JPH042468A - Cut-off grinding device - Google Patents

Abstract

PURPOSE:To form the shapes of the side face and tip of a thin bladed cutting grindwheel in a high accuracy, by providing a set up protection circuit which cuts off the set up circuit detecting a grinding contact origin at the feeding time of an electric discharging liquid. CONSTITUTION:An electric discharging liquid solenoid valve 11 is opened by turning on an electric discharge liquid feeding switch and an electric discharge liquid is fed between a grindwheel 1 and electrodes 5a, 5b. A set up protection circuit 13 is actuated by opening this electric discharge liquid solenoid valve 1 and the structure that high voltage is not impressed on the set up detection circuit 12 is made. Also, an electric discharge power source 15 is made so as to be turned on only when the electric discharge liquid solenoid valve 11 is in an open state. Consequently, an air bearing does not cause seizure, etc., by electric discharging.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a grinding and cutting device that is capable of truing a grinding wheel on a grinding cutting machine that uses a conductive cutting wheel.

(Prior art) Machining of hard brittle materials such as ferrite used in electronic components such as magnetic heads requires high dimensional accuracy, and in particular, the surface runout of the side surface of the grinding wheel and the shape of the tip of the cutting edge of the grinding wheel are particularly important when processing hard brittle materials such as ferrite used in electronic components such as magnetic heads. The influence on machining accuracy is extremely large. Regarding the processing and forming of this type of whetstone, please refer to Japanese Patent Application Laid-Open No. 51-93493.
There is a technique disclosed in the publication No. Furthermore, regarding a grinding and cutting device that performs truing of the grindstone on a grinding and cutting machine, there is a technique disclosed in Japanese Patent Application No. 131053/1983.

(Problems to be Solved by the Invention) The invention of JP-A No. 51-93493 discloses that processing and forming of a diamond grinding wheel, such as truing and dressing of a diamond grinding wheel, requires
A general grindstone in the shape of a rectangular rod called a stick is pressed against the formed grindstone surface to be processed, or a green carborundum grindstone (abbreviated as GC) is attached to a brake dresser or the like and brought into contact with each other. Therefore, in order to precisely process the side surface or tip shape of the thin-blade conductive cutting grindstone used for processing electronic components, processing and forming without applying contact pressure is required. Patent application 1986-131053
It was created in response to Invention Request No. 31053,
The present invention further includes an electric discharge machining device suitable for truing the side surface or tip shape of a thin-bladed conductive cutting wheel with high precision and for protecting a circuit for setting up the conductive cutting wheel from high voltage discharge voltage. The object of the present invention is to provide a grinding and cutting device.

(Means for Solving the Problems) The above object is to provide a circuit that detects the origin of grinding contact between a rotating conductive grindstone and a workpiece, and a circuit that sandwiches the grindstone from both sides and connects a pair of conductive wheels parallel to the grindstone surface. a power supply device for applying a discharge voltage between an electrode made of a flexible plate-like body and the grinding wheel; a means for supplying electrical discharge machining fluid between the grinding wheel and the electrode; A set-up protection circuit is provided to cut off a set-up circuit for detecting the origin of grinding contact, and a cross section of the electrode facing the side surface of the tip of the grinding wheel has a slope that widens toward the cutting direction of the grinding wheel, and during the electrical discharge machining, This is achieved by a grinding and cutting device having a control device that calculates and controls the feeding speed of the electrode relative to the grindstone so that the gap between the side surface of the electrode and the tip of the grindstone becomes a constant size.

(Function) With the above configuration, when processing with a conductive grindstone,
The set-up circuit is prevented from being burnt out due to the application of high voltage, and the mutual positions of the electrode and the grinding wheel are accurately set;
It is possible to improve the shaping accuracy of the side or tip of the grindstone.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of a grinding and cutting device 20 according to the present invention. In the figure, there is a spindle 3 supported by an arm 2 that rotates in the direction of arrow A around a support shaft 2a, and a thin-blade conductive grindstone (hereinafter abbreviated as grindstone) 1 is connected to the spindle 3 through an insulating sleeve (not shown). It is fixed to a flange 3a provided at the tip of the flange 3a. The spindle 3 is rotationally driven by a direct motor (not shown), and is preferably supported by an air bearing.

