JPH02198745A - Detecting mechanism for breakdown of tap - Google Patents

Abstract

PURPOSE:To surely detect the breakdown of a small diameter tap as well, by detecting the breakdown of the tap by detecting the load fluctuation applied on the tap and displaying an alarm by stopping a machine, in the case of tapping work within a monitoring area in a tap breakdown detecting mechanism. CONSTITUTION:On starting of tapping, load is applied on a tap T by the cutting resistance, a tap holding shaft 15 is slightly revolved against the spring force, a short circuit piece is separated from the tip of a contact pin and a contact point becomes open electrically between two contact pins. When the tip of the tap T reaches a monitoring area G, the gate inside a monitoring zone setting circuit 24 is opened to enable the passage of the detection signal fed from a detection circuit 23. In case of the breakdown of the tap T being generated by any chance within the range of this monitoring zone Z, the load applied on the tap T is eliminated, the contact point is closed and a detection signal is output from the detection circuit 23. Then, a servomotor 9 and main shaft motor 3 are stopped by a driving control circuit 25 to stop the operation of the machine and simultaneously an alarm is displayed by an alarm display device 27.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a tap breakage detection mechanism during tapping processing using automatic feeding.

In conventional tapping processing using automatic feed, automatic feed continues even if the tap breaks, causing a major accident similar to a mechanical collision. For this reason, conventional methods have been used to detect tap breakage by detecting changes in the load current of a rotation motor or a feed motor during tapping.

Problems to be Solved by the Invention The conventional method of detecting tap breakage by detecting changes in the motor load current is difficult to detect when the load is small, such as with a small diameter tap. This method had a problem in that the timing at which an abnormality was detected was considerably delayed.

The present invention has been made in view of the problems of the conventional technology, and its purpose is to provide a tap that directly detects the breakage of the tap within the holder and stops the operation of the machine based on the detection signal. This is intended to include a breakage detection mechanism.

Means for Solving the Problems In order to achieve the above object, the tap breakage detection mechanism of the present invention includes a detection means for detecting tap breakage by opening and closing contacts provided on the tap holder due to fluctuations in cutting resistance; The apparatus includes a monitoring area setting circuit that sets a monitoring area during the tapping cycle, and a drive control circuit that stops the operation of the machine or device in response to a detection signal from the detection means within the monitoring area.

When the tip of the operating tap faces the pilot hole of the workpiece and tuffing begins, cutting resistance applies a load to the tap, opening the contact, and when the tapping progresses slightly, it enters a preset monitoring area. If a breakage of the tap should occur within this monitoring range, the load on the tap is removed, the contact closes, a detection signal is output, and the drive control circuit stops the operation of the machine or device. All contact opening/closing operations outside the monitoring range are ignored.

Example Examples will be described with reference to FIGS. 1 to 3.

A chuck 5 is fitted to the tip of a main shaft 2 which is rotatably supported by a plurality of bearings on a headstock l, and the main shaft 2 is rotated by a main shaft motor 3 via a heald 4. On the other hand, a tool rest 6 is movably mounted on a sliding guide surface in the Z-axis direction on a fixed stand (not shown), a tap holder 7 is mounted on the tool rest concentrically with the main shaft, and a tap T is mounted on the tap holder 7. It is being

The tool rest 6 is moved and positioned via a ball screw lO by a servo motor 9 driven by an NC device 8, and a detector 11 that outputs the current position of the tool rest 6 to the NC device 8 is concentric with the servo motor 9. installed on.

The tap holder 7 is attached to a frame 14 as shown in FIGS. 2 and 3.
A tap holding shaft 15 is rotatably supported by a plurality of bearings 16 in the center hole of the tap holding shaft. The rotation of the tap holding shaft is limited to a rotation by a gap δ, and the tap T is removably fitted into the center hole at the tip. Furthermore, a groove 15b in the axial direction is carved in a position close to the upper corner of one side of the square shaft portion tSa of the tap holding shaft, and an insulating piece 18 with a shorting piece 17 affixed to the surface thereof is embedded in the IJIB 15b. There is. Further, in the square hole 14a of the frame 14, two holes opening at positions corresponding to the shorting pieces are arranged in the axial direction and perpendicular to the outer periphery, and the insulating bushing 19 is fitted into this hole. A contact pin 20 is fitted into the center hole so as to be movable in the axial direction. The contact pin is biased toward the short-circuited side by the spring 21, and its tip slightly protrudes into the square hole 14a, and is connected to the NG device 8 by the electric wire 22.
It is electrically connected to the detection circuit 23 inside.

