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Cnc 2 unit palanivendhan cnc elements

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Cnc 2 unit palanivendhan cnc elements

  1. 1. Computer Aided Manufacturing M.PALANIVENDHAN Department of Automobile Engineering SRM University, kattankulathur campus
  2. 2. HISTORY  US Air Force commissioned MIT to develop the first "numerically controlled" machine in 1949. It was demonstrated in 1952.  At 1970-1972 first Computer Numeric Control machines were developed.  Today, computer numerical control (CNC) machines are found almost everywhere, from small job shops in rural communities to companies in large urban areas.
  3. 3. Basics of CNC  A numerical control, or “NC”, system controls many machine functions and movements which were traditionally performed by skilled machinists.  Numerical control developed out of the need to meet the requirements of high production rates, uniformity and consistent part quality.  Programmed instructions are converted into output signals which in turn control machine operations such as spindle speeds, tool selection, tool movement, and cutting fluid flow.
  4. 4. Coordinates of CNC  All computer controlled machines are able to accurately and repeatedly control motion in various directions. Each of these directions of motion is called an axis. Depending on the machine type there are commonly two to five axes.  Additionally, a CNC axis may be either a linear axis in which movement is in a straight line, or a rotary axis with motion following a circular path.
  5. 5. Basic principle of CNC Each axis consists of a mechanical component, such as a slide that moves, a servo drive motor that powers the mechanical movement, and a ball screw to transfer the power from the servo drive motor to the mechanical component. These components, along with the computer controls that govern them, are referred to as an axis drive system.
  6. 6. CNC SYSTEM ELEMENTS A typical CNC system consists of the following six elements 1. Part program 2. Program input device 3. Machine control unit 4. Drive system 5. Machine tool 6. Feedback system
  7. 7. CNC CLASSIFICATION 1.Motion control: point to point (PTP) continuous (contouring) path 2. Control loops: open loop closed loop 3. Power drives: hydraulic, electric or pneumatic 4. Positioning systems: incremental absolute positioning 5. Hardwired NC and soft wired Computer Numerical Control (CNC)
  8. 8. Classification of CNC system  Point-to-Point . each axis driven separately and at different velocities  Moves at max velocity initially then slows as gets to desired position  After operation complete tool is retracted and moved rapidly to next position and repeats operation  Eg:Mainly used in drilling, punching, and straight milling operations
  10. 10. Classification of CNC system  Continuous Path . positioning and cutting operations both controlled along paths but at different velocities  Tool is cutting as it travels  Requires synchronization of velocities and movements
  11. 11. Continuous path control
  12. 12. Open and closed loop control
  13. 13. OPEN LOOP SYSTEM  In open-loop control system step motors are used  Step motors are driven by electric pulses  Every pulse rotates the motor spindle through a certain amount  By counting the pulses, the amount of motion can be controlled  No feedback signal for error correction  Lower positioning accuracy
  14. 14. CLOSED LOOP SYSTEM  In closed-loop control systems DC or AC motors are used  Position transducers are used to generate position feedback signals for error correction  Better accuracy can be achieved  More expensive  Suitable for large size machine tools
  15. 15. INTERPOLATION Types of Interpolation  Linear . tool moves in straight line from start to end in 2 or 3 axes  Circular . needs start and end points, coordinates of center of circle, radius, and direction of tool along the arc  Parabolic and Cubic . paths approximated by curves using higher order mathematical equations
  17. 17. CNC MILLING
  19. 19. CNC Plasma cutting
  20. 20. AUTOMOTIVE INDUSTRY Engine Block
  21. 21. Different products
  22. 22. AEROSPACE INDUSTRY Aircraft Turbine Machined by 5-Axis CNC Milling Machine
  23. 23. Advantages of CNC  Productivity Machine utilisation is increased because more time is spent cutting and less time is taken by positioning. Reduced setup time increases utilisation too.  Quality Parts are more accurate. Parts are more repeatable. Less waste due to scrap.
  24. 24. Advantages of CNC  Reduced inventory Reduced setup time permits smaller economic batch quantities. Lower lead time allows lower stock levels. Lower stock levels reduce interest charges and working capital requirements.  Machining Complex shapes Slide movements under computer control. Computer controller can calculate steps. First NC machine built 1951 at MIT for aircraft skin milling.
