Design analysis and optimization of machining fixture layout under dynamic conditions

Abstract

Nowadays modern manufacturing industries are struggling to improve dimensional accuracy, surface finish and productivity during the multioperation machining process which in turn reduces scrap rate and production cost. Fixture plays a major role to improve the machined surface quality of machining operation. The fixture and its elements are the essential tools to hold, secure and restrain the workpiece during various operations in the machining process. The locators and clamps are the elements of the fixture and their positions are known as fixture layout. The improper fixture layout increases the machining vibration which in turn affects the accuracy of the finished product. The accurately designed fixture layout assists the designer to minimize vibration during machining so that the required machining accuracy can be achieved. Mostly in the milling process, the intermittent engagement of multi-tooth cutter with workpiece results in vibration of the fixture-workpiece system which affects the surface finish of the machined workpiece which in turn reduces the quality of machining operation. This vibration is increased at a higher level when the frequency of exciting of multi-toothed milling cutter corresponds with any one of the natural frequencies of the fixture-workpiece system and it leads to the condition of resonance. The vibration increases under these conditions, which reduces machining accuracy and surface finish of the machined workpiece. Hence, the problems related to the design of fixture layout are to be addressed by recognizing the dynamic behavior of the fixture workpiece system. newline