1. Machine Design I (MCE-C 203) Mechatronics Dept., Faculty of Engineering, Fayoum University Dr. Ahmed Salah Abou Taleb Lecturer, Mechanical Engineering Dept., Faculty of Engineering, Fayoum University 1

2. The Traditional Design Process 2

3. Preliminary Design Phase 3 Often the first step in which a designer becomes involved, and may not involve intense iteration. In this phase, we deal with the entire machine: Define function Identify constraints involving cost, size, etc. Develop alternative conceptions of mechanism/process combinations that can satisfy the constraints Perform supporting analyses (thermodynamic, heat transfer, fluid mechanics, kinematics, force, stress, life, cost, compatibility with special constraints) Select the best mechanism Document the design Alternative design concepts for cross members in a light-duty truck floorpan assembly Concept 1 Two longitudinal members, one trans-verse split-end cross member, small transverse member in transmission tunnel, rear transverse member similar to original, gauge reduction. Concept 6 Two integrated, split transverse cross members, rear transverse member similar to original, reduced sheet thickness in cross members.

4. 4 Intermediate Design Phase Generally occurs after preliminary design, but the two phases may overlap. Intermediate design always involves iterations. In this phase, we deal with individual components of the machine: Identify components Define component functions Identify constraints involving cost, size, etc. Develop tentative conceptions of the components mechanism/process combinations using good form synthesis principles Perform supporting analyses (including analyses at each critical point in each component) Select the best component designs Document component designs; prepare a layout drawing A-pillar component geometries Corner Reinforcement Front Reinforcement

5. 5 Detailed Design Phase Subsequent to intermediate and. In this phase, we deal with individual components of the machine and the machine as a whole: Select manufacturing and assembly processes Specify dimensions and tolerances Prepare component detail drawings Prepare assembly drawings Line rendering of a pickup box assembly showing geometric details such as wheel well openings, cross members, and bed corrugation

6. 6 Design Affecting Factors The design of a component or system may be influenced by a number of requirements. If a requirement affects design, it is called a design affecting factor/design consideration. For example, if the ability to carry large loads without failure is important, we say that strength is a design consideration. Most product development projects involve a number of design affecting factors: - Strength/stress- Cost - Thermal properties - Distortion/stiffness- Processing requirements - Surface finish - Wear- Weight - Lubrication - Corrosion- Life - Marketability - Safety- Noise - Maintenance - Reliability- Aesthetic considerations - Volume - Friction- Shape - Liability - Usability- Size - Scrapping/recyclability

7. 7 Economics Strength, safety, reliability, and cost are perhaps the most important design considera-tions. In general the design alternative that satisfies other design considerations at the lowest costs is to be preferred. Issues affecting the “cost” of a design include: Product development costs Material choice Manufacturing processes involved Economies of scale Tolerances specified Use of standard sizes and components Breakeven point for two different screw manufacturing processes

8. 8 Materials Selection The designer of any product, other than software must get involved with material selection. Only occasionally will the exact grade of material be specified by the customer. Even then the designer must understand the material to be able to design the product.

9. 9 Materials Selection Decisions, decisions! So many materials, so much information. How do we decide? How do we begin to choose? First we need to look at the function of the product – product analysis

10. 10 Materials Selection Product Analysis Every product is designed in a particular way - product analysis enables us to understand the: important materials, processing, economic and aesthetic decisions which are required before any product can be manufactured. Just what it says – analyse the product! What does it do? How does it do it? Where does it do it? Who uses it? What should it cost? What does it look like?

11. 11 Materials Selection Case Study – a bike

12. 12 Materials Selection Case Study – a bike What is the function of a bike – obvious? How does the function depend on the type of bike? [Racing – Touring - Mountain bike –Commuter- Childs] How is it made to be easily maintained? What should it look like (colours etc.)? What should it cost? How has it been made comfortable to ride? How do the mechanical parts work and interact?

13. 13 Materials Selection Case Study – a bike Component or system? 1 st problem is……. Is it one component or a system of components working together? A spanner is a component, a cordless screwdriver is a system.

14. 14 Materials Selection Case Study – a bike When we analyse a system we need to break the system down into individual components and then analyse each one. System Analysis

15. 15 Materials Selection Case Study – a bike System Analysis The bike breaks down into various parts: Frame – pedals – Wheels – Saddle - Etc. We now need to look at the following for each part: Requirements (mechanical, ergonomic, aesthetic etc.) What is the function of each component, and how do they work? How many are going to be made? What is each part made of and why? What manufacturing methods are we going to use? Are there alternative materials or design in use and can you propose improvement?

16. 16 Materials Selection Case Study – a bike Manufacturing Oh No! We have to actually make it! This is a key question which has a massive influence on materials selection. e.g. The frame, what materials could we use?

17. 17 Materials Selection Case Study – a bike Manufacturing Steel – Strong, stiff, heavy, but cheap Aluminium – weaker, lighter, more expensive than steel Composite (CFRP) – strong, stiff, very light, but expensive to buy and to fabricate

18. 18 Materials Selection Case Study – a bike Manufacturing

19. 19 Materials Selection What Properties? Mechanical – Strength, modulus etc. Physical – Density, melting point. Electrical – Conductivity, resistivity. Aesthetic – Appearance, texture, colour Processability – Ductility, mouldability And last, but not least………. Cost, cost, cost!

20. 20 Materials Selection Choose the right materials Given the specification of the requirements on each part, we can identify the material properties which will be important - for example: RequirementMaterial Property must conduct electricityelectrical conductivity must support loads without breakingstrength cannot be too expensivecost per kg

21. 21 Materials Selection Where do I find the data? Textbooks Databooks Manufacturer’s literature Internet Sites

22. 22 Materials Selection Textbooks Good for general information Some have tables of properties Not good for detailed specifications and properties. A useful first point of call Databooks One of the quickest sources of detailed information. Usually contain grades and specifications as well as properties. Small and perfectly formed – pocketbooks Easy to navigate around

23. 23 Materials Selection Manufacturer’s Literature Internet Sites Variable in quality and usefulness. Often only cover their products. Usually do not compare materials. Can be biased. Good for final selection before ordering. Can be a real minefield. Lots of poorly presented information. Google searches bring up lots of rubbish. Hard to find technical information. Best to use non-commercial sites.

24. 24 Materials Selection Charts

25. 25 Materials Selection Charts

26. 26 Materials Selection Charts

27. 27 Materials Selection Charts Allow easy visualisation of properties Show lots of different materials Can be ‘drilled down’ to specifics Show balances of properties e.g. strength v cost Ideal for a first ‘rough cut’ selection

28. 28 Materials Selection Bigger Picture Is the product performance driven or cost driven? This makes a huge difference when choosing materials.

29. 29 Materials Selection Choose Between Different Materials There are three main things to think about when choosing materials (in order of importance): – Will they meet the performance requirements? – Will they be easy to process? – Do they have the right properties? For now it is sufficient to note that experienced designers aim to make the decisions for materials and processes together to get the best out of selection. Most products need to satisfy some performance target, which we determine by considering the design specification e.g. they must be cheap, or stiff, or strong, or light, or perhaps all of these things...

30. 30 Materials Selection Case Study – Drink Container What are the requirements?