JPH0372420B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to electric discharge machining of a roll, which finishes the outer peripheral surface of a roll-shaped workpiece (hereinafter simply referred to as a roll) with a constant surface roughness by electric discharge machining. It is about the method.

[Prior art]

Conventionally, when finishing the surface of steel strip rolling rolls, especially cold rolling rolls, with a satin finish, a method has been used to create impressions on the roll surface by projecting hard metal particles such as shot or grit onto the polished roll surface. It was getting worse.

However, in recent years, attempts have been made to perform this type of machining by electrical discharge machining.

As is well known, electrical discharge machining involves interposing an insulating liquid, such as kerosene, between the electrode and the workpiece, and periodically applying a pulse voltage between the electrode and the workpiece. This is a method of machining a workpiece by causing electrical discharge.

By repeating such electrical discharge machining on the roll surface, rotating the roll in the circumferential direction, and at the same time gradually moving the electrode in the direction of the rotation axis of the roll, the roll surface will undergo a continuous spiral satin finish.
The roll surface can be covered with discharge marks. This is a method of uniformly applying a satin finish to the surface of the roll using electrical discharge machining.

The pear surface obtained in this way not only has a larger difference in unevenness and a much more regular shape than mechanical impressions made by metal particle projection, but the shape is also influenced by the manufacturing method and hardness of the roll. Zumata,
It has many advantages, such as the metal structure on the roll surface being hardened by electrical discharge, making it ideal for use as a rolling roll.

However, in recent roll processing methods,
In order to shorten processing time, processing using multi-segmented electrodes has come to be performed. In this way, when the number of divisions of a multi-segmented electrode becomes very large, in order to prevent the division processing efficiency from decreasing and to make the mechanical structure stable, it is necessary to A head column (hereinafter referred to as the head and column as one unit) is provided, and a split electrode is attached to each head column, and during machining, electrical discharge machining is performed while moving the plurality of head columns in the direction of the rotation axis of the roll. Methods of doing this have begun to be attempted.

Figure 1 is for explaining the conventional roll electric discharge machining method using multi-segmented electrodes.
57-57213 is a schematic configuration diagram showing an electric discharge machining apparatus disclosed in Publication No. 57-57213. In Fig. 1, 1 is a bed, 2 and 2' are bearings installed in the bed 1,
Reference numeral 3 denotes a roll of the workpiece supported horizontally by the bearings 2 and 2', 4 a keel for chucking one end of the roll 3, and 5 a roll rotation drive device installed on the bed 1, which 4 to rotate the roll 3 at a constant speed. Reference numeral 6 denotes a base, which is configured to be slidable on the bed 1 from side to side in the figure by the action of a column lateral feed drive device 7 and a feed screw 8. 9, 9' are head columns fixed on the base 6; 10, 10' are the head columns 9,
The electrode holders 11, 11' attached to the holder 9' are connected to the holders 10, 1 through the insulating plates 12, 12'.
With multiple electrodes installed at equal pitches at 0',
These electrodes 11, 11' are opposed to the roll 3 through a machining gap, and are made of copper plates having the shape shown in a perspective view in FIG. 2, and are also formed in the same shape. . 13 is a machining tank held on the roll 3; 14 is a machining fluid supplied into the machining tank 13 by a pump (not shown); the machining fluid 14 overflows from the machining tank 13;
It is configured so that it is passed through and supplied to the processing tank 13 again. Further, reference numerals 15 and 15' denote pulse power supply devices, which are connected to form a discharge between each of the electrodes 11 and 11' and the roll 3. In the figure, the positive electrode is connected to the electrodes 11 and 11', and the negative electrode is connected to the roll 3, but processing can also be performed in the reverse direction. Further, the main shaft feeding of the electrodes 11, 11' in the direction perpendicular to the processing surface of the roll 3 during rotation, that is, the feeding in the direction in which the electrodes 11, 11' approach the processing surface of the roll 3, is carried out by each head column 9. , 9' are performed independently.

In such a configuration, conventionally, electric discharge machining is performed by generating electric discharge between the roll 3 and the electrodes 11, 11' while rotating the roll 3 at a constant speed using the celery 4, and then moving the base 6 to the feed screw 8. The head columns 9, 9' are slid from side to side by the action.
I am trying to move it from side to side.

