CN100404183C - Discharge machining machine and machining method of electrodes and rolls for electrical discharge machining - Google Patents

Abstract

The present invention provides an electrode for electrical discharge machining, an electrical discharge machining machine, and an electrical discharge machining method for performing electrical discharge machining capable of preventing the concentration of electrical discharge and having no spiral machining marks on a roll for matte finishing. It has an inner cavity from which the machining fluid can flow out from the front end, project the end surface of the electrode front end on the electrode projection plane perpendicular to the electrode length direction, and the area of the part excluding the hole corresponding to the inner cavity is less than 70 mm ² , In addition, the end surface of the electrode front end is a flat shape with a flatness rate of 1.5 or more expressed by the ratio (L/T) of the maximum length (L) on the projection plane to the length (T) in the direction perpendicular to it. The electric discharge machine of the electrode in which the maximum length (L) of the projected surface is substantially parallel to the axial direction of the roller moves the roller and the electrode relatively in the circumferential direction and the axial direction of the roller while the machining fluid flows out of the inner chamber , EDM the roller in a spiral shape.

Description

Discharge machining machine and machining method of electrodes and rolls for electrical discharge machining

technical field

The present invention relates to an electrode for electric discharge machining having a cavity for allowing a machining fluid to flow out from the inside of the electrode, and an electric discharge machine for rollers having the electrode. This electrical discharge machine is suitable for electrical discharge machining of rolls such as rolls for dull finish. The present invention also relates to an electric discharge machining method for rolls such as rolls.

Background technique

The surface of the roll itself used for the mat finish of the steel strip is given a mat finish. In addition to the existing method of projecting metal particles, the matting process of the roll is also recently carried out by electric discharge machining.

Electrical discharge machining is a machining method in which a pulse waveform voltage is periodically applied between the workpiece and the electrode in an insulating machining fluid to generate arc discharge, and its heat is used to melt and remove the surface of the workpiece. Crater-shaped pits are formed on the surface of the roll where the electric discharge occurs, making the surface of the roll rough. The machining fluid makes the discharge have the necessary insulating environment, and at the same time, it also has the function of driving away the processed powder of the removed dross generated in the discharge machining from around the electrode, absorbing the processing heat, and cooling the processed part.

Typically, electrical discharge machining of a roll is performed by using an electrical discharge machine having an electrode disposed facing the roll as a workpiece, and rotating the roll while moving the electrode in the axial direction of the roll (generally reciprocating). Therefore, the surface of the roller is continuously subjected to spiral electric discharge machining, and spiral processing stripes are generated on the surface of the roller. If the electrode moves repeatedly toward the roll axis, the entire roll surface can be roughened by machining discharge. To generate discharge, it is necessary to narrow the gap between the electrode and the roller, so the electrode is advanced or retracted by a servo motor mounted on the electrode, and the gap is controlled to a size suitable for power generation.

If the matted roll is used in the matte finishing of the steel strip, the service life of the general roll surface is several hours to several days due to the rapid wear of the surface unevenness. Surface irregularities are ground by worn rolls to smooth the surface, and then matte processing is performed with machining discharge. That is, the roll is repeatedly used through a cycle of grinding→discharge machining→rolling until the roll diameter becomes the specified effective use diameter. Therefore, electric discharge machining is required to be performed in the shortest possible time.

In order to rapidly perform matting processing of rolls by electric discharge machining, and to increase the processing area in one electric discharge, an electric discharge machine in which a plurality of electrodes are arranged side by side at regular intervals in the axial direction and circumferential direction of the roll can be used.

There are the following problems in the matting process of rolls by electric discharge machining.

In the case of performing spiral electric discharge machining on the surface of the roller as described above, if the intensity of the electric discharge machining is too strong, serious spiral processing stripes will be generated, and it will also remain on the surface of the processed roller and be copied on the surface of the processed roller. On the rolled steel strip, rolling defects are produced.

In addition, there is a phenomenon of discharge concentration in electric discharge machining. This is because (1) discharge is easily generated at the narrowest gap between the workpiece (roller) and the electrode; (2) the processing powder (cutting residue of the roller and electrode) generated by the discharge is conductive, and because it becomes The medium that spreads the discharge is caused by the discharge that is likely to occur at the place where the processing powder stays.

For example, the tip of the electrode is consumed due to the electric discharge machining of the roll. Therefore, after the discharge machining is completed, the outer shape of the end surface of the electrode facing the roll along the roll circumferential direction and the convex shape in the roll axial direction become a curved shape. If this electrode is used to discharge the next roll with different roll diameter or different convex shape, the gap between the roll and the electrode will be narrowed, and the discharge will be concentrated in this part.

