A machine is a combination of interrelated bodies, links or elements, which are characterized by being resistant and in general, rigid.
These links are sop chosen and arranged that in operation they can collectively either transfer other forms of energy into mechanical energy or receive mechanical energy power, from external sources, transmit and modify it, thus doing work in performing some task.
Thus doing work in performing some task.
It is the creation of new and better machines and improving the existing ones. A new machine is one which is more economical in the over all cost of production and operation. In designing a machine part or a machine as a whole, all types of forces stresses involved should be given due consideration so that it withstand under these forces with out rupture or undue distortion.
The following are the some general characteristics, which influence the design of elements or the entire machine.
- Thermal consideration
- Surface finish
Procedure in design:
In designing a machine there is no specific rule, it can be done in some many ways. How ever generally a procedure to solve the problem can be adopted as follows.
- First make a complete statement of the problem, clearly indicating the purpose of the machine to be designed.
- Select the possible groups of mechanisms, which will give the desired motion.
- Find the forces acting on each member of the machine and the energy transmitted by each member.
- Select the best material.
- Fined the size of each member of the machine, considering the forces acting and the stresses within permissible limits.
- Modify the size of the member of the machine to agree with the past experience and judgment to facilitate manufacture.
- Draw the detail drawing of each component and the assembly of the machine with complete specification for the material and manufacturing processes suggested.
Uses of a machine:
A machine may also used to change the direction of a force. A single pulley at the top of a flagpole enables one end of the rope to exert an upward force on the flag as a downward force is exerted on the other end. Another use of a machine is to transform energy. A generator transforms mechanical energy into electrical energy. A steam turbine transforms heat energy into mechanical energy.
We use machines to transfer energy from one place to another. The connecting rods, crankshafts, and axles transfer energy from the cylinders in the combustion engine of a car to the tires. We also use machines to multiply speed. A bicycle is a machine that gains speed by exerting a greater force on it. No machine can be used to gain both force and speed at the same time.
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