Conventionally, the movement of the head columns 9, 9' in the direction of the roll rotation axis (hereinafter referred to as head column machining feed) is controlled at a constant speed based on values determined experimentally or empirically, depending on the desired surface accuracy and roll diameter. is carried out, and regarding the moving distance, the electrodes 11,
11' is set equal to the mounting pitch in the direction of the roll rotation axis. Therefore, the machining time is the value obtained by dividing the electrode mounting pitch by the machining feed rate of the head column.

Next, the relationship between the finished surface roughness, roll diameter, and machining feed rate will be considered.

The concept of machining speed in satin finish processing is expressed as the surface area that can be completely finished to a satin finish per unit time. In other words, the larger the area of completely satin finished per unit time, the faster the processing speed becomes.

As shown in Fig. 5, the satin finish processing speed G when performing satin finish processing on the roll 3 rotating at a constant speed is as follows (1)
It is expressed by the formula.

G = π・D・W/T …(1) Here, G = Satin finishing speed (cm ² /min) D = Roll diameter (cm) W = Machining width (cm) T = Overall satin finishing time (min) Note that the processing width W corresponds to the width of the electrode 11.

Next, we conducted an experiment by setting the optimal electrical machining conditions for each finished surface roughness, as shown in Figure 6. The rougher the finished surface roughness (hereinafter simply referred to as surface roughness), the faster the processing speed. is early. From this figure 6, the surface roughness
If R ₀ is determined, the satin finishing speed G ₀ is uniquely determined.
That is, once the desired surface roughness is determined, the satin finishing speed is uniquely determined.

As shown in FIG. 7, the surface area S to be machined when the electrode 11 is fed for machining and satin finish is expressed by equation (2).

S=π・D・L…(2) Here, S: Machining surface area (cm ² ) L: Machining feed amount of the electrode 11 In other words, if the machining feed amount L of the electrode 11 is kept constant, the machining surface area S will be equal to the roll diameter. is proportional to. S and D
The relationship is shown in Figure 8.

In order to process and feed the electrode 11 by L (one-way feed) and perform satin finish on the entire surface area of that part, the process feed rate V (cm/min) of the electrode 11 is expressed by equation (3).

V=L/S/G=L・G/S...(3) In other words, since the machining feed amount L is constant and the satin finish machining speed G is also constant once the desired surface roughness is determined,
The machining feed rate V is inversely proportional to the machining surface area S. Also, since S=π・D・L according to equation (2), V=L・G/π・D・L=G/π・D=K _R ×1/D
...(4) Here, K _R : A constant uniquely determined by the desired surface roughness. In other words, once the desired surface roughness is determined, the electrode 11
The machining feed rate V is inversely proportional to the roll diameter D. D
The relationship between V and V is expressed in a graph as shown in FIG.

From the above, the machining feed rate of the electrode 11, that is, the machining feed rate of the head columns 9, 9' is:
It should be determined for each roll according to the surface roughness and roll diameter, but since there was no way to automatically measure the roll diameter in the past, roll diameters may differ for rolls of the same type. Constant speed feed control was performed at the same speed. For this reason, the machining feed rate was not necessarily the optimum speed corresponding to the roll diameter.

[Summary of the invention]

The present invention was invented in view of this situation, and it automatically measures the roll diameter, calculates the machining feed rate of the head column based on this roll diameter and the desired surface roughness, and calculates the machining feed rate of the head column. The present invention provides a method for electrical discharge machining of a roll-shaped workpiece in which the workpiece is moved at a constant speed.

The method according to the present invention includes providing a plurality of head columns equipped with electrodes having a predetermined width facing a roll-shaped workpiece that rotates at a constant speed, and moving the plurality of head columns in the direction of the rotational axis of the roll-shaped workpiece. In the electric discharge machining method for a roll-shaped workpiece in which the outer peripheral surface of the roll-shaped workpiece is finished with a satin finish by moving the workpiece to The distance to the head column is read, the roll diameter is calculated based on the read value, and the moving speed of the head column roll in the direction of the rotation axis is calculated using the calculated roll diameter and the desired finished surface roughness. It is characterized in that the head column is moved at a constant machining feed rate.

In this way, the machining feed rate of the head column is calculated after calculating the roll diameter, so machining can be performed at the machining feed rate that is optimal for the roll diameter, eliminating wasted machining time and creating a uniform satin surface. You can get a roll of

[Embodiments of the invention]

This will be explained below based on the drawings. FIG. 3 is for explaining one embodiment of the present invention, and the same parts as in FIG. 1 are given the same reference numerals, and the explanation thereof will be omitted. In the figure, 16 is an absolute value reading device attached to the electrode feeding mechanism, that is, an absolute value reading counter, which reads the position where the electrodes 11, 11' contact the roll, that is, the discharge start position. 17 is an arithmetic circuit that calculates the roll diameter D from the value read by the absolute value reading counter 16, and further calculates the diameter of the head column using a constant K _R that is uniquely determined by the roll diameter D and the desired surface roughness. This is a circuit that calculates the processing feed rate V. The machining feed rate of the head column determined here is set in the drive device 7.