  25. 25. Advantages of CNC  Management Control CNC leads to CAD Process planning Production planning
  26. 26. Draw backs of CNC  High capital cost Machine tools cost $30,000 - $1,500,000  Retraining and recruitment of staff  New support facilities  High maintenance requirements  Not cost-effective for low-level production on simple parts  As geometric complexity or volume increases CNC becomes more economical  Maintenance personnel must have both mechanical and electronics expertise
  27. 27. Features of CNC Machining Centers
  28. 28. CNC Machine Components  Cutting Tool / Collet Caddy  Very common to have 100 or more diverse cutting tools loaded into a collet caddy  They are numbered for ease of identification  The operator must know the common tools by simple visual observation
  29. 29. Boxford Vertical Mill Cutting Tools Collet Caddy # Tool in Collet (different lengths) 5 2mm end mill, ball end 6 2mm end mill, slot drill 3 4mm end mill, slot drill 4 6mm end mill, slot drill 1 8mm end mill, slot drill 2 25 mm end mill, facing cutter
  30. 30. CNC Bench Vise Notice the smooth machined surfaces; be careful not to damage surfaces
  31. 31. CAM & X-axis Table Alignment To machine a part with CNC, the end of the tool must be known relative to the bench vise, x-axis table, or some other fixed distance
  32. 32. Z-axis Arbor  Keep the lands clean and oiled  A slight tilt will cause noticeable cut deformations  Align the protrusions with slots in the cutting tool quick change adapter body
  33. 33. Air Nozzle Used for:  Keeping cutting area free of excessive cutting debris  Quick cleaning  When supplied with misting, provides cutting tool cooling
  34. 34. End Mill / Facing Cutter  Hogs off large amounts of material  Radius of cut very large  Provides a known surface from which to measure from  Requires workpiece to be robustly supported due to high torque created
  35. 35. Quick Change End Mill Adapter  Helps provide quick changing of cutting tools without having to use complex setup procedures
  36. 36. Power Panel  Lockable On-Off Switch  Circuit Breakers  Power Cord
  37. 37. Control Panel 1. FEED HOLD Acts as an interrupt control to the program when pressed, preventing any further tool movement until canceled. During an Automatic cycle, after canceling CYCLE START must be pressed to resume the cycle. 2. SINGLE BLOCK With machine running in automatic mode controlled from the PC, this allows the operation of only a single block (line) of the program at a time to be toggled on/off. Press CYCLE START to proceed. 3. CYCLE START This sets the machine in automatic mode and starts the machining from the PC program. Also used to resume an Automatic cycle after a FEED HOLD is canceled and to action the next line if Single Block is active.
  38. 38. Control Panel 4. FEED SPEED CONTROL Provides stepless control of tool feed speed in the X, Y and Z axes from 0 to 100% in 10% increments. 5. JOG TABLE AXIS CONTROLS These four buttons control manual movement of the table in the X and Y axes. Move the table in the X axis while held pressed. Move the table in the Y-axis while held pressed. 6. JOG HEAD AXIS CONTROLS Move the head in the Z axis while held pressed. Pressing this button together with any of the other six axis control buttons provides rapid movement of the axes in the indicated direction.
  39. 39. Control Panel 7. MANUAL When lit, machine is operated from control panel (Manual mode). Pressing MAN puts light out and machine is controlled by computer (Automatic mode). Press MAN again to revert to manual mode operation. 8. AIR MIST CONTROL Switches on or off the optional air mist coolant when fitted. 9. DATUM M/C - PROGRAM ABORT After initially powering up the machine and pressing the Power Reset button (23), with the machine in Manual mode (Manual mode button lit) press to datum the machine axes. • With the machine in Manual mode, the machine can be re-datumed at any point. This should always be done if a physical stall of the axes has occurred. •During an Automatic Cycle with a Feed Hold (1) active, pressing will Abort the current job.
  40. 40. Control Panel 10. TOOL CHANGE With auto tool changer fitted, press to change to next tool automatically. 11. TOOL RELEASE Releases the tool holder from the spindle if fitted with the auto tool changer. Guard door must be open and tool holder held. 12. WORK HOLDING UN-CLAMP Controls un-clamping of workpiece in pneumatic work holder vice, when fitted. 13. WORK HOLDING CLAMP Controls clamping of workpiece in pneumatic work holder vice, when fitted. 14. DOOR OPEN Controls opening of the automatic doors when fitted.
  41. 41. Control Panel 15. DOOR CLOSE Controls closing of the automatic doors when fitted. 16. SPINDLE CONTROLS These control the speed and direction of rotation of the spindle. Spindle Forward - Pressing this button starts the spindle rotating forward. Holding it down increases forward speed. Pressing and holding the 'Spindle Reverse' button reduces speed in the forward direction. Spindle Reverse - Pressing this button starts the spindle rotating in reverse direction. Holding it down increases spindle speed in reverse direction. Pressing and holding the 'Spindle Forward' button reduces speed in the reverse direction. Spindle Stop - Pressing this button stops spindle rotation.
  42. 42. Control Panel 17. EMERGENCY STOP Pressing this pushbutton stops all machine movement and switches off the electronics, and the button locks in the depressed position. If the machine is in production, an appropriate message is displayed on the PC screen. The button must be turned to release it and the Hard Reset button (23) pressed to enable the machine to be started. The machine must be datumed using the Datum M/C key (9). If the machine was performing a production cycle, the cycle must be repeated from the beginning.
  43. 43. CNC Machine Tool Assembly
  44. 44. CNC Machine Tool Assembly
  45. 45. CNC Machine Tool Assembly
  46. 46. CNC Machine Tool Assembly
  47. 47. CNC Machine Tool Assembly
  48. 48. CNC Machine Tool Assembly
  49. 49. CNC Machine Tool Assembly
  50. 50. CNC Machine Tool Assembly
  51. 51. CNC Machine Tool Assembly
  52. 52. CNC Machine Tool Assembly
  53. 53. CNC Machine Tool Assembly
  54. 54. CNC Machine Tool Assembly
  55. 55. CNC Machine Tool Assembly
  56. 56. CNC Machine Tool Assembly
  57. 57. CNC Machine Tool Assembly
  58. 58. CNC Machine Tool Assembly
  59. 59. CNC Machine Tool Assembly
  60. 60. CNC Machine Tool Assembly
  61. 61. CNC Machine Tool Assembly
  62. 62. CNC Machine Tool Assembly
  63. 63. Courtesy: UTS(EMCO) CNC Machine Tool Assembly
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