JPS59175942A - Rms processing unit in cutting edge damage detecting device for intermittent cutting machine - Google Patents

Abstract

PURPOSE:To detect the damage in the cutting edge of a tool accurately in process by a method wherein the unit is constituted so as to be capable of processing an intermittent signal from a pickup with a high speed, in the RMS processing unit in the cutting edge damage detecting device for the intermittent cutting machine. CONSTITUTION:In case an intermittent cutting tool, in which the damage of the cutting edge is to be detected, is a face mill, an acceleration pickup 2 is mounted at the rear side of the tool 1 to pick up an acceleration signal. This signal is divided into several frequency bands near respective vibration frequencies proper for this tool system by a plurality of band pass filters 11-13 and the outputs of respective filters 11-13 are converted into actual value signals corresponding to acceleration levels respectively by the RMS processing units 21-23. An RMS value, corresponding to the vibration level, increases in accordance with the chipping or the damage of the tool, therefore, the damage may be detected by comparing with a proper threshold value in a chipping deciding device consisting of comparators.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an R
M S (root mtam zzrbare)
It relates to a processing device.

The cutting edge of a tool often suddenly develops chipping defects during cutting, and it is very difficult to predict this. Therefore, the tool cutting edge is continuously monitored and
Research on methods for detecting the occurrence of chipping and chipping has been actively carried out, and the present inventors have previously discovered in Japanese Patent Application No. 57-24794 that the occurrence of relatively small chipping can be detected by detecting and analyzing vibration changes in tools. We also propose a method for detecting

To explain more specifically, this previously proposed detection method is
A vibration pickup is attached to the tool system of a cutting machine to detect vibrations during cutting, and the output signal is measured in advance by measuring the unique vibration frequencies that occur in the tool system during cutting, and setting a frequency band around these frequencies. After passing through a plurality of bandpass filters, RMS processing is performed, and cutting edge defects are detected based on fluctuations in the RMS value obtained thereby.

However, when implementing this detection method, RM
There are some problems with the S processing method, for example, the thermal integral method (
When using offline), there is a significant time delay and high-speed signal processing is not possible.

Although a method using an A/D converter and a microcomputer is also effective, such a computer is insufficient for signal processing during high-speed cutting. In particular, when performing RMS processing on intermittent signals obtained by intermittent cutting, if such processing with a large time delay is performed, an appropriate effective value cannot be obtained.

The present invention aims to provide an RMS processing device for a cutting edge defect detection device that solves the problem and makes it possible to perform accurate detection.

In order to achieve such an object, the present invention uses a vibration pickup to detect vibrations accompanying cutting of an intermittent cutting tool, and uses the output signal of the vibration pick amplifier to detect vibrations of the unique vibration frequency generated during cutting in the tool system. In a cutting edge defect detection device that performs RMS processing after passing through a plurality of band-pass filters with frequency bands set in the vicinity, and detects cutting edge defects based on the fluctuation of the RMS value obtained by the RMS processing, the above-mentioned RM The RMS processing device that performs S1A3ff is composed of a power p circuit that squares the input acceleration signal;
A CR integration circuit that integrates the output over time, and a gate pulse generated in synchronization with the intermittent cutting cycle of the tool, performs the above integration only during a certain cutting period, and clears the integration circuit in vain during that period. The device is characterized in that it is constructed by a gate control circuit that controls the gate, and a root circuit that performs the square root of the output.

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

When the intermittent cutting tool whose cutting edge loss is to be detected is a face milling cutter as shown in FIG. 1, an acceleration pickup 2 is attached to the back side of the tool 1 to collect acceleration signals. The above-mentioned tool may be not only a face milling cutter but also a tool that performs other interrupted cutting, and a vibration pickup may be attached to the tool system to detect the vibration inherent in the tool system that occurs during cutting. The pick-up can optionally also be attached to the cutting machine or to the workpiece.

In the experiments conducted by the present inventors, the power spectrum of the vibration detected by pink-up was found to be such that multiple frequency components unique to the tool system were prominently present. When the acceleration signal from the pickup is divided into multiple frequency bands using a band-pass filter and changes in the acceleration level of each are detected, it can be seen that chipping has occurred in the portion of the cutting edge that corresponds to the frequency band.

