Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
  • B23H9/00—Machining specially adapted for treating particular metal objects or for obtaining special effects or results on metal objects
  • B23H9/003—Making screw-threads or gears
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S204/00—Chemistry: electrical and wave energy
  • Y10S204/09—Wave forms

Definitions

• the invention relates to a method for spark-erosive and / or electrochemical machining, in particular of bevel gears with curved teeth from a workpiece, the workpiece to be machined being in an electrode having its negative shape of a machine operating in a spark-erosive or electrochemical way by means of a screw-shaped machine relative to the electrode Movement is lowered.
• Bevel gears with curved teeth are mainly used in vehicle and helicopter transmissions. They are manufactured from high-alloy steels in a soft state on special gear cutting machines in rolling or in part processes with profiled cutting tools. Then they are hardened.
• a cylindrical or conical thread can only be produced with a constant thread pitch. If the thread pitch on the entire spiral changes more than the technologically determined width of the working gap, which is between the electrode and the workpiece, a positive connection will occur when the workpiece is screwed into the electrode. If the thread pitch along the entire thread spiral changes as little as the technologically determined width of the working gap, the thread is partially damaged when the workpiece is screwed into the electrode. It should also be noted here that in all three cases the workpiece and the electrode are equidistant in the end position.
• the bevel gears with curved teeth are complex three-dimensional bodies.
• the other data and properties of the bevel gears are determined by the generating machines.
• the required vibration and noise tolerances require that the geometrical accuracies have to be kept in the order of a few pm. It is not possible to machine bevel edges with curved teeth by screwing them into the electrode, which has the negative shape of the bevel gear, although the electrode would be equidistant from the bevel gear in the end position.
• the tooth flanks are partially or more severely damaged along the tooth width during the insertion of the workpiece into the electrode, and in the less favorable cases even a positive fit occurs.
• the invention solves the problem of creating a method for spark erosion and / or electrochemical machining of bevel gears with curved teeth or similar parts, in which the electrode is designed so that the negative tooth flanks against the The middle of the negative tooth gaps are screwed in at such a large angle that while the workpiece is being sunk into the electrode with a first spiral screwing movement, according to the gradient curve of the dental arch, between the electrode and the tooth flanks along the entire dental arch, at least there is such a large distance that no material is removed on the tooth flanks; the teeth are only pre-machined, positive locking and / or flank damage can no longer take place, and then the tooth flanks are rotated counterclockwise with a second rotation and clockwise with a third rotation. In the clockwise direction, separately depending on the direction of rotation, finished that the parameters of the machining generator are continuously adjusted during the movements depending on the distance still to be covered in order to obtain the desired surface without structural changes.
• the method according to the invention also allows the production of bevel gears with curved teeth from hard metals and other materials which are difficult to machine.
• the method according to the invention also allows the production of negative forms of bevel gears with curved teeth, which are used as very precise forging tools, die casting tools and as electrodes.
• FIG. 2 shows an electrode on the same scale, which has the exact negative shape of the workpiece and on which, according to the invention, the screwing in of the negative tooth flanks against the center of the negative tooth gap is indicated by dash-dot lines;
• Electrode with turned tooth flanks and
• FIG. 4 shows a spark-erosive machine for processing the workpieces shown in FIG. 1 by means of the electrode of FIGS. 2 and 3.
• an electrode 1 which is suitable for machining a workpiece 2 with the aid of relative movements between the electrode and the workpiece.
• the electrode and the workpiece are e.g. arranged on a spark erosion or electrochemical machine.
• the electrode 1 is designed such that the negative tooth flanks 3 are screwed in against the center 4 of the negative tooth gaps 5 with a large angle y.
• the angle / is selected such that while the workpiece 2 is sunk into the electrode 1 with a first spiral screw movement, which takes place according to the gradient curve of the dental arch, there is a distance between the screwed-in negative tooth flanks 7 and the tooth flanks 8 am entire dental arch. This distance is so large that material can no longer be removed from the tooth flanks 8.
• the teeth 9 are only pre-processed. Form locking or flank damage can no longer take place.
• the tooth flanks 8 are then finished with a second clockwise rotation and a third counterclockwise rotation, separated in time depending on the direction of rotation.
• the parameters of the machining generator such as ignition voltage, pulse shape, pulse current, pulse duration, pause, mean current value, working voltage, flushing pressure, flushing quantity, are continuously adapted depending on the distance still to be covered in order to achieve the desired surface without structural changes to obtain.