Next, the operation will be explained.

First, an absolute value reading counter attached to the electrode feeding mechanism reads the distance from the upper limit position of the electrode to the outer surface of the roll, and based on the read value, the arithmetic circuit 17 calculates the roll diameter D.

FIG. 4 is a diagram showing the principle of calculating the roll diameter. If the distance (fixed value) from the upper limit position of the electrode 11 to the roll center is "L", and the distance from the upper limit position of the electrode 11 to the outer surface of the roll 3 (discharge start position) is "l", then the roll diameter is D is 2(L
-l). Note that the same applies to the electrode 11'.

In other words, the roll diameter D has been automatically measured in the process up to this point.

Note that the value of L may be stored in advance in a memory included in the arithmetic circuit 17.

Next, the arithmetic circuit 17 calculates the machining feed rate V of the head column using the constant K _R that is uniquely determined by the roll diameter D calculated above and the desired surface roughness.
is calculated by the above-mentioned equation (4) V=K _R /D.

The constant K _R is calculated by G/π since the satin finishing speed _G is determined from FIG. It is sufficient to store it in the memory in advance and refer to the constant K _R for the desired surface roughness when calculating the machining feed rate V.

The roll diameter D is calculated as described above, and if the surface roughness is determined, the arithmetic circuit 17 calculates the machining feed rate V of the head column that is optimal for the calculated roll diameter D.
is calculated, and based on this, the drive device 7 moves the head columns 9, 9' along the roll 3 rotating at a constant speed at the machining feed rate V.

In other words, the head columns 9, 9' are fed at a constant speed at a machining feed speed that is optimal for the calculated roll diameter D.

〔Effect of the invention〕

According to the present invention, a plurality of head columns equipped with electrodes having a predetermined width facing a roll-shaped workpiece rotating at a constant speed are provided, and the plurality of head columns are moved in the rotational direction of the roll-shaped workpiece. In the electrical discharge machining method for a roll-shaped workpiece in which the outer peripheral surface of the roll-shaped workpiece is finished with a satin finish, first, the roll diameter is calculated, and when the surface roughness is constant, that is, the desired surface roughness is calculated. Once determined, the machining feed speed is fixed according to the roll diameter, so the smaller the roll diameter, the faster the machining speed, and the larger the roll diameter, the slower the machining time, and the time required for machining depends on the surface roughness and roll diameter. The required minimum time is eliminated, there is no wasted time, and rolls with a uniform pear surface can be obtained.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram for explaining the conventional method, Fig. 2 is a perspective view of the electrode, Fig. 3 is a schematic diagram for explaining the method according to the embodiment of the present invention, and Fig. 4 is a roll diagram. Principle diagram of diameter calculation, Figure 5 is an explanatory diagram for explaining satin finishing speed, Figure 6 is a graph showing the relationship between surface roughness and satin finishing speed, and Figure 7 is an explanation for explaining machined surface area. 8 is a graph showing the relationship between the roll diameter and the machining surface area, and FIG. 9 is a graph showing the relationship between the roll diameter and the machining feed rate. In the figure, 3 is a roll, 7 is a column traverse drive device, 9 and 9' are head columns, 11 and 11' are electrodes, 15 and 15' are pulse power supplies, 16 is an absolute value reading device, and 17 is an arithmetic circuit. . In addition,
In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A plurality of head columns equipped with electrodes having a predetermined width facing a roll-shaped workpiece rotating at a constant speed are provided, and the plurality of head columns are arranged in the direction of the rotational axis of the roll-shaped workpiece. In the electric discharge machining method for a roll-shaped workpiece, in which the outer peripheral surface of the roll-shaped workpiece is finished with a satin finish, an absolute value reading device installed in the electrode feeding mechanism is used to determine the discharge start position from the upper limit position of the electrode. The distance to the head column is read, the roll diameter is calculated based on the read value, and the moving speed of the head column roll in the direction of the rotation axis is calculated using the calculated roll diameter and the desired finished surface roughness. A method for electric discharge machining of a roll-shaped workpiece, characterized in that a head column is moved at a constant machining feed rate according to the moving speed determined by the machining process.