ABEN 4511_ Machinery Design for AB Production.pdf

ABEN 4511: Machinery Design for AB Production Machine design is a systematic process of selection of the materials, shapes, sizes and arrangements of mechanical elements so that the resultant machine will perform the prescribed task. Machine Design is the creation of new and better machines and imp...

ABEN 4511: Machinery Design for AB Production Machine design is a systematic process of selection of the materials, shapes, sizes and arrangements of mechanical elements so that the resultant machine will perform the prescribed task. Machine Design is the creation of new and better machines and improving the existing ones 3 Classifications of Machine Design. Adaptive design. In most cases, the designer's work is concerned with adaptation of 2 existing designs. This type of design involves minor alterations or modifications to existing designs. Designers with ordinary technical training can attempt this type of design.. Development design. This type of design needs considerable great or a naute. The tal product 1 may significantly differ from the original.. New design. This type of design demands extensive research, technical skills and creative thinking. Only designers with exceptional qualities can take up the work of a new design. The designs, depending upon the methods used, may be sub-classified as follows : Rational design. This type of design depends upon mathematical formula of principle of mechanics.  Empirical design. This type of design depends upon empirical formula based on the practice and past experience. Industrial design. This type of design depends upon the production aspects to manufacture any machine component in the industry. Optimum design. It is the best design for the given objective function under the specified constraints. It may be achieved by minimizing the undesirable effects. System design. It is the design of any complex mechanical system like a motor car. Element design. It is the design of any element of the mechanical system like piston, crankshaft, connecting rod, etc. Computer aided design. This type of design depends upon the use of computer systems to assist in the creation, modification, analysis and optimization of a design General Considerations in Machine Design Following are the general considerations in designing a machine component:. Load and stresses caused by the load. The load, on a machine component, may act in several ways due to which the internal stresses are set up.. Motion of the machine parts. The successful operation of any machine depends largely upon the simplest arrangement of the parts which will give the motion required.  The motion of the parts may be: ○ Rectilinear motion which includes unidirectional and reciprocating motions ○ Curvilinear motion which includes rotary, oscillatory and simple harmonic ○ Constant velocity ○ Constant or variable acceleration. Selection of materials. It is essential that a designer should have a thorough knowledge of the properties of the materials and their behavior under working conditions. Some of the important characteristics of materials are: strength, durability, flexibility, weight, resistance to heat and corrosion, ability to cast, welded or hardened, machinability, electrical conductivity, etc.. Form and size of the parts. The form and size are based on judgement. The smallest practicable cross-section may be used, but it may be checked that the stresses induced in the designed cross-section are reasonably safe. In order to design any machine part for form and size, it is necessary to know the forces which the part must sustain. It is also important to anticipate any suddenly applied or impact load which may cause failure.. Frictional resistance and lubrication. There is always a loss of power due to frictional resistance and it should be noted that the friction of starting is higher than that of running friction. It is, therefore,  essential that a careful attention must be given to the matter of lubrication of all surfaces which move in contact with others (rotating, sliding, or rolling).. Convenient and economical features. In designing, the operating features of the machine should be carefully studied. The starting, controlling and stopping levers should be located on the basis of convenient handling. If parts are to be changed for different products or replaced on account of wear or breakage, easy access should be provided and the necessity of removing other parts to accomplish this should be avoided if possible. ○ The economical operation of a machine which is to be used for production, or for the processing of material should be studied, in order to learn whether it has the maximum capacity consistent with the production of good work.. Use of standard parts. The use of standard parts is closely related to cost, because the cost of standard or stock parts is only a fraction of the cost of similar parts made to order.. Safety of operation. Any moving part of a machine which is within the zone of a worker is considered an accident hazard and may be the cause of an injury. It is, therefore, necessary that a designer should always provide safety devices for the safety of the operator.. Workshop facilities. A design. engineer should be familiar with the limitations of his employer's workshop, in order to avoid the necessity of having work done in some other workshop.. Number of machines to be manufactured. The number of machines to be manufactured affects the design in a number of ways. The engineering and shop costs which are called fixed charges or overhead expenses are distributed over the number of machines to be manufactured. Cost of construction. The cost of construction of a machine is the most important consideration involved in design. In some cases, it is quite possible that the high cost of may immediately bar it from further considerations.. Assembling. Every machine or structure must be assembled as a unit before it can function. Large units must often be assembled in the shop, tested and then taken to be transported to their place of service. The final location of any machine is important and the design engineer must anticipate the exact location and the local facilities for assembly General Procedure in Machine Design. Recognition of need. First of all, make a complete statement of the problem, indicating the need, aim or purpose for which the machine is to be designed.. Synthesis (Mechanisms). Select the possible mechanism  or group of mechanisms which will give the desired motion.. Analysis of forces. Find the forces acting on each member of the machine and the energy transmitted by each member. Material selection. Select the material best suited for each member of the machine.. Design of elements (Size and Stresses). Find the size of each member of the machine by considering the force acting on the member and the permissible stresses for the material used. It should be kept in mind that each member should not deflect or deform than the permissible limit.. Modification. Modify the size of the member to agree with the past experience and judgment to facilitate manufacture. The modification may also be necessary by consideration of manufacturing to reduce overall cost.. Detailed drawing. Draw the detailed drawing of each component and the assembly of the machine with complete specification for the manufacturing processes suggested.. Production. The component, as per the drawing, is manufactured in the workshop