DD243448B1 - CIRCUIT ARRANGEMENT FOR DETECTING PROCESS STABILITIES WHILE TURNING - Google Patents

Description

Field of application of the invention

The invention relates to a circuit arrangement for detecting process instabilities when turning, by evaluating the structure-borne sound vibrations at the lathe, which it is exposed during the Spanungsprozesses, and the signaling of impermissible states.

Characteristic of the known technical solutions

There is known an arrangement for displaying modified cutting edge geometries on cutting tools (DD-PS 209405) in which, on the basis of pre-programmed sizes, a comparison is made with a signal which is processed by means of a vibration pickup, an amplifier, a narrowband filter and an analog-to-digital converter, takes place in a microcomputer and an indication or machine shutdown is triggered when the setpoints are exceeded. The disadvantage of this arrangement is that only one frequency range can be selected by means of the programmable narrowband filter and the preprogrammed setpoints must be formed for each operation, so that a high adjustment effort arises for each processing task. Further, a method for maintaining the maximum metal removal speed while avoiding Werkzeugprellungen in the machining of a workpiece by a machine tool and a bruising device for performing the method (DE-OS 1763224) is known in which selected by rectification and filtering a frequency range and its amplitude as a measure is rated for rattle phenomena.

A major disadvantage of this method is that only one frequency range is used for the evaluation, so that only chatter phenomena can be detected in a small part of possible processing conditions.

Furthermore, a circuit arrangement for tool breakage detection on rotary tools (DD-PS 234378) is known, in which a frequency is selected by filtering, the amplitude change is utilized in tool breakage for its signaling. The disadvantage is that slow changes, which are characteristic of process instabilities, are not recognized.

From DE-OS 271 0834 an alarm system is known which generates electrical signals by incident on a transducer oscillations. The disadvantage of this system is that there is no possibility of threshold influence and a switching on and off or branches of the branches is not provided.

In DE-OS 2423277 a space protection system is presented, the evaluation circuit has a plurality of frequency channels with different pass bands for the frequency shifts and only triggers an alarm signal when the recorded frequency-shifted oscillations in at least one frequency channel exceed a corresponding threshold.

Frequencies in the ultrasonic range are evaluated and frequency changes are evaluated.

The disadvantage is that the threshold influence can not be used for turning. Switching on, off and on of the branches is not planned.

Furthermore, an optoelectronic wear sensor for automated contactless tool wear and tool breakage identification (DD-PS 244282) is known in which the average wear mark width, the partial cutting breakouts, the built-up edge, the maximum wear and tool breakage are determined and signaled in conjunction with a microcomputer.

Optoelectronic signals are evaluated and evaluated. The disadvantage is that the circuit is used for counting pulses only in a post-process measurement.

Object of the invention

The object of the invention is to provide a circuit arrangement which monitors the clamping process in the lathe and guarantees an immediate detection of unstable states, increases the reliability in automatic operation, is simple in construction and requires minimal setup effort with high flexibility.

Explanation of the essence of the invention

The invention has for its object to provide a circuit arrangement for detecting process instabilities when turning by evaluating structure-borne sound vibrations that generates a signal when process instabilities occur requires minimal preparation and adjustment by a self-learning component, monitoring all active cuts allows, none Standardization of the individual sections required and the evaluation requires only one measurand. Process instabilities are understood to mean the occurrence of tool or workpiece vibrations and collisions. According to the invention, the object is achieved in that the signal generated by a vibration sensor is fed via an impedance transformer a plurality of identical parallel arranged measuring chains, each consisting of an analog switch, bandpass and full-wave rectifier.

The output signals of the full-wave rectifiers are supplied to comparators whose threshold values are provided by a microcomputer via digital-to-analog converters. The outputs of the comparators are connected to a logic block which is interconnected to the microcomputer and the machine tool Steerung, the logic block always outputs an instability signal when one or more threshold values are exceeded and abut the release signals from the machine tool control and the microcomputer. The output signals of the full-wave rectifier are further supplied to the microcomputer via analog-to-digital converters, the microcomputer always outputting an instability signal when the amplitude differences of the output signals of the full-wave rectifiers exceed a value learned automatically after the beginning of the cut.

embodiment

The solution according to the invention will be explained in more detail on an exemplary embodiment. In the accompanying drawing shows:

Fig. 1: Block diagram of the solution according to the invention

The signal obtained by a vibration sensor 1 mounted on the machine tool and converted into an impedance converter 2 is simultaneously supplied to π parallel measuring chains consisting of analog switch 3.i, bandpass filter 4.І, full-wave rectifier 5.i and comparator 6.І, the threshold values the comparators 6.1 to 6.η via digital-to-analog converter 8 are provided by a microcomputer 9.

The outputs of the comparators 6.1 to 6.η are connected to a logic block 10, which is interconnected to a microcomputer 9 and the machine tool control, the logic block 10 outputs a turn-off signal whenever one or more thresholds are exceeded and the enable signals from the Machine control and the microcomputer 9 abut.

The outputs of the full-wave rectifier 5.1 to 5.n are connected via analog-to-digital converter 7 in addition to the microcomputer 9, wherein the microcomputer 9 always outputs an instability signal when the amplitude differences of the output signals of the full-wave rectifier 5.1 to 5.η a after cutting automatically exceed the learned value. About the analog switch 3.1 to 3.n can be turned off for special cases of processing individual electrodes on the microcomputer 9.

Claims (1)

Circuit arrangement for detecting process instabilities when turning, consisting of vibration sensor, impedance converter, a plurality of similarly composed of analog switch, bandpass and full-wave rectifier and arranged parallel to each other electrodes, comparators, analog-to-digital converter, digital-to-analog converter, microcomputer and logic block, said the signal obtained at the machine tool mounted vibration transducer is supplied to an impedance converter whose output is connected to the mutually parallel measuring chains, and in which the full-wave rectifier outputs are each connected to a comparator, the comparators are connected via a digital-to-analog converter to a microcomputer, characterized in that the outputs of the full-wave rectifiers (5.1 to 5.n) are connected via an analog-to-digital converter (7) to a microcomputer (9) for providing actual in-process measurement values therefor,which is connected to a logic block (10) for the assignment of correction values to the voltage values, the inputs of which are each connected to an output which is controlled by the comparator (1) to (6) via the digital-to-analog converter (8) from the microcomputer (9) with respect to the comparator threshold allocation. n) are connected and whose output is connected to the machine tool. For this 1 page drawing