JP3737552B2 - Machine tool with machining tool breakage detection function - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is suitable for application to an automatic machine tool, about the machine tools having a machining tool breakage detection.
[0002]
[Prior art]
Generally, in an automatic machine tool, it is required to accurately detect breakage of a processing tool. If the processing operation is continued with the processing tool damaged, all subsequent processed products will be defective.
[0003]
Conventionally, as this type of processing tool breakage detection device, for example, a device shown in FIG. 4 is known. This detects breakage of the tap 103 as a processing tool for processing the workpiece 101. The tap 103 is mounted on the tapping unit 105 and is movable up and down. A gear 105a is provided at the lower end of the tapping unit 105, and another gear 107b is engaged with the gear 105a. The output shaft 107a of the servo motor 107 is attached to the gear 107b. In addition, the servo motor 107 is provided with a pulse coder 107c.
[0004]
A receiving plate 113 is provided above the workpiece 101 and a limit switch 115 is provided above the receiving plate 113. The limit switch 115 and the servo motor 107 are connected to the control device 111.
[0005]
With the above configuration, when the servo motor 107 is driven and the gear 107b is rotated via the output shaft 107a, the tap 103 is rotated via the gear 107a and the tapping unit 105. In addition, the tap 103 is moved up and down by a vertical movement mechanism provided in the tapping unit 105. Therefore, when the tap 103 is lifted and completely screwed into the workpiece 101, the receiving plate 113 is pushed up by the tip of the tap 103 protruding from the upper surface of the workpiece 101, and the limit switch 115 is operated by this. In this way, when the limit switch 115 is activated, the tap 103 is normal, and when the tap 103 is folded and shortened, the limit switch 115 is not activated, so that the breakage of the tap 103 can be detected.
[0006]
[Problems to be solved by the invention]
However, in the above-described prior art, depending on the shape of the work 101, such as when a protrusion is formed on the back surface of the work 101, the switch may malfunction and an accurate detection operation may not be performed. Moreover, when the tap hole is not penetrating, it is not applicable in principle. Furthermore, since the detection device is necessarily disposed close to the chip generation site, there is a possibility that the limit switch 115 may malfunction due to the chip being caught between the mechanical movable parts. Further, since the detection member is brought into direct contact with the tap 103, the tool may be damaged.
[0007]
The present invention has been made in view of the above problems, and an object thereof is to provide a machine tool having a risk-free machining tool breakage detection function of malfunction with the breakage of the machining tool can be accurately detected.
[0008]
[Means for Solving the Problems]
The present invention has been made in view of the above-described problems, and includes a machining tool for machining a workpiece, feed means for feeding and driving the machining tool relative to the workpiece, the machining tool, and the workpiece. Contact detecting means for detecting the contact / non-contact state of the machine and a control means to which an output from the contact detecting means is input. The control means detects damage of the machining tool at the start of machining and at the end of machining. In order to detect, RAM which memorizes the contact position of the work and processing tool at the time of trial machining, and the input from the contact detection means when the current feed position and return position by the feed means become the contact position Judgment means for judging whether or not the machining tool is damaged by a signal is provided.
[0010]
The “machining tool” for detecting breakage in the present invention can be widely applied to machining tools in general, such as a drill, a milling cutter, and a tool, in addition to a tap.
[0011]
The “contact detection means” only needs to detect whether the workpiece and the processing tool are in contact with each other, and various detection means such as electrical, mechanical, and optical can be applied. For example, specific examples of electrical detection include: (1) When the material of the workpiece is conductive, such as metal, an electrical loop including the machining tool and the workpiece is formed, and the contact between the two is determined by changes in current and voltage. Can be detected. (2) For non-conductive workpieces such as plastic, the magnitude of the power load of the feed means (feed motor) may be detected to determine from the increase in load that the processing tool has come into contact with the workpiece. (3) In the case of a lathe or a milling machine (not a feed motor), the contact of a machining tool may be determined from a load change of a drive motor that rotationally drives a workpiece. In addition to these electrical detections, it is also possible to detect contact with a tap or drill with a torque sensor, or to detect contact with a workpiece from the force acting on the tool by attaching a component force sensor to the tool table. Further, it is possible to modify such that the contact between the processing tool and the workpiece is monitored by optical means such as a CCD. In short, the contact detection means in the present invention may be any means as long as it can detect whether the workpiece and the processing tool are in contact with each other.