• the electrode 1 can also carry out the following alternative processing.
• the workpiece 2 is moved into the electrode 1 only to a depth at which the gap at the tooth head 9 and at the tooth base 10 is reduced to such an extent that material removal could also begin at these points under roughing conditions .
• This depth is referred to as the neutral position, because in this position neither the tooth flanks 8 nor the tooth base 10 nor the tooth head 9 can be damaged under roughing conditions.
• the tooth flanks 8, processed according to the direction of rotation are processed in a clockwise direction with a second movement sequence, which can be composed of screwing and rotating movements as desired.
• the workpiece 2 is returned to the neutral position with a third movement sequence. and finished with a fourth movement in the counterclockwise direction.
• the order of processing clockwise and counterclockwise can also be reversed.
• the parameters of the machining generator have to be continuously adapted as a function of the distance traveled, in order to obtain the desired surface without structural changes.
• the electrode 1 is expediently composed of a large number of parts which are electrically insulated from one another. Each electrode part is electrically connected to the spark erosion or electrochemical generator by its own cable. This enables multichannel machining with significantly shorter machining times.
• Electrodes 1 When machining bevel gears with curved teeth from the full piece or with too much material addition, it is expedient to use several electrodes 1 according to the invention in order to machine a workpiece with high accuracy. These electrodes can have the same or different spatial dimensions to have.
• FIG. 4 shows an electrical discharge machine 11 with which the workpiece 2 of FIG. 1 is produced.
• the workpiece can also be produced by an electrochemical machine tool.
• the dielectric container 13, in which the workpiece 2 is mounted is fastened on the machine table 12.
• the container 13 is drawn cut open for better illustration.
• the workpiece 2 is immersed in dielectric, which is a liquid.
• the suction cup 14 which sucks the dielectric through the working gap, which separates the electrode 1 and the workpiece 2 from one another during machining and is indispensable for spark machining.
• the dielectric is conveyed via the suction openings 15 and via lines, not shown, to a pump, not shown, and is pumped back into the container 13 after it has been cleaned.
• a gas escapes from the dielectric, which is removed by the symbolically drawn gas extraction system 16.
• the machine head 23, to which the electrode 1 is fastened as a tool for machining the workpiece, is slidably attached to the electrical discharge machine 11. Its displacements take place via the electric drive motor 27, which receives the control commands from the NC or CNC control system 29.
• the tachogenerator 28 transmits the rotations of the drive motor 27 to the control system 29.
• the control system receives the information about the executed movements of the machine head 23 via the linear scale 17 and measuring sensor 18 for the Z-axis 21
• the Z-axis is used for the feed and lift-off movements of the electrode 1.
• the electrode 1 can also move in the C-axis, whose circular directions of movement are represented by the arrows 20. These movements are carried out by the control system 29 by means of the electric drive motor 25.
• the tachometer generator 26 transmits the information about the executed rotations of the drive motor to the control system 29.
• the measuring system 23 transmits the executed movements of the electrode 1 in the C-axis to the control system 29.
• the spark erosion generator 30 generates the necessary for the current processing Ignition voltage, working voltage, pulse shape, pulse duration, pause between the pulses, pulse current, average current and gives the electrical machining parameters to the electrode 1 via the slip rings 22 and to the workpiece 2 via the machine table 12.
• the values of these electrical machining parameters change continuously during the machining of the workpiece 2 by the electrode 1.
• the Values of the pressure and the amount of the liquid dielectric The control system 29 always controls the spark erosion generator 30 in such a way that these electrical parameters are optimally adapted to the path still to be covered during the entire machining process.
• the control system also controls the flushing system, not shown, so that the dielectric liquid is optimally adapted to the conditions prevailing in the working gap during the machining process, the distance still to be covered being taken into account.
• the electrode 1 is advanced in the direction of the workpiece 2 and works the tooth flanks 8 of the teeth out of the full material.
• the finished workpiece 2 has been drawn in FIG. 4 because of the better overview.
• the movements in the Z and C axes are controlled in the manner described in connection with FIGS. 1, 2 and 3.

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• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)

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Publications (1)

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• 1986
  • 1986-08-08 JP JP61504178A patent/JPS63500442A/ja active Pending
  • 1986-08-08 EP EP86904757A patent/EP0230462A1/de not_active Withdrawn
  • 1986-08-08 WO PCT/CH1986/000113 patent/WO1987000782A1/de not_active Application Discontinuation
  • 1986-08-08 US US07/046,885 patent/US4772368A/en not_active Expired - Fee Related

Non-Patent Citations (1)

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