JP3851332B2 - EDM machine - Google Patents

Description

  The present invention relates to an electric discharge machining apparatus that performs three-dimensional control of an electrode having a simple shape and performs mold fabrication and component machining.

  2. Description of the Related Art Conventionally, there is known an electric discharge machining apparatus that processes a desired three-dimensional shape by performing three-dimensional control on an electrode having a relatively simple shape such as a column, cylinder, or prism by an NC controller. In such an electric discharge machining apparatus, it is not necessary to produce a complicated three-dimensional shape total electrode, and the die production cost and production time can be greatly improved. In addition, since the electrode shape can be defined in advance, it is easy to introduce a CAM system and the like, and automation of the machining process can be expected.

  However, in such electric discharge machining, electrode consumption becomes a serious problem in terms of machining accuracy as compared with electric discharge machining using a total-type electrode. In order to solve such problems, a series of research reports “three-dimensional controlled electrical discharge machining with cylindrical electrodes (1st report)” by Tatsuya Kaneko and others at Yamagata University, Vol. 17, no. 33, p31 / 44 (1983), “Three-Dimensional Controlled Electrical Discharge Machining with a Cylindrical Electrode (2nd Report)” Journal of the Electromachining Society, Vol. 17, no. 34, p. In 1/12 (1984), when cutting a certain amount into the Z axis while rotating a columnar or cylindrical electrode and then performing planar machining with the X and Y axes, correction data for the electrode wear length obtained in advance from measured data is obtained. A method has been proposed in which the electrode is fed by the amount of wear that is given during the program and predicted as the machining progresses.

FIG. 7 is a block diagram showing the configuration of a conventional electric discharge machining apparatus that employs the above-described correction of electrode wear.
In the figure, 1 is an XY table driven in the X and Y directions by drive motors 2 and 3, 4 is a workpiece placed on the XY table 3, 5 is a main shaft, and 6 is the tip of the main shaft 5. A machining electrode fixed in correspondence with the workpiece 4 and having a simple shape such as a cylinder or a cylinder, for example, 7 is an electrode for transmitting the driving force of the drive motor to the machining electrode 6 via the main shaft 5 and rotating it. It is a rotation mechanism.

  9 is a machining power source for applying a pulsed current between the machining electrode 6 and the workpiece 4, 10 is a machining path storage means in which machining paths not considered for correction are stored, and 11 is the consumption of the machining electrode 6. A correction data storage means 12 that stores correction data for correction, and 12 uses the correction data stored in the correction data storage means 11 to correct the machining path stored in the machining path storage means 10 to provide an electrode path. 13 is an electrode path command means for sending an electrode path command based on the electrode path generated by the electrode path generation means 12, and 14 is an electrode path sent by the electrode path command means 13. It is an electrode position control means for setting the position of the machining electrode 6 by controlling the drive motors 2 and 3 based on the command.

Next, the operation of the conventional electric discharge machining apparatus configured as described above will be described.
First, prior to machining, a wear compensation parameter is determined by a preliminary experiment. If the electrode wear is in a steady state, the relationship z = mL is established between the trajectory feed length L and the electrode wear length z via the correction data m, so that machining is performed over an appropriate machining length L, What is necessary is just to calculate m by measuring the electrode consumption length z. Of course, if m can be determined based on previous experiments, known experience, knowledge, theory, etc., preliminary experiments are unnecessary.

  Now, since the machining path set according to the machining shape of the workpiece 4 and stored in the machining path storage means 10 does not consider the consumption of the machining electrode 6, the electrode path generation means 12 performs correction data storage means. 11 is used to generate corrected trajectory data in which a trajectory with a consumption length Δz = m · ΔL in the longitudinal direction of the electrode is added for each unit trajectory feed length ΔL to compensate for the amount of electrode consumption. An electrode path is created and sent to the electrode path command means 13.

Next, an electrode path command is sent out based on this electrode path by the electrode path command means 13, and the electrode position control means 14 moves the XY table 1 by controlling each drive motor 2, 3 by this electrode path command, The position of the machining electrode 6 with respect to the workpiece 4 is set, and the workpiece 4 is machined into a desired shape.
That is, as shown in the flow in FIG. 8, the machining path is corrected using the correction data m to generate an electrode path, and the machining is performed based on the electrode path.

Needless to say, the amount of consumption of the machining electrode 6 needs to be determined by taking into account the machining amount difference caused by the machining locus, and the correction data m has a coefficient depending on the machining amount.
Further, a consumption correction method similar to that described above is described in, for example, Japanese Patent Laid-Open No. 5-345229.

