The Machine And Its Designer
A machine is known to be a device that transmits motion and force in a controlled manner. A machine is made up of some elements in such a way that every element will move in coherence along with other and force will be transmitted from element to element. The force and motion at various points will constitute mechanical work or energy. Hence, the prime function of machine can also be regarded as getting energy at input point and transmitted it to some other body at output point. Between the output and input points the form of energy may or may not change. For illustration as, an internal combustion engine is a machine. This receives thermal energy at the top of piston in the cylinder and delivers kinetic energy at the crank shaft. A lathe machine or a milling machine obtains mechanical energy and transmits mechanical energy to work piece through removal of material at cutting point extremely close to machines are the structures such are also made up of elements and are subjected to forces however they differ from machines in that they do not have elements moving in relation to each other. In reality all elements there are stationary. Many of them can be designed like machines.
In fact in machine designing we divide activity in the separate steps. One in which simply motion is considered and analyzed with no considering forces that may be the reason of motion. For such step the elements of machines are regarded as rigid or non-deforming. In the 2nd step the elements are regarded like stationary and forces that are transmitted from connecting link or created because of motion are consider being acting on the element. The element is assumed to be deforming and thus internal resistance named as stress is considered for calculating the size of the element. The subject of Mechanical Design, Design of Machine Elements, Mechanical Engineering Design or Machine Design after deals along with 2nd step. The first step as comprised in design procedure at steps 2nd and 3rd is often taken separately which is outside the purview of the subject of Machine Design. On the other hand design of structures several of them are in involved in this subject.
Designing will appear like a decision making process whether the sizes of various elements will be decided. In simpler designs, sufficient background knowledge and information are available by way of which a particular element may be regarded to be loaded purely axially, like a beam or as a shaft. Several may be beneath combined leading while all three or two of these load conditions may exist. A designer's capability is tested by the fact that he creates a similarity among a machine element and any type of the standard loading situations. For illustrations, treating a gear tooth, like a cantilever beam can be an illustration of ingenuity of the designer or regarding belt to be bent like a beam over pulley could other such illustration. Now we will be considering some such illustrations in which similarity among a machine member and other loaded in a standard fashion that is: axially and bending, combination or torsion thereof, will be brought out. And after that the standard formulae of the subject of Strength of Materials or Mechanics of Solids may be utilized. The designer will have to be sensitive to determination of forces that may happen from any source. For illustration, a steam turbine is designed thermodynamically for its major reasons of converting thermal energy into mechanical energy or design of a hydraulic turbine will employ principles of Fluid Mechanics however a designer of machine will be concerned along with the forces that arise from flow of steam or water upon the elements like blades and rotors. Needless to say that designer will determine it difficult to visualize all the forces comprehensively if he does not possess comprehensive knowledge of Fluid Mechanics and thermodynamics. We might end up by collecting different characteristics a designer should possess.
(a) He must have sound and comprehensive knowledge in specific field of engineering to which the design belongs as: Thermodynamics, Refrigeration, and Fluid Mechanics.
(b) He invariably should be conversant along with Mechanics, Structures, Mechanisms, Engineering Manufacturing and Materials Processes.
(c) Comprehensive knowledge of Mechanics of solids for correlating sheers, deformation, forces loads and geometry is a must however in specific cases whereas the element may not determine a parallel in any of standard strength of Material solution the designer may be required to employ advanced techniques of Theory of elasticity. The expertise in this way is an added feature.
(d) Some conditions which are out of the purview of Strength of Material may need experimental methods as: Photo-elasticity or Strain Gauge Survey. Along with the advent of fast computers the Numerical Techniques of Finite Elements has become a handy and strong tool in the hands of designer of machines.
(e) The national and international standards and professional codes make the job or task of designing much easier. Many times they are basically to be followed beneath orders of government or by law. Those standards are useful in infusing safety of operation and economy. Thus this is imperative that a designer is well versed along with standards and codes.
(f) A designer must be capable to employ his experience and knowledge and must usually be ready to learn from his own experiences and those of others. Hence, a constant touch along with current literature is required. Though, the designer should be cautious for his experience of past does not become an obstacle in innovation.
(g) The ease of operation, safety during operation and convenient repairs and maintenance along with the cost of equipment are such factors such are related to ultimate user. The designer must make him aware of human nature and preferences hence his design may be acceptable and continues safe in all aspects of operation, repair, maintenance and last disposal.
(h) The appearance of the product should be attractive to buyers along with whose requirements in mind the design was made. The designer must have understanding of aesthetics to make the product attractive.