On the work table 9 of the grinding and cutting device 20, there is a chuck table 7 for fixing the workpiece through an insulating plate 8.
is attached. The chuck table 7 is preferably a vacuum chuck or an electromagnetic chuck. The electrodes 5a and 5b are fixed on the chuck table 7 via an electrode holding jig 5 in parallel to the feeding direction (arrow X direction) of the work table 9, and are fixed on the chuck table 7 via an electrode holding jig 5.
and 5b.

A machining fluid supply nozzle 4 includes a grinding fluid solenoid valve 10 that adjusts the supply amount of the machining fluid for grinding and cutting, and a discharge fluid solenoid valve 11 that adjusts the supply amount of the electrical discharge machining fluid. Claim 1
The described means for supplying the electrical discharge machining fluid between the grinding wheel and the electrodes refers to, for example, the electrical discharge machining fluid supply pipe 17, the discharge fluid solenoid valve 11, the machining fluid supply nozzle 4, and the unillustrated fluid supply tank in the embodiment. .

Reference numeral 6 denotes a set-up position detection unit for the grinding wheel L, 12 a set-up detection circuit, 13 a set-up protection circuit, and 14 a control device that controls the feed of the work table 9 of the grinding and cutting device 20 (
(arrow X direction and anti-X direction), spindle 3b feed (arrow Y direction and anti-Y direction), infeed feed (counter-arrow Z direction)
And, the rotation of the spindle 3 is controlled respectively. The spindle 3 is electrically connected via a carbon brush, and power is supplied from the electric discharge machining power source 15 when the grindstone 1 is set up. The other end of the electrical discharge machining power supply 15 is connected to the electrical discharge electrodes 5a and 5b.
It is connected to the.

In the above configuration, the grinding wheel 1 is attached to the flange 3a,
When the spindle 3 is rotated and the setup setting switch of the control device 14 is turned on, the spindle 3 rises in the direction of arrow Z, and then changes to the position of the setup detection section 6.
After moving the work table 9 in the counter-arrow X direction and the spindle 3 in the counter-arrow Y direction, or in the counter-Y direction depending on the position at the start of the setup operation, rotate the arm 2 and lowering it in the counter-arrow Z direction. As a result, the grinding edge of the grindstone 1 comes into contact with the setup detection section 6, and the origin is detected. The arm 2 rotates, and the spindle 3 moves in the direction of arrow Z again until it reaches the specified position.
By rising in the direction, the origin detection operation is completed.

Next, the chuck table 7 installed on the work table 9
A dummy material is placed on top, a predetermined cut is made and grooved using the grindstone 1, and the width of the grindstone 1 is detected by a microscope observation device (not shown) and displayed on a monitor.

Next, the electrode holding jig 5 placed on the chuck table 7
The electrodes 5a, 5b attached above are displayed on a monitor using the microscope observation device, and the electrodes 5a, 5b are adjusted to maintain an appropriate spacing corresponding to the detection width of the grinding wheel 1 using the electrode spacing adjustment screw. Adjust.

Subsequently, by turning on an electric discharge machining liquid supply switch (not shown), the electric discharge liquid solenoid valve 11 is opened, and electric discharge machining liquid is supplied between the grinding wheel 1 and the electrodes 5a and 5b. When the discharge liquid electromagnetic valve 11 opens, the setup protection circuit 13 is activated and high voltage is not applied to the setup detection circuit 12. Further, the electric discharge machining power source is turned on only when the spindle 3 is rotating and the electric discharge liquid electromagnetic valve 11 is in an open state. Thereby, when the spindle 3 is in a stopped state, consideration is given to preventing the air bearing from seizing due to electrical discharge.

