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Although a slow and relatively limited process by today’s standards, its use spread quickly as its accuracy and effectiveness became apparent. It is capable of producing complex shapes such as taper, involutes, parabolas, ellipses,etc. BRIEF HISTORY OF EDM : BRIEF HISTORY OF EDM The process was accidentally discovered when a necessity arose in finding methods to avoid erosion of electrical contacts used in circuit breakers and relay systems. Development of the process occurred on the following years after the Investigations made by Russian Scientists namely: 1948 - U. N. GUSEV (developed the process called- ANODO MECHANICAL) 1943 - N.I. LAZARENKO and B.R. LAZARENKO 1952-53 - an American scientist developed machine using the process ”X“ method for spark machining. Patented in U.S.A and it was named “SPAREATRON” which is very similar to RC type pulse generator. DEFINITION OF WIRE CUT EDM : DEFINITION OF WIRE CUT EDM it is a machine which uses a very thin wire mainly brass with a diameter of 0.1 - 0.3 mm to cut the workpiece into two dimensional shapes． Slide 5: WIRE CUT EDM PRINCIPLE THE STEP BY STEP EDM PROCESS : THE STEP BY STEP EDM PROCESS Power Supply Generates Volts and Amps Deionized water surrounds the wire electrode as the power supply generates the Volts and amperes to produce the spark. Slide 7: Controlled Spark Erodes Material During On Time The generated spark precisely melts and vaporizes the material. THE STEP BY STEP EDM PROCESS Slide 8: Off Time Allows to remove Eroded Particles During the off cycle, the dielectric fluid immediately cools the material and flashes out the eroded particles. THE STEP BY STEP EDM PROCESS Slide 9: Filter Removes Chips While Cycle is Repeated New wire is constantly provided while the eroded particles are removed and separated by a filter system THE STEP BY STEP EDM PROCESS SUPER PRECISION BAND SAW : SUPER PRECISION BAND SAW SUBMERGED MACHINING TYPES OF WIRE EDM : TYPES OF WIRE EDM TWO AXIS Slide 12: SIMULTANEOUS FOUR AXIS TYPES OF WIRE EDM INDEPENDENT FOUR AXIS : INDEPENDENT FOUR AXIS TYPES OF WIRE EDM Materials That Can be EDMed : Materials That Can be EDMed Tool steel Carbide Graphite Aluminum Copper Brass Cold roll steel Hot rolled steel Stainless steels Ferro - Tic PCD Diamond Titanium Nitronic Beryllium copper Hastalloy Stellite BASIC SUBSYSTEM OF WIRE EDM : BASIC SUBSYSTEM OF WIRE EDM POWER SUPPLY DIELECTRIC SYSTEM WIRE FEEDING SYSTEM POSITIONING SYSTEM ELEMENTS OF WIRE FEEDING MECHANISM : ELEMENTS OF WIRE FEEDING MECHANISM Large spool of wire Rollers that direct the wire to the machine A metal contact that conduct power to the wire Guides to keep the wire straight into cut Pinch rollers that provide drive and wire tension A system to thread wire from upper to lower guide A sensor to detect when wire runs out or breaks A bucket to collect used wire DIELECTRIC FLUID : DIELECTRIC FLUID Dielectric oil TYPES FUNCTIONS Use to flush away the eroded particles Deionized water Acts as an insulator of wire and workpiece Acts as coolant of wire and workpiece Use to thread the wire automatically TYPES OF WIRE : TYPES OF WIRE COPPER first material used in WIRE EDM but today it is used to machines with power supply designed for copper wire. BRASS first logical alternative to copper. It is a combination of copper and zinc, typically alloyed in the range of 63-65% copper and 35-37% zinc. COATED it is called “ stratified wire” having a core of brass or copper for conductivity and tensile strength, electroplated with coating of pure or diffused zinc for enhanced spark formation and flush characteristics. FINE WIRES (MOLY & TUNGSTEN) high precision work on wire EDM machines and advantage for small diameter work with range of 0.001-0.004. It is used as substitute to low load carrying capacity of brass and coated wire. WIRE SELECTION : WIRE SELECTION APPLICATION MACHINE PERFORMANCE ECONOMICS ADVANTAGES OF EDM WIRE CUT : ADVANTAGES OF EDM WIRE CUT Electrically conductive material can be cut Work can be machined in a hardened state It does not create stresses in work Process is burr free Secondary finishing are eliminated Thin, fragile sections