DE2155574A1 - Method for determining a thrust vector and the vibration vector of a spindle and arrangement for its implementation - Google Patents

Description

■ - FILE NO.! 17/1946

ALlEIT-SIiADLEY COMPANY, 12o1 South Second Street, Milwaukee, Wisconsin 532o4 (USA)

"Method for determining a thrust vector and the vibration vector a spindle and arrangement for its implementation "

The invention relates to a method for determining the thrust vector and the vibration vector of the spindle of a machine tool in operation, as well as an anondnuaig to it Execution.

The determination of the shock or vibration amplitude Such a spindle is important as it is a measure of the vibrations of the tip of the cutting tool of the machine and thus a measure of the influence of the spindle vibrations on the surface quality of the workpiece. the Spindle vibrations themselves have a very detrimental effect on the bearings of the spindle, especially when Ball and roller bearings are used. It is therefore desirable to check the amplitude of the Seibat vibrations of the spindle as low as possible.

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In systems "in which there is an interest in the maximum Removal speed on the tool, "with a given surface quality, as high as possible, such as B. in the processing of aluminum in the aerospace industry, are the The thrust force and the amplitude of the spindle vibrations are sufficient parameters for controlling the machining process. It is therefore desirable to have a method and arrangement for carrying it out that utilizes these parameters of a spindle measures quickly, easily and economically.

The object of the invention is to provide such a method create. According to the invention, this object is achieved by a A method, which is characterized in that of right-angled points around the spindle first and second signals are derived which correspond to the thrust vector and the vibration vector components of the spindle that from these first and second signals are generated signals which correspond to the thrust vector and that from the first and second Signals signals are generated which correspond to the vibration vector.

The inventive arrangement for performing this method is characterized by converters for deriving first and second signals from the spindle, which correspond to the combined thrust and resonance vibration vector components, a first and a second circuit arrangement for generating a vector, switching means for supplying the said first and second signals to said circuit ^{arrangement for generating a signal which the c} 2Q982A / 062A

The thrust vector corresponds to the spindle and splitting means for feeding the first and second signals to the second circuit arrangement for generating a signal representative of the vibration vector of the spindle is equivalent to.

An embodiment of the invention is based on the following the accompanying drawing explained in more detail. Show it:

Pig. 1 shows a block diagram of an exemplary embodiment of the invention and

Pig. 2 shows the block diagram of a circuit arrangement for generating a vector which is used in the system according to Pig. 1 can be used.

Pig. 1 shows the block diagram of an embodiment of a system according to the invention. The tool head 1o of a machine tool carries a motor 12 _t which drives a spindle H. A putter in the spindle holds a tool 16 which processes a workpiece 18 arranged on a plate 20.

When the tool against the W _e is pressed rkstück, the spindle is deflected slightly. In addition, the rotating tool has grooves of teeth which, when they come into contact with the workpiece, vibrate to the pole, the frequency of which is equal to the number of revolutions of the spindle multiplied by the number of teeth of the tool when cutting continuously. If machining takes place intermittently (i.e. if

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the workpiece through. Slots, depressions, etc. is interrupted), the specified frequency has to be multiplied by the number of interruptions per revolution of the tool. Typical maximum cutting frequencies with conventional spindles with 1o revolutions per second (600 revolutions per minute) and possibly 8 to 10 interruptions on the tool are therefore approximately 12o Hz or less, normally these are

^ less than 5o Hz with usual profile milling and step as Vibration of the spindle. However, they create resonance vibrations in the spindle, the lowest of which in a range between 600 and 900 Hz, depending on the tool and tool holder used. Self-oscillations at on-. approximately I400 Hz are also used as resonance vibrations of the spindle the first harmonic possible. There is no guarantee that the damping of the second and higher harmonics of the spindle is less than or equal to that of the fundamental wave. The self-oscillations or vibrations caused by the machining process

W shocks are the vibrations which, like the instantaneous deflection of the spindle, are to be measured by the system according to the invention. To achieve this, an X converter 22 and a Y converter 24 are used to scan the movement of the spindle in the same plane but at right angles to one another. These converters can be constructed in any way and convert the mechanical displacement of the spindle into

■ \ ■ an electrical signal. You can e.g. B. piezoelectric - ■ converter or contactless magnetic .Umsetzer, the output signals of which are supplied to two band filters 26 and 28 and a circuit arrangement 3o for generating a vector.

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2T55574

-The output signals of the converters contain a low-frequency ' periodic component representing the successive contacts of the tool corresponds to the workpiece as well as a high frequency Component insofar as resonance vibrations of the spindle occur. This high frequency component occurs at the resonance points the spindle on, the s.B. ' "are 600 Hz or higher. The circuit arrangement 3υ speaks to the low-frequency Components of the signals fed to their input that are practical which ■ form thrust signals. It generates an output signal which corresponds to the resulting thrust which can be read on a correspondingly rear-sonicated display instrument 32.

The band filters 26 and 23 are tuned so that they pass the higher resonance frequency of the spindle, the bandwidth is large enough to accommodate small changes in the resonance frequency of the spindle caused by changes in the tool and the tool holder, and resonance vibrations higher order to admit. However, they hold the down- ^ frequent, periodic component. The band filters extract the component of the spindle resonance frequency that the shock vibrations in the X and Y directions These two signals then become two demodulators and 36, which generate DC signals, which in turn a second circuit arrangement 38 for generating a vector. This circuit arrangement 38 generates an output signal corresponding to the amplitude of the r-resulting Yi-:

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- ο -

bj-ations of the spindle corresponds. This signal is indicated by a suitable indicating instrument 40, which is referred to here as an indicating instrument for the resulting vibration level. Both the thrust indicator and the indicator for the resulting vibration level can be used as a Votfcmeter or cathode ray tube. . ^;

i'ig. 2 shows a schematic block diagram of a circuit arrangement for generating a vector, aia sur application in the Circuit arrangement according to Pig. 1 is suitable. Such a circuit arrangement for generating a vector is the subject of an older German patent application by the Annelderin with the Sitel "Method for generating a vector and circuit arrangement to be carried out" (P .. .........)

The two input signals Z and X are fed to two circuits * 42 and 44. These gate circuits are constructed as analog τ circuits. Two square waves with a frequency of the order of magnitude of 1 kHz are fed to the other inputs of these gate circuits Both square waves are offset from one another by 90 ° in phase. The two gate circuits modulate the amplitude of the square waves with the input signals X and Y. They end output signals from these gate circuits before an adder circuit 43 which adds these two signals «, Bas output signal of the

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Adding circuit is fed to a band filter 5o, which its first harmonic, the one generated by the input signals X and Y is amplitude modulated sine wave. These Siiiuswelle is then fed to a demodulator 52, whose Output signal the vector resulting from the input signals represents. Designates the input signals with X and Y,

2 2 the output signal is the square root of X + Y.

Claims;

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Claims (4)

Paterite claims: 1. Method for determining the thrust vector and the vibration vector of a spindle, characterized in that of points at right angles to each other around the spindle first and second signals are derived, which the thrust vector and the vibration vector components of the 'spindle correspond to that of these first and second' signals signals are generated that correspond to the thrust vector and that off fc the first and second signals signals are generated ', the correspond to the yi "br at ions vector. 2. The method according to claim 1, characterized in that the generation of the signals corresponding to the vibration vector the following steps from said first and second signals includes: 1.) The separation of a signal corresponding to the components of the vibration vector whose frequency is above the Resonance frequency of the spindle, from the first and second signals and 2.) the rectification of these signals corresponding to the components of the vibration vector. 3. Arrangement for performing the method according to claim 1 or 2, characterized by converters (22, 24) for deriving first and second signals from the spindle (H) representing the combined thrust and resonance vibration vector components 209824/0624 a first and a second "circuit arrangement (po, 38) for generating a vector, switching means for supplying said first and second signals to said circuit arrangement for generating a signal which corresponds to the thrust vector of the spindle and switching means (26, 28, 34> 36) for supplying the first and second signals to the second circuit arrangement for generating a signal which corresponds to the vibration vector of the spindle. 4. Circuit arrangement according to claim 3 »characterized in that that the switching means for supplying the first and second signals to the second circuit arrangement (38). to generate a vector switching means (26, 28) for deriving a signal corresponding to the vibration above the resonance frequency the spindle from the first and second signals, and switching means (34, 36) for rectifying said the Include vibration corresponding signal. 209 824/0624 Emptied