JP2021053792A - Drill processing device and drill processing method - Google Patents

Abstract

To surely detect breakage of a drill in drill processing using the drill in which the whole of a cutting edge part is covered with an insulator such as a diamond coating.SOLUTION: A drill processing device, which comprises a motor-integrated type spindle 6 and is configured to drill a work-piece 1 placed on a table 2 with a drill 4 that is mounted on a rotor shaft of the spindle, further comprises: an electrode provided at a stator side of the spindle, which is electrostatically coupled to the rotor shaft; a capacitance variation detecting part that detects variation of capacitance of a capacitor between an earth detected in the electrode and the part; and a control part 18 that determines that the drill is broken at the timing when the capacitance variation detecting part detects the variation of the capacitance.SELECTED DRAWING: Figure 1

Description

The present invention relates to a drilling apparatus and a drilling method for drilling, for example, a printed circuit board with a drill.

Conventionally, as a drill breakage detection function in a drilling apparatus, there is a function called DBDD (Direct Broken Drill Detection) that directly detects physical breakage of a drill immediately before the drill comes into contact with a workpiece during machining. For example, as disclosed in Patent Document 1, a light emitting portion for projecting light and an optical sensor for receiving light from the light emitting portion are mounted in a structure for holding the printed circuit board, and an optical axis connecting the two is attached. The breakage of the drill is detected by the degree of shading of the optical sensor by the drill located above.
The disadvantage of this method is that due to its structure, the optical axis between the light emitting part and the optical sensor is formed at a position a certain amount above the tip of the drill, so if the drill is a small chipping that breaks at the tip. It cannot be detected, and the drilling operation is performed in a broken state, which roughens the surface of the printed circuit board and causes non-through holes.

As a solution to the drawbacks of the above method, there is a method called TBDD (Touch Broken Drill Detection) that detects the physical breakage of the tool when the tool comes into contact with the workpiece during machining. This is detected, for example, as disclosed in Patent Document 2, when the axial voltage generated in the rotor shaft of the spindle is transmitted from the conductive drill to the work when the drill comes into contact with the printed circuit board to be machined. However, the breakage of the drill is detected by comparing the difference between the detected position and the reference position.

In addition, the change in the capacitance of the capacitor between the rotor shaft and the ground detected by the electrostatically coupled electrode is detected, the normality of the position where the drill contacts the workpiece is compared with the reference position, and the drill breakage is prevented. The determination method is disclosed in, for example, Patent Document 3.
In the case of this method, it is necessary to grasp the normal reference position of the drill in advance every time the drill is mounted on the spindle, which complicates the process of determining the breakage of the drill. Further, in the case of this method, it is necessary to provide a predetermined width as a reference position, and this width also causes an erroneous determination.

U.S. Pat. No. 3912925 Japanese Unexamined Patent Publication No. 2001-341052 JP-A-2015-223685

Recently, in order to improve the life of a drill, an increasing number of drill bites are covered with a diamond coating as an insulator. When this drill is used, the method of Patent Document 2 cannot be used because the shaft voltage generated in the rotor shaft of the spindle is not transmitted to the work even if the drill comes into contact with the printed circuit board.
Therefore, an object of the present invention is to reliably detect a drill breakage in a drilling process using a drill that covers the entire drill bit edge portion with an insulator such as a diamond coating.

In order to solve the above problems, among the inventions disclosed in the present application, a typical drilling apparatus is provided with a spindle integrated with a motor, and is placed on a table by a drill mounted on the rotor shaft of the spindle. In a drilling device for drilling a work piece, between an electrode provided on the stator side of the spindle that is electrostatically coupled to the rotor shaft and the ground detected by the electrode. It is characterized by including a capacitance change detecting unit for detecting a change in the capacitance of the capacitor and a control unit for determining that the drill is broken when the change in the capacitance is detected by the capacitance change detecting unit. ..

Further, among the inventions disclosed in the present application, a typical drilling method is to drill a work piece placed on a table by a drill mounted on a rotor shaft of a motor-integrated spindle. In the drilling method, when the drill is broken and the metal portion of the broken portion comes into contact with the workpiece, the electrode provided on the stator side of the spindle is electrostatically coupled to the rotor shaft. It is characterized in that it is determined that the drill is broken when a change in the capacitance of the capacitor with respect to the ground is detected.

The typical features of the invention disclosed in the present application are as described above, but the features not described here are applied to the examples described below, and are also included in the claims. As shown.

According to the present invention, breakage of a drill can be reliably detected in drilling using a drill whose entire surface is covered with an insulator such as a diamond coating.

It is a figure which shows the structure of the drilling apparatus which becomes one Example of this invention. It is sectional drawing which shows the structure of the drill used in the drilling apparatus of FIG. It is a figure for demonstrating the part related to the electric system of the spindle in the drilling apparatus of FIG. It is a circuit diagram for demonstrating the resonance detection part in FIG. It is a figure which shows the state which the broken drill is in contact with a work in one Example of this invention.

FIG. 1 is a diagram showing a configuration of a drilling apparatus based on the present invention. Each component and connecting line in FIG. 1 mainly show what is considered necessary for explaining this embodiment, and does not show all necessary for a drilling apparatus.
In FIG. 1, 1 is a printed circuit board to be drilled, 2 is a processing table on which the printed circuit board 1 is placed, and 4 is a drill. The processing table 2 is horizontally driven and positioned by the table driving unit 5 so that the drill 4 faces the position where a hole is to be drilled in the printed circuit board 1. Reference numeral 6 denotes a spindle for rotating the drill 4. The spindle 6 has a structure integrated with a motor driven by an inverter 7. Reference numeral 8 denotes a spindle unit for holding the spindle 6, which is driven in the vertical direction by the spindle vertical drive unit 9.
As shown in FIG. 2, the drill 4 here is formed by covering the entire surface of the metal portion 4a of the drill bit with a diamond coating 4b as an insulator.

Returning to FIG. 1, reference numeral 3 denotes a conductive sheet placed on the printed circuit board 1, which serves to improve the bite of the drill 4 to the printed circuit board 1 and prevent the occurrence of burrs and the like. .. Reference numeral 3b is a lower plate that prevents the drill 4 from penetrating the printed circuit board 1 and coming into contact with the processing table 2. The workpieces here are the printed circuit board 1, the conductive sheet 3a and the lower plate 3b that sandwich the printed circuit board 1, but the conductive sheet 3a and the lower plate 3b are not always necessary.

On the lower side of the spindle 6, a pressure foot 12 for pressing a workpiece including a conductive sheet 3a against the processing table 2 during drilling is engaged with the spindle unit 8 via a cylinder 13. When the drilling process 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 shown in the figure.
The spindle unit 8 and the pressure foot 12 are engaged with each other at a predetermined distance in the vertical direction, and when the spindle unit 8 is lowered, the spindle unit 8 is until the pressure foot 12 abuts on the surface of the conductive sheet 3a. It descends with.

When the pressure foot 12 comes into contact with the surface of the conductive sheet 3a, the pressure foot 12 stays at that position thereafter, the engaged state is displaced, and only the spindle unit 8 is lowered so that a hole can be drilled with the drill 4. ..
When one drilling is completed, the spindle unit 8 is raised, but at that time, the pressure foot 12 is also raised. When machining the next hole position, the machining table 2 is positioned so that the hole position can be machined, and the spindle unit 8 is lowered. In this case as well, the pressure foot 12 is also lowered as before. It has become.

Reference numeral 14 denotes a displacement detector composed of a sensor 15 fixed to the spindle unit 8 and a rod 16 fixed to the pressure foot 12. When the spindle unit 8 is lowered, the pressure foot 12 comes into contact with the surface of the conductive sheet 3a, and only the pressure foot 12 cannot be lowered any further. Therefore, the spindle unit 8 and the pressure foot 12 are engaged with each other. When it is detected that the combined states are displaced from each other in the vertical direction, the deviation detection signal S is output.
17 will be described in detail later, but is a resonance detection unit that detects that resonance has occurred in the capacitor existing in the spindle 6, and the resonance detection signal R from this unit is sent to the overall control unit 18.

The overall control unit 18 controls the entire drilling apparatus, and inside the overall control unit 18, the spindle vertical drive is performed while recognizing the current height position of the tip of the drill 4 based on the feed position information from the spindle vertical drive unit 9. The spindle drive control unit 19 that controls the unit 9, the table drive control unit 20 that controls the table drive unit 5 while recognizing the two-dimensional position of the machining table 2 based on the feed position information from the table drive unit 5, and the deviation detector. A surface height storage unit 21 is provided to detect the surface height of the conductive sheet 3a based on the feed position information from the spindle vertical drive unit 9 when the deviation detection signal S is detected in 14, and to store the surface height. There is.
The spindle drive control unit 19 controls the depth when a blind hole is drilled with reference to the detected surface height of the conductive sheet 3a, and is disclosed in Japanese Patent Application Laid-Open No. 2003-1509 (paragraph 0004). By adopting the technique, the feed rate of the spindle unit 8 is switched before and after the drill 4 comes into contact with the conductive sheet 3a.