  Furthermore, a research report by Yamagata University "Learning prediction correction control in contour electric discharge machining", Journal of Electromachining Society, Vol. 11, no. 33, p7 / 11 (1987), in order to make the correction data m more accurate, contact data is detected during processing to confirm the actual consumption amount, and the correction data stored in the correction data storage means 11 A method for changing m in accordance with the amount of wear has also been proposed.

FIG. 9 is a block diagram showing a configuration of an electric discharge machining apparatus that employs the above-described correction of electrode consumption.
In the figure, the same parts as those in the electric discharge machining apparatus shown in FIG. Reference numeral 15 denotes an electrode consumption measuring means for measuring electrode consumption by contact detection for each fixed measurement section ΔL, and 16 denotes correction data m in the correction data storage means 11 measured by the electrode consumption measurement means 15 according to the electrode consumption. Correction data correction means 17 for correction is a correction means for correcting the position setting of the machining electrode 6 by correcting the control amount by the electrode position control means 14 based on the correction data m corrected by the correction data correction means 16. is there.

Next, the operation of the conventional electric discharge machining apparatus configured as described above will be described.
First, the correction means 17 uses the correction data m stored in advance in the correction data storage means 11 to add a trajectory having a consumption length Δz = m · ΔL in the electrode longitudinal direction for each unit trajectory feed length ΔL. Thus, the electrode path commanded from the electrode path command means 13 to the electrode position control means 14 is corrected. Next, based on the corrected electrode path, the electrode position control means 14 sets the position of the machining electrode 6, and machining proceeds by the machining electrode 6.

On the other hand, the electrode consumption measuring means 15 sends a signal to the machining power supply 9 every time the position advances X in the plane direction from the position of the machining electrode 6 set by the electrode position control means 14 to turn off the machining power supply 9. The actual electrode consumption length Δz is measured by contact detection. When the measurement is completed, the machining electrode 6 is returned to the original position and the machining power source 9 is turned on. The correction data correction means 16 calculates Δz = m ·· obtained by the correction data m stored in the correction data storage means 11. The correction data m is corrected by comparing ΔL with Δz ₂ actually obtained by the contact detection as described above. FIG. 10 is a flowchart showing the above operation.

“Three-Dimensional Controlled Electrical Discharge Machining Using Cylindrical Electrodes (1st Report)” Journal of the Electromachining Society, Vol. 17, no. 33, p31 / 44 (1983) “Three-Dimensional Controlled Electrical Discharge Machining Using Cylindrical Electrodes (2nd Report)” Journal of the Electromachining Society, Vol. 17, no. 34, p. 1/12 (1984) "Learning prediction correction control in contour electric discharge machining", Journal of Electromachining Society, Vol. 11, no. 33, p7 / 11 (1987)

  A conventional electric discharge machining apparatus for performing three-dimensional machining is configured as described above. By the way, since electric discharge machining is non-contact machining, disturbance is included and machining is not necessarily performed as expected. For example, machining powder generated during machining affects the state of the machining gap and changes the clearance.

  For example, taking the rotation direction of the machining electrode 6 as an example, as shown in FIG. 11A, the machining electrode 6 is rotated in the direction of rotation while discharging the machining liquid as shown in FIG. As shown in B), when the machining progresses while the machining liquid is involved in the rotation direction of the machining electrode 6, machining powder tends to accumulate around the machining electrode 6. Therefore, with a slight disturbance such as unstable machining and wide clearance, the predictions made before machining will be greatly deviated. Further, an error generated at a certain point also affects subsequent processing, and the error is accumulated.

  Further, in the conventional apparatus whose structure is shown in FIG. 9, the problem of the consumption error of the machining electrode 6 is partially solved. However, it is wasteful to measure the electrode wear error for every certain section, and the shape disturbance due to the error generated before the measurement is not taken into consideration. In general, three-dimensional electrical discharge machining does not proceed at a desired machining depth by a single operation, but performs so-called multi-layer machining, in which thin layers are processed little by little, but the shape of the previous layer No consideration is given to anyone.

  In addition, if the processing is as stable as possible and the processing can be performed in an ideal state, the wear error should be minimized in the first place, but such consideration is not made. In multilayer processing, no consideration is given to how the thickness of each layer is determined and how the processing conditions are switched. In addition, since machining with a simple-shaped machining electrode consumes more electrode than with a total electrode, it is necessary to replace the electrode at some timing. There were many problems, such as not being done.

  The present invention has been made to solve the above-described problems, and provides an electric discharge machining apparatus in which the machining state is always constant and a uniform machining surface can be obtained. It is another object of the present invention to provide an electric discharge machining apparatus that enables high-speed and high-precision machining.