can be machined Intricate shape can be machined Dies can be produced at lower cost Slight hardening occurs DISADVANTAGES OF EDM WIRE CUT : DISADVANTAGES OF EDM WIRE CUT Material must be electrically conductive Rapid wire wear can be costly Only through hole can be machined Machining rate is low Machining the bottom is impossible Sharp inner corner can not be made WIRE CUT EDM COORDINATE SYSTEMS : WIRE CUT EDM COORDINATE SYSTEMS TYPES Machine coordinate system Work coordinate system Local coordinate system THE MACHINE AXES : THE MACHINE AXES The X and Y axes move the bottom head on the horizontal plane. The U and V axes move the top head on the horizontal plane. The Z axis sets vertically the position of the top head in relation to the upper face of the part. Slide 24: TYPES OF PROGRAMMING Manual programming - refers to the act of creating a NC program entirely through manual calculations. Automatic programming - as the geometries to be machined get complex, it becomes difficult to create program through, annual calculation. Such programs are created by the help of a special - purpose computer. CODES AND DATA : CODES AND DATA N,O (Sequence Number) - Sequence number should normally be input as four digits. G (Preparatory function) - G codes are used used to specify preparatory functions such as the linear and circular interpolation function. X, Y, Z, U, V, W (Axis Travel) - Data for axis travel specification can be input within the range ± 999999.999 mm or ± 99999.9999 inches (Digit = 0), or ± 99999.9999 mm or ± 999.99999 inches (Digit = 1). Slide 26: I, J (Coordinate of Center of Circular Arc) - Data for circular arc center coordinate specification can be input within the range ±999999.999 mm or ± 9999.9999 inches (digit = 0), or ±99999.9999 mm or ± 9999.99999 inches (Digit = 1). T (Machine Control Items) - Input item relating to machine control in two digits. D, H (Offset Number) - Designate offset numbers in three digits. A (Angle in Taper machining) - Data for designation taper machining angles can be input in the range ± 999999.999 or ± 99999.9999 when Digit = 1. CODES AND DATA CODES AND DATA : CODES AND DATA P (subprogram number) - Subprogram numbers should be normally input as 4 digits. L (Number of Repetition of Subprogram0 - The number of repetition of a subprogram can be designated within the range of 0 – 9999. C (Machining Condition File number) - Input the machining condition number in three digits. CODES AND DATA : CODES AND DATA M (auxiliary Function) - Input auxiliary function which determines program or specifies ON/OFF output to the machine in three digits or less. Q (File Call – Up) - Q commands call up programs in the flash disk in the units during cutting, and execute these programs. F(Feedrate) - F commands designate the cutting response speed (SF) at which the wire - travels. Values can be input within the range of 20 – 400. CLASSIFICATION OF G CODES : CLASSIFICATION OF G CODES G Codes whose functions are limited to blocks to which they are assigned. G Codes whose functions are effective until another G code of the same group appears. (such G Codes are referred to as “Modal Codes”). Example: G00 X 100.0 Y 100.0 Z 100.00; Example: G00 X 100.0; Y 100.0; Z 100.0; G CODES : G CODES G00 (positioning) G00 establishes the mode to move the specified axes to the specified position without machining. Example: G00 X+100.0 Y+200.0; G01 (linear interpolation) G01 establishes the linear interpolation mode in which the specified axes travel to the specified end point to cut the workpiece. Simultaneous travel on all axes is possible. Example: G01 X+100.0 Y+200.0; G CODES : G02 , G03 (circular interpolation) G02 and G03 establish a circular interpolation mode in which the coordinated movement of the specified axes cuts the arc defined by the specified command. Example: G03 X20.0 Y10.0 J-10.0 Example: G02 X20.0 Y10.0 J-10.0 G CODES Slide 32: G05, G06, G08, G09 (mirror image and cancel) The mirror image function reverses the signs of the command values for each axis during machining. Original programmed path G06 G05 G08 G CODES Slide 33: G40, G41, G42 (wire diameter offset) The wire diameter offset functions as