Therefore, the acceleration signal output from the acceleration pickup 2 is output via a slip ring or an FM transmitter/receiver, and is temporarily recorded in a data recorder if necessary. The acceleration signal is divided by a plurality of bandpass filters 11, 12, and 13 into frequency bands around each vibration frequency specific to the tool system, or into frequency bands around the main vibration frequencies, respectively. The output of each bandpass filter is processed by RMS processing unit w21.
, 22.

The signal shall be an effective value corresponding to the acceleration level by Party B.

The frequency band of the upper WC bandpass filter is determined by measuring the vibration frequency generated during cutting in the tool system in advance, and if the vibration frequency falls around 0.65, 2, or 4.7 KH2, for example, the frequency band of the 14 ~22KH2,3,5
~7.5KHz, 5.8~7.5KHz (0,6
Since the frequency of 5KH2 has little relevance to tinobing, it can be set to 5KH2 (ignored).

Further, the RMS processing devices 21, 22, and 23 equalize the output of the bandpass filter, eliminate noise (for example, spike noise N as shown in FIG. 6), and convert it into an effective signal corresponding to the vibration level. Although it is converted into a value signal, online processing is possible by performing discontinuous RMS processing on intermittent input signals by swifting with a pulse signal that corresponds to the rotation of the main shaft 3. It is characterized by the following features and is constructed as shown in FIG. That is, the waveform of the acceleration signal X from the bandpass filter is squared in a multiplier circuit, and then
Integration circuit B intermittently integrates for a certain period of time.

The gate control circuit 26 that controls the time integration in this integration circuit section controls the integration circuit by using a gate pulse synchronized with the intermittent cutting cycle of the tool, which is output from the rotating system of the main shaft 3 of the tool 1 by appropriate means. Gate n.

By opening and closing these gates 27 and 28, the above-mentioned integration is performed only during a certain intermittent cutting period, and at an appropriate time after that period, the integration circuit is activated in preparation for the next integration. The integral value held in is cleared. The output of this integrating circuit section is then subjected to square rooting in the root circuit 29 at the next stage, whereby an RMS value, which is the effective value of the acceleration signal X, is output.

FIG. 6 shows an example of the gate pulse from the tool rotation system described above, the acceleration signal from the pickup, and the RMS value output from the RMS processing device.

The RMS corresponding to the level of vibration thus obtained
Since the value increases in response to chipping or defects, chipping or defects can be detected by displaying it on the record display needle side or by comparing it with an appropriate threshold value in a chinoping judgment device consisting of a comparator. can do.

As is clear from the detailed description above, R of the present invention
With the MS processing device, the intermittent signal from the pickup can be processed at high speed by analog processing and switching integral processing, thereby making it possible to design the averaging time constant (CR product in Figure 2) to be sufficiently large. Even when the process is performed, the response is fast and processing can be performed with high average accuracy, making it possible to accurately detect chipping or chipping of the cutting edge of the tool using in-busses.

FIG. 2 is a block diagram of the RMS processing device, and FIG. 6 is an explanatory diagram of signal waveforms.

11, 12, 13... band pass filter, 21
, 22, 23...RM8 processing device, Sae...multiplying circuit, 5...CR integration circuit, uh...φ gate control circuit, n, 28...gate, addition...root circuit, - Add...Record display meter.

Claims (1)

[Claims] 1 The vibration accompanying cutting of an intermittent cutting machine is detected by a vibration pickup, and the output signal of the vibration pickup is
After passing the tool system through multiple band-pass filters whose frequency band is set near the natural vibration frequency that occurs during cutting, RMS processing is performed, and cutting is performed based on the fluctuation of the RMS value obtained thereby. In a cutting edge defect detection device that detects a blade defect, an RM that performs the above RMS processing.
8 Processing device is controlled by a multiplication circuit that squares the input acceleration signal, a CR integration circuit that integrates the output over time, and a gate pulse that is generated in synchronization with the intermittent cutting cycle of the tool to perform constant cutting. A cutting blade of an intermittent cutting machine characterized by comprising a gate control circuit that performs the above-mentioned integration only during the period and controls the gate to clear the integration circuit after the period, and a root circuit that performs the square root of the output thereof. RMS processing device in defect detection device.