CN102896557A - Milling composite machining cutting force measuring method - Google Patents

Abstract

The invention discloses a milling composite machining cutting force measuring method which comprises the following steps of: respectively fixedly installing three-way displacement sensors in two directions, namely at the left and right and front and back vertically perpendicular to a milling cutter shaft, below a workpiece and in up and down direction parallel to the milling cutter shaft, wherein the sensors are connected with a computer; adjusting the distance between the sensors and the workpiece, starting a milling composite machining machine tool after achieving the requirements; cutting a rotary body workpiece; obtaining a dynamic milling cutter displacement signal through the displacement sensors; eliminating interference signals during the machining process through a wavelet signal processing method; subsequently converting a time domain displacement signal into a frequency domain displacement signal; obtaining frequency domain cutting force functions by using transmission functions of the milling cutter and the workpiece' and finally converting the frequency domain signal into a time domain signal so as to obtain the magnitude of the cutting force. The method is simple and easy to carry out; the displacement signal is directly obtained through the sensors; a low-pass filter and relevant theories are adopted for calculation; interference factors in a machining environment are eliminated; the measurement result is reliable; and reference basis for revealing the milling composite machining mechanisms and researching the machining vibration is provided.

Description

A kind of turnning and milling Compound Machining cutting force measurement method

Technical field

The present invention relates to cut force measurement, particularly a kind of to turnning and milling Compound Machining numerical control machine tool cutting force measuring method.

Background technology

Along with the fast development of science and technology, the Digit Control Machine Tool with turnning and milling complex function becomes the very fast machine of development in recent years because having the characteristics such as the complicated processing of adaptation and production high efficiency.This lathe can adopt the kinds of processes processing method to complex surface machining simultaneously, and the war products productions such as Aeronautics and Astronautics are particularly needed.But because the technical data that at present shortage abroad can reference makes the development of these class high-grade, digitally controlled machine tools of China be subject to very big restriction.Therefore, further investigate and inquire into the turnning and milling Compound Machining mechanism of this class lathe, it is significant that China is developed this type of high-grade, digitally controlled machine tools equipment.

In the turnning and milling compound processing course, cutting force is one of key technology of turnning and milling Compound Machining mechanism.Because existing dynamometer is difficult to install at turn-milling complex machining center, can not be installed on the knife rest such as turning processing, can not be installed on the workbench such as Milling Process, so use the actual uplink of dynamometer measurement turnning and milling Compound Machining cutting force obstructed.

The retrieval domestic and foreign literature does not have good method so far for turnning and milling Compound Machining cutting force measurement as can be known, and this is a technical barrier of this field further investigation of puzzlement.

The CN101804584A patent application specification discloses a kind of three-way cutting force measurement instrument for turning and milling processing.This measuring instrument adopts at milling cutter rear end seat the three-way piezoelectric crystal probe is installed, and the cutting force that milling cutter is produced changes into piezoelectric signal, through radioing to computer system, by obtaining three-dimensional cutting force data after the Computer Processing.This measuring instrument not only complex structure, manufacture the cost height, and signal collecting element and milling cutter directly join, and under the high-speed cutting processing environment, adds various external disturbance, makes the accuracy of measurement result be difficult to guarantee.

Summary of the invention

The objective of the invention is provides a kind of turnning and milling Compound Machining cutting force measurement method for the problem that above-mentioned prior art exists, for the research of turnning and milling Compound Machining Digit Control Machine Tool equipment creates conditions.

The principle of measuring method of the present invention is: obtain milling cutter dynamic displacement signal by displacement sensor, by the small echo signal processing method noise signal in the process is removed, then convert the time domain displacement signal to the frequency domain shift signal; Utilize the transfer function of milling cutter and workpiece, obtain the function of frequency domain cutting force, convert frequency-region signal to time-domain signal more at last, obtain the size of cutting force.

Based on above-mentioned principle, turnning and milling Compound Machining cutting force measurement method provided by the invention may further comprise the steps:

1) with cutter spindle about vertical and on former and later two directions and workpiece bottom, with the above-below direction of milling cutter axially parallel on respectively with anchor clamps fixed installation triple channel displacement transducer, displacement transducer is joined with computer respectively, utilize aluminium-foil paper that various holding wires and the data wire that displacement transducer connects computer wrapped, prevent the smear metal damage sensor that splashes, adjust the distance between sensor and milling cutter and workpiece, make it to reach the instructions for use of displacement transducer;

2) open the turnning and milling composite processing machine tool, the cutting revolving body workpieces, measure respectively milling cutter by three displacement transