JPS61131808A - Drill break detecting device - Google Patents

Abstract

PURPOSE:To detect automatically and accurately whether the drilling condition of a small type drill is good or bad by detecting drill break magnetically by utilizing the principle of differential transformer in the drilling or the like of printed wiring substrate by an NC drilling machine. CONSTITUTION:A drill break detecting device is composed of the supporting section 3 provided perpendicularly under the lower part of a spindle housing through elastic springs 2, the differential transformer section 4 provided on the inner periphery of this supporting section 3, a displacement meter section electrically connected to the differential transformer section 4, and a break detecting section connected to the output side of this displacement meter and to detect the break of a drill 6. In the differential transformer section 4, a secondary coil 10, a primary coil 11, and a secondary coil 12 are layered in order. And the drill 6 made of strong magnetic substance, e.g., high speed steel or the like and passing through a through hole 9 magnetically combines the primary coil 11 and the secondary coils 10 and 12 to make the secondary coils 10 and 12 generate the induced electromotive force corresponding to the positions of the drill.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a drill breakage detection device that is capable of detecting breakage of a drill in an autogenous manner.

[Technical background of the invention and its problems]

In the near future, with the automation of machining operations, there is a trend to automate the detection of tool damage. For example, in drilling operations, automatic detection of drilling abnormalities caused by breakage of the drill, for example, has been put into practical use in some areas. In this case, there are generally two methods of detection: detecting abnormal vibrations caused by the breakage of the drill, or using a photoelectric element to detect the passage of chips generated during drilling. Conduct/
It is.

However, the conventional drill breakage detection method described above is effective for detecting breakage of a drill for drilling a relatively large hole when the object to be drilled is steel, steel, etc.; A printed wiring board made of synthetic resin,
Moreover, it is not suitable for detecting breakage of a drill for drilling small diameter holes with a drill diameter of 0.8 μ or less. This is because the synthetic resin chips obtained by drilling small diameter holes are extremely small and semi-transparent, making it difficult to detect with a photoelectric element. In addition, if the object to be perforated is synthetic resin,
This is because even if the drill breaks, almost no vibration is generated that can be used to distinguish between abnormality and normality. Generally, drilling of printed wiring boards is performed using a numerically controlled (NC) drilling machine. Therefore, if the broken drill is overlooked, after the drill is replaced, the drill is air-feeded from the initial position to the drill broken position, stopped once, and then the drilling operation is resumed. As a result, work efficiency is greatly reduced, which is an obstacle to improving production efficiency.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances.

It is an object of the present invention to provide a drill breakage detection device that can automatically and accurately detect the quality of drilling with a small-diameter drill.

[Summary of the invention]

A displacement signal indicating the amount of displacement of the drill is obtained using the principle of a differential transformer, and when this displacement signal is compared with a threshold value, breakage of the Kl drill is detected.

[Embodiments of the invention]

An embodiment of the present invention will be described below in detail with reference to the drawings.

1 and 2 show the drill breakage detection device of this embodiment. In other words, this drill breakage detection device has 1
A cylindrical support part (3) is vertically installed on the lower end of the cylindrical spindle housing (1) via an elastic spring (2), and is attached to the inner part of this support part (3). a cylindrical differential transformer part (4), and a differential transformer part (4) with
), and a breakage detection section (7) connected to the output side of the displacement measurement section (5) to detect breakage of the drill (6). . However, 1. The spindle housing (1) has a spindle coaxially installed therein, one end of which is connected to a motor (not shown).The other end of the spindle (1a) is
A chaff (8) for gripping the drill (6) is coaxially mounted. Further, the lower end surface of the support part (3) is set upward so that the lower end of the drill (6) is also downward when no external force is applied.

The differential transformer section (4) has a through hole (9) into which the drill (6) is loosely inserted, and has a secondary coil hole, a primary coil hole 9, and a secondary coil a from above. are laminated in order. A drill (6) made of a ferromagnetic material such as high-speed steel passes through the through hole (9) and serves as a movable core to connect the primary coil, secondary coil /I/(1G , (1) are magnetically coupled to generate an induced electromotive force in the secondary coil Q1 (12) according to the position of the drill.On the other hand, the displacement meter section (5).

Those installed separately from the differential transformer section (4),
, an oscillation circuit (13) that supplies power to the primary coil 1v (II) with 1 to 5 sine wave signals, and a secondary coil (11,
(An input circuit I that is connected to la and inputs the induced current, an AC amplifier that is connected to the output side of the input circuit I and that amplifies the induced current, and an AC amplifier that is connected to the output side of this AC amplifier α [with] A that converts (AC) signals to direct current (DC) signals
It consists of a C-DC converter αe and a filter aη connected to the output side of the AC-DC converter αe and mainly for removing ripples in the excitation frequency component. moreover.

