TWI825238B - Drilling device and drilling method - Google Patents

Abstract

[Problem] An object of the present invention is to reliably detect breakage of a drill bit during drilling using a drill bit whose entire tip portion is covered with an insulator such as a diamond coating. [Solution] A drilling processing device is provided with a motor-integrated spindle, and a drill bit installed on the rotor shaft of the spindle is used to drill a workpiece placed on a table. It is characterized in that the drilling processing device has : a capacitance change detection unit that detects a change in capacitance of a capacitor between an electrode provided on the fixed side of the main shaft and electrostatically coupled to the rotor shaft and the ground, and the capacitance of the capacitor is detected using the electrode; and, the control unit, The capacitance change detection unit detects the time point at which the capacitance changes and determines that the drill bit is broken.

Description

Drilling device and drilling method

The present invention relates to a drilling processing device and a drilling processing method, which use a drill to drill holes in, for example, a printed circuit board.

As the drill bit breakage sensing function of drilling processing equipment, there is currently a method called DBDD (Direct Broken Drill Detection), which directly detects the physical properties of the drill bit at the moment before the drill bit contacts the workpiece during processing. damaged. This method is disclosed in Patent Document 1, for example. In a structure for pressing a printed circuit board, a light-emitting part for projecting light and a light sensor for receiving light from the light-emitting part are installed. The drill bit on the optical axis blocks light from the light sensor to detect drill bit breakage. The disadvantage of this method is that because of its structure, the optical axis between the light-emitting part and the light sensor is formed at a certain distance from the front end of the drill bit, so it cannot be detected when the drill bit is broken due to tiny cracks at the front end. If the punching operation is performed in a broken state, the surface of the printed circuit board may be damaged or incomplete holes may be formed.

As a method to solve the shortcomings of the above method, there is a method called TBDD (Touch Broken Drill Detection), which detects physical breakage of the tool at the point when the tool contacts the workpiece during machining. This method is disclosed in Patent Document 2, for example. When the drill bit comes into contact with the printed circuit board of the processing object, the axis voltage generated on the rotor shaft of the spindle is detected by conducting the shaft voltage from the conductive drill bit to the workpiece, and The breakage of the drill bit is sensed by comparing the difference between the detection position and the reference position.

In addition, for example, the method disclosed in Patent Document 3 detects the capacitance change of the capacitor between the ground and the ground, and compares the normality of the position of the drill bit against the workpiece with the reference position to determine the drill bit breakage. The capacitance of the capacitor is Detected by electrodes electrostatically coupled to the rotor shaft. In this method, every time a drill bit is installed on the spindle, the movement of the drill bit's normal reference position needs to be known in advance, which will make the determination of drill bit breakage more complicated. Moreover, if this method is used, a predetermined width must be set as the reference position, but this width may also cause misjudgments. [Known technical documents] [Patent Document]

[Patent Document 1] U.S. Patent No. 3912925 Specification [Patent Document 2] Japanese Patent Application Publication No. 2001-341052 [Patent Document 3] Japanese Patent Application Publication No. 2015-223685 [Patent Document 4] Japanese Patent Application Publication No. 2003-1509

[Problem to be solved by the invention] Recently, in order to extend the service life of drill bits, an increase in the number of drill bits that cover the entire tip of the drill bit with a diamond coating that acts as an insulator. When using this type of drill, even if the drill contacts the printed circuit board, the shaft voltage generated on the rotor shaft of the spindle will not be transmitted to the workpiece, so the method of Patent Document 2 cannot be used. Therefore, an object of the present invention is to reliably detect breakage of the drill bit during drilling using a drill bit whose entire tip portion is covered with an insulator such as a diamond coating.

[Technical means to solve the problem] In order to solve the above problems, in the invention disclosed in this application, a typical drilling processing device is equipped with a motor-integrated spindle, and a drill bit installed on the rotor shaft of the spindle is used to drill holes into the workpiece placed on the table. The drilling processing device is characterized in that it is provided with: a capacitance change detection unit that detects the capacitance change of a capacitor between an electrode provided on the fixed side of the main shaft and electrostatically coupled with the rotor shaft and the ground, and the capacitance of the capacitor is as described above. Electrode detection; and a control unit that determines that the drill bit is broken at the time when the capacitance change detection unit detects the capacitance change.

Furthermore, in the invention disclosed in this application, the representative drilling method is to use a drill bit installed on the rotor shaft of the motor-integrated spindle to drill the workpiece placed on the table. It is characterized by: When the drill bit is broken and the metal part of the broken part comes into contact with the workpiece, the change in capacitance of the capacitor between the electrode provided on the fixed side of the spindle and electrostatically coupled to the rotor shaft and the ground is detected, and the drill bit is determined to be damaged.

