The Need for New Structures

Some of the Problems associated with Conventional Machine Tool Structures:

• Limited degrees of freedom: Most of the common conventional machine tools have about three degrees of freedom. Some of the modern conventional machines have upto five degrees of freedom, but the arrangement is not very efficient. The lack of degrees of freedom is a tangible limitation in the present competitive manufacturing environment. The development of flexible manufacturing systems and agile manufacturing stresses on machine tools which can perform a wide variety of machining operations. An ideal machine tool is envisioned as a cutting tool free enough for any spatial movement. This can be achieved with a six degree of freedom machine tool.
• Problems of Heavy Mass: Problems of rigidity frequently arise due to accelaration and decelaration of heavy masses. Increasingly as an effort is being made to produce light and portable machine tools, this factor assumes greater importance.
• Accuracy: The movements of the machine tool are dependent on linear ways and bearings. During the life of a machine as these wear out the accuracy of the machine is affected. This has an important bearing on the concept of volumetric accuracy. In a conventional three-axis we have 21 position variables to consider.
• Vibration and Stiffness Problems: As the structures are composed of heavy parts and are not very symmetrical this factor has a great effect on machine tool performance. Individual axes take unproportional amount of forces.
• Fixturing Requirements: In conventional machine tools as the degrees of freedom are limited the fixturing requirements are large. Special tools are needed for various purposes like machining thin wall sections or when parts of workpiece surface are inaccessible. The need for extra tools and fixtures increases machining time and cost to a great degree for applications which require them.
  
  A horizontal milling Tool
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

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