9.FABRICATION OF PNEUMATIC QUICK RETURN MECHANISM - Copy.docx - CHAPTER-1 INTRODUCTION In mechanical design the designer often has need of a linkage


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CHAPTER-1 INTRODUCTION In mechanical design, the designer often has need of a linkage that provides a certain type of motion for the application he/she is designing. Since linkages are the basic building blocks of almost all mechanisms it is very important to understand how to design linkages for specific design characteristics. Therefore, the purpose of this lab is to offer practical experience in designing and building three and four-bar quick-return mechanisms that convert rotational to translational motion. Fig 1.1 Quick return mechanism To that end, a description of how to design these linkages, a laboratory activity, a pre- lab exercise, and follow-up questions are included in the following paragraphs. A quick return mechanism is a mechanism that converts rotary motion into reciprocating motion at different rate for its two strokes. When the time required for the working stroke is greater than that of the return stroke, it is a quick return mechanism. It yields a significant improvement in machining productivity. Currently, it is widely used in machine tools, for instance, shaping machines, power-driven saws, and other applications requiring a working stroke with intensive loading, and a return stroke with non-intensive loading. In an earlier lecture, we have already mentioned that there are two types of problems in kinematics namely, kinematic analysis and kinematic synthesis. In kinematic analysis, we determine the relative motion characteristics of a given mechanism. From today’s lecture, we shall start the discussion on this topic of kinematic analysis. 1
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CHAPTER-2 PNEUMATIC SYSTEMS A pneumatic system is a system that uses compressed air to transmit and control energy. Pneumatic systems are used in controlling train doors, automatic production lines, mechanical clamps, etc (Fig. 1). (a) Automobile production lines (b) Pneumatic system of an automatic machine Fig: No 2.1 Common pneumatic systems used in the industrial sector (a) The advantages of pneumatic systems: Pneumatic control systems are widely used in our society, especially in the industrial sectors for the driving of automatic machines. Pneumatic systems have a lot of advantages. (i) High effectiveness: Many factories have equipped their production lines with compressed air supplies and movable compressors. There is an unlimited supply of air in our atmosphere to produce compressed air. Moreover, the use of compressed air is not restricted by distance, as it can easily be transported through pipes. After use, compressed air can be released directly into the atmosphere without the need of processing. (ii) High durability and reliability: Pneumatic components are extremely durable and cannot be damaged easily. 2
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Compared to electromotive components, pneumatic components are more durable and reliable.
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