In addition, if the supply or flow of the machining fluid is insufficient, the machining powder tends to stay near the electrodes, and the discharge is often concentrated near the place where the discharge once occurred.

If the concentration phenomenon of discharge occurs, severe spiral processing traces are formed on the surface of the roller along the path of the electrode, which is copied on the steel strip rolled by the roller, and the result is also the cause of defective rolling. reason.

In order to prevent the concentration of discharge, Japanese Patent Laid-Open No. 53-72296 discloses a technique of dividing electrodes into small pieces.

US Pat. No. 4,870,243 describes a technique in which a machining fluid contains a small amount of powder of conductive materials such as graphite and metal particles for the purpose of stabilizing and dispersing the discharge.

Regarding the configuration of the electrodes, JP-A-55-150923 discloses that in order to prevent short circuits caused by the contact between the electrodes and the rollers, the electrodes are not arranged to face the axis of the rollers, but to be arranged in the opposite direction to the direction of rotation of the rollers. Inclined technology.

Contents of the invention

The present invention provides an electrical discharge machine and an electrical discharge machining method capable of preventing occurrence of severe machining streaks and concentration of electrical discharge, and an electrical discharge machining electrode used therein.

In order not to produce serious processing streaks in EDM, methods such as (a) reducing the number of discharges per unit time; or (b) increasing the relative moving speed of the roller and the electrode as the workpiece can be considered. However, the method (a) is unacceptable in electric discharge machining of rolls that require rapid machining because the machining efficiency is lowered. The method of (b) must increase the conveying speed of the electrode and the number of revolutions of the roller, but considering the mechanical limitations of the electrical discharge machine and the need to control the gap between the electrode and the roller to be around several 10 μm for discharge, this method is unrealistic.

In order to avoid the phenomenon of discharge concentration, in addition to the above (a) method of reducing the processing efficiency and (b) method of increasing the relative speed of the electrode and the roller, (c) the method of reducing the area of the electrode end surface where the discharge occurs can be considered . However, with the method (c), the processing density per unit area becomes higher, and severe processing streaks are easily generated.

As mentioned above, when replacing the roll to be processed, if the roll diameter and crown shape of the replaced roll are different from those of the previously processed roll, the gap between the electrode and the roll (the gap between the electrode/roller) is partially narrowed, and the discharge is concentrated in this part , resulting in spiral processing traces. Regarding this phenomenon, since the area of the end surface of the electrode is large, the consumption of the electrode is reduced, and the roll diameter and convex shape of the previously processed roll remain on the electrode for a long time, and processing due to concentrated discharge occurs instead.

The present inventors focused on the change of the electrode/roll gap accompanying the change of the diameter of the processed roll. If the electrode is lengthened into a flat shape in the axial direction, the influence will be reduced and it will be easy to correspond to the change of the roll diameter. Since the curvature of the roll diameter is much larger than the curvature of the convex surface (the radius of curvature is much smaller than the curvature radius of the convex surface), the influence of the change of the roll diameter is minimized, which is effective in preventing the concentration of discharge.

In addition, if a flat electrode that is elongated in the axial direction of the roller is used, the roughened processing part formed with the rotation of the roller is flat and wide in the lateral direction, so the processing density is reduced, and the occurrence of serious processing streaks can be prevented, and it is difficult to form processing marks.

In order to avoid the concentration of the discharge caused by the processing powder staying near the electrode, it is effective to make the electrode hollow and let the processing liquid flow out from the inner cavity of the electrode to form the flow of the processing liquid from the electrode to the outside.

When such a hollow electrode is used, since the machining liquid flows out more from the electrode/roller with a wide gap, processing powder tends to stay in the narrow gap than in the wide gap. Therefore, the part with a narrow gap is very likely to cause discharge concentration due to two reasons: the narrowness of the gap and the retention of processing powder. To minimize discharge concentration and to make the gap as uniform as possible, it is preferable to arrange the electrodes toward the center of the roll axis.

In one aspect, the present invention is an electrode for electrical discharge machining, which has an inner cavity from which a machining fluid can flow out from the front end of the workpiece, and is characterized in that the end face of the front end of the electrode is projected on a plane perpendicular to the length direction of the electrode. On the projected surface of the electrode (hereinafter referred to as the projected surface of the front end), the area of the part (hereinafter referred to as the projected area of the front end) excluding the hole corresponding to the inner cavity is less than 70 mm ² and more than 10 mm ² , and the end surface of the electrode front end is useful. A flat shape in which the flattening rate represented by the ratio (L/T) of the maximum length (L) on the projection plane to the length (T) in the direction perpendicular thereto is 1.5 or more.

