Camsys overview

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note on modern machining CAM

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  • An example of creating a CNC program using a simple hole drilled on a computer numerical controlled (CNC) vertical milling machine.
  • In this case, we are using a simple analogy to stress how a programmer must be able to visualize a CNC program’s execution. We first look at how a machinist would machine a hole in a work piece held in a vise on a milling machine. Then we’ll show how the same operation will be performed with a CNC program. The machinist standing in front of the milling machine has everything they need right in front of them. They wouldn’t forget something as simple as turning the spindle on before trying to drill the hole. On the other hand, a CNC programmer must typically work with nothing more than a blueprint, a pencil, a calculator, and a blank piece of paper. They must be able to visualize every motion and function of the program’s execution in their minds .
  • Here is the same operation (drilling a hole) performed by a CNC program. Each step will be explained.
  • Camsys overview

    1. 1. CAM Systems & CNC Machine Overview - Lecture 3Overview to Computer Aided Manufacturing - ENGR-2963 - Fall 2005 Class Manager - Sam Chiappone
    2. 2. History1955 - John Parsons and US Air Force define aneed to develop a machine tool capable ofmachining complex and close tolerance aircraftparts with the same quality time after time(repeatability). MIT is the subcontractor andbuilds the machine for the project. Intro to CAM Rensselaer Polytechnic Chiappone Institute
    3. 3. History: Continued1959 - MIT announces Automatic ProgrammedTools (APT) programming language1960 - Direct Numerical Control (DNC). Thiseliminates paper tape punch programs and allowsprogrammers to send files directly to machinetools Intro to CAM Rensselaer Polytechnic Chiappone Institute
    4. 4. History: Continued1968 - Kearney & Trecker machine tool buildersmarket first machining center1970’s - CNC machine tools & DistributedNumerical Control1980’s - Graphics based CAM systemsintroduced. Unix and PC based systems available Intro to CAM Rensselaer Polytechnic Chiappone Institute
    5. 5. History: Continued1990’s - Price drop in CNC technology1997 - PC- Windows/NT based “Open ModularArchitecture Control (OMAC)” systemsintroduced to replace “firmware” controllers. Intro to CAM Rensselaer Polytechnic Chiappone Institute
    6. 6. Control SystemsOpen-Loop Control– Stepper motor system– Current pulses sent from control unit to motor– Each pulse results in a finite amount of revolution of the motor001” is possible Intro to CAM Rensselaer Polytechnic Chiappone Institute
    7. 7. Control SystemsOpen-Loop Limitations– Control unit “assumes” desired position is achieved– No positioning compensation– Typically, a lower torque motorOpen-Loop Advantages– Less complex, Less costly, and lower maintenance costs Intro to CAM Rensselaer Polytechnic Chiappone Institute
    8. 8. Control SystemsClosed-Loop Control– Variable DC motors - Servos– Positioning sensors -Resolvers » Feedback to control unit » Position information compared to target location » Location errors corrected Intro to CAM Rensselaer Polytechnic Chiappone Institute
    9. 9. Control SystemsClosed-Loop Advantages– DC motors have the ability to reverse instantly to adjust for position error– Error compensation allows for greater positional accuracy (.0001”)– DC motors have higher torque ranges vs.. stepper motorsClosed-loop limitations– Cost Intro to CAM Rensselaer Polytechnic Chiappone Institute
    10. 10. Three Basic Categories of Motion SystemsPoint to Point - No contouring capabilityStraight cut control - one axis motion at a time iscontrolled for machiningContouring - multiple axis’s controlledsimultaneously Intro to CAM Rensselaer Polytechnic Chiappone Institute
    11. 11. Three Basic Categories of Motion Systems Intro to CAM Rensselaer Polytechnic Chiappone Institute
    12. 12. CNC vs. NC Machine ToolsComputer Numerical Control (CNC) - Anumerical control system in which the datahandling, control sequences, and response to inputis determined by an on-board computer system atthe machine tool. Intro to CAM Rensselaer Polytechnic Chiappone Institute
    13. 13. CNCAdvantages– Increased Program storage capability at the machine tool– Program editing at the machine tool– Control systems upgrades possible– Option -resident CAM system at machine tool– Tool path verification Intro to CAM Rensselaer Polytechnic Chiappone Institute
    14. 14. NCNumerical Control (NC) - A control system whichprimarily processes numeric input. Limitedprogramming capability at the machine tool. Limitedlogic beyond direct input. These types of systems arereferred to as “hardwire controls” and were popularfrom the 1950’s to 1970’s. Intro to CAM Rensselaer Polytechnic Chiappone Institute
    15. 15. Machining CentersA machining center can be defined as a machine toolcapable of:– Multiple operation and processes in a single set-up utilizing multiple axis– Typically has an automatic mechanism to change tools Intro to CAM Rensselaer Polytechnic Chiappone Institute
    16. 16. Machining Centers– Machine motion is programmable– Servo motors drive feed mechanisms for tool axis’s– Positioning feedback is provided by resolvers to the control system Intro to CAM Rensselaer Polytechnic Chiappone Institute
    17. 17. Machining CentersExample - A turning center capable of ODturning, external treading, cross-hole drilling,engraving, and milling. All in machining isaccomplished in one “set-up.” Machine may havemultiple spindles. Intro to CAM Rensselaer Polytechnic Chiappone Institute
    18. 18. Machining Centers Intro to CAM Rensselaer Polytechnic Chiappone Institute
    19. 19. Programming MethodsAutomatically Programmed Tools (APT)– A text based system in which a programmer defines a series of lines, arcs, and points which define the overall part geometry locations. These features are then used to generate a cutter location (CL) file. Intro to CAM Rensselaer Polytechnic Chiappone Institute
    20. 20. Programming Methods-APT– Developed as a joint effort between the aerospace industry, MIT, and the US Airforce– Still used today and accounts for about 5 -10% of all programming in the defense and aerospace industries Intro to CAM Rensselaer Polytechnic Chiappone Institute
    21. 21. Programming Methods-APT– Requires excellent 3D visualization skills– Capable of generating machine code for complicated part programs » 5 axis machine tools Intro to CAM Rensselaer Polytechnic Chiappone Institute
    22. 22. Programming Methods-APTPart definition P1=Point/12,20,0 C1=Circle/Center,P1,Radius,3 LN1=Line/C1. ATANGL,90Cutter Commands TLRT,GORT/LN1.TANTO,C1 GOFWD/C1,TANTO,L5 Intro to CAM Rensselaer Polytechnic Chiappone Institute
    23. 23. Programming Methods-CAMComputer Aided Machining (CAM) Systems– Graphic representation of the part– PC based– Integrated CAD/CAM functionality– “Some” built-in expertise Speed & feed data based on material and tool specifications Intro to CAM Rensselaer Polytechnic Chiappone Institute
    24. 24. Programming Methods-CAM– Tool & material libraries– Tool path simulation– Tool path editing– Tool path optimization– Cut time calculations for cost estimating Intro to CAM Rensselaer Polytechnic Chiappone Institute
    25. 25. Programming Methods-CAM– Import / export capabilities to other systems » Examples: Drawing Exchange Format (DXF) Initial Graphics Exchange Standard (IGES) Intro to CAM Rensselaer Polytechnic Chiappone Institute
    26. 26. The Process CAD to NC FileStart with graphic representation of part– Direct input– Import from external system » Example DXF / IGES– 2D or 3D scan » Model or Blueprint(At this point you have a graphics file of your geometry) Intro to CAM Rensselaer Polytechnic Chiappone Institute
    27. 27. The Process CAD to NC File Define cutter path by selecting geometry – Contours – Pockets – Hole patterns – Surfaces – Volume to be removed(At this point the system knows what you want to cut) Intro to CAM Rensselaer Polytechnic Chiappone Institute
    28. 28. The Process CAD to NC File Define cut parameters – Tool information » Type, Rpm, Feed – Cut method » Example - Pocket mill zig-zag, spiral, inside-out » Rough and finish parameters(At this point the system knows how you want to cut the part) Intro to CAM Rensselaer Polytechnic Chiappone Institute
    29. 29. The Process CAD to NC File Execute cutter simulation – Visual representation of cutter motion Modify / delete cutter sequences(At this point the system has a “generic” cutter location (CL) file of the cut paths) Intro to CAM Rensselaer Polytechnic Chiappone Institute
    30. 30. The Process CAD to NC FilePost Processing– CL file to machine specific NC codeFilters CL information and formats it into NCcode based on machine specific parameters– Work envelope– Limits - feed rates, tool changer, rpm’s, etc.– G & M function capabilities Intro to CAM Rensselaer Polytechnic Chiappone Institute
    31. 31. Output: NC CodeNumerical Control (NC) Language– A series of commands which “direct” the cutter motion and support systems of the machine tool. Intro to CAM Rensselaer Polytechnic Chiappone Institute
    32. 32. Output: NC CodeG-Codes (G00, G1, G02, G81)Coordinate data (X,Y,Z)Feed Function (F)Miscellaneous functions (M13)N - Program sequence numberT - Tool callS - Spindle command Intro to CAM Rensselaer Polytechnic Chiappone Institute
    33. 33. Output: NC CodeNC Program Example– N01G90 G80– N03 GOO T12 M06– N05 GOO X0 Y0 Z.1 F10 S2500 M13– N07 G1Z-.5– N09 G02 X-10. I0J0F20– N13 X0Y10– N17 X10Y0– N19 X0Y-10– N21 X-10Y0– N23 M2 Intro to CAM Rensselaer Polytechnic Chiappone Institute
    34. 34. Example of CNC ProgrammingWhat What Must Be Done To Drill A Hole On ACNC Vertical Milling Machine Intro to CAM Rensselaer Polytechnic Chiappone Institute
    35. 35. Tool Home Top View 1.) X & Y Rapid To Hole PositionFrontView Intro to CAM Rensselaer Polytechnic Chiappone Institute
    36. 36. TopView 2.) Z Axis Rapid Move Just Above Hole 3.) Turn On Coolant 4.) Turn On SpindleFront .100”View Intro to CAM Rensselaer Polytechnic Chiappone Institute
    37. 37. Top View 5.) Z Axis Feed Move to Drill HoleFrontView Intro to CAM Rensselaer Polytechnic Chiappone Institute
    38. 38. Top View 6.) Rapid Z Axis Move Out Of HoleFrontView Intro to CAM Rensselaer Polytechnic Chiappone Institute
    39. 39. Top View 7.) Turn Off Spindle 8.) Turn Off Coolant 9.) X&Y Axis Rapid Move HomeFrontView Intro to CAM Rensselaer Polytechnic Chiappone Institute
