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CNC milling machine and WEDM

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  1. 1. Industrial Training on Production ShopIndustrial Training on Production Shop
  2. 2. I, Ashutosh Kumar Mishra, studying in 7 semester of Bachelor of Technology in Mechanical Engineering at IIMT College Of Engineering, Greater Noida, hereby declared that this project entitled “Industrial Training on Production Shop” which is being submitted by me under the guidance of Prof. Dr Devraj kr Tiwari and Prof. KP Singh, Department Of Mechanical Engineering, IIMT College Of Engineering, Greater Noida. I further undertake that the matter embodied in the dissertation has not been submitted previously for the Industrial Training. Place :- Greater Noida Ashutosh Kumar Mishra
  3. 3. CNC MILLINGCNC MILLING
  4. 4. At the end of this module, I am able to:At the end of this module, I am able to:  Apply and practice workshop safetyApply and practice workshop safety regulations during working in CNC workshop.regulations during working in CNC workshop.  Apply the concept of CNC metal cuttingApply the concept of CNC metal cutting operation correctly in milling process.operation correctly in milling process.  Carry out CNC mill machining proceduresCarry out CNC mill machining procedures systematically.systematically.  Utilize the important parameters in CNCUtilize the important parameters in CNC millmill machining operation effectively according tomachining operation effectively according to a given task.a given task.
  5. 5.  Milling is a cutting operation with a geometrically specified cutting edge in which the tool makes the rotating main movement, and the feed as well as the infeed movement are generally made by the work part.  Milling operations are classified according to the position of the milling axis towards the work part, i.e. between face milling and peripheral milling. In case of face milling, the milling axis is located vertically to the machining.  The work part surface is machined by the main cutting edges. Also, the work part surface is further finished with auxiliary cutting edges.
  6. 6.  Figure 1.1 : Milling Cutting Operation
  7. 7. Figure 1.2 : End Milling Figure 1.3 : Plain Milling
  8. 8.  synchronous and conventional milling (Figure 1.4 and 1.5) are differentiated.  In case of conventional milling the rotation direction of the milling tool is opposite to the feed direction of the work part.  The milling tool chamfer edge starts with chip thickness zero.  The milling tool cutting edge slides in front of the chip chamfer edge until the required minimum chip thickness has been achieved for chip building.
  9. 9.  Figure 1.4 : Conventional Milling
  10. 10.  For synchronous milling the rotation direction of the milling tool and the feed movement of the work part are parallel.  The tooth of the milling cutter immediately penetrates into the work part.  Since the milling tool cutting edge is exposed to impact forces the feed drive needs to be play free. Several cutters should always be in operation.  The surface quality is flatter and duller when synchronous milling is used.  Compared with conventional milling higher feed movements and cutting speeds within the same cutting edge life can be achieved.
  11. 11.  Figure 1.5 : Synchronous Milling
  12. 12. Figure 2.6 : Milling Plan
  13. 13. 1.3.1 Characteristics of CNC Milling Machine Tools  Work part machining on CNC machine tools requires controllable and adjustable infeed axes which are run by the servo motors independent of each other.  CNC- milling machines (Figure 1.7) on the other hand have at least 3 controllable or adjustable feed axes marked as X, Y, Z.
  14. 14.  Figure 2.7 : Controllable NC Axes on a Milling Machine
  15. 15. a) Coordinate Systems On CNC Machine Tools Coordinate systems enable the exact description of all points on a work plane or room. Basically there are two types of coordinate systems
  16. 16.  A Cartesian coordinate system, also called rectangular coordinate system includes for the exact description of the points › Two coordinate axes (two-dimensional Cartesian coordinate system) or also. › Three coordinate axes (three-dimensional Cartesian coordinate system), located vertically to each other
  17. 17.  Figure 1.8 : Cartesian Coordinate System
  18. 18.  In the Cartesian coordinate system a point is described, for instance, by its X and Y coordinates. For rotation symmetrical contours, such as circular boring patterns, calculating the needed coordinates requires extensive computing.  In the polar coordinate system a point is specified by its distance (radius r) to the point of origin and its angle (α) to a specified axis. The angle (α) refers to the X axis in the X,Y coordinate system.  The angle is positive, if it is measured counterclockwise starting from the positive X axis (Figure 1.9)
  19. 19.  Figure 1.9 : Polar Coordinate System (Positive Angle α)
  20. 20.  The specifications of the three axes as well as the three coordinates are done as a so-called clockwise-rotating system and follow the right-hand-rule (Figure 1.10). The fingers of the right hand always show to the positive direction of each axis. This system is also called the clockwise-rotating coordinate system. Figure 1.10 : Right-Hand-Rule
  21. 21.  Machine Coordinate System › The machine coordinate system of the CNC machine tool is defined by the manufacturer and cannot be changed. › The point of origin for this machine coordinate system, also called machine zero point M, cannot be shifted in its location.  Work Part Coordinate System › The work part coordinate system is defined by the programmer and can be changed. The location of the point of origin for the work part coordinate system, also called work part zero point W, can be specified as desired.
