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Sổ tay thiết kế hệ thống cơ khí P4

4 Machine Tool Dynamics and Vibrations 4.1 4.2 4.3 Introduction Mechanical Structure • Drives • Controls Chatter Vibrations in Cutting Stability of Regenerative Chatter Vibrations in Orthogonal Cutting Yusuf Altintas The University of British Columbia Analytical Prediction of Chatter Vibrations in Milling Dynamic Milling Model • Chatter Stability Lobes 4.1 Introduction The accuracy of a machined part depends on the precision motion delivered by a machine tool under static, dynamic, and thermal loads. The accuracy is evaluated by measuring the discrepancy between the desired part dimensions identified on a part drawing and the actual part achieved after machining operations. The cutting tool deviates from a desired tool path due to errors. | 4 Machine Tool Dynamics and Vibrations 4.1 Introduction Mechanical Structure Drives Controls 4.2 Chatter Vibrations in Cutting Stability of Regenerative Chatter Vibrations in Orthogonal Cutting 4.3 Analytical Prediction of Chatter Vibrations Yusuf Altintas in Milling The University of British Columbia Dynamic Milling Model Chatter Stability Lobes 4.1 Introduction The accuracy of a machined part depends on the precision motion delivered by a machine tool under static dynamic and thermal loads. The accuracy is evaluated by measuring the discrepancy between the desired part dimensions identified on a part drawing and the actual part achieved after machining operations. The cutting tool deviates from a desired tool path due to errors in positioning the feed drives thermal expansion of machine tool and workpiece structures static and dynamic deformations of machine tool and workpiece and misalignment of machine tool drives and spindle during assembly. Because the parts to be machined will vary depending on the end-user the builder must design the machine tool structure and control of drives to deliver maximum accuracy during machining. A machine tool system has three main groups of parts mechanical structures drives and controls. 4.1.1 Mechanical Structure The structure consists of stationary and moving bodies. The stationary parts carry moving bodies such as table and spindle drives. They must be designed to carry large weights and absorb vibrations transmitted by the moving and rotating parts. The stationary parts are generally made of cast iron concrete and composites which have high damping properties. The contact interface between the stationary and moving bodies can be selected from steel alloys that allow surface hardness in order to minimize wear. 4.1.2 Drives In machine tools moving mechanisms are grouped into spindle and feed drives. The spindle drive provides sufficient angular speed torque and power to a rotating spindle shaft which is held in 2002 by CRC .