In another aspect, the present invention is an electrical discharge machine for a roll, which has one or more than two electrodes arranged facing the roll, and is characterized in that the electrodes have an inner chamber that allows the machining fluid to flow out from the front end facing the roll, This electrode is configured such that the end surface of the electrode front end is projected on the electrode projection plane (hereinafter referred to as the front end projection plane) on a plane perpendicular to the electrode length direction, and the area of the part corresponding to the hole of the inner cavity (hereinafter referred to as the front end) is removed. The projected area) is less than ^70mm2 and more than ^10mm2 , and the end surface of the electrode tip is expressed by the ratio (L/T) of the maximum length (L) on the projected surface and the length (T) in the direction perpendicular to it (L/T) A flat shape greater than or equal to 1.5, and the maximum length (L) of the above-mentioned projected surface is substantially parallel to the axial direction of the roller.

Here, "substantially parallel" means that the angle between the direction of the maximum length (L) of the projected surface and the axial direction of the roller is within 10°. This angle is preferably within 5°, most preferably 0°.

In a suitable form, the one or more electrodes are arranged such that the longitudinal direction of the electrodes faces the axis of the roller. When the electrical discharge machine has a plurality of electrodes, it is preferable that the electrodes are arranged in a zigzag shape in a plurality of rows in the circumferential direction of the roll.

According to the present invention, it is possible to provide an electric discharge machining method using the roll of the above-mentioned electric discharge machine, which is characterized in that the roll and the electrode are relatively moved in the circumferential direction and the axial direction while the machining fluid flows out of the above-mentioned inner cavity, and the spiral Shaped rollers are subjected to electric discharge machining.

In the electric discharge machining having the electrodes arranged in a zigzag shape, it is preferable that the roller is subjected to electric discharge machining in such a manner that no region that has not been electric discharge machined remains by adjusting the relative moving speed of the roller in the circumferential direction and/or the axial direction. .

Description of drawings

FIG. 1 is a schematic explanatory diagram of an electric discharge machine for rolls.

Fig. 2 shows, together with the projected front area (cross-sectional area), the shape of the projected front end of representative hollow electrodes A to D used in the test and the arrangement direction when the roll axis is taken as the horizontal direction.

FIG. 3 is a schematic diagram of a machined surface when electric discharge machining is performed using the electrodes A to D of FIG. 2 .

FIG. 4 is an explanatory diagram showing an example in which electrodes are arranged in a zigzag shape in multiple columns.

FIG. 5 is an explanatory view showing the shape of the projection surface of the tip of the electrode used in the example.

6 to 11 are explanatory diagrams showing the arrangement of electrodes with respect to the roll, and all are side views viewed from the axial direction of the roll.

Fig. 6 is a diagram showing a state where the electrodes are shifted toward the axial center of the roll.

Fig. 7 shows a state in which electrodes are arranged in the direction of the axis of the roll.

Fig. 8 shows the situation when the roller processed by the electrode shown in Fig. 6 is changed from a smaller-diameter roller [Fig. 8(a)] to a larger-diameter roller [Fig. 8(b)].

Fig. 9 shows the situation when the roller processed by the electrode shown in Fig. 7 is changed from a smaller-diameter roller [Fig. 9(a)] to a larger-diameter roller [Fig. 9(b)].

Fig. 10 shows a case where a plurality of electrodes are arranged in a plurality of rows in the circumferential direction of the roll, facing the center of the roll axis.

Fig. 11 is a graph showing the positional relationship of the electrodes and the large-diameter and small-diameter rolls in the case where the electrodes are not directed toward the roll axis.

Detailed ways

FIG. 1 schematically shows an example of an electrical discharge machine used in roll electrical discharge machining. A roll 8 of a workpiece is rotatably attached to this electric discharge machine. That is to say, the roller support parts on both sides are placed on the bearing stand 11, and after positioning with the end surface fixtures 5 and 6, the roller driving device 9 is rotated to drive the roll 8 to rotate. On the electrode holder 7 of this electrical discharge machine, generally a plurality of electrodes are mounted in an appropriate arrangement. The electrode holder 7 reciprocates across the width of the roll in the roll axis by rotating a Bowl Screw mechanism 12 passing through its head with a drive device 10 .