The electric discharge machining apparatus according to the present invention is a discharge machining apparatus that performs three-dimensional shape machining using a rotating electrode having a simple shape, and calculates a machining amount with respect to an electrode path obtained by correcting the consumption of the electrode in the machining path. And electrode rotation speed control means for controlling the rotation speed of the electrode in proportion to the processing amount.

According to the present invention, in an electric discharge machining apparatus that performs three-dimensional shape machining using a rotating electrode having a simple shape, a machining amount is calculated for an electrode path obtained by correcting the consumption of the electrode in the machining path. Since the electrode rotation speed control means for controlling the rotation speed of the electrode in proportion to the amount is provided, it is possible to provide an electric discharge machining apparatus in which the machining state is always constant and a uniform machining surface can be obtained.

Reference form of the present invention.
Hereinafter, a reference embodiment of the present invention will be described with reference to the drawings. 1 is a block diagram showing the configuration of an electric discharge machining apparatus according to a reference embodiment of the present invention , FIG. 2 is a flowchart showing the operation of the electric discharge machining apparatus in FIG. 1, and FIG. 3 is the rotation direction of the machining electrode of the electric discharge machining apparatus in FIG. FIG. 4 is a diagram for explaining the control of the rotation direction at a location where it is difficult to discharge the machining powder of the machining electrode of the electric discharge machining apparatus in FIG. 1.

  In the figure, the same parts as those of the conventional apparatus shown in FIG. Reference numeral 18 denotes an electrode rotation direction determining means for predicting the discharge state of the machining powder with respect to the electrode path generated by the electrode path generation means 12, and determining the rotation direction of the processing electrode 6 in accordance with the discharge state. This is an electrode rotation direction control means for controlling the rotation direction of the machining electrode 6 via the electrode rotation mechanism 7 based on the rotation direction determined by the rotation direction determination means 18.

Next, the operation of the electric discharge machining apparatus according to the reference embodiment configured as described above will be described based on the flow shown in FIG.
First, based on the correction data stored in the correction data storage unit 11, the electrode path generation unit 12 corrects the amount of electrode consumption in the machining path stored in the machining path storage unit 10, and generates an electrode path. (step _S 1). Next, the discharge state of the machining powder is predicted from the electrode path by the electrode rotation direction determining means 18, and the rotation direction of the machining electrode 6 is determined so that the machining powder is easily discharged according to this discharge state (step S). ₂ ). For example, as shown in FIG. 3, when the machining electrode 6 is at the point A and the machining allowance is on the right side with respect to the traveling direction of the machining electrode 6, it is determined to rotate left as indicated by the arrow in the figure. The

When the rotation direction of the machining electrode 6 is determined in this way, the electrode path is checked for each predetermined section K. Then, for example, as shown in FIG. 3, when it is confirmed that the machining electrode 6 has moved to the position of point B and the machining allowance has changed to the left with respect to the traveling direction of the machining electrode 6 (step S ₃ ). The electrode rotation direction determining means 18 sends an electrode reverse rotation command (step S ₄ ) so that the machining powder is easily discharged. In addition, it is sequentially checked whether or not the machining powder is likely to be discharged together with the direction of the machining allowance (step S ₅ ). , The rotation direction is switched every appropriate number of times, such as 10 rotations to the right and 10 rotations to the left (step S ₆ ).

In this manner, when the electrode path is generated by the electrode path generation unit 12 and the rotation direction of the machining electrode 6 is determined by the electrode rotation direction determination unit 18 (step S ₇ ), the electrode path command unit 13 sets the electrode path. Based on this electrode path command, the electrode position control means 14 controls the drive motors 2 and 3 to move the XY table 1 to set the position of the workpiece 4 with respect to the processing electrode 6. At the same time, the electrode rotation direction control means 19 sets the rotation direction of the machining electrode 6 via the electrode rotation mechanism 7 to machine the workpiece 4 into a predetermined shape (step S ₈ ).

As described above , according to the reference embodiment , when the machining allowance is on the left side with respect to the traveling direction of the machining electrode 6 with respect to the electrode path generated by the electrode path generation unit 12, the machining electrode 6 is rotated to the right. When the machining allowance is on the right side, the machining electrode 6 is set to the left rotation by the electrode rotation direction determining means 18 so that the machining powder is easily discharged, and is set in advance at a place where the machining powder is difficult to be discharged. Since the rotation direction of the machining electrode 6 is switched and controlled every number of times, the machining state is always constant and a uniform machining surface can be obtained.

