CNC Machining Centres

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This presentation gives an information about: CNC Machining centers covering syllabus of Unit-7, Sub: Computer Integrated Manufacturing (10ME61) for BE course.

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CNC Machining Centres

  1. 1. 4/4/2014 1Hareesha N G, Dept of Aero Engg, DSCE, Blore
  2. 2. 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 2
  3. 3. Hareesha N G, Dept of Aero Engg, DSCE, Blore 34/4/2014
  4. 4. 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 4
  5. 5. Numerical Control is a system in which actions are controlled by the direct insertion of numerical data at some point. The system must automatically interpret at least some portion of the data 54/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore
  6. 6. Data is sent to the machine tool by means of punch cards or tapes. The reader at the machine performs no calculations or interpolations. 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 6
  7. 7. •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. 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 7
  8. 8. • By integrating a computer processor, computer numerical control, or “CNC” as it is now known, allows part machining programs to be edited and stored in the computer memory as well as permitting diagnostics and quality control functions during the actual machining. • All CNC machining begins with a part program, which is a sequential instructions or coded commands that direct the specific machine functions. • The part program may be manually generated or, more commonly, generated by computer aided part programming systems. 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 8
  9. 9. • CNC : Computer and Numeric Control • Conventionally, an operator decides and adjusts various machines parameters like feed , depth of cut etc depending on type of job , and controls the slide movements by hand. In a CNC Machine functions and slide movements are controlled by motors using computer programs. 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 9
  10. 10. MACHINE UNIT NUMERICAL CONTROLLER NUMERICAL DATA (NC CODE) MANUFACTURING OPERATOR PROCESSED PART Drive Control 104/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore
  11. 11. 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. 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 11
  12. 12. Absolute Coordinate System Incremental Coordinate System4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 12
  13. 13. •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. 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 13
  14. 14. • Using a vertical mill machining center as an example, there are typically three linear axes of motion. Each is given an alphabetic designation or address. The machine table motion side to side is called the “X” axis. Table movement in and out is the “Y” axis, while head movement up and down the column is the “Z” axis. 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 14
  15. 15. If a rotary table is added to the machine table, then the fourth axis is designated the “b” axis. 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 15
  16. 16. •The method of accurate work positioning in relation to the cutting tool is called the “rectangular coordinate system.” On the vertical mill, the horizontal base line is designated the “X” axis, while the vertical base line is designated the “Y” axis. The “Z” axis is at a right angle, perpendicular to both the “X” and “Y” axes. •Increments for all base lines are specified in linear measurements, for most machines the smallest increment is one ten-thousandth of an inch (.0001). If the machine is graduated in metric the smallest increment is usually one thousandth of a millimeter (.001mm). •The rectangular coordinate system allows the mathematical plotting of points in space. These points or locations are called “coordinates.” The coordinates in turn relate to the tool center and dictate the “tool path” through the work. 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 16
  17. 17. 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 17
  18. 18. Advantages: • High Repeatability and Precision e.g. Aircraft parts • Volume of production is very high • Complex contours/surfaces need to be machined. E.g. Turbines • Flexibility in job change, automatic tool settings, less scrap • More safe, higher productivity, better quality • Less paper work, faster prototype production, reduction in lead times Disadvantages: • Costly setup, skilled operators • Computers, programming knowledge required • Maintenance is difficult 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 18
  19. 19. • Lathes for metal and plastics – Used to produce 3D product shapes and moulds for plastic products. • Milling machine for mould making and surface milling. – Used to produce dies for die cutting printed products. 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 19
  20. 20. • Automated version of a manual lathe. • Programmed to change tools automatically. • Used for turning and boring wood, metal and plastic. 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 20
  21. 21. • Has 3 to 5 axes. • Used for wood, metal and plastic. • Used to make 3D prototypes, moulds, cutting dies, printing plates and signs. 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 21