[0012]
In addition, because the control means is “configured so that the current feed position can be known” by the feed means, for example, by a feedback signal of a feed drive servo motor or a feedback signal from a position sensor attached to the feed member. Although the feed position can be known, the present invention is not limited to this, and any control means may be used as long as the control means can grasp the current feed position internally even in open loop control such as a stepping motor. The “feed position” may be an absolute position or a relative position.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a machine tool having a machining tool breakage detection function according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing a machine tool having a machining tool breakage detection function.
[0014]
In FIG. 1, a plate material 1 as a workpiece is made of a conductive metal, and a pilot hole 1a is previously drilled by a drill, and an insulating metal fitting (not shown) is provided on the stage of the machine tool body. The stage is fastened and fixed, and is supported in an electrically insulated state from the stage.
[0015]
In this embodiment, the processing tool 3 for processing the workpiece 1 is embodied as a tap that performs female threading on the inner peripheral surface of the lower hole 1a of the workpiece 1.
[0016]
By rotating the gear 5a provided at the lower end of the tapping unit 5 for chucking the tap 3, the upper end tap 3 is rotated and moved up and down by a vertical movement mechanism (not shown). Yes. Here, when the tap 3 is driven by one rotation, the up and down feed is advanced and retracted by one pitch. In other words, since the tap 3 is used as a processing tool in this embodiment, the feed and drive have a subordinate relationship with one degree of freedom, and in the following description, the relationship of drive = feed is also given. What is being fed is the movement of the tap 3 in the vertical direction. This can be easily understood by referring to the following description assuming that a drill is used instead of the tap 3.
[0017]
A servo motor 7 for driving the tapping unit 5 is provided, and a gear 7b is fixed to a rotating shaft 7a of the servo motor 7, and is engaged with the gear 5a to transmit a driving force. ing. The servo motor 7 is provided with a pulse encoder 7c, which generates a pulse signal corresponding to the rotation of the rotary shaft 7a. In the present embodiment, the tapping unit 5 and the servo motor 7 constitute feed means for feeding the machining tool 3 relative to the workpiece 1.
[0018]
A touch sensor circuit 9 is configured as a contact detection means for detecting a contact / non-contact state between the processing tool 3 and the workpiece 1. Specifically, a pull-up circuit including a power source 9a and a resistor 9b is conductive. The electric potential is connected to the work 1 via the brush 9c, and this electric potential is inputted as a touch sensor signal 9d to the control device 11 described later. Here, since the work 1 is always pulled up to the positive potential of the power supply 9a, the touch sensor signal 9d is always at the Hi level. However, since the machining tool 3 is grounded to the machine tool body as indicated by a broken line, when the machining tool 3 comes into contact with the workpiece 1, the potential of the touch sensor signal 9d changes to the Lo level. Therefore, if the touch sensor signal 9d is monitored, it can be detected whether the machining tool 3 and the workpiece 1 are in contact or non-contact.
[0019]
The control device 11 includes a control device that performs drive control of the entire machine tool and a control unit according to the present invention. Specifically, a main CPU that is in charge of controlling the entire machine tool, A sub-CPU for processing a machining tool breakage detection function characteristic of the invention is incorporated. The main CPU is in charge of overall control of functions as a machine tool including drive control of the servo motor 7. On the other hand, the sub CPU performs a process of detecting the presence or absence of tap damage in response to a command from the main CPU. Here, the drive control of the servo motor 7 is performed by the main CPU, but the feedback signal from the pulse encoder 7c at that time can also be read from the sub CPU. The touch sensor signal 9d is connected to the input port of the sub CPU.
[0020]
Next, the operation of the machine tool provided with the machining tool breakage detection function of the present embodiment configured as described above will be described.
[0021]
FIG. 2 is a flowchart showing the operation of the sub CPU built in the control device 11. The operation of the sub CPU is divided into processing (S101 to S111) when actually machining the workpiece and trial machining (S201 to S204) for performing calibration work prior to this.
[0022]
The sub CPU is normally in a waiting state until there is a command for tapping from the main CPU (S100). If there is a tapping command, it is first determined which of the above operations is selected (S101).
[0023]
In the apparatus of this embodiment, since it is necessary to perform trial machining at least once at first, if the trial machining (S201 to S204) is described in advance, the operator does not break into the tap unit 5 and is normal. After mounting the tap, turn on the trial machining switch (not shown) of the device. Then, the main CPU starts tapping, and the sub CPU repeats input of a signal from the touch sensor circuit (S201) until the signal is turned on, that is, until the contact state between the tap 3 and the work 1 is detected (S202). When the signal is turned ON, the feed position at that time, specifically, the motor position indicated by the pulse encoder 7c is read (S203). Is stored in a predetermined storage area (S204). FIG. 3A shows the positional relationship between the tap 3 and the workpiece 1 at this moment. The above is the operation in the trial machining. As a result, when the normal tap 3 that is not broken is used, the feed position at which the tap 3 and the work 1 contact each other is determined by the RAM of the control device 11. It will be stored in.
[0024]
Next, when the workpiece 1 is actually machined (S102 to S111), the main CPU waits until a command for raising the tap is received (S102). When the tap rise starts, the motor position reading operation is performed (S103). ), Until the contact position registered in step S204 of the previous trial machining is reached (S104), and when the contact position is reached, a signal is input from the touch sensor circuit 9 (S105). At this time, if the machining tool tap 3 and the workpiece 1 are in contact with each other, the signal is ON. If not, the OFF value is input. If the signal is not ON (S106), the tap 3 is It is determined that the length is shorter than that in the trial machining, that is, the tap is broken as shown in FIG. 3B (S120). Next, in the step of lowering the tap (S107), as in the case described above, reading of the motor position (S108) is repeated until the registered contact position is reached (S109). When becomes the contact position, the circuit signal of the touch sensor is input (S110). If the signal is not ON at this time (S111), it is determined that the tap is broken as shown in FIG. 3C (S120). When it is determined that the tap breaks, the main CPU is interrupted, and the operation of the apparatus is stopped, an alarm to the operator, a display, etc. are made. As described above, in the present invention, the presence or absence of breakage of the machining tool 3 is determined from the change in the feed position when the contact / non-contact state between the machining tool 3 and the workpiece 1 is changed.
[0025]
Although not directly related to the present invention, if the contact detection means that is a part of the configuration of the present invention is applied, it is determined that the machining tool 3 is in rapid contact while the workpiece 1 is not in contact with the workpiece 1 and is in contact with the workpiece 1. It is also possible to obtain a feed speed control device that switches to low speed feed for machining as soon as it is detected.
[0026]
【The invention's effect】
Since the present invention is configured as described above, the following effects can be obtained.
[0027]
Regardless of the shape of the workpiece, it is possible to accurately detect breakage of the machining tool and there is no risk of malfunction. Moreover, since there is no member which contacts especially for a detection other than a workpiece | work in a processing tool, a processing tool is not damaged. It can also be applied to existing machine tools by simply adding simple parts.
[0028]
In addition, if the processing tool is broken before the start of processing, this can be detected at the start of processing, as well as when the processing tool is damaged during processing, this should be detected immediately at the end of processing. Can do. Accordingly, it is possible to reliably prevent a situation in which a workpiece with a damaged portion of the machining tool clogged continues to flow in the line.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a machine tool having a machining tool breakage detection function according to an embodiment of the present invention.
FIG. 2 is a flowchart showing an operation of a machine tool provided with the machining tool breakage detection function of FIG.
3 is an explanatory diagram showing an operation of a machine tool having the machining tool breakage detection function of FIG. 1; FIG.
FIG. 4 is a front view showing a machining tool breakage detection device according to the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Work 1a Pilot hole 3 Processing tool 5 Tapping unit 5a Gear 7 Servo motor 7a Rotating shaft 7b Gear 7c Pulse encoder 9 Contact detection means 9a Power supply 9b Resistance 9c Conductive brush 9d Touch sensor signal 11 Control device

Claims (1)

A machining tool for machining a workpiece, a feeding means for feeding and driving the machining tool relative to the workpiece, a contact detection means for detecting a contact / non-contact state between the machining tool and the workpiece, Control means to which an output from the contact detection means is input, and the control means contacts the workpiece and the machining tool at the time of trial machining in order to detect breakage of the machining tool at the start of machining and at the end of machining. RAM for storing the position, and determination means for determining whether or not the machining tool is damaged by an input signal from the contact detection means when the current feed position and return position by the feed means become the contact position. A machine tool equipped with a machining tool breakage detection function.

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