In addition, although the representative features of the invention disclosed in this application are as described above, features not described here are also applicable to the embodiments described below and are also shown in the scope of the patent application.

[Invention effect] According to the present invention, drill bit breakage can be reliably sensed during drilling processing using a drill bit whose entire body is covered with an insulator such as diamond coating.

Example FIG. 1 is a diagram showing the structure of a drilling device according to the present invention. Each component or connecting line in FIG. 1 mainly represents the necessary components for explaining this embodiment, and does not represent all necessary components of the drilling processing device. 1 in Figure 1 is a printed circuit board that needs to be punched, 2 is a processing table on which the printed circuit board 1 is placed, and 4 is a drill. The processing table 2 is driven in the horizontal direction by the table driving part 5 and is positioned so that the drill bit 4 faces the position where the printed circuit board 1 is to be punched. 6 is a spindle for rotating the drill bit 4 . The spindle 6 is integrated with the motor driven by the inverter 7 . 8 is a spindle unit that holds the spindle 6 and is driven in the vertical direction by the spindle vertical drive unit 9 . In the drill 4 here, as shown in FIG. 2 , the entire surface of the metal portion 4 a of the drill tip portion is covered with a diamond coating 4 b as an insulator.

Returning to FIG. 1 , 3 a is a conductive sheet placed on the printed circuit board 1 , which plays a role in improving the engagement of the drill bit 4 with the printed circuit board 1 and preventing the occurrence of burrs. 3b is a bottom plate for preventing the drill bit 4 from penetrating the printed circuit board 1 and contacting the processing table 2. The workpiece here is the printed circuit board 1, the conductive sheet 3a and the base plate 3b sandwiching the printed circuit board 1, but the conductive sheet 3a and the base plate 3b are not essential.

On the lower side of the spindle 6, a presser foot 12 for pressing the workpiece containing the conductive sheet 3a against the processing table 2 during punching processing is engaged with the spindle unit 8 through the cylinder 13. When the hole processing is started, the processing table 2 is positioned so that the hole position can be processed, and the spindle unit 8 is lowered from the state in the figure. The spindle unit 8 and the presser foot 12 are engaged while maintaining a predetermined distance in the vertical direction. When the spindle unit 8 descends, the presser foot 12 descends together with the spindle unit 8 until it contacts the surface of the conductive sheet 3a.

After the presser foot 12 contacts the surface of the conductive sheet 3a, the presser foot 12 stops at this position, and the engagement state is shifted and only the spindle unit 8 descends, that is, the drill 4 can be used to drill holes. When a hole is completed, the spindle unit 8 is raised, but at this time the presser foot 12 is also raised. When the next hole position is to be processed, the processing table 2 is positioned so that the hole position can be processed, and the spindle unit 8 is lowered, but at this time, the presser foot 12 is also lowered together as before.

14 is a deflection detector, which is composed of a sensor 15 fixed to the spindle unit 8 and a rod 16 fixed to the presser foot 12 . When the offset detector 14 lowers the spindle unit 8, the presser foot 12 will contact the surface of the conductive sheet 3a, and the presser foot 12 alone cannot continue to lower, and detects the engagement of the spindle unit 8 and the presser foot 12. When the states deviate from each other in the vertical direction, the offset detection signal S is output. 17 is a resonance detection unit, which will be described in detail later, and detects the resonance occurring in the capacitor existing in the spindle 6 , and the resonance detection signal R is transmitted from here to the overall control unit 18 .

The overall control unit 18 controls the entire drilling processing device, and is internally provided with a spindle drive control unit 19 that uses the feed position information from the spindle vertical drive unit 9 to identify the current height position of the front end of the drill bit 4 and controls the spindle vertical drive. part 9; the table drive control part 20 uses the feed position information from the table drive part 5 to identify the two-dimensional position of the processing table 2, and controls the table drive part 5; and the surface height memory part 21 to offset When the movement detector 14 detects the offset detection signal S, it detects the surface height of the conductive sheet 3a based on the feed position information from the spindle vertical driving part 9 and stores it in memory. The spindle drive control unit 19 uses the detected surface height of the conductive sheet 3a as a reference to control the depth when drilling a blind hole, or uses the technology disclosed in Patent Document 4 (paragraph 0004) to control the depth before and after the drill bit 4 contacts the conductive sheet 3a. Switch the feed speed of spindle unit 8.

The overall control unit 18 has control functions other than those described here, and is connected to blocks not shown in the figure. The overall control unit 18 is configured around a processing device controlled by a program, for example, and each component or connection line also includes a logical component. In addition, a part of each component may be provided separately from the overall control unit 18 .

