Apparatus for monitoring tool life
First Claim
1. A method of monitoring the operating condition of a cutting tool during machining of a workpiece comprising the steps of(a) monitoring the level of vibration of the tool on commencement of machining and generating a first signal representative of said monitored level,(b) applying said first signal to a variable gain circuit means to provide a second signal which is a function of said first signal,(c) adjusting the gain of said gain circuit means to adjust said second signal to a preselected value,(d) generating a first reference value which is a preselected function of said preselected value and generating a second reference value representing a minimum reference level generated when the cutting tool commences machining a workpiece,(e) storing said first and second reference values and a factor representing the adjusted gain of said gain circuit means,(f) prior to commencing subsequent machining under the same or similar machining conditions, adjusting the gain of said gain circuit to said adjusted gain, and on commencement of said subsequent machining(g) monitoring the level of vibration of the tool to generate a further second signal,(h) comparing said further second signal with said first reference value and generating a first control signal in dependence on said further second signal level exceeding said reference value and generating a second control signal if the monitored level is less than the second reference value for a predetermined length of time;
- whereby generation of the first control signal is indicative of a worn or defective cutting tool and generation of the second control signal is indicative of a broken or missing cutting tool.
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Accused Products
Abstract
A system for monitoring the vibration of a power driven cutting tool during machining first produces a signal proportional to the vibration spectrum of the tool over a preselected band width. This is passed through a digitally controlled attenuator which is adjusted to provide an output signal at a preselected level. The degree of attenuation is stored, as is a reference value which is generated as a function of the attenuated signal. Then, during subsequent machining operations under the same machining conditions the attenuator is controlled to provide the same degree of attenuation and the reference value, which is in the form of a digital signal, is compared with the rectified and digitized output of the attenuator. When the latter exceeds the reference value a control signal is generated which either provides an audible or visual warning that the cutting tool is worn and therefore due for replacement or initiates an automatic tool changing operation. The system effectively monitors the wear of the tool and, in providing its own reference, i.e. the reference value which is generated, caters automatically for changes in the machining conditions such as use of a different tool or change in workpiece material.
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Citations
40 Claims
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1. A method of monitoring the operating condition of a cutting tool during machining of a workpiece comprising the steps of
(a) monitoring the level of vibration of the tool on commencement of machining and generating a first signal representative of said monitored level, (b) applying said first signal to a variable gain circuit means to provide a second signal which is a function of said first signal, (c) adjusting the gain of said gain circuit means to adjust said second signal to a preselected value, (d) generating a first reference value which is a preselected function of said preselected value and generating a second reference value representing a minimum reference level generated when the cutting tool commences machining a workpiece, (e) storing said first and second reference values and a factor representing the adjusted gain of said gain circuit means, (f) prior to commencing subsequent machining under the same or similar machining conditions, adjusting the gain of said gain circuit to said adjusted gain, and on commencement of said subsequent machining (g) monitoring the level of vibration of the tool to generate a further second signal, (h) comparing said further second signal with said first reference value and generating a first control signal in dependence on said further second signal level exceeding said reference value and generating a second control signal if the monitored level is less than the second reference value for a predetermined length of time; whereby generation of the first control signal is indicative of a worn or defective cutting tool and generation of the second control signal is indicative of a broken or missing cutting tool. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A system for monitoring the operating condition of a cutting tool during machining of a workpiece comprising monitoring means for monitoring the level of vibration of the tool on commencement of machining and generating a first signal representative of said monitored level;
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a variable gain circuit means for providing a second signal which is a function of said first signal; control means for automatically adjusting the gain of said gain circuit means to adjust said second signal to a preselected value; reference means for generating a first reference value which is a preselected function of said preselected value and for generating a second reference value representing a minimum reference level generated when the cutting tool commences machining a workpiece; store means for storing said first and second reference values and a factor representing the adjusted gain of said gain circuit means; first comparator means for real-time comparing further second signals generated during subsequent machining under the same or similar machining conditions with said first reference value and generating a first control signal in dependence on said further second signal level exceeding said first reference value; and
second comparator means for generating a second control signal if the monitored level is less than the second reference signal for a predetermined length of time;whereby generation of the first control signal is indicative of a worn or defective cutting tool and generation of the second control signal is indicative of a broken or missing cutting tool. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. A method for monitoring the operating codition of at least one power driven cutting tool during machining of a workpiece comprising the steps of
(a) monitoring the level of vibration of the tool on commencement of machining and generating a first signal representative of said monitored level; -
(b) applying said first signal to a variable gain circuit means to provide a second signal which is a function of said first signal, (c) adjusting the gain of said gain circuit means to adjust said second signal to a preselected value, (d) generating a first reference value which is a preselected function of said preselected value and generating a second reference value representing a minimum reference level generated when the cutting tool commences machining a workpiece, and on commencement of subsequent machining (e) comparing further second signals with said first reference value and generating a first control signal in dependence on said further second signal level exceeding said reference value and generating a second control signal if the monitored level is less than the second reference value for a predetermined length of time; whereby generation of the first control signal is indicative of a worn or defective cutting tool and generation of the second control signal is indicative of a broken or missing cutting tool.
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29. A system for monitoring the operating condition of a power driven cutting tool during machining of a workpiece comprising monitoring means for monitoring the level of vibration of the tool on commencement of machining and generating a first signal representative of said monitored level;
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a variable gain circuit means for providing a second signal which is a function of said first signal; control means for automatically adjusting the gain of said gain circuit means to adjust said second signal to a preselected value; reference means for generating a first reference value which is a preselected function of said preselected value and for generating a second reference value representing a minimum reference level generated when the cutting tool commences machining a workpiece; first comparator means for comparing further second signals generated during subsequent machining with said first reference value and generating a first control signal in dependence on said further second signal level exceeding said reference value; and
second comparator means for generating a second control signal if the monitored level is less than the second reference signal for a predetermined length of time;whereby generation of the first control signal is indicative of a worn or defective cutting tool and generation of the second control signal is indicative of a broken or missing cutting tool.
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30. A system for monitoring the operating conditions of a cutting tool during machining of a work piece comprising:
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(a) means for monitoring the level of vibration of the tool on commencement of machining and generating a first signal representative of said monitored level; (b) a variable gain circuit means for providing a second signal which is a function of said first signal; (c) control and reference means for automatically adjusting the gain of the gain circuit means so as to adjust the second signal to a preselected value wherein said control and reference means includes means for (1) deriving from the second signal a product signal greater than the second signal which is also a preset function of the second signal, (2) comparing the product signal with a first preselected reference value, (3) increasing the gain of the gain circuit means if the product signal value is less than the first reference value, (4) repeating subelements (1) through (3) until the product signal value is greater than the first reference value, and (5) reducing the gain of the gain circuit means by a preset factor and deriving a further product signal for storing as a second reference value; (d) means for storing the second reference value and a factor representing the adjusted gain of the gain circuit means; and (e) comparator means for real-time comparing further second signals generated during subsequent machining under the same or similar machining conditions with the second reference value and generating a control signal dependent on the further second signal level if it exceeds the second reference value. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37, 38, 39, 40)
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Specification