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Designing Products & Engineering. What is Engineering Design?. The systematic and creative application of scientific and mathematical principles to practical ends such as the design, manufacture, and operation of efficient and economical structures, machines, processes, and systems.
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What is Engineering Design? • The systematic and creative application of scientific and mathematical principles to practical ends such as the design, manufacture, and operation of efficient and economical structures, machines, processes, and systems.
The basic purpose of any organization is to provide products or services to their customers. Thus, the design of these products and services is essential to the livelihood of a company. But, what are the characteristics of an Effective Design?
Effective Design • Effective designs provide a competitive edge by: • Bringing new ideas to the market quickly • Doing a better job of satisfying customer needs • Making new products easier to manufacture, use, and repair than existing products
Types of Design and Redesign • Original Design (or Inventing) Involves elaborating, original solutions for a given task. The result of original design is an invention. • Adaptive Design (or Synthesis) Involves adapting a known system to a changed task or evolving a significant subsystem of a current product (such as antilock brakes). • Variant Design (or Modification) Involves varying the parameters (size, geometry, material properties, control parameters, etc.) of certain aspects of a product to develop a new and more robust design.
Product Design: • Specifies which materials are to be used • Determines dimensions and tolerances • Defines the appearance of the product • Sets standards for performance.
Design has a tremendous impact on the quality of a final product or service. Quality in the design process involves: • Matching product or service characteristics with customer requirements • Ensuring that customer requirements are met in the simplest and least costly manner • Reducing the time required to design a new product or service, and • Minimizing the revisions necessary to make a design workable.
Sources of idea generation • Surveying suppliers, distributors, and salespersons • Monitoring trade journals • Analyzing warranty claims, customer complaints, and other failures • Surveying potential customers • Bench marking: Comparing a product or process against the best-in-class product. • Reverse engineering: Carefully dismantling a competitor’s product in order to improve one’s own product.
Involvement of Different Functional Departments in the Design Process Marketing Department takes the idea and: • Forms a product concept • Conducts a study on the feasibility of the proposed product or service • If the proposed product meets certain expectations, performance specifications are developed.
Involvement of Different Functional Departments in the Design Process • Design Engineers take the performance specifications and: • Develop preliminary technical specifications, and later • Develop detailed design specifications. • Manufacturing/Industrial Engineers take the detailed performance specifications and: • Develop a process plan that includes specific requirements for equipment, tooling, and fixtures. • Production/Industrial Engineers take these manufacturing specifications and schedule production
Feasibility study Idea generation Product feasible? Preliminary design Final design Process planning Prototype Design & Manufacturing Specifications Manufacturing The Design Process Yes No
Flexibility Cost A Decision Making Process • Idea generation & pre-design planning • Customer Requirements • Functional Specification • Product Specifications • Concept Generation • Concept Selection • Engineering Design • Engineering Evaluation • Prototype and Testing • Manufacturing Design
Final design is concerned with how the product will perform. It consists of three phases: 1. Functional design is concerned with how the product will perform. 2. Form design refers to the physical appearance of a product. 3. Production design is concerned with the ease and cost of manufacturing the product.
Functional Design(How The Product Performs) • Reliability • probability product performs intended function for specified length of time • A measure for reliability is Mean Time Between Failures (MTBF). • Maintainability • ease and/or cost or maintaining/repairing product • A measure for maintainability is Mean Time To Repair (MTTR).
DFM Guidelines 1. Minimize the number of parts 2. Develop a modular design 3. Design parts for multi-use 4. Avoid separate fasteners 5. Eliminate adjustments
7. Design for minimum handling 8. Avoid tools 9. Minimize subassemblies 10. Use standard parts when possible 11. Simplify operations 12. Design for efficient and adequate testing 13. Use repeatable & understood processes 14. Analyze failures 15. Rigorously assess value
Design Simplification (a) The original design (b) Revised design (c) Final design Assembly using common fasteners One-piece base & elimination of fasteners Design for push-and-snap assembly
Customers’ Requirements • Normal Requirements are typically what we get by just asking customers what they want. • Expected Requirements are often so basic the customer may fail to mention them - until we fail to perform them. For example, if coffee is served hot, customers barely notice it. If it's cold or too hot, dissatisfaction occurs. Expected requirements must be fulfilled. • Exciting Requirements are difficult to discover. They are beyond the customer's expectations. For example, if full meals were served on a flight from Chicago to Indianapolis, that would be exciting. If not, customers would hardly complain.