  22. 22. Figure 2.11 : Machine Coordinate System Figure 2.12 : Work Part Coordinate System
  23. 23.  The design of the CNC machine specifies the definition of the respective coordinate system.  Correspondingly, the Z axis is specified as the working spindle (tool carrier) in CNC milling machines (Figure 1.13), whereby the positive Z direction runs from the work part upwards to the tool.  The X axis and the Y axis are usually parallel to the clamping plane of the work part. When standing in front of the machine, the positive X direction runs to the right and the Y axis is away from the viewer.  The zero point of the coordinate system is recommended to be placed on the outer edge of the work part.
  24. 24. Figure 1.13 : Milling Part In Three-Dimensional Cartesian Coordinate System
  25. 25. a) Types of Zero And Reference Points Table 1.1 : Types of zero and references points
  26. 26.  Each numerically controlled machine tool works with a machine coordinate system.  The machine zero point is the origin of the machine- referenced coordinate system.  It is specified by the machine manufacturer and its position cannot be changed.  In general, the machine zero point M is located in the center of the work spindle nose for CNC lathes and above the left corner edge of the work part carrier for CNC vertical milling machines.
  27. 27.  A machine tool with an incremental travel path measuring system needs a calibration point which also serves for controlling the tool and work part movements.  This calibration point is called the reference point R. Its location is set exactly by a limit switch on each travel axis.  The coordinates of the reference point, with reference to the machine zero point, always have the same value. This value has a set adjustment in the CNC control.
  28. 28. Figure 1.14 : Location Of The Zero And Reference Point For Milling
  29. 29. a) Structure of an NC-Block (Format) › Unlike the conventional milling machine, a modern machine tool will be equipped with a numerical control system. The machining of a work part can be executed automatically, provided that each machining cycle has been described in a "language" (code) which can be read by the control system. › The total of coded descriptions relating to a work part is called an NC-program.
  30. 30. * Blocks › Each NC-program consists of a number of so-called blocks, which contain the commands to be executed. The blocks are consecutively numbered; each block number consisting of a letter "N" plus a (e.g. three-digit) numeral. Block numbers appear at the beginning of each program line * Words Address, Value › As a rule an NC block is comprised of several words. Each word consists of an address (letter) and a value or code (numerals).
  31. 31.  A numeral can either represent a code (e.g. G01: Linear feed motion) or a real value (e.g. X+60 : Approaching the target coordinate X=60).  Example of part program: N110 F95 S850 M03 N115 G00 X+25 Y+30 N120 G01 Z-8 N125 X+105 N130 Y+80
  32. 32.  Explanation: Block-No. N110 A feed rate of 95 mm/min and a spindle speed of 850 U/min is programmed. N115 The tool is moved in the rapid traverse motion from its current position to the starting point (X+25 Y+30)t N120 Infeed in the Z-axis at the programmed feed rate (G01) N125 Because G01 is a modal command, the tool will continue to move at the programmed feed rate on a straight line to the target position X=105 N130 The tool moves in the Y-axis to the target position Y=80.  The technology data programmed in block N110 (feed rate, speed and sense of cutter rotation) will be retentive and take effect through blocks N120 to N130.
  33. 33. Figure 1.15 : Tool motions effected by modal commands (G01)
  34. 34.  G00 Rapid move G0 X# Y# Z# up to 6 axis or G0 Z# X# G01 Linear feedrate move G1 X# Y# Z# up to 6 axis or G1 Z# X# G02 Clockwise move G03 Counter clockwise move G04 Dwell time G08 Spline smoothing on, optional L# number of blocks to buffer G09 Exact stop check, spline smoothing Off G10 Linear feedrate move with decelerated stop G11 Controlled Decel stop G17 X Y Plane G18 X Z Plane G19 Y Z Plane G28 move to position relative to machine zero G53 Cancel fixture coordinate offsets G54-G59 fixture coordinate offsets 1 through 6
  35. 35.  G70 Inch mode G71 Millimeter mode G80 Cancels canned cycles and modal cycles G81 Drill cycle G82 Dwell cycle G83 Peck cycle G84 Tapping cycle G85 Boring cycle 1 bore down, feed out G86 Boring cycle 2 bore down, dwell, feed out G88 Boring cycle 3 bore down, spindle stop, dwell, feed out G89 Boring cycle 4 bore down, spindle stop, dwell, rapid out G90 Absolute mode G91 Incremental mode G92 Home coordinate reset G93 cancel home offsets G98 - G199 User-definable G codes
  36. 36.  With each NC-block a number of additional functions (M- Functions) can be programmed, such as machine functions and switches, e.g. to specify the feed rate, the spindle speed and the tool change.  List of M Codes
  37. 37.  Feed Rate, F The feed rate is programmed in millimeters per minute (mm/min). Example: F080.000; Here the programmed feed rate is 80 millimeters per minute.  Spindle Speed, S The spindle speed is programmed in revolutions per minute (RPM). Example: S500; Here the programmed spindle speed is 500 revolutions per minute.  Tool Change, T A tool change is programmed by a four-digit number at the address T. The first two positions of that number indicate the tool position in the magazine; the last two positions indicate the tool compensation storage. Example: T0808; This command effect the loading of the tool to position No.8 of the current tool magazine and the reading-in of the corresponding compensation value storage No.8.
