JPS622938B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tool abnormality detection device for detecting wear, damage, etc. of a metal cutting tool.

Conventional abnormality detection devices for this type of tool include those that monitor the current and power of the spindle motor of the machine tool. In other words, the current or power of the spindle motor during cutting with a normal tool is memorized according to the NC program, and this memorized value is used as a standard and compared with the current value, and if the ratio exceeds the set upper and lower limits. This was determined to be abnormal.

Such conventional tool abnormality detection devices are
Since it can only be used when machining the same workpiece with the equipment, it cannot be used when machining a small amount of workpieces with the same machine tool and the same tool. Additionally, there were drawbacks such as the inability to detect minute tool chips during light loads such as finish cutting.

This invention attempts to eliminate these drawbacks of the conventional methods, and uses an eddy current detector installed near the tool to measure the distance to the cutting surface and the roughness of the cutting surface, and detect tool abnormalities from these values. The present invention provides a device for

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. That is, in Figs. 1 to 3, 1 is a tool mount of the lathe, 2 is a cutting tool fixed to the tool mount 1, and 3 is a tool fixed to the tool mount 1, and the distance to the cutting surface and the roughness of the cutting surface are measured. an eddy current detector for measuring; 4 a processing unit that processes the output signal of the eddy current detector 3 and determines an abnormality in the cutting tool 2; 5 a workpiece;
51 is a machined surface of the workpiece 5 machined by the cutting tool 2.

With this structure, the cutting tool 2 is fixed to the tool mount 1, and the cutting tool 2 cuts the surface 51 of the workpiece 5 as the tool mount 1 is fed. Since the eddy current detector 3 is also fixed to the tool mount 1 together with the cutting tool 2, the machining surface 51 of the workpiece 5 and the eddy current detector 3 always maintain a constant relative position during cylindrical cutting.

On the other hand, the eddy current detector 3 has an output voltage V according to the distance L between the eddy current detector 3 and the workpiece 5, which is a conductor, or the surface roughness Ra of the workpiece 5, as shown in FIG. derived.

That is, in Fig. 2, when the horizontal axis is L and Ra and the vertical axis is V, the output voltage VL according to L is Ra.
If L is kept constant, the voltage VRa corresponding to Ra will be like the solid line VL, and if L is constant, the voltage VRa will be like the dashed-dotted line VRa.

Now, when the cutting tool 3 is chipped and the machining dimensions of the workpiece 5 change, the eddy current detector 3 detects the distance L and roughness.
When a voltage corresponding to both Ra is detected, and the output voltage V changes at time t ₁ with time on the horizontal axis and voltage on the vertical axis as shown in FIG.
It is determined by In addition, wear on the tip of the cutting tool can be detected in the same way as chipping. Furthermore, abnormalities in the cutting edge as well as increases in surface roughness due to vibration of the cutting edge can be detected as changes in the output voltage of the eddy current detector.

The relationship between the output voltage V _L depending on the distance L between the eddy current detector 3 and the workpiece 5 and the output voltage V _Ra depending on the surface roughness Ra of the workpiece 5 will be explained. If abnormal cutting occurs, tool chipping and wear will lead to an increase in finished dimensions, and V _L will increase. On the other hand, when chatter occurs, the surface of the workpiece becomes rough and V _Ra increases. In either case, abnormal cutting results in an increase in output, and whether the increase in output is due to V _L or V _R
There is no need to distinguish whether it is due to _a . Conversely, in any of the above cases, a single sensor can detect abnormal cutting. The output change is V _L
It is necessary to distinguish whether this is caused by V Ra or by V _Ra , as the finished dimensions decrease and at the same time the surface roughness increases. There are two cases where the finished dimensions increase and the surface roughness decreases at the same time, but this is never the case in reality.

In the above embodiment, the eddy current detector 3 is fixed to the tool mounting base 1, but the eddy current detector 3 is mounted on a movement mechanism configured to move at a position symmetrical to the tool on the cross feed base. A similar effect can be obtained by attaching a container.

In addition, although the above embodiment was explained using an example of a lathe,
The present invention can also be applied to a milling machine that cuts a workpiece 5 with a tool 2, as shown in FIG. 4, and similar effects can be obtained. The present invention can also be applied to other types of machine tools such as shaping machines and planing machines.

As described above, the tool abnormality detection device according to the present invention includes eddy current detection devices arranged facing each other at a predetermined interval so as to follow the machined surface of a workpiece made of a conductive material cut by a tool. It is configured to derive an output signal according to the gap, machined surface, and surface roughness, and also detects abnormalities in the tool based on fluctuations in the output signal of the eddy current detector. etc. can be detected with high precision.

[Brief explanation of the drawing]

Figures 1 to 3 all show one embodiment of the present invention; Figure 1 is a side view of the main part, Figures 2 and 3 are explanatory diagrams of the operation, and Figure 4 is an embodiment of the present invention. FIG. In the figure, 1 is a tool stand, 2 is a cutting tool, 3 is an eddy current detector, 4 is a processing section, and 5 is a workpiece. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A vortex which is arranged oppositely at a predetermined interval so as to follow the machined surface of a workpiece made of a conductive material cut by a tool, and which derives an output signal according to this gap. A tool abnormality detection device comprising a current detector, and detecting an abnormality in the tool based on fluctuations in an output signal of the eddy current detector. 2. The tool abnormality detection device according to claim 1, wherein the eddy current detector is attached to a mounting base of the tool.