The breakage detection section (7) is connected to the output side of the filter (7) and has a threshold value vT set therein, and when the voltage value E of the displacement signal 8D output from the filter (7) is υ larger than the threshold value vT. Based on the comparator outputting the breakage detection signal 8M and the control signal SC output from the control circuit 0 of the drilling machine, it is determined that the comparator 9m<the drill (6) is currently drilling the workpiece (21). a timing signal output circuit (2) that outputs a timing signal ST indicating the breakage detection signal S;
It consists of an alarm device (c) which issues an alarm when M is input and outputs a processing interruption signal 8H to the control circuit member.

The comparator a is provided so as to perform a predetermined comparison operation only during the period when the timing signal 8T is input and during the drilling process by the ocitrile (6). That is, the breakage detection signal SM is output only when the voltage value E of the displacement signal SD is larger than the threshold value VT.

In the drill breakage detection device having the above configuration, first, the workpiece (goods) is fixed on the workpiece holding table (c) of the drilling machine. This processed product (goods) is, for example, a printed wiring board made of synthetic resin such as glass epoxy resin or imide resin. Then, the spindle (1a) and the drill (6) are driven to rotate based on the control signal from the control circuit α-yu, and are lowered toward the workpiece (goods). At this time, the lower end surface of the support portion (3) first comes into contact with the workpiece (goods). The drill (6) is then lowered due to the support (3) being elastically suspended on the spindle housing (1). On the other hand, for −th coil function η.

A 1-5 kHz sine wave signal is supplied from the oscillation circuit country 0. Therefore, the drill (6) drills the through hole (9) into the workpiece (
As the displacement signal 8D passes through the filter (7), the voltage value E of the displacement signal 8D output from the filter (7) gradually decreases as shown in FIG. If the drill (6) is not broken and can normally perform the drilling operation of the pick-up workpiece 4, the drill (6).

Completely passes through the through hole (9). The voltage value E of the displacement signal 8D at this time (position xt in FIG. 3) is smaller than the threshold value vT. Therefore, the breakage detection signal 8M is not output from the comparator (Ill). However, the drill (
6) is broken, the tip of the drill (6) may be damaged, for example, in the middle of the secondary coil (13 (position x in Figure 3)).
t). As a result, the voltage value E of the displacement signal SD at this time becomes Et, which is larger than the threshold value vT.

Therefore, from the comparator (t8), the breakage detection signal SM is output to the alarm device (to). Note that the determination process in the comparator (18) is performed only during the input period of the timing signal ST. The alarm device (c) to which the detection signal SM is input issues an alarm and outputs a processing interruption signal 8H to the control circuit member.

Drilling work is temporarily stopped. After replacing the broken drill (6), the drilling operation is restarted.

Secondly, the drill breakage detection device of this embodiment is as follows:
Since drill breakage is detected using the principle of a differential transformer, drill breakage can be reliably detected without oversight or misunderstanding. Toshiwake, S/
A round drill with a small N (Sipnal/No1se) ratio is particularly effective in detecting breakage of a small-diameter drill used for drilling printed circuit boards, which makes it difficult to detect breakage. therefore,
For example, it can contribute to improving the production efficiency of printed wiring boards.

In the above embodiment, two secondary coils are provided with the primary coil in between, but only one secondary coil may be provided. Furthermore, the voltage value E of the displacement signal SD may be increased as the drill (6) approaches the workpiece (goods) by reversing the role of the secondary coil member α2. In this case, the comparator αυ is set to output the breakage detection signal SM which is activated when the voltage value E becomes smaller than the threshold value vT. Furthermore, in the above embodiment, the support portion (
3) is the spindle housing (which is part of the drilling machine).
1), but it may be arranged independently from the drilling machine.

〔Effect of the invention〕

Since the drill breakage detection device of the present invention magnetically detects drill breakage using the principle of a differential transformer, the detection accuracy of drill breakage is significantly increased. In particular, this is particularly effective in detecting breakage of small-diameter drills used for drilling holes in synthetic resin members, which often causes misunderstandings and misunderstandings when detecting breakage due to the small S/c ratio.

Therefore, it can become a part of improving the production efficiency of, for example, printed wiring boards.

[Brief explanation of the drawing]

Fig. 1 is a top view showing the differential transformer section of a drill breakage detection device according to an embodiment of the present invention, Fig. 2 is an electric circuit diagram, and Fig. 3 is a diagram showing the relationship between the displacement amount of the drill and the output voltage. This is a graph showing. (4): Differential transformer section, (!5): Displacement meter section. (6) Nidril, (7): Breakage detection part. αI, (13: Secondary coil, (11): Primary coil. (13: Oscillation circuit. Agent: Patent attorney Noriyuki Chika (and 1 other person)

Claims (1)

[Claims] A differential transformer section that has a primary coil and a secondary coil disposed at a position substantially coaxially surrounding the drill as the drill made of ferromagnetic material moves in the axial direction, and forms a differential transformer together with the drill. and an oscillation circuit that outputs an alternating current signal to the primary coil, and when the oscillation circuit outputs an alternating current signal to the primary coil, the position of the drill is determined based on the current induced in the secondary coil. What is claimed is: 1. A drill breakage detection device comprising: a displacement meter section that converts the displacement signal into a displacement signal indicating the displacement signal; and a breakage detection section that determines whether or not the drill is broken based on the displacement signal.