Making Economic Decisions • Engineering economy: the discipline concerned with the economic aspects of engineering. It involves the systematic evaluation of the costs and benefits of proposed technical projects.
Rational Decision-Making Process • Recognize a decision problem • Define the goals or objectives • Collect all the relevant information • Identify a set of feasible decision alternatives • Select the decision criterion to use • Select the best alternative
Example: Equipment & Process Selection • How do you choose between Plastic Composite and Steel sheet stock for the auto body panel? • The choice of material will dictate the manufacturing process for the body panel as well as manufacturing costs.
Engineering Costs General Cost Terms • Manufacturing Costs Direct materials Direct labor Mfg. Overhead • Non-manufacturing Costs Overhead Marketing Administrative
Cost Classification for Predicting Cost Behavior • Cost Behaviors Fixed costs Variable costs • Average unit costs
Fixed Costs Fixed costs per unit of production (F/Q) Total fixed costs (F) Production volume (Q) Productionvolume (Q)
Variable Costs • Def: Costs that vary depending on the level of production or sales • Cost behavior: Increase or decrease proportionally according to the level of volume • Examples: Costs of raw material, packaging material, direct labor, machine utilities are main variable costs.
Total variable costs (TV) Variable Costs Variable costs per unit of production (V) Production volume (Q) Production volume (Q)
Break-Even Analysis (BEA) • The total revenue depends on the production level. • The higher the production, the higher the total variable costs. • In BEA, it is assumed that price of product is fixed.
Total revenue (TR) BEA Price per unit (P) Production (and sales ) volume (Q) Production (and sales) volume (Q)
BEA • Therefore, the overall break-even analysis can be pictorially represented in the following graph Profit Total costs (F+VQ) BEP: F+VQ=PQ loss Total revenue (PQ) Production (and sales) volume (Q)
BEA Total Cost (TC) = Total Revenue (TR) TC=F+VQ TR=PQ At the break-even point: F+VQ=PQ QBEQ = F/ (P-V)
Example • 500,000$ total yearly fixed costs. • 150$ / unit variable costs • 200$ / unit sale price • QBEQ=500000/(200-150) =10000 units • If our market research indicates that the present demand is > 10000, then this manufacturing system is economically feasible.
QUALITY FUNCTION DEPLOYMENT • Quality Function Deployment • Voice of the customer • House of quality QFD: An approach that integrates the “voice of the customer” into the product and service development process.
THE QFD APPROACH CUSTOMER REQUIREMENTS FUNCTIONAL MEASURES PARTS CHARACTERISTICS MANUFACTURING PROCESS PRODUCTION REQUIREMENTS
Quality Function Deployment • Identify customer wants • Identify how the good/service will satisfy customer wants • Relate customer wants to product hows • Identify relationships between the firm’s hows • Develop importance ratings • Evaluate competing products
Importance Competitive assessment House Of Quality Tradeoff Matrix Product characteristics Relationship matrix Customer requirements Technical assessment and target values
Customer Requirements CUSTOMER COMMENTS • Peels a variety of produce • Works both right and left handed • Creates minimal waste • Saves time • Durable • Easy to clean • Safe to use and store • Comfortable to use • Stays sharp or is sharpenable “Carrots and potatoes are very different.” “I cut myself with this one.” “I just leave the skin on.” “I’m left-handed. I use a knife.” “This one is fast, but it takes a lot off.” “How do you peel a squash?” “Here’s a rusty one.” “This looked OK in the store.”
Select a household product of your choice, your goal will be to describe how you think this design evolved. By looking at the product, can you tell: • How and why the device functions? Can you describe how it works, what energy sources are used, and what purpose that function serves? • How was human engineering involved? How would the human/machine interface affect this design? What safety issues would have been involved? • Why the original designers selected the materials used? What properties of the materials were most important in selecting them? • What features make this product unique? Compared to similar items, are there features on your example that would identify this as a better product? • How was the production process affected by this design? Are there specific features that might have been added to make production more efficient?
As your analysis continues, choose one aspect of the design that intrigues you. Study the design used, and consider how you might improve on it. • Develop a list of alternatives, and compare them to the existing design. • Develop some criteria that may help you select one of your alternatives as most likely to succeed. • Finally, select one alternative, and describe how it improves on the existing design, what its limitations are, and why you think this is a better alternative than the existing design.