The overall control unit 18 has a control function other than that described here, and is also connected to a block (not shown). The overall control unit 18 is configured around, for example, a program control processing device, and each component and connection line in the overall control unit 18 includes logical ones. Further, a part of each component may be provided separately from the overall control unit 18.

FIG. 3 is a diagram for explaining a portion of the spindle 6 related to the electrical system in FIG.
In FIG. 3, the spindle 6 for rotating the drill 4 is integrated with the motor driven by the inverter 7, and the rotor of the motor is the rotor shaft 22 on which the drill 4 is mounted. Reference numeral 23 denotes an electrode attached close to the rotor shaft 22 on the stator side of the spindle 6 for electrostatic coupling with the rotor shaft 22, and is also a terminal of a capacitor detected to and from the ground. The resonance detection unit 17 detects the resonance that occurs in the capacitor through the electrode 23.

FIG. 4 is a circuit diagram for explaining the resonance detection unit 17 in FIG.
In FIG. 4, 25 is a capacitor detected between the electrode 23 and the ground, 26 is a transformer whose secondary side is connected to the capacitor 25 via the electrode 23, and 27 is a frequency that causes parallel resonance when the capacitor of the capacitor 25 is small. The oscillation circuit 28 that oscillates the alternating current is a resonance detection circuit that detects that a parallel resonance occurs in the capacitor 25 and the voltage on the primary side of the transformer 26 changes significantly, and outputs a resonance detection signal R.
The capacitance of the capacitor 25 is large when a normal drill 4 without breakage covered with a diamond coating 4b whose entire surface of the metal portion 4a of the drill cutting edge portion is an insulator is in contact with the conductive sheet 3a. As shown in the above, when the diamond coating 4b of the broken portion is peeled off and the metal portion 4a is in contact with the conductive sheet 3a, the size becomes smaller.

In the above configuration, in the drilling operation, the spindle unit 8 is lowered and the drill 4 comes into contact with the conductive sheet 3a to perform the drilling operation. In this case, even if a normal drill 4 without breakage, in which the entire surface of the metal portion 4a of the drill cutting edge is covered with a diamond coating 4b as an insulator, comes into contact with the conductive sheet 3a, it is detected by the electrode 23. Since the capacitor 25 does not have a capacitance that causes resonance, no abnormality is detected.
However, when the drill 4 is broken, the metal portion 4a of the drill 4 comes into contact with the conductive sheet 3a, so that the capacitance of the capacitor 25 becomes small and resonance occurs, and the resonance detection circuit 28 detects that resonance has occurred. The resonance detection signal R is sent to the overall control unit 18.
When the overall control unit 18 receives the resonance detection signal R from the resonance detection unit 17, it determines that the drill 4 is broken, raises the spindle 6, and stops the drilling operation.

According to the above embodiment, the metal portion 4a of the drill 4 comes into contact with the conductive sheet 3a and the capacitance changes not only when the drill breakage occurs at the central portion of the drill bit edge portion but also when a small chipping occurs at the tip end. Therefore, it can be immediately determined that the drill is broken.
Further, since it is not necessary to perform an extra operation of grasping the normal reference position of the drill in advance each time the drill is mounted on the spindle, the drill breakage determination process becomes simple.
Further, since it is not necessary to compare with the reference position having a predetermined width, there is no need to worry about erroneous determination.

By the way, in the conventional method of comparing the normality of the position where the drill abuts on the work piece with the reference position, it is impossible to detect the breakage of the drill in the machined state where the drill is inserted into the work piece. For this reason, there is a drawback that machining is continued with the broken drill and the defective portion is enlarged.
According to the above embodiment, although it depends on the configuration of the workpiece, if the drill is broken in the machined state, the capacitance changes, so that the drilling operation can be stopped at that point. Therefore, the machining with the broken drill is not continued, and the expansion of the defective portion can be prevented.