Furthermore, a spring 26 is installed in the frame 14 in a hole parallel to the contact pin 20 that opens near the lower corner of one side of the square hole 14a, and the spring 26 has a stronger spring force than the spring 21. When the tap holding shaft 15 is used, the lower corner of the square shaft portion 15a of the tap holding shaft 15 is constantly pressed by the force of the spring 26, and the square shaft portion 15a is tilted to the right with respect to the square hole 14a by the gap δ. , the shorting piece 17 contacts the contact pin 20, and 2
The contacts of the two contact pins are electrically closed (conducting), and when the tapping process begins and a load is applied to the tap T, the tap holding shaft 15 rotates slightly against the force of the spring 26, causing the short circuit 17 separates from the contact pin and the contact opens (non-conducting)
becomes. This state is maintained while tapping is being performed smoothly, and when the load is removed due to breakage of the tap T, the tap holding shaft is slightly rotated by the force of the spring 26 and closed, and the detection circuit 23 detects A detected tap breakage detection signal is output to the monitoring area setting circuit 24. The Z-axis coordinate value of the distance G in the Z-axis direction, which is slightly shorter than the tuffing processing length in the tap insertion direction, is input and recorded in advance into the monitoring area setting circuit 24 along with the monitoring command. 11, the current position signal of the tool post 6 is manually input. While the tip of the tap is being sent to the spindle side through the monitoring area G, the detection signal from the detection circuit 23 is ignored and the drive control circuit 2
5 and the alarm display device 27.

Next, the operation of this embodiment will be explained. The main shaft 2 is rotated, and the rotation of the servo motor 9 moves the tool post 6 toward the main shaft at a predetermined feed rate via the ball screw lO, and the tip of the tap T is inserted into the prepared hole of the workpiece W gripped by the chuck 5. When the tapping process is started, a load is applied to the tap T due to cutting resistance, the tap holding shaft 15 is slightly rotated against the force of the spring 26, and the shorting piece 17 is moved to the contact pin 20.
When the tip of the tap T moves away from the tip of the tap T, the contact between the two contact pins becomes electrically open, and when the tip of the tap T reaches the monitoring area G, the gate in the monitoring area setting circuit 24 opens, preventing the detection signal from the detection circuit 23 from passing through. It becomes possible. When the tip of the tap escapes from the monitoring area G, the gate of the monitoring area setting circuit closes and cuts off the detection signal, and all signals generated by the opening and closing operations of the contacts are ignored.

When the remaining tapping process is completed, the main spindle motor 3 and the servo motor 9 are simultaneously rotated in the opposite direction, and the tapping cycle begins in the return stroke.

In the unlikely event that the tap tip is within the monitoring area G and the tapping is being performed with automatic feed toward the ball shaft,
When the tap T is broken, the load on the tap T is removed, and the tap holding shaft 15 is slightly rotated by the gap δ due to the force of the spring 26, and the shorting piece 17 is separated from the contact bottle, and the two The contact between the contact bottles is opened, and the detection circuit 2
A detection signal is output from 3. The detection signal then passes through the open gate of the monitoring area setting circuit to the drive control circuit 2.
5, the servo motor 9 and spindle motor 3 are stopped, and the machine operation is stopped.At the same time, the detection signal also reaches the alarm display device 27, and the CRT display or patrol lamp lights up.
An alarm is displayed by means such as an audible alarm.

Effects of the Invention Since the present invention is configured as described above, it produces the following effects.

During tapping within the monitored area, changes in the load that causes the tap to break are directly detected, tap breakage is detected, machine operation is stopped, and an alarm is displayed. Breakage of the tap can also be reliably detected, preventing secondary accidents caused by breakage of the tap, eliminating the need to produce a large number of defective products, and achieving unmanned operation.

[Brief explanation of the drawing]

FIG. 1 is a structural explanatory diagram of the tap breakage detection mechanism of the present invention including a partial block diagram, FIG. 2 is a cutaway diagram of the tap holder,
FIG. 3 is an enlarged view of the sectional view taken along the line AA in FIG. 2. 7...Tap holder 17...Short-circuiting piece 20...Contact bottle 24...Monitoring area setting circuit 25...
Drive control circuit T...Tap G...Monitoring area

Claims (1)

[Claims] (1) Detection means that detects breakage of the tap (T) by opening and closing contacts (17, 20) provided on the tap holder (7) due to fluctuations in cutting resistance, and a monitoring area (G) in advance during the tapping cycle. a monitoring area setting circuit (24) for setting the monitoring area; and a drive control circuit (25) for stopping the operation of the machine or device based on the detection signal of the detection means within the monitoring area.
A tap breakage detection mechanism comprising: