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Similar to CNC lathe programming for new learners of CNC
CNC lathe programming for new learners of CNC
- 1. What is aCNC 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. How CNC Works •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. .
- 5. Tool Paths, Cutting andPlotting Motions • 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.
- 6. CNC Programming Basics •CNC instructions are called part program commands. • When running, a part program is interpreted one command line at a time until all lines are completed. • Commands, which are also referred to as blocks, are made up of words which each begin with a letter address and end with a numerical value.
- 7. CNC Programming Basics •Each letter address relates to a specific machine function. “G” and “M” letter addresses are two of the most common. A “G” letter specifies certain machine preparations such as inch or metric modes, or absolutes versus incremental modes. • A “M” letter specifies miscellaneous machine functions and work like on/off switches for coolant flow, tool changing, or spindle rotation. Other letter addresses are used to direct a wide variety of other machine commands.
- 8. CNC programming •Programming consistsof a series of instructions in form of letter codes •Preparatory Codes: •G codes- Initial machining setup and establishing operating conditions •N codes- specify program line number to executed by the MCU •Axis Codes: X,Y,Z - Used to specify motion of the slide along X, Y, Z direction •Feed and Speed Codes: F and S- Specify feed and spindle speed •Tool codes: T – specify tool number •Miscellaneous codes – M codes For coolant control and other activities
- 9. Programming Key Letters O- Program number (Used for program identification) N - Sequence number (Used for line identification) G - Preparatory function X - X axis designation Z - Z axis designation R - Radius designation F – Feed rate designation S - Spindle speed designation H - Tool length offset designation D - Tool radius offset designation T - Tool Designation M - Miscellaneous function
- 10. G codes, Mcodes and cycle parameters These are group of commands to create and start a program. G – codes M - codes G00 ..... Positioning (Rapid traverse) G01 ..... Linear interpolation (feed) G02 ..... Circular interpolation clockwise G03 ..... Circular interpolation counterclockwise G04... Dwell G72... Finishing cycle G73... Stock removal in longitudinal turning G74... Stock removal in facing G78... Multiple threading cycle G80..... Cancel cycle G83 ..... Drilling cycle G84 ..... Tapping cycle G85 ..... Reaming cycle G90 ..... Absolute programming G91 ..... Incremental programming G94 ..... Feed per minute G95 ..... Feed per revolution G96 ..... Constant cutting speed G97..... Constant spindle speed G98..... Return to initial plane G99 ..... Return to withdrawal plane M00 Program stop M01 Optional program stop M02 Program end M03 Spindle on clockwise M04 Spindle on counterclockwise M05 Spindle stop M06 Tool change M08 Coolant on M09 Coolant off M10 Clamps on M11 Clamps off M30 Program stop, reset to start
- 11. Carbide Tool (inserts) Thechief constituent of cemented carbide is tungsten or molybdenum, cobalt and carbon. At a temperature of 90deg Celsius cemented carbide still maintains a good cutting capability and as such it can be used for operations which require high spindle speed. Right hand turning tool The right-hand turning tool is shaped to be fed from right to left. Different Cutting Tool and its Application
- 12. Left hand turningtool The left-hand turning tool is just the opposite of the right-hand turning tool, being designed to cut the metal when fed from left to right. External threading tool Use to cut external threads in a work Boring tool -Boring tools are used to cut, finish and enlarge inner diameter of holes. It is also use to remove extra material from the inside diameter of an existing hole, such as drilled Use to enlarge a drilled hole
- 13. Internal threading tool Basicallyuse for inside/internal threading. Commonly used threading tools are carbide inserts and HHS. Twist Drill Bits Twist drill bits are some of the most common shop tools to create holes, They're available in a wide range of sizes. Material composes of titanium coated, black oxide and cobalt.
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- 15. PROGRAM STRUCTURE (CNC Lathe) Example: O0001(Shaft) N5 T0101 N10 G96 S___ M___ N15 G95 F___ O0001 – program number T0101- tool call and correction number T01- tool holder 1 01 -correction number N5 – block number G96 s200 m3 G96-constant cutting speed S200-spindle speed in m/min M3-spindle on forward G95 f.2 G95-feed in mm/revolution (f=.2)
- 16. G Codes andCycle parameters G00 – position of the tool and not concerned with the path that is followed in arriving at the final destination. Format:
- 17. G01 – Toolis required to move in a straight line connecting current position and final position. Used for tool movement without any machining- point to point control. (linear interpolation) Format:
- 18. G02 – Circularin interpolation (clockwise) -This command is anything with circular interpolation Format:
- 19. G03– Circular in interpolation(Counter clockwise) -This command is anything with circular interpolation Format:
- 20. G04 - Dwell -Thiscommand is used when drilling -when the drilling tool dips at the end of the drilling depth tool will stops in a matter of seconds depending on the program.
- 21. G40 – CancelRadius compensation This command is used cancel the radius Compensation of a tool used. Format:
- 22. G41 – Cutterradius compensation left This command is used when your tool Is viewed at the left side of the contour Format:
- 23. G41 – Cutterradius compensation right This command is used when your tool Is viewed at the right side of the contour Format:
- 24. G72 – Finishingcycle This cycle will start its cycle from the very first path until the end path of the machining operation Format:
- 25. G73 – Stockremoval turning This will start its cycle from the very first path until the end path of the machining operation removing stock within depth and width of material to be remove. Format:
- 26. G74 – Stockremoval facing This will start its cycle from the very first path until the end path of the machining operation removing stock within the width of material to be remove. Format:
- 27. G77 – Cut-in-Cycle This will start its cycle from the first path to be cut off until the end path of The machining operation removing stock within the width of material to be remove considering the tool width. Format:
- 28. G78 In this cycleall information of like pitch, depth, angle of thread, length and minor diameter must be in this cycle. Format:
- 29. G83 – Drillingcycle In this cycle all information in drilling must be entered like final drilling depth, the path to drill X and Z coordinates, retraction path and cutting depth per cut. Format:
- 30. G94 – Feedper minute With G94 all feed is in Feed in millimeters/min G95 – Feed per revolution With G95 all feed is in Feed in millimeters/rev. - it is seen in chart/table the different feed per revolution of a material Material Rough cut Finish Cut in mm in mm Machine Steel 0.010 - 0.020 0.025 - 0.050 0.003 - 0.010 0.007 - 0.025 Tool Steel 0.010 - 0.020 0.025 - 0.050 0.003 - 0.010 0.007 - 0.025 Cast Iron 0.015 - 0.025 0.040 - 0.065 0.005 - 0.012 0.013 - 0.030 Bronze 0.015 -0.025 0.040 - 0.065 0.003 - 0.010 0.007 - 0.025 Aluminum 0.015 - 0.030 0.040 - 0.075 0.005 - 0.010 0.013 - 0.025
- 31. G96 – Constantcutting speed With G96 the cutting speed of a material is programmed. -with the cutting speed of a material the spindle speed is computed constantly. Material Rough cut Finish Cut Threading ft/min. m/min. ft./min m/min. ft./ min m/min. Machine Steel 90 27 100 30 35 11 Tool Steel 70 21 90 27 30 9 Cast Iron 60 18 80 24 25 8 Bronze 90 27 100 30 25 8 Aluminum 200 61 300 93 60 18 G97 – Revolutions per minute (RPM) - The spindle speed is computed with this formula: english RPM=4 X CS/D metric RPM=320 X CS/D where: RPM = Revolutions per minute CS = Cutting speed (f/min or m/min) D = Diameter of Workpiece (inch or mm) IPR /mmpr= Inches per rev./millimeters per rev.
- 32. Starting a Program 22.5 17.5 20 30 O0001– program number T0101- tool call and correction number T01- tool holder 1 01 -correction number N5 – block number G96 s200 m3 G96-constant cutting speed S200-spindle speed in m/min M3-spindle on forward G95 f.2 G95-feed in mm/revolution (f=.2) SAMPLE PROGRAM O0001 N05 T0101 N10 G96 S200 M3 N15 M8 N20 G95 F0.2 N25 G0 X26 Z0 N30 G1 X-0.8 N35 G0 X28 Z5 N40 G73 U0.5 R0.5 N45 G73 P50 Q65 U0.2 W0.05 N50 G1 X17.5 Z0 N55 G1 Z-20 N60 G1 X22.5 N65 G1 Z-30 N70 G1 X28 N75 G0 Z2 N80 G72 P50 Q65 N85 G0 X50 Z50 N90 M30 25