Not shown in the figure, in order to control the gap between the tip of the electrode and the roller to be the most suitable size for discharge, the electrode is mounted on the electrode holder through a servo motor and a screw mechanism. The gap between the electrode and the roll is filled with machining fluid.

In roll electrical discharge machining using the electrical discharge machine shown in the figure, the electrode holder is moved in the roll axial direction while the roll is rotated, so that the electrode is moved in the roll axial direction. That is to say, the roller and the electrode as the workpiece move relatively in both the circumferential direction and the axial direction of the roller during the electric discharge machining, so the processing stripes formed by the electric discharge machining go in a spiral shape on the surface of the roller.

In the example shown in the figure, the electric discharge machine is shown in which the roller is driven to rotate and the electrode is moved in the axial direction. Regarding the relative movement in the circumferential direction of the roller, the electrode may be moved in the circumferential direction of the roller instead of rotating the roller. , or both can be used together. Similarly, with respect to the relative movement of the roller in the axial direction, instead of the electrode, the roller or both the roller and the electrode may be moved in the axial direction.

The electrode for electric discharge machining of the present invention has a cavity for flowing out the machining fluid, and the machining fluid can flow out from the tip of the electrode to the workpiece (for example, a roll). Typically, the electrode is a tubular hollow electrode having a through hole inside. However, as long as the outlet of the inner cavity is located at the front end of the electrode, it is not necessary to penetrate the entire length of the electrode in its length direction. For example the inlet for the machining fluid may be located in the middle of the electrode length. A well-known and appropriate method can be used to supply the machining fluid to the electrode lumen.

The term "longitudinal direction of the electrode" refers to the longitudinal direction of the generally elongated electric discharge machining electrode, intersecting the end surface of the electrode tip. However, since the end face may be bent or inclined due to electrode wear during discharge, the longitudinal direction of the electrode is not limited to be perpendicular to the end face of the tip. In the present invention, the machining fluid flows out from the front end of the electrode through the lumen provided in the electrode. Therefore, the longitudinal direction and the outflow direction of the machining fluid are substantially the same.

By allowing the machining fluid to flow out from the tip of the electrode, a flow of the machining fluid from the narrow gap between the electrode and the workpiece to the outside of the periphery is formed. Therefore, it is possible to reliably drive away the machining powder generated in the electric discharge machining from the vicinity of the electrode, and prevent the discharge concentration caused by the machining powder remaining near the electrode.

In the electrode for electric discharge machining according to the present invention, the end surface of the electrode tip facing the workpiece is projected on the electrode projection plane (hereinafter referred to as the tip projection plane) on a plane perpendicular to the electrode length direction, and the portion corresponding to the inner cavity is removed. The area of the part of the hole (hereinafter referred to as the projected area of the front end) is less than ^70mm2 , and the end face of the electrode front end has a ratio of the maximum length (L) on the projected plane to the length (T) in the direction perpendicular to it (L/ A flat shape with a flattening rate greater than or equal to 1.5 indicated by T).

The projected area of the electrode tip excluding the portion corresponding to the hole in the cavity means the area of the electrode end surface which becomes the discharge surface. If the projected area of the tip of the electrode exceeds 70 mm ² , the tip of the electrode will be consumed slowly, and when the roll as the workpiece is replaced with a workpiece of another shape, the shape of the tip of the electrode will change to the shape along the replaced roll. It takes time to form the shape, and it is not possible to sufficiently prevent the generation of processing marks due to the concentration of discharge.

If the projected area of the front end of the electrode is too small, the frequency of replacing the electrode will increase due to the rapid consumption of the electrode, so the lower limit is preferably about 10 mm ² . The front end projected area is more preferably 15 to 50 mm ² .

When performing electrical discharge machining on a roll, the electrode having a flat shape according to the present invention is mounted on an electrode holder of an electrical discharge machine such that the maximum length (L) of the projected front end is substantially parallel to the axial direction of the roll. In this way, the discharge is dispersed without dividing the electrodes, and the concentration of the discharge can be suppressed.

Fig. 2 shows the shape and arrangement of the front end projection surfaces of various hollow electrodes together with the front end projected area (shown as a cross-sectional area in the figure). The axial direction of the roller in the figure is the horizontal direction. Fig. 3 is a view showing the processed state of the roller surface when electric discharge machining is performed using the electrodes A, B, C, and D of Fig. 2 together with electrode cross-section formation.