  22. 22. • Controlled by G and M codes. • These are number values and co-ordinates. • Each number or code is assigned to a particular operation. • Typed in manually to CAD by machine operators. • G&M codes are automatically generated by the computer software. 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 22
  23. 23. • The tool or material moves. • Tools can operate in 1-5 axes. • Larger machines have a machine control unit (MCU) which manages operations. • Movement is controlled by a motors (actuators). • Feedback is provided by sensors (transducers) • Tool magazines are used to change tools automatically. 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 23
  24. 24. • Most are made from high speed steel (HSS), tungsten carbide or ceramics. • Tools are designed to direct waste away from the material. • Some tools need coolant such as oil to protect the tool and work. 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 24
  25. 25. • Tool paths describes the route the cutting tool takes. • Motion can be described as point to point, straight cutting or contouring. • Speeds are the rate at which the tool operates e.g. rpm. • Feeds are the rate at which the cutting tool and work piece move in relation to each other. • Feeds and speeds are determined by cutting depth, material and quality of finish needed. e.g. harder materials need slower feeds and speeds. • Rouging cuts remove larger amounts of material than finishing cuts. • Rapid traversing allows the tool or work piece to move rapidly when no machining is taking place. 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 25
  26. 26. 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 26
  27. 27. Is a method where a single computer controls many numerical control machine tools. These machine tools may or may not be of a similar nature 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 27
  28. 28. Computer Numerical Control (CNC) 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 28
  29. 29. o Reduces time for delivery of part Reduces scrap rate of material o Reduces tooling costs o Reduces layout time o Increases machine and tool life o Reduces storage problems o Less setup time o Reduces actual machining time Allows rapid design changes in part Less jigs and fixtures are needed 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 29
  30. 30. Top View Front View Tool Home 1.) X & Y Rapid To Hole Position 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 30
  31. 31. Top View Front View 2.) Z Axis Rapid Move Just Above Hole 3.) Turn On Coolant 4.) Turn On Spindle .100” 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 31
  32. 32. Top View Front View 5.) Z Axis Feed Move to Drill Hole 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 32
  33. 33. Top View Front View 6.) Rapid Z Axis Move Out Of Hole 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 33
  34. 34. Top View Front View 9.) X&Y Axis Rapid Move Home 7.) Turn Off Spindle 8.) Turn Off Coolant 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 34
  35. 35. 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 35
  36. 36. 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 36
  37. 37. Top View Front View Tool At Home O0001 N005 G54 G90 S600 M03 N010 G00 X1.0 Y1.0 N015 G43 H01 Z.1 M08 N020 G01 Z-.75 F3.5 N030 G91 G28 X0 Y0 Z0 N035 M30 N025 G00 Z.1 M09 Here’s The CNC Program! 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 37
  38. 38. Top View Front View Tool At Home O0001 O0001 Number Assigned to this program 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 38
  39. 39. Top View Front View Tool At Home O0001 N005 G90 S600 M03 N005 Sequence Number G90 Absolute Programming Mode S600 Spindle Speed set to 600 RPM M03 Spindle on in a Clockwise Direction 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 39
  40. 40. Top View Front View O0001 N005 G90 S600 M03 N010 G00 X1.0 Y1.0 G00 Rapid Motion X1.0 X Coordinate 1.0 in. from Zero Y1.0 Y Coordinate 1.0 in. from Zero 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 40
  41. 41. Top View Front View O0001 N005 G90 S600 M03 N010 G00 X1.0 Y1.0 N015 Z.1 M08 Z.1 Z Coordinate .1 in. from Zero M08 Flood Coolant On 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 41
  42. 42. Top View Front View O0001 N005 G90 S600 M03 N010 G00 X1.0 Y1.0 N015 Z.1 M08 N020 G01 Z-.75 F3.5 G01 Straight Line Cutting Motion Z-.75 Z Coordinate -.75 in. from Zero F3.5 Feed Rate set to 3.5 in./min. 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 42
  43. 43. Top View Front View O0001 N005 G90 S600 M03 N010 G00 X1.0 Y1.0 N015 Z.1 M08 N020 G01 Z-.75 F3.5 G00 Rapid Motion Z.1 Z Coordinate .1 in. from Zero M09 Coolant Off N025 G00 Z.1 M09 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 43
  44. 44. Top View Front View O0001 N005 G54 G90 S600 M03 N010 G00 X1.0 Y1.0 N015 G43 H01 Z.1 M08 N020 G01 Z-.75 F3.5 N030 G91 G28 X0 Y0 Z0 G91 Incremental Programming Mode G28 Zero Return Command X0, Y0, Z0 X,Y,& Z Coordinates at Zero N025 G00 Z.1 M09 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 44
  45. 45. Top View Front View O0001 N005 G54 G90 S600 M03 N010 G00 X1.0 Y1.0 N015 G43 H01 Z.1 M08 N020 G01 Z-.75 F3.5 N035 M30 N030 G91 G28 X0 Y0 Z0 N025 G00 Z.1 M09 M30 End of Program 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore 45
  46. 46. Example: A Milling Operation 46 X Z Y (0,0,0) NC CODE (Word Address Format) N50 G00 X15 Y12.5 Z0 N55 M03 N60 G01 Z-2.5 F500 M08 N65 G01 X50 N70 G01 Y45 N75 G01 X15 N80 G01 Y12.5 N85 G00 Z0 M09 N90 M04 SPINDLE STARTED ! SPINDLE STOP ! 4/4/2014 Hareesha N G, Dept of Aero Engg, DSCE, Blore

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