the path of the wire center from the programmed path to machine the workpiece to the programmed dimensions. G29 (main reference point) Specifies the current position as the reference point. Programmed path G42 G40 G41 G CODES Slide 34: G50, G51, G52 (taper machining) In the taper machining mode, the wire is inclined by specified angle in the specified direction. G51 G52 G50 Programmed direction G CODES Slide 35: G54, G55, G56, G57, G58, G59 (work coordinate systems 0 to 5) These codes are used to select the work coordinates system from 0 to 5. G54 G55 G56 G58 G57 G59 G CODES Slide 36: G CODES G80 (travel until contact sensor operates) In the G80 mode, the wire travels from the present position to the point where the wire makes contact with the workpiece. Example: G80 X ± G80 Y ± Slide 37: G CODES G81 (travel to limit of mechanical system.) The wire travels to the mechanical system limit on the axis specified after G81. Example: G81 Y ± G81 X ± Slide 38: G CODES G82 (travel to half of distance between present position and origin) the wire travels to the mid-point between the present position and origin of the specified axis. Example: G80 X+ G80 X - X 100.0; G82 X X 0 X 50.0; Workpiece Slide 39: G CODES G90 (absolute programming mode) The command travel according to the coordinate system. Example: G91 (incremental programming mode) The command specifies the distance and the direction the specified axis should travel, starting from the present position. G54 G91 G92 X 10.0 Y 10.0; G01 X 20.0 Y 20.0; G54 G90 G92 X 10.0 Y 10.0; G01 X 30.0 Y 30.0; Slide 40: G CODES G92, G97 (coordinate system shift) G92 ‐ shifts the coordinate system so that the coordinate values of the present position will be specified by the coordinate values following G92. G97 － shift the coordinate systems except the machine coordinate system. Slide 41: M CODES M00 (program stop) After execution of M00, program execution is suspended with all modal information up to that point saved, as is the case when a single block stop is executed. Press the [RST] key to resume execution of the program following M00. The command travel according to the coordinate system. M01 (optional stop) M01 provides the same function as M00. M02 (end of program) M02 indicates the end of a main program. Slide 42: M CODES M98 (subprogram call) M98 is used to call subprograms. M99 end of subprogram) M99 indicates the end of the subprogram. When M99 has been executed program execution returns to the main program. used to call subprograms. Slide 43: T CODES T80 (wire run) and T81 (wire run stop) These are used to start and stop wire run. T82 (auto drain off) and T83 (auto drain on) These codes are used to open and close the work tank drainage valve. T84 (pump on) and T85 (pump off) These codes start and stop the high – pressure flushing pump. T86 (flushing on) and T87 (flushing off) These codes are used to turn flushing ON and OFF. Slide 44: T88 (oil submerged machining) T89 (water flush machining) and T94 (water submerged machining) these codes select the type of machining to be performed. T CODES T90 (AWT I) and T91 (AWT II) these codes select the type of automatic wire threading operation. The operations called out by these codes are the same as the operation performed manually. T96 (fluid feed on) and T97 (fluid feed off) these codes are used to start and stop supplying dielectric fluid to the work tank. Slide 45: Sample program for wire cut EDM (Punch shape) N0000; G54; G90; G92 X 0 Y 8.0 Z 0; C890; T85; G01 Y 5.5; C420; T82; G42 H130; G01 Y 5.0; X - 5.0; X 5.0; Y 5.0; X 2.0; G40 Y 5.5; M00; T85; C890; G01 X0; M02; Slide 46: N0000; G54; G90; G92 X 0 Y 2.0 Z 0; G29; T94; G42 H001; G50 A0; C000; T85; G01 X - 1.0; Y 4.0; T85; T84; G42 H158; G50 A0; C149; M98 P0010; T85; T94; M02 ; Sample program for wire cut EDM (Die Circle) N0010 (SUB. PRO. 1 / G42); G02 X 0 Y 5.0 I 1.0; G01 X 5.0; Y - 5.0; X - 5.0; Y 5.0; X - 1.0; M00; X 0; G02 X 1.0 Y 4.0 J - 1.0; G01 Y 2.0; G40 G50 X 0; M99; Slide 47: MACHINING SAMPLE Slide 48: SURFACE FINISHING Slide 49: RELATIONSHIP BETWEEN THE MACHINING SPEED AND WIRE DIAMETER Slide 50: NOZZLE POSITION You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.