Electrodes A and B are cylindrical hollow electrodes for comparison with a circular cross section, and the front end projected areas are different from each other. Electrodes C and D are hollow electrodes with the same shape and a flat section according to the present invention, but they are installed in different directions on the electrode bracket. That is, the maximum length (L) (hereinafter also referred to as the long axis) of the projected surface of the front end of the electrode C faces the circumferential direction of the roll, whereas the long axis of the electrode D faces the axial direction of the roll.

If the electrode A with a circular cross-section with a large front projected area is used to discharge the roller, as shown in Figure 3, due to the low discharge density, the spot-shaped unevenness generated by the discharge on the surface of the roller does not reach the outer diameter of the electrode (roughly equivalent to Due to the size of the electrode wall thickness), the remaining parts are uneven and sparse. On the roll, a spiral pattern composed of such uneven groups is formed, and the uneven groups expand every time it is repeated, and the processing progresses. When the entire surface of the roll is formed of unevenness groups, the helical pattern seen first on the surface of the roll cannot be seen, but in fact, more discharges are generated at the part of the spiral unevenness group than in other parts, so it becomes The state of the slight concave. This depression is replicated on the strip when it is rolled with rolls.

In the case of using the electrode B with a circular cross-section having a much smaller projected area of the front end, the discharge is generally dispersed across the width of the electrode, and spot-like irregularities are not formed. However, since the width of the discharge generation (the width of the processing stripes) is narrow and the processing density is high, serious spiral processing traces have been generated from the initial stage of processing.

It can be said that the result is the same as that of the electrode B for the electrode C in which the long axis of the flat electrode is oriented in the circumferential direction (rotational direction) of the roll. This is because the relative movement speed (peripheral speed) of the roller/electrode in the circumferential direction due to the rotation of the roller is much greater than the relative movement speed in the axial direction of the roller. For example, the relative moving speed of the roller/electrode is 100-800mm/sec in the circumferential direction of the roller, 1-20mm/sec in the axial direction of the roller, and the included angle between the helix and the circumferential direction of the roller is less than 10°. Therefore, the relative movement is mainly in the circumferential direction. The width of the electrode in the circumferential direction of the electrode C (the electrode dimension in the axial direction perpendicular to the circumferential direction) is a small size corresponding to the short axis of the projected surface of the tip of the electrode, so the width of the electric discharge machining is small, and it becomes an electrode with a small diameter. B same result.

On the other hand, if according to the present invention, the electrode D with the long axis of the projected surface of the front end of the flat electrode is oriented toward the axial direction of the roller, and the roller is subjected to electromechanical processing, then small concavo-convex groups of the thickness of the electrode are formed to reach the electrode length. The processing pattern that the width of the shaft is dispersed. The width of the electrode arranged in the circumferential direction of the roller thus becomes the dimension of the major axis of the projected surface of the tip of the electrode, and the width of the electric discharge machining is widened. Therefore, D has the best discharge dispersion. Since the shape of such small-width concavo-convex groups forms a spiral shape, and the severity of each group formed at the beginning is small, if repeated, the spiral pattern will not be obvious, and the overall quality of uniform concavo-convex can be formed.

That is, if the long axis of the flat electrode is arranged parallel to the axial direction of the roller, since the processing stripes are expanded and dispersed, even if the projected area of the front end is small, the processing will not be strong, thereby preventing processing marks caused by strong processing.

In the matte rolling of the steel strip, in the case of using the roll with the surface roughened by the electric discharge machining using the above-mentioned electrodes A to D, the roll that is electric discharge machined with the electrodes A, B, or C, after rolling, even if no abnormality is found on the surface of the steel sheet In abnormal cases, such as grinding inspection with a grindstone, it is found that the quality is poor. That is to say, at the part of the spiral pattern that was originally processed, due to the severe depression on the surface of the roll, protrusions are displayed on the steel strip, and the spiral convex pattern is exposed after grinding, which becomes poor quality.

On the contrary, in the roll subjected to electrical discharge machining using the electrode D, the concavo-convex group of the part of the helical pattern machined initially has very fine depressions. As a result, even if this roll is used for rolling, the quality of the steel strip will not be defective.

In the electrode for electrical discharge machining according to the present invention, the flatness ratio (L/T) represented by the ratio (L/T) of the maximum length (L) on the projected surface of the electrode tip to the length (T) in the direction perpendicular thereto is set to be 1.5 or more. If the flattening rate is less than 1.5, the dispersion of the discharge is insufficient, and the result is similar to that of the electrode B.

