Dinesh machine design
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The document discusses machine design and provides examples. It defines machine design as the process of selecting materials, shapes, sizes, and arrangements of mechanical elements so a machine can perform its intended task. As an example, it describes the process of designing a belt drive, which involves selecting elements like pulleys and belts, their shapes and materials, and their sizes. It also mentions classification and considerations in machine design processes, and provides a simple example of designing an L-shaped bracket.
Dinesh machine design
- 1. Prepared by : Dinesh Gupta, G. L Bajaj Group of Institutions, Mathura
- 2. Machine Design is the process of selection of the materials, shapes, sizes and arrangements of mechanical elements so that the resultant machine will perform the prescribed task What is Machine Design?
- 3. For example, the process of design of a belt drive consists of : 1. Selection of arrangement of mechanical elements like : pulleys, belt, shafts, keys, bearings, etc; 2. Selection of shapes of these mechanical elements; 3. Selection of materials for these mechanical elements; and 4. Selection of sizes of these mechanical elements.
- 4. Belt drive design arrangement in a Centrifugal Blower
- 5. Classification of Machine Design
- 7. Design Considerations Design considerations are the characteristics which influence the design of the element or, perhaps, the entire system. Normally, a number of such characteristics have to be considered in any design problem. In a given design problem, the design engineer should identify the various design considerations and incorporate them in the design process in their order of importance. For example, in the design of a spring, two most significant design considerations are : strength and stiffness.
- 9. Simple Design Problem Let’s talk about design of a simple “L" shaped bracket, one side of it is clamped and at the other side it is carrying some amount of load.
- 10. For initial design we have started with 5 mm thick plate. The following steps need to be followed for finding out the actual thickness needed for the bracket: 1. Calculating maximum bending moment: To find out the section where the maximum bending stress occurs So, the maximum bending moment M=750 kg-mm 2. The area moment of inertia for this section = (bd^3)/12 = 1041.667 mm4 3. Calculating bending stress: The classic formula for determining the bending stress in a member is: f/y=M/ I f = M.y/ I = 750 X 2.5/1041.667 kg/mm2 = 1.8 kg/mm2 If we consider a steel with yield strength is 25 kg/mm2, then we can see that stress generated in the clip is substantially low , so we have the chance to further reduce the thickness of the clip.
- 11. The HAL Tejas is an Indian single- seat, single-jet engine, multi-role light fighter designed by the Aeronautical Development Agency and Hindustan Aeronautics Limited.
Editor's Notes
- #2: Machine Design is the creation of newer and better products and improving the existing products. Newer and better products mean which is economical in overall cost of production and operation. Design is a long and time consuming process. Many existing ideas are studied and best idea is conceived. The best idea is studied keeping in mind the commercial success and given shape and form in the form of production drawings. In preparation of drawings we take care of the availability of resources for successful completion of idea into reality. To design a component knowledge of many subjects are required.
- #6: System design is the design of any complex mechanical system. Each mechanical system consists of number of sub-systems and each sub-system consists of number of mechanical elements. Examples of the system design are : design of car, design of EOT crane, design of conveyer, etc. Product design is the design of a product which is a sub-system of any mechanical system. Examples of the product design are : design of gearbox, design of brake, design of clutch, etc. Element design is the design of any mechanical element which is a part of mechanical sub-system or product. Examples of element design are : design of gear, design of shaft, design of key, etc. Empirical design is the design using empirical formulae and relations. These empirical formulae are developed based on the past experience and practice. Examples of empirical design are : design of gear box casing and design of machine tool body. An optimum design is the best design solution from the possible design solutions. An optimum design minimizes the undesirable effects like : cost, weight, size, etc or maximizes the useful parameters like : load carrying capacity, power transmitting capacity, etc. In computer aided design, computer system is used to assist in the creation, modification, analysis, and optimization of a design.
- #7: Define the design problem giving all input parameters, output parameters, and constraints. Once the problem is defined, the next step is synthesis. Synthesis is the process of selecting or creating the mechanism for the machine and the shapes of the mechanical elements so as to get the desired output with given input. Draw the force body diagram of each element of the machine. Find out the forces (including moments and torque) acting on each element by force analysis. Select the suitable material for each element. Four basic factors that are to be considered while selecting the material are : availability, cost, mechanical properties, and manufacturing considerations. Before finding out the dimensions of the element, it is necessary to know the type of failure by which the element will fail when put into the use. Based on the application, select the factor of safety. Knowing factor of safety and material strength, determine the permissible or design stresses Find the dimensions of each element of the machine by considering the forces acting on the element and the permissible stresses. Modification of Dimensions : Modify the dimensions of the elements on the higher side, if required, based on the following considerations : (i) Selection of standard parts available in the market; (ii) Convenience of assembly; and (iii) Convenience of manufacturing. Step 9 : Preparation of Drawings : Prepare working drawing of each element or component with minimum two views showing following details : (i) Dimensions; (ii) Dimensional tolerances; (iii) Surface finish; (iv) Geometrical tolerances; and (v) Special production requirements like heat treatment. Prepare assembly drawing giving part numbers, overall dimensions, and part list. The component drawing is supplied to the shop floor for manufacturing purpose, while assembly drawing is supplied to the assembly shop. Step 10 : Preparation of Design Report : Prepare design report containing details about step 1 to step 8.