Electrodes 5a set at predetermined intervals by electrode holding jig 5
, 5b, and lower the grinding wheel l to a predetermined cutting depth with respect to the electrodes 5a and 5b.
Move the work table 9 in the opposite direction of the arrow X.

The electrical discharge machining voltage and the gap between the electrodes 5a, 5b and the grinding wheel 1 are as follows:
Electric discharge machining is started based on the initial setting value, changes in the discharge voltage accompanying the feeding of the work table 9 are detected, and the electrode 5
The relative movement speed between the grindstone 1 and the electrodes 5a, 5b is calculated and controlled by the control device 14 so that the gaps between the grindstone 1 and the grindstone 1 are maintained at a constant value.

As the shaping of the grinding wheel 1 progresses through the electrical discharge machining,
When the electrodes 5a and 5b themselves are worn out and the distance between the electrodes becomes wider, the discharge voltage increases and becomes close to the initially set discharge voltage, so the electrode feeding speed is increased.

Further, as the electrodes 5a and 5b are fed, the gap between the unused portions of the electrodes and the side surface of the grindstone 1 becomes narrower, and the discharge interval also becomes smaller, so that the discharge voltage decreases. At this time, if the feeding speed increases, the grinding wheel l and the electrodes 5a, 5b will come into contact and short circuit, so the electrodes 5a, 5b will move back, and when the predetermined voltage is reached, the electrode 58.5b will be moved again. send, electrode 5
The feed speed of the work table 9 is calculated and controlled so that the gaps between the grinding wheel 1 and the grinding wheel 1 are constant.
, 5b, so that the shaped shape of the grinding wheel I can be stably maintained.

The shape of the electrodes, especially when shaping the side surface of the grinding wheel 1, the thickness d of the electrodes 5a, 5b and the electrode 5 shown in FIGS. 4 and 5.
The surface runout of the side surface of the grindstone 1 is greatly influenced by the value of the inclination Δt/d of a and 5b. In the figure, T indicates the amount of protrusion of the cutting edge of the grindstone 1, and C indicates the amount of cut.

Fig. 2 is a characteristic diagram showing the relationship between the inclination of the electrode and the inclination of the side surface of the grinding wheel, and Fig. 3 is a characteristic diagram showing the relationship between the thickness of the electrode and the inclination of the side surface of the grinding wheel. big,
By reducing the thickness d, local wear of the cutting edge of the grinding wheel l due to concentrated discharge can be reduced. Furthermore, since the side surface of the grinding wheel 1 is gradually shaped by electric discharge, by increasing the electrode dimensions in the feeding direction (arrow X direction) of the work table 9, wear and deterioration of the electrodes 5a and 5b can be reduced. . FIGS. 8(a), (b), and (C) are enlarged views showing the front shapes of various grinding wheels 1 of this embodiment and the positional relationships between the electrodes 5a and 5b. Regardless, the gap between the grindstone 1 and the electrodes 5a, 5b gradually increases toward the cutting direction of the grindstone 1. Further, a preferable result has been obtained in which the thickness d of the electrodes 5a and 5b does not exceed about 0.5 mm.

The following description will be made based on the experimental results of this example.

(Experiment 1) The grindstone was shaped under the following processing conditions.

Whetstone material: Metal bond diamond (SDC800
) Grinding wheel thickness t = 0.3 mm Grinding wheel diameter D = 58 mm Grinding wheel tip protrusion T = 5th generation Grinding wheel rotation speed = 30000 r/min Electrode material: Copper electrode thickness d = o, 5 mm Electrode length Size = 20mm Voltage: DC 150V Pulse width = 2μm Pulse interval = 17μs Peak current = 0.8A The shaping results are: Inclination of the side surface of the grinding wheel before shaping = 10 μm 75 mm Inclination of the side surface of the grinding wheel after shaping: 2 μm 75 mm and a clear shaping effect was gotten.