On the other hand, if the flattening ratio of the electrode is too large, the electrode bracket must be enlarged, and a part of the electrode at the edge of the roll may deviate from the roll. Generally, it is preferable that the flatness ratio is 10 or less. More preferably, the flatness ratio is 3-8. According to the instructions of the device and where the edge of the roll needs to be processed, the appropriate flatness ratio can be selected.

The electrode for electrical discharge machining of the present invention can be made of copper, graphite, or a composite material of both, and materials that have been used so far.

Discharge machining can also be performed with one electrode, but it is preferable to arrange a plurality of electrodes side by side on an electrode holder in order to widen the processing area after one processing. In the case of using a plurality of electrodes, as shown in FIG. 4, it is preferable to arrange the electrodes in a zigzag manner in a plurality of rows in the circumferential direction of the roll.

In the example shown in FIG. 4 , 12 electrodes are arranged so that the major axis direction of its front end projection surface is parallel to the axial direction of the roller (horizontal direction in the drawing), and are arranged in a row of four, divided into three rows. The three columns are therefore columns separated in the circumferential direction of the roll. The distances between the electrodes of each row are the same, and the rows are slightly shifted in the axial direction of the roller to form a zigzag arrangement.

If a plurality of columns in the circumferential direction of the roller are arranged in a zigzag shape, the area of the electrode group EDM of the first column partially overlaps the area of the electrode group EDM of the second column, and there is no remaining undischarged area between the EDM areas. processed area. In addition, by adjusting the rotational speed of the roller and the speed at which the electrode for electrical discharge machining is conveyed to the axial direction of the roller (that is, the relative moving speed of the roller and the electrode in the circumferential direction of the roller and the axial direction of the roller), the first row and the second The discharge machined regions of the columns partially overlap, so that no regions not subjected to discharge machining remain between the discharge machined regions. The same applies to the electrode groups of the second and third columns.

The machining fluid used in electrical discharge machining is generally insulating oil. In order to improve the stability of the discharge, the machining fluid may contain one or more powders selected from conductors or semiconductors such as carbon (such as graphite), metal, and silicon. Particularly preferred addition to the machining fluid is carbon.

In the present invention, the machining fluid is passed through the inner cavity of the electrode, and flows out from the tip of the electrode to the surface of the roller. If necessary, a part of the machining fluid may also be supplied to a path that does not pass through the electrodes. The used machining fluid can be used again in electric discharge machining after removing the machining powder by magnetic means, for example.

Example

(Example 1)

Hollow electrodes having various tip projection shapes a to k shown in FIG. 5 were mounted on the electric discharge machine described with reference to FIG. 1, and an electric discharge machining test was carried out.

In each test, 12 electrodes having the same projection shape were arranged in a zigzag shape as shown in FIG. 4 . In the case of flat electrodes, each electrode is arranged such that the maximum longitudinal direction of the projected front end is parallel to the axial direction of the roller. The electric discharge machining test was performed by reciprocating the electrode in the axial direction of the roll while rotating the roll. The machining fluid used is insulating oil, which flows out from the front end through the inner cavity of the electrode during electric discharge machining.

Discharge machining was performed under the condition that unevenness with a center line average roughness Ra=1.0 μm or 3.0 μm was formed on the surface of the roll. Table 1 shows the inspection results of the steel strips rolled with the rolls thus electro-discharge machined.

In Table 1, the symbol "*" indicating the projected area of the tip of the electrode and the flatness ratio indicate that it is out of the scope of the present invention. The symbol "×" of the inspection result indicates that the processing stripes are obviously seen, and the roll must be changed. "△" indicates that processing streaks are not very conspicuous, but processing streaks can be confirmed visually. "◯" indicates that processing streaks were not seen at all.

Table 1

As shown in Table 1, if an electrode with a projected area of the front end of the electrode is less than 70 mm ² and the flatness rate is more than 1.5, the roll is subjected to electrical discharge machining, and good results are obtained in the inspection of the steel strip rolled by this roll. .

With the electrode of the present invention, if the electric discharge machining of the centerline average roughness Ra=0.6～4.0 μm that is generally used is carried out on the roll, in the inspection process to the steel strip rolled by this roll, there is no quality defect. The frequency of electrode replacement can also be maintained to meet the operating level.

(Example 2)

In this embodiment, the effect of arranging the electrode for electric discharge machining having the cavity through which the machining fluid flows out according to the present invention so that its longitudinal direction is oriented toward the axial center (rotation axis) of the roller will be described and illustrated by way of example.

