JPS6336885B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tap for detecting damage to a tap during cutting by acoustic emission.

Detection of tool damage during cutting is an essential function for unmanned operations such as NC machining, and conventional methods include detecting changes in the load of the spindle motor or feed motor, and detecting changes in the amplitude of acceleration vibration. Methods and the like have been put into practical use.

However, with the above method, it is difficult to distinguish between the damaged state and the no-load state of small diameter tools (φ5 or less).
There are many problems with damage detection, and it is normal that damage cannot be detected at all or that detection errors occur frequently.

Therefore, in order to compensate for this drawback, acoustic emission (hereinafter referred to as
A method using AE (referred to as AE) has been developed and is currently being used effectively for small diameter drills and end mills. However, when this AE method is used to detect damage to small-diameter taps using a regular tapper, the AE due to tap damage as shown in Figure 1.
The detection signals a and b have a larger level difference than the detection signal c caused by damage to a drill of the same diameter, and the level variations are also large, so that they are difficult to use in practice. This is because the taps currently in use have a structure as shown in Figure 2, which takes into consideration factors such as easy attachment and detachment, self-alignment, and safety due to the torque adjustment function. AE wave propagation state is Tap 1
This is due to large damping and damping fluctuations due to unstable connections at the joint between the tap collet 2 and the tap collet 2, the torque adjustment mechanism of the tap collet 2, the joint between the tap collet 2 and the tap holder 3, and the front and rear float mechanism of the tap holder 3. ing. What's more, these things have changed significantly over time.

In general, NC machines have good positioning accuracy, so self-alignment is not required when tapping, and by being equipped with a tap damage detection function, a torque adjustment function is also not required.

The present invention was developed focusing on the above points, that is, it improves the propagation state of AE waves in order to improve the tap damage detection function.The configuration of the present invention will be explained below with reference to the drawings. be.

In Fig. 3, 11 is the tap holder body;
2 is a shaft member inserted into the tap holder body, and this shaft member 12 has a ball 13 and a ball bearing 1.
4. It is installed so that it can float in the axial direction with respect to the tap holder main body 11 by means of springs 15, 16 and a spacer 17. 18 is a core shaft fixed to the center of the tap holder main body 11, 19 is a cylindrical cover for preventing the ball 13 from falling off, and 20 is a snap ring.

A large diameter hole 22 for fitting and mounting a tap collet 21 is provided at the tip of the shaft member 12.
A set screw 23 for fixing the tap collet is screwed into the position. Tap collection 21 is the fourth
As shown in the figure, it has a half-split structure with a single slit 24, and a square hole 26 is formed at the back of the tap insertion hole 25.

Attach the tap to the tap holder as follows. That is, after attaching the tap to the tap collet 21 before being attached to the shaft member 12, the tap collet 21 is fitted into the hole 22 of the shaft member 12, and the tap collet 21 is fixed in the hole with the set screw 23. That is, when the set screw 23 is screwed in, a portion of the tap collet 21 is strongly pressed and deformed within the hole, causing the set screw 2 on the inner peripheral surface of the hole 22 to deform.
The outer surface of the tap collet 21 is brought into pressure contact with the portion facing the tap collet 3, and the tap collet 21 is firmly installed in the hole. This tap collet 21 and shaft member 1
Since the contact surface with the shaft member 2 has an optimal surface roughness, the above configuration allows the AE waves to be propagated well to the shaft member without being attenuated. Further, the shaft member floats in the front and back direction with respect to the tap holder main body 11 via the ball 13 and the ball bearing 14.
The ball has optimal preload and lubrication, and AE wave propagation is good.

Since the tapper of the present invention has the above configuration, the AE waves can propagate without being attenuated at the joint A between the tap and the tap collet 21, the joint B between the shaft member 12 and the tap collet 21, and the joint c of the float mechanism. The contact area and contact pressure required for this can be maintained in a stable state at all times, and detection accuracy (detection signal level and variation) can be greatly improved. That is, when using the tapper of the present invention, the AE wave detection signal when the φ5 tap broke is as shown in FIG. 5, and a large AE detection signal equivalent to that of the φ5 drill shown in FIG. 1c was obtained.

Usually, the optimum value of the cutting speed during cutting is determined depending on the tool diameter, material, etc. and generally AE
In addition to the AE waves caused by tool damage, the conversion element simultaneously detects signal components (hereinafter referred to as DC components) such as bearing friction noise and gear impact noise due to spindle rotation, and the magnitude of this DC component is shown in Figure 6. It changes depending on the rotation speed like this. Furthermore, as shown in FIG. 7, the AE wave due to tool damage is displayed as a value obtained by adding the above DC component. Therefore, when performing signal processing using the discrimination method, it is necessary to link the threshold value to the rotation speed, but if the DC component can be removed as noise, signal processing becomes very easy.

FIG. 8 is a block diagram of a detection system for removing the DC component, in which the AE signal converted by the AE conversion element 31 passes through a preamplifier 32 and an average value detector 33, and is subjected to average value detection. Normally, a method is adopted in which the average value signal on which this DC component is superimposed is directly input to the comparator, but in the detection system according to the present invention, the DC component is Since the components are removed, tool damage can be detected with high accuracy regardless of the spindle rotation speed. Note that 35 is a flip-flop.

As explained above, the present invention makes the tap collet have a half-split structure, and elastically deforms the tap collet by tightening the tap collet in the radial direction with a set screw within the insertion hole at the tip of the shaft member. , the tap collet and the shaft member are brought into close contact with each other over a wide area with a predetermined contact pressure, thereby ensuring that the AE waves generated from the tap are transmitted to the tap collet and the shaft member at a high level without being attenuated too much. can be done.

Furthermore, by fitting the shaft member into the tap holder body so as to rotate integrally through the balls incorporated under preload, the shaft member and the tap holder body are pressed together under contact pressure due to the preload force of the balls. This allows for strong contact through the balls, and as a result, the AE waves can be reliably transmitted to the spindle and spindle head side at a high level without being significantly attenuated, making it possible to detect damage to small diameter taps with high precision. It can be done with

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a general example of an AE detection signal due to tap damage; FIG. 2 is an explanatory diagram of a known tap; FIG. 3 is an explanatory diagram of a tap according to the present invention;
The figure is a sectional view taken along the line of figure 3, figure 5 is an explanatory diagram of the AE detection signal by the tapper according to the present invention,
The figure is an explanatory diagram of the DC component generated by noise other than the AE wave, Figure 7 is an explanatory diagram of the signal in which the DC component is added to the AE wave, and Figure 8 is an illustration of the detection system for removing the DC component. It is a block diagram. 11...Tap holder body, 12...Shaft member,
13...Ball, 14...Ball bearing, 1
5, 16... Spring, 17... Spacer, 1
8... Core shaft, 19... Cylindrical cover, 20... Snap spring, 21... Tap collet, 22...
Hole, 23...set screw, 24...slit.

Claims (1)

[Claims] 1 A tap holder body and a ball that is inserted into the tap holder body under preload so as to rotate integrally and to be able to float in the axial direction,
Furthermore, the shaft member has a hole for inserting a collector chuck at its tip, a tap collet with a half-split structure that is inserted into the hole for inserting a collector chuck at the tip of the shaft member and holds the base of the tap, and a tap collet with a half-split structure that holds the base of the tap. Tap damage detection by AE, characterized in that it is equipped with one set screw that is screwed into the tip of the shaft member from the radial direction perpendicular to the halving direction and brings the tap collet into surface contact with the shaft member. Tatsupa for.