Mechatronics 1 3
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Fundamentals of machining

Fundamentals of machining
Method to increase accuracy and productivity
Special Tool Holders



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Mechatronics 1 3 Mechatronics 1 3 Presentation Transcript

  • Mechatronics Module 1
  • Topics • Fundamentals of machining • Method to increase accuracy and productivity • Special Tool Holders
  • Fundamentals of machining • Machining is the manufacturing process in which the size, shape or surface properties of a part are changed by removing excess materiel. • High Accuracy and good surface finish are required.
  • Basic machine Tool • • • • • Lathe or turning machine Drilling or boring machine Milling machine Shaper or planer Grinder
  • Material Removal • Chemical – Electro Chemical machining(ECM) • Electrical – electrical discharge machining (EDM) • Thermal – laser beam machining.
  • Metal removal rate • Cutting speed • Size of cut – Feed – depth
  • Cutting Speed (v) • Cutting speed defined as the relative velocity between cutting tool and work materiel. • Unit- feet per minute , meters per minute • NC- Spindle speed (angular velocity of work piece , rev/min) • Spindle speed N= 12v/∏D • D average diameter in inches
  • Depth of cut (d) • Defined as the distance the cutting tool projects below the original surface of the work • Expressed in thousandths in an inch or in millimeter
  • Feed (f) • Defined as the relative lateral movement between tool and work piece during the machine operation. • Inches per revolution , mm per revolution • Milling operation- length units per tooth – inches per tooth, mm per tooth • NC machine- length per minute- feed rate. • Feed rate – feed X spindle speed
  • Metal removal rate • The product of proper speed feed, and depth of cut determines the metal removal rate(MPR) • Volume – units per minute. • Productivity of the machine during cutting is proportional to MPR
  • Methods of Improving Machine Accuracy • Tool Deflection & Chatter • Lead screws • Thermal Deformations
  • Tool Deflection & Chatter • The force of the tool edge against the work piece in milling & turning deflects the tool and tool holder and causes dimensional error. • This error can be removed by increasing stiffness of the construction of tool mounting
  • • Chatter -Vibratory response due to tool deflection • If cutting tool deflects at one more than average, and as result a lump is left on the workpiece at the point . • Chatter occurs as a function Of the machine structure, too, workpiece material, and cutting condition.
  • Lead screws • In accuracies due to mechanical linkage between leadscrew and the tool. • In order to improve the accuracy , this mechanism must be time in varient ( no heating effect) and linear ( no backlash and friction)
  • Thermal deformation • Sources of heat – Marching process – Spindle and driving motors – Friction of slideways & lead screws
  • • A temp difference of 1˚C along 1000 mm can cause an error of 0.01 mm • Machine tool manufacture must take the thermal effects into considerations in design stage of the machine. • It can avoid by removing hi-power motor, providing large heat removing surface, use of low friction bearings,symmetrical distribution of heat sources.
  • • Heat effect can not completely removed • Precise machining are always located in an airconditioned environment or separate room