FIG. 6 shows a state in which the electrode 1 for electric discharge machining is arranged at an angle in which its longitudinal direction does not face the axis 3 of the roller 2 . On the other hand, FIG. 7 shows a state in which the longitudinal direction of the electrode 1 is arranged at an angle toward the axis 3 of the roller 2 according to a suitable mode of the present invention. Since these are side views and cannot be seen in the drawings, a lumen for the machining fluid to flow out of the inside of the electrode 1 penetrates in the longitudinal direction.

FIG. 8( a ) shows the electrode arrangement shown in FIG. 6 , showing a state in which the electric discharge machining is performed on the small-diameter roller while the machining fluid is flowing out from the tip of the electrode. The end surface of the electrode 1 facing the roller 2 is consumed by electric discharge machining, and becomes a curved surface along the curvature of the small-diameter roller. The arrows in the figure schematically indicate the flow of the machining fluid. In FIG. 8( a ), since the gap between the roller 2 and the electrode 1 is uniform, the machining fluid supplied through the electrode flows at a substantially uniform flow rate from anywhere in the gap.

FIG. 8( b ) shows a state in which a large-diameter roll is subjected to electrical discharge machining using the electrode 1 whose end surface becomes a curved surface along the curvature of the small-diameter roll. In this case, discharge is likely to occur from the portion A where the gap between the roller 2 and the electrode 1 is the narrowest. On the other hand, as shown by the thick arrow, the machining fluid flows out easily from the part B where the gap is wide, and the amount of outflow becomes smaller at the part A, as shown by the thin arrow. Therefore, the discharge is easy to occur in the A part where the processing powder is generated in a large amount, and the discharge is generated due to the retention of the processing powder, so the discharge is concentrated, and processing streaks are likely to occur.

On the other hand, regarding the preferred electrode configuration shown in Figure 7 (the length direction of the electrode 1 faces the axis 3 of the roll 2), Figure 9(a), (b) shows the transition from small diameter rolls to large diameter rolls The state of the roll during processing. As shown in FIG. 9( a ), by performing electrical discharge machining on the small-diameter roll 2 , the end surface of the electrode 1 becomes a curved shape along the curvature of the small diameter.

If this electrode 1 is used in the discharge machining of a large-diameter roll, as shown in FIG. 9(b), discharge tends to occur around the electrode where the gap is the narrowest. However, unlike FIG. 8(b), since the entire gap becomes uniform around the electrode periphery, discharges are similarly induced on either side of the A site and the B site. The flow of the machining fluid is also substantially uniform at the A site and the B site. Therefore, machining powder generated by electric discharge does not stay locally, and electric discharge machining is difficult to occur.

If the electrode is cylindrical, the machining fluid flows out more from both axial sides of the electrode roller, and the flow of the machining fluid may become uneven. However, in the present invention, electrodes having a flat cross section are arranged such that the major axis of the cross section is parallel to the axial direction of the roll. Therefore, since the increase of the machining fluid flowing out from both axial sides of the roller can be suppressed to the minimum, the discharge concentration can be effectively prevented.

FIG. 10 shows a case where electrical discharge machining is performed using a plurality of electrodes arranged as shown in FIG. 9( a ). The electrodes 1, 1 ', 1 " that are arranged in three sections in the circumferential direction of the roller are all arranged towards the axis of the roller. Can not be seen in the figure, for example as shown in Figure 4, it is preferred that each section consists of a plurality of electrodes ( For example, 3 to 6 electrodes are formed in a column, and the electrode positions of each segment are staggered from each other, and the electrodes are arranged in a zigzag shape so that they do not overlap with the electrodes of other segments. In order to control the gap between each electrode and the roller, a servo motor and The lead screw mechanism 4, 4', 4" can advance or retreat in the length direction of the electrode.

Fig. 11 shows a case where the electrodes are arranged as shown in Fig. 8(a) and (b), and the electric discharge machining is performed on the small-diameter roll 2 and the large-diameter roll 2'. D is the diameter of the large-diameter roller, d is the diameter of the small-diameter roller, and α is the intersection point between the electrode axis (length direction) and the circumferential surface of the roller in the processing of the small-diameter roller and the axis center of the roller, and the intersection angle between the electrode axis . Since the intersection angle in the case of the large-diameter roll 2' is smaller than α, it can be understood that the intersection angle changes with the roll diameter. On the other hand, when the electrodes are arranged as shown in Fig. 10, naturally α does not change depending on the roll diameter, and is always 0°.