Furthermore, similar shaping accuracy was obtained when the above experiment was conducted with the electrode slope being 20 μm/4 mm.

(Experiment 2) Grindstone material: Metal bond diamond (SDC800
) Thickness of the grinding wheel t = 0.3 Diameter of the grinding wheel D = 58 (Foundation) Amount of protrusion of the cutting edge of the grinding wheel T = 5 Number of revolutions of the grinding wheel = 3000 Or7min Material of the electrode:
Thickness of copper electrode d = 4 Inclination of working electrode = 20μffl/4 Length of taming electrode = 20 Voltage: DC 200V Working fluid: Tap water Shaping results are as follows: Flow rate 0.5Q/min ~ 1. For shaping at OQ/min,
Compared to the flow rate of 0.3Q/min, the electrical contact consumption is approximately 1
/3, the grindstone shaping efficiency was improved five times, and the shaping accuracy was at the same level as (Experiment Part 1).

(Experiment 3) Under the conditions of (Experiment 2), the machining fluid flow rate was set to IQ/m.
in, when the processing voltage is changed from 100V to 300V,
In the case of a voltage of 100V, compared to voltages of 150V and 200V, the electrode wear rate increases by about 1.5 times, but the surface runout accuracy on the side of the grinding wheel improves, and before shaping = lOμm 75M After shaping: 5μm) 75mm. Ta.

(Effects of the Invention) By carrying out the present invention, an electric discharge machining apparatus is provided that protects the circuit that sets up the machining origin using a conductive cutting wheel, and is suitable for shaping the side surface and tip of a thin-blade cutting wheel with high precision. A grinding and cutting device can be provided.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an embodiment of the grinding and cutting device according to the present invention, Fig. 2 is a characteristic diagram showing the relationship between the inclination of the electrode and the inclination of the side surface of the grinding wheel, and Fig. 3 is a diagram showing the relationship between the thickness of the electrode and the side surface of the grinding wheel. Fig. 4 is a diagram showing the positional relationship between the front of the grinding wheel and the electrode, Fig. 5 is a front view showing the shape of the shaped grinding wheel, and Fig. 6 is the flow rate of machining fluid and the electrode. FIG. 7 is a characteristic diagram showing the relationship between the wear rate and the applied voltage. FIG. be. 1... Thin blade conductive grindstone 2... Arm 2a...
Support shaft 3... Spindle 3a... Flange 4... Machining liquid supply no. 5... Electrode holding jig 5a, 5b... Electrode 6... Set-up position detection part 7... Chuck table lO...Grinding fluid solenoid valve 11...Discharge fluid solenoid valve 12...Set-up detection circuit 13...Set-up protection circuit 14...Control device 1 20...Grinding and cutting device 5... Electrical discharge machining power supply diagram 2

Claims (1)

[Scope of Claims] 1. A circuit that detects the origin of grinding contact between a rotating conductive grindstone and a workpiece, and a pair of conductive plate-shaped circuits that sandwich the tip of the grindstone from both sides and are parallel to the side surface of the grindstone. a power supply device for applying a discharge voltage between the grinding wheel and the electrode; means for supplying electrical discharge machining fluid between the grinding wheel and the electrode; A grinding and cutting device characterized by being equipped with a setup protection circuit that shuts off a setup circuit that detects a grinding contact origin. 2. The grinding and cutting device according to claim 1, wherein a gap between a portion where the tip of the grindstone and the electrode face each other gradually increases toward the cutting direction of the grindstone. 3. Grinding and cutting according to claim 2, wherein the tip of the grindstone has parallel side surfaces, and the cross section of the electrode facing the tip has a slope that widens toward the cutting direction of the grindstone. Device. 4. A control device that calculates and controls the feed rate of the electrode relative to the grindstone so that the gap between the side surface of the electrode and the tip of the grindstone becomes a constant size during the electrical discharge machining. Item 1. Grinding and cutting device according to item 1.