    40. 40. Here’s The CNC Program! Tool At Home Top O0001 View N005 G54 G90 S600 M03 N010 G00 X1.0 Y1.0 N015 G43 H01 Z.1 M08 N020 G01 Z-.75 F3.5 N025 G00 Z.1 M09Front N030 G91 G28 X0 Y0 Z0View N035 M30 Intro to CAM Rensselaer Polytechnic Chiappone Institute
    41. 41. Tool At Home Top O0001 View O0001 Number Assigned to this programFrontView Intro to CAM Rensselaer Polytechnic Chiappone Institute
    42. 42. Tool At Home Top O0001 View N005 G54 G90 S600 M03 N005 Sequence Number G54 Fixture Offset G90 Absolute Programming Mode S600 Spindle Speed set to 600 RPM M03 Spindle on in a Clockwise DirectionFrontView Intro to CAM Rensselaer Polytechnic Chiappone Institute
    43. 43. Top O0001 View N005 G54 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 ZeroFrontView Intro to CAM Rensselaer Polytechnic Chiappone Institute
    44. 44. Top O0001 View N005 G54 G90 S600 M03 N010 G00 X1.0 Y1.0 N015 G43 H01 Z.1 M08 G43 Tool Length Compensation H01 Specifies Tool length compensation Z.1 Z Coordinate .1 in. from ZeroFront M08 Flood Coolant OnView Intro to CAM Rensselaer Polytechnic Chiappone Institute
    45. 45. Top O0001 View N005 G54 G90 S600 M03 N010 G00 X1.0 Y1.0 N015 G43 H01 Z.1 M08 N020 G01 Z-.75 F3.5 G01 Straight Line Cutting Motion Z-.75 Z Coordinate -.75 in. from ZeroFront F3.5 Feed Rate set to 3.5 in./min.View Intro to CAM Rensselaer Polytechnic Chiappone Institute
    46. 46. Top O0001 View N005 G54 G90 S600 M03 N010 G00 X1.0 Y1.0 N015 G43 H01 Z.1 M08 N020 G01 Z-.75 F3.5 N025 G00 Z.1 M09Front G00 Rapid Motion Z.1 Z Coordinate .1 in. from ZeroView M09 Coolant Off Intro to CAM Rensselaer Polytechnic Chiappone Institute
    47. 47. O0001 N005 G54 G90 S600 M03 Top View N010 G00 X1.0 Y1.0 N015 G43 H01 Z.1 M08 N020 G01 Z-.75 F3.5 N025 G00 Z.1 M09 N030 G91 G28 X0 Y0 Z0 G91 Incremental Programming ModeFront G28 Zero Return CommandView X0, Y0, Z0 X,Y,& Z Coordinates at Zero Intro to CAM Rensselaer Polytechnic Chiappone Institute
    48. 48. Top O0001 View N005 G54 G90 S600 M03 N010 G00 X1.0 Y1.0 N015 G43 H01 Z.1 M08 N020 G01 Z-.75 F3.5 N025 G00 Z.1 M09Front N030 G91 G28 X0 Y0 Z0View N035 M30 M30 End of Program Intro to CAM Rensselaer Polytechnic Chiappone Institute
    49. 49. Output: NC Code - Canned Cycles Intro to CAM Rensselaer Polytechnic Chiappone Institute
    50. 50. CAD to NC Code Import DXF Geometry File IGES Direct input Tool Path Generation What you want to cut How you want to cut Tool Type CL Rpm’s – Feeds Post Process Method File Canned cycles Cut direction NC Code OEMN1 G80 G90 CustomN3 G0 T01 M06 LanguageN5 G0 X0 Y0 Intro to CAM Rensselaer Polytechnic Chiappone Institute
    51. 51. Advantages of CNC Machine ToolsEase of part duplicationFlexibilityRepeatabilityQuality control through process control Intro to CAM Rensselaer Polytechnic Chiappone Institute
    52. 52. Advantages of CNC Machine ToolsAccommodates simple to complex parts geometryImproved part aestheticsIncreased productivityTechnology costs are decreasing Intro to CAM Rensselaer Polytechnic Chiappone Institute
    53. 53. Advantages of CNC Machine ToolsReduced set-up timeReduced lead timesReduced inventoryBetter machine utilizationJob advancement opportunities Intro to CAM Rensselaer Polytechnic Chiappone Institute
    54. 54. Advantages of CNC Machine ToolsCNC machine tools are more rigid thanconventional machine tools– $$$- Climb milling requires about 10 - 15 % less horsepower vs. conventional cutting, but requires a ridged machine tool with no backlash– Increased Rpm’s and feeds Intro to CAM Rensselaer Polytechnic Chiappone Institute

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