Embodiment 1 FIG.
FIG. 5 is a block diagram showing the configuration of the electric discharge machining apparatus according to Embodiment 1 of the present invention , and FIG. 6 is a flowchart showing the operation of the electric discharge machining apparatus in FIG.
In the figure, parts similar to those of the reference embodiment shown in FIG. Reference numeral 20 denotes an electrode rotation number determination means for calculating the machining amount for the electrode path generated by the electrode path generation means 12, and determines the rotation number of the machining electrode 6 in proportion to the machining amount, and 21 denotes the electrode rotation number. This is an electrode rotation speed control means for controlling the rotation speed of the machining electrode 6 via the electrode rotation mechanism 7 based on the rotation speed determined by the determination means 20.

Next, the operation of the electric discharge machining apparatus according to Embodiment 1 configured as described above will be described based on the flow shown in FIG.
First, based on the correction data stored in the correction data storage unit 11, the electrode path generation unit 12 corrects the amount of electrode consumption in the machining path stored in the machining path storage unit 10, and generates an electrode path. (step _S 11). Then, the calculation processing amount to the electrode path by the electrode rotation speed determining means 20, the rotational speed of the working electrode 6 is determined in proportion to the amount of machining (step S _12).

When the rotational speed of the machining electrode 6 is determined in this way, the electrode path is checked for each predetermined section K. When the change in the machining amount is confirmed (step S ₁₃ ), the electrode rotation speed determining means 20 sends an electrode rotation speed change command (step S ₁₄ ) so that the machining powder is easily discharged. Further, during the check of the electrode path, whether or not the machining powder is likely to be discharged is also checked sequentially (step S ₁₅ ). The speed is further increased by p · m (step S ₁₆ ).

In this way, when the electrode path is generated by the electrode path generation unit 12 and the rotation number of the machining electrode 6 is determined by the electrode rotation number determination unit 20 (step S ₁₇ ), the electrode path command unit 13 sets the electrode path. Based on this electrode path command, the electrode position control means 14 controls the drive motors 2 and 3 to move the XY table 1 to set the position of the workpiece 4 with respect to the processing electrode 6. At the same time, the electrode rotation speed control means 21 sets the rotation direction of the machining electrode 6 via the electrode rotation mechanism 7 to machine the workpiece 4 into a predetermined shape (step S ₁₈ ).

As described above, according to the first embodiment, the machining amount is calculated by the electrode rotation number determining unit 20 for the electrode path generated by the electrode path generating unit 12, and the machining electrode 6 is proportional to the machining amount. Is set so that the machining powder can be easily discharged, and at places where it is difficult to discharge the machining powder, the rotation speed is further increased by a predetermined value Cr · p · m to discharge the machining powder. Therefore, there is an effect that the processed state is always constant and a uniform processed surface can be obtained.

It is a block diagram which shows the structure of the electric discharge machining apparatus in the reference form of this invention . It is a flowchart which shows operation | movement of the electric discharge machining apparatus in FIG. It is a figure for demonstrating the relationship between the rotation direction of the machining electrode of the electric discharge machining apparatus in FIG. 1, and the position of a machining allowance. It is a figure for demonstrating control of the rotation direction in the location where discharge | emission of the process powder of the process electrode of the electric discharge machining apparatus in FIG. 1 is difficult. It is a block diagram which shows the structure of the electric discharge machining apparatus in Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the electric discharge machining apparatus in FIG. It is a block diagram which shows the structure of the conventional electric discharge machining apparatus. It is a flowchart which shows operation | movement of the principal part of the electric discharge machining apparatus in FIG. It is a block diagram which shows the structure of the other conventional electric discharge machining apparatus different from what is shown in FIG. It is a flowchart which shows the operation | movement of the principal part of the electric discharge machining apparatus in FIG. It is a figure for demonstrating that the discharge degree of a process liquid changes with the relationship between the rotation direction of a process electrode, and the position of a process allowance.

Explanation of symbols

1 XY table, 2, 3, 8 drive motor, 4 workpiece, 5 spindle,
6 machining electrodes, 7 electrode rotation mechanisms, 9 machining electrodes, 10 machining path storage means,
11 correction data storage means, 12 electrode path generation means, 13 electrode path command means,
14 electrode position control means, 18 electrode rotation direction determination means, 19 electrode rotation direction control means,
20 electrode rotation speed determination means, 21 electrode rotation speed control means.

Claims (2)

In an electric discharge machining apparatus that performs three-dimensional shape machining using a rotating simple-shaped electrode, the machining amount is calculated for the electrode path obtained by correcting the consumption of the electrode in the machining path, and is proportional to the machining amount. And an electrode rotation speed control means for controlling the rotation speed of the electrode. 2. The electric discharge machining apparatus according to claim 1, wherein the discharge rate is controlled by increasing the number of revolutions of the electrode at a location where the discharge of the machining powder is difficult.

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