functions, characteristics v.s. alternative solutions Previously, problem was clarified by use of four design tools Objectives Tree: A way to analyze customer needs and to group them logically Functional Model: An engineering first step at thinking about the general functions that the device must be able to do Engineering Specifications: A first step to specifying performance of the product or process to be designed The Quality Function Deployment Method – Design Matrix: Tool which helps to specify what the product must achieve and the criteria by which the alternative solutions will be judged. These clarify the problem - they do not give the solution
65	Background: Thinking Creatively Successful designers think creatively Successful designs are those that are fresh, innovative, and elegant, while yet being simple and direct They are artful and functional Many good designs, once unveiled, seem obvious People say, “Why didn’t I think of that?” Good designers “think of that” because they have developed the skills of: Brainstorming Lateral thinking
66	Brainstorming Brainstorming is process of generating as many ideas for solving a problem as possible in a short period of time. Keys to successful brainstorming: No criticism of ideas! Evaluation comes later Criticism quenches creative fire; it shuts off the flow of ideas Welcome creative thinking Encourage wild ideas They expand the envelope of ideas, possibly leading to workable solutions we otherwise never would have reached Aim for quantity of ideas Allow combining and extending ideas Encourage interaction among team members “Run the rut” on an idea
67	Preparing for Brainstorming Make sure the problem is clearly defined and understood by all Objectives Trees help with this Focus on a sub-function rather than on the whole product. Functional Models and Morphological Charts help with this Assign one person to be the moderator Moderator manages the session Make sure the rules are followed Assign another person to be the note-taker or scribe Scribe writes down all ideas suggested Rotate this responsibility so all have a chance to participate in brainstorming (scribes typically cannot record and generate ideas)
68	Vertical vs. Lateral Thinking
69	Brainstorming Exercise Use brainstorming session to generate as many ideas for each of four functions in a mousetrap design problem with the following required sub-functions:
70	Morphological Chart Used to generate possible design solutions After the problem and the function of the device is understood, brainstorming can be used to generate potential solutions Very useful visual way of organizing and assessing the range of possible solution combinations for a problem Very simple – it is a table Sub-functions listed in the first column Possible solutions to each sub-function shown in the rows to the right Possible solutions then selected to form a concept variant
71	DECISION MAKING
72	Design Process Overview To clarify the design problem, we created: Objectives tree Functional model Engineering specifications Design Matrix To generate concepts, created are: Morphological chart Concept variants
73	Design Process Overview Where we are going Select a single concept to fabricate Concept selection by Decision Matrix Build proof of concepts to test critical components of the overall solution
74	Why to use a Decision Matrix? From the Morphological Chart: Generated a large number of solutions Assembled “concept variants” How to evaluate these solutions? What makes one “better” than another? Knowing how to choose between alternatives is an important design activity! One can choose by some arbitrary manner, but it is best to use a rational approach that can be clearly explained to managers and clients. What makes a Decision Matrix a rational approach? Weighted numerical scores are assigned to various sub-objectives Individual scores are summed to give each overall solution choice a numerical score
75	How to Create a Decision Matrix List the design objectives Use the Objectives Tree The initial list might have been changed Rank order these from most to least important A rank order is a list from most important to least. Pair-wise comparison may help in ordering them (see lecture 3). Rank ordering is an example of and ordinal scale. Assign relative weighting to these objectives
76	How to Create a Decision Matrix Establish performance parameters (utility scores) for each of the objectives It is necessary to convert the statement of objectives into parameters that can be measured. The easiest way is to use five grades scale (0-4) with the following ranking: Far above average – Excellent (4) Above average – Very good (3) Average - Good (2) Below average - Satisfactory (1) Far below average - Not satisfactory (0) Base the parameter estimation on common sense, your existing knowledge, calculations, research on web, catalogs, etc. REMEMBER: If your estimates are bad, then the resulting decision matrix results will be bad Calculate and compare the relative utility values of the alternative designs In general, higher values mean better concept variant
77	Example Decision Matrix
78	Design Reviews Objectives To encourage communication between team members and sub teams To review progress, time keeping and project standards To set targets for further tasks To meet experts when necessary To meet people from project management and planning, manufacturing or administration
79	Proposed VEB PAGE Development of virtual reality learning environment for Design teams at City University Project plan and specification Equipment: computers, cameras … Recording of all meetings and other phases of project Final report, oral presentations, panels …
80	Learning = minds in communication²