  38. 38.  In the CNC Simulator there is a maximum of 99 magazine positions available, as well as 99 compensation value registers. This provides the opportunity, for example, to assign the compensation value register No. 36 to the tool in the magazine position No. 12). The applicable NC-command would then be programmed as follows: T1236
  39. 39.  The following clamping variations can be distinguished for milling machine. › Jaw Chucking › Magnetic Chucking › Modular Chucking  The milling cutter machine table with its T-slots is the basis for work part clamping. Depending on how the work part is to be clamped, the following clamping devices can be distinguished:   › Mechanical clamping devices › Hydraulic clamping devices › Pneumatic clamping devices › Electric clamping devices
  40. 40. Figure 1.16 : Clamping Devices
  41. 41. Figure 1.17 : Clamping Iron And Clamping Bard
  42. 42. Figure 2.18 : Shallow Clamp
  43. 43.  Machine vises are easy to use and reliable. They are used for clamping smaller work parts. Alignment is achieved with a measuring gauge. Figure 1.19 : Machine Vise
  44. 44. Figure 2.20 : Power Transmission
  45. 45.  Universal machine vises can be horizontally as well as vertically turned. Furthermore, there are also vises that pneumatically generate clamping power. Figure 2.21 : Precision Sine Vise
  46. 46.  Work parts made of iron can be clamped with electromagnetic devices. The work part is drawn to the clamping plate after a current is switched on. It can be easily removed after the current is switched off. Figure 1.22 : Electromagnetic Clamping Plate
  47. 47.  Milling is a cutting operation with a rotating tool, whereby the cutting edges are not in operation all the time. The cutting movement is caused by the rotation of the tool. Feed direction and cutting direction do not depend on each other. It is realized either by the tool or by the work part or by both of them (Figure 2.23).  The Cutting Speed (Vc) and the Feed Speed (Vf) is overlap to each other and results in a continuous cutting operation.
  48. 48.  The cutting movement is the movement between the tool and the work part, generating only one nonrecurrent chip cut during one rotation without a feed movement. Cutting speed corresponds to circumferential speed of the milling tool on the current cutting edge. It is expressed as Vc and m/min. Under consideration of the number of rotations of the spindle n the following formula is received   Vc = π * d * n in m/min    The cutting speed of a cutting tool depends on the number of the rotations. The direction constantly changes however during cutting operation.
  49. 49. Figure 1.23 : Cutting Values For Milling
  50. 50.  The feed movement together with the cutting movement enables a constant chip removal during several rotations. In milling, the feed can be indicated in three ways: › Feed speed (Vf) in mm / min › Feed per tooth (fz) in mm › Feed per milling rotation (f ) in mm
  51. 51.  Also known as wire-cut EDM and wire cutting.  A thin single-strand metal wire (usually brass) is fed through the workpiece submerged in a tank of dielectric fluid (typically deionized water).  Used to cut plates as thick as 300 mm and to make punches, tools, and dies from hard metals that are difficult to machine with other methods.  Uses water as its dielectric fluid; its resistivity and other electrical properties are controlled with filters and de-ionizer units.  The water flushes the cut debris away from the cutting zone.  Flushing is an important factor in determining the maximum feed rate for a given material thickness.  Commonly used when low residual stresses are desired, because it does not require high cutting forces for material removal. IntroductionIntroduction
  52. 52. • Computerized Numerical Control (CNC) - The Brains. • Power Supply -The Muscle • Mechanical Section - The Body • Dielectric System -The Nourishment -four major components
  53. 53. • Better stability and higher productivity . • Higher machining rate with desired accuracy and minimum surface damage. • Uses in the production of forming tools. • To produce plastics moldings, die castings, forging dies etc. • Can be applied to all electrically conducting metals and alloys irrespective of their melting points, hardness, toughness, or brittleness.
  54. 54. Special form of EDM - uses a continuously moving conductive wire electrode. Material removal occurs as a result of spark erosion as the wire electrode is fed, from a fresh wire spool, through the workpiece. Horizontal movement of the worktable (CNC) determines the path of the cut. Application - Machining of super hard materials like polycrystalline diamond (PCD) and cubic boron nitride (CBN) blanks, and other composites. Carbon fiber composites are widely used in aerospace, nuclear, automobile, and chemical industries, but their conventional machining is difficult

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