FIG. 3 is a diagram for explaining the relevant parts of the electronic system of the spindle 6 in FIG. 1 . In Figure 3, the spindle 6 that rotates the drill bit 4 is integrally formed with the motor driven by the inverter 7. The rotor of the motor is the rotor shaft 22 on which the drill bit 4 is installed. 23 is used for electrostatic coupling with the rotor shaft 22 and close to the rotor. The shaft 22 has an electrode mounted on the fixed side of the spindle 6 and is also the terminal of a capacitor sensed to ground. The resonance detection unit 17 detects the resonance occurring in the capacitor via the electrode 23 .

FIG. 4 is a circuit diagram for explaining the resonance detection unit 17 in FIG. 3 . In Figure 4, 25 is a capacitor detected between electrode 23 and ground, 26 is a transformer whose secondary side is connected to capacitor 25 through electrode 23; 27 is an oscillation circuit that oscillates alternating current, and the frequency of the alternating current is When the capacitance of the capacitor 25 is small, parallel resonance will occur; 28 is a resonance detection circuit, which outputs a resonance detection signal R when a parallel resonance occurs in the capacitor 25 and a huge change in the voltage on the primary side of the transformer 26 is detected. When the entire surface of the metal portion 4a of the drill tip portion is covered with the diamond coating 4b as an insulator and the drill 4 is not damaged and is in contact with the conductive sheet 3a, the capacitance of the capacitor 25 becomes larger. However, as shown in Fig. 5 When the diamond coating 4b of the broken part is peeled off and the metal part 4a is in contact with the conductive sheet 3a, the capacitance becomes smaller.

In the above structure, the drilling operation is that the spindle unit 8 is lowered and the drill bit 4 contacts the conductive sheet 3a to perform drilling. In this case, if the entire surface of the metal portion 4a of the drill tip portion is covered with a diamond coating 4b as an insulator and is not broken, the capacitor 25 detected by the electrode 23 will not be damaged even if it contacts the conductive sheet 3a. The capacitance causes resonance so no abnormality is sensed. However, if the drill bit 4 is broken, the metal part 4a of the drill bit 4 contacts the conductive piece 3a, which will reduce the capacitance of the capacitor 25 and cause resonance. The resonance detection circuit 28 will detect the occurrence of resonance, and the resonance detection signal R will be sent to the whole body. Control unit 18. Once the overall control unit 18 receives the resonance detection signal R from the resonance detection unit 17, it will determine that the drill bit 4 is damaged, and then raise the spindle 6 to stop the drilling operation.

According to the above embodiment, it is not necessary to say that the drill bit is broken in the center of the drill tip. Even if a slight crack occurs at the tip, the capacitance will change when the metal part 4a of the drill bit 4 contacts the conductive sheet 3a, so it can be immediately determined. Broken drill bit. In addition, since each time a drill bit is installed on the spindle, there is no need to know the redundant movement of the drill bit's normal reference position in advance, which makes the determination and processing of drill bit breakage simpler. And since there is no need to compare with a reference position of a predetermined width, there is no need to worry about misjudgment.

In addition, in the existing method of comparing the normality of the position where the drill bit contacts the workpiece with the reference position, it is impossible to detect breakage of the drill bit while the drill bit is inserted into the workpiece. Therefore, there is a disadvantage that processing is continued with a broken drill bit, thereby enlarging the unprocessed portion. According to the above embodiment, although it also depends on the composition of the workpiece, the capacitance of the drill bit will change when it is damaged during processing, so the punching operation can be stopped at that time point. Therefore, processing will not be continued with a broken drill bit, and the expansion of poorly processed parts can be prevented.

Although the present invention has been specifically described based on the embodiments above, the present invention is not limited to the above-mentioned embodiments, and various changes can be made without departing from the scope of the gist, and various modifications are included. For example, in the above-mentioned embodiment, the resonance detection part 17 uses the transformer 26 with the secondary side connected to the capacitor 25. However, the inductor may be connected in series to the capacitor 25 to form a series resonance circuit, and the metal part 4a of the drill bit 4 may be used. The conductive piece 3a is contacted and the series resonance caused by the decrease in capacitance is detected.