Although the present invention has been specifically described above based on the embodiments of the examples, it goes without saying that the present invention is not limited to the above-described embodiments and can be variously modified without departing from the gist thereof. However, various modifications are included.
For example, in the above embodiment, the resonance detection unit 17 uses a transformer 26 in which the secondary side is connected to the capacitor 25, but an inductance is connected in series to the capacitor 25 to form a series resonance circuit, and the metal of the drill 4 is formed. When the portion 4a comes into contact with the conductive sheet 3a, the capacitance thereof may be lowered to detect that a series resonance has occurred.

Further, in the above embodiment, the capacitor 25 is made to resonate to detect the change in capacitance, but the change in capacitance may be detected by a method that does not cause resonance.
For example, alternating current may be applied to the capacitor 25 to monitor the voltage across the capacitor 25, and it may be detected that the capacitance of the capacitor 25 decreases due to the contact between the drill 4 and the conductive sheet 3a and the voltage across the capacitor 25 decreases.
Further, in the above embodiment, the conductive sheet 3a is placed on the printed circuit board 1, but the conductive sheet 3a is not placed and the conductive layer is formed on the inner layer of the printed circuit board 1. However, if the metal portion 4a of the drill 4 comes into contact with the printed circuit board 1, the capacitance of the capacitor 25 changes, and the drill breakage can be detected.

1: Printed circuit board 2: Processing table, 3a: Conductive sheet 4: Drill,
4a: Metal part, 4b: Diamond coating, 5: Table drive part, 6: Spindle,
7: Inverter, 8: Spindle unit, 9: Spindle vertical drive unit,
12: Pressure foot, 14: Deviation detector, 17: Resonance detector, 18: Overall control unit,
19: Spindle drive control unit, 20: Table drive control unit, 21: Surface height storage unit,
22: Rotor shaft, 23: Electrode, 25: Capacitor, 26: Transformer,
27: Oscillation circuit, 28: Resonance detection circuit,

Claims (10)

In a drilling device having a spindle integrated with a motor and having a drill mounted on the rotor shaft of the spindle for drilling a work piece placed on a table, the spindle is provided on the stator side of the spindle. A capacitance change detection unit that detects a change in the capacitance of the capacitor between the electrode that is electrostatically coupled to the rotor shaft and the ground detected by the electrode, and a capacitance change detection unit that detects the change in the capacitance of the capacitor. A drilling apparatus including a control unit that determines that the drill is broken when a change is detected. The drilling apparatus according to claim 1 includes a deviation detecting unit for detecting a deviation in the engaged state between a substrate pressing unit for pressing the workpiece against the table and a spindle unit holding the spindle. A drilling apparatus characterized in that the surface height of the work piece is detected when the deviation detection unit detects the deviation. In the drilling apparatus according to claim 1 or 2, the capacitance change detection unit resonates with a circuit including the capacitor when the drill is broken and the metal portion of the broken part comes into contact with the workpiece. A drilling device characterized in that a change in capacitance is detected by causing a change in capacitance. The drilling apparatus according to any one of claims 1 to 3, wherein the drilling operation is stopped when the change in capacitance is detected. In the drilling apparatus according to any one of claims 1 to 4, the surface position of the work piece is detected when the pressure foot for pressing the work piece against the work piece comes into contact with the work piece. A drilling machine characterized by the fact that it is designed to be used. In a drilling method in which a drill mounted on a rotor shaft of a motor-integrated spindle is used to make a hole in a workpiece placed on a table, the drill is broken and the metal portion of the broken portion is covered. The drill breaks when it detects a change in the capacitance of the capacitor between the electrode provided on the stator side of the spindle and electrostatically coupled to the rotor shaft and the ground when it comes into contact with the work piece. A drilling method characterized by determining that the drilling is performed. In the drilling method according to claim 6, when a deviation in the engagement state between the substrate pressing portion for pressing the workpiece against the table and the spindle unit holding the spindle is detected, the workpiece is processed. A drilling method characterized by detecting the surface height. In the drilling method according to claim 6 or 7, when the drill is broken and the metal part of the broken portion comes into contact with the workpiece, the capacitor is resonated to detect a change in capacitance. A drilling method characterized by that. The drilling method according to any one of claims 6 to 8, wherein the drilling operation is stopped when a change in the capacitance is detected. The drilling method according to any one of claims 6 to 9, wherein the entire cutting edge portion of the drill is covered with a diamond coating.

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