Tables 2 and 3 show the results when the electrodes were arranged as shown in FIGS. 10 and 11, respectively, and the large-diameter roll and the small-diameter roll were subjected to electrical discharge machining. The electrodes were arranged in three stages in the row of four electrodes in each row in the circumferential direction of the roller. The electrodes used for the test were flat electrodes shown by symbol f in Table 1. In the electrode arrangement shown in FIG. 11 shown in Table 3, each electrode was positioned at an intersecting angle α with the small-diameter roller in the range of 2° to 5°.

In the change of the roll diameter in the table, for example, "600→500" indicates that the roll with a diameter of 500 mm is processed after the roll with a diameter of 600 mm is processed. Machining roughness means that electrical discharge machining was performed under the condition that the center line average roughness (Ra) was the value indicated. As the working liquid, the same working liquid as in Example 1 was used. The evaluation in each test was carried out by observing the surface of the roll after a certain period of time had elapsed from the start of machining, and whether or not spiral machining streaks due to concentrated discharge were seen. ○ means the case where no processing streaks were seen, and × means the case where the processing streaks were seen.

Table 2

table 3

When the electrodes were arranged toward the axis of the roll as shown in Fig. 10, as shown in Table 2, even if the machined roll diameter was changed, no spiral machining marks could be confirmed in all tests, which was a good result.

On the other hand, in the case where the electrodes are arranged to be inclined from the direction toward the axis of the roll as shown in FIG. Check the traces of spiral processing. It is considered that the bad result when the machining roughness is finer is that the finer the roughness is, the smaller the gap between the electrode and the roller is, and the unevenness of the flow of the machining fluid significantly affects the machined surface. In machining with rough roughness, it is estimated that because the gap between the electrode and the roller is wide, even if the flow of the machining fluid is not uniform, the machining powder can be sufficiently discharged from the gap.

As mentioned above, although the aspect suitable for this invention was demonstrated, this invention is not limited to the aspect demonstrated above. For example, the flat shape of the projected surface of the electrode tip is preferably an ellipse, but may be a rectangle.

Claims (9)

1. electrode use in a discharge processing, have can from the inner chamber of the opposed front end outflow of machined object working fluid, it is characterized in that,

The end face of electrode front end on the electrode perspective plane of projection on the face vertical with the electrode length direction, is removed area corresponding to the part in the hole of this inner chamber at 70mm ²Below, 10mm ²More than, and the end face of electrode front end to have ratio L/T with the length T of maximum length L on this perspective plane and perpendicular direction be shape more than 1.5.

2. a roller discharging processing machine has one or more electrode that disposes with the roller subtend, it is characterized in that,

This electrode has can make the inner chamber of working fluid from flowing out with the opposed front end of roller, this electrode is configured to the end face of electrode front end on the electrode perspective plane of projection on the face vertical with the electrode length direction, removes area corresponding to the part in the hole of this inner chamber at 70mm ²Below, 10mm ²More than, and the end face of electrode front end to have ratio L/T with the length T of maximum length L on this perspective plane and perpendicular direction be flat pattern more than 1.5, and the maximum length L on the described perspective plane axially parallel of roller therewith.

3. discharging processing machine as claimed in claim 2 is characterized in that, described electrode is configured to the axle center of the length direction of electrode towards roller.

4. as claim 2 or 3 described discharging processing machines, it is characterized in that having two the above electrodes, these electrodes form multiple row at the circumferencial direction of roller, are configured to zigzag.

5. the discharge-treating method of a roller uses the described discharging processing machine of claim 2, it is characterized in that,

By on one side working fluid being flowed out from described inner chamber, Yi Bian make roller and electrode at the circumferencial direction of roller with axially relatively move, thus the pair roller processing of discharging twist.

6. the discharge-treating method of a roller uses the described discharging processing machine of claim 3, it is characterized in that,

By on one side working fluid being flowed out from described inner chamber, Yi Bian make roller and electrode at the circumferencial direction of roller with axially relatively move, thus the pair roller processing of discharging twist.

7. the discharge-treating method of a roller uses the described discharging processing machine of claim 4, it is characterized in that,

By on one side working fluid being flowed out from described inner chamber, Yi Bian make roller and electrode at the circumferencial direction of roller with axially relatively move, thus the pair roller processing of discharging twist.

8. discharge-treating method as claimed in claim 7 is characterized in that,

Rotary speed by adjusting described roller and/or described electrode be to the axial feed rate of roller, with not residual by the processing of discharging of the mode pair roller in the zone of discharge processing.

9. as each described discharge-treating method in the claim 5～8, it is characterized in that described roller is matt finishing roll.

Images