In addition, in the above embodiment, although resonance is caused in the capacitor 25 to detect the pattern of capacitance change, the capacitance change can also be detected using a method that does not cause resonance. For example, the alternating current may be supplied to the capacitor 25 and the voltage at both ends thereof may be monitored. After the capacitance of the capacitor 25 is reduced due to the contact between the drill bit 4 and the conductive sheet 3a, the decrease in the voltage at both ends may be detected. In addition, in the above embodiment, although the conductive sheet 3a is placed on the printed circuit board 1, the conductive layer is formed on the inner layer of the printed circuit board 1 without placing the conductive sheet 3a. When the metal part 4a of the drill bit 4 contacts The capacitance of the capacitor 25 also changes when the substrate 1 is printed, and drill bit breakage can be sensed.

1: Printed substrate 2: Processing table 3a: Conductive sheet 3b: Bottom plate 4:Drill bit 4a:Metal Department 4b:Diamond coating 5: Desk drive department 6: Spindle 7:Inverter 8: Spindle unit 9:Spindle vertical drive part 12: Presser foot 13:Cylinder 14:Offset detector 17: Resonance detection department 18:Overall Control Department 19:Spindle drive control department 20: Desk drive control department 21: Surface height memory part 22:Rotor shaft 23:Electrode 25:Capacitor 26:Transformer 27: Oscillation circuit 28: Resonance detection circuit S: Offset detection signal R: Resonance detection signal

FIG. 1 is a diagram showing the structure of a drilling processing device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the structure of a drill bit used in the drilling device of FIG. 1 . FIG. 3 is a diagram for explaining the relevant parts of the electronic system of the spindle in the drilling processing device of FIG. 1 . Figure 4 is a circuit diagram used to illustrate the resonance detection section in Figure 3. FIG. 5 is a diagram showing a state in which a broken drill bit contacts a workpiece in one embodiment of the present invention.

1: Printed substrate

2: Processing table

3a: Conductive sheet

3b: Bottom plate

4:Drill bit

5: Desk drive department

6: Spindle

7:Inverter

8: Spindle unit

9:Spindle vertical drive part

12: Presser foot

13:Cylinder

14:Offset detector

15: Sensor

16: Rod body

17: Resonance detection department

18:Overall Control Department

19:Spindle drive control department

20: Desk drive control department

21: Surface height memory part

R: Resonance detection signal

S: Offset detection signal

Claims (10)

A drilling processing device is provided with a motor-integrated spindle, and a drill bit installed on the rotor shaft of the spindle is used to drill a workpiece placed on a table. It is characterized in that the drilling processing device is equipped with: capacitance change detection a unit that detects changes in capacitance of a capacitor between an electrode provided on the fixed side of the main shaft and electrostatically coupled to the rotor shaft and ground, and the capacitance of the capacitor is detected using the electrodes; and a control unit that uses the change in capacitance to detect The drill bit is determined to be damaged at the time point when the change in capacitance is detected. The drill bit has a metal part and an insulating coating covering the entire surface of the metal part. A damaged part where part of the insulating coating has been peeled off exists in the drill bit. In this case, the capacitance change detection unit detects the change in capacitance. The drilling processing device according to claim 1, further comprising a deflection detection unit for detecting the deflection of the engagement state between the presser foot used to press the workpiece on the table and the spindle unit holding the spindle. When the offset is detected by the offset detection unit, the surface height of the workpiece is detected. The drilling processing device according to claim 1, wherein the capacitance change detection part causes resonance in a circuit including the capacitor when the drill bit is broken and the metal part of the broken part contacts the workpiece, to detect changes in capacitance. In the drilling processing device described in claim 1 of the patent application, the drilling operation is stopped at the time when the capacitance change is detected. The drilling processing device according to claim 1, wherein the surface position of the workpiece is detected when the presser foot for pressing the workpiece on the table comes into contact with the workpiece. A drilling processing method that uses a drill bit installed on the rotor shaft of a motor-integrated spindle and having a metal part and an insulating coating covering the entire surface of the metal part to drill holes into a workpiece placed on a table. Its characteristics are: When the metal part of the broken part of the drill bit is broken and part of the insulating coating is peeled off comes into contact with the workpiece, the capacitor between the electrode provided on the fixed side of the spindle and electrostatically coupled to the rotor shaft and the ground is detected. At the time when the capacitance changes, the drill bit is determined to be damaged. The drilling processing method described in Item 6 of the patent application, wherein when a deviation in the engagement state between the presser foot used to press the workpiece on the table and the spindle unit holding the spindle is detected, The surface height of the aforementioned workpiece. The drilling processing method described in claim 6, wherein when the drill bit is broken and the metal part of the broken part contacts the workpiece, resonance is caused in the capacitor to detect changes in capacitance. In the drilling processing method described in Item 6 of the patent application, the drilling operation is stopped at the time point when the capacitance change is detected. The drilling processing method described in item 6 of the patent application, wherein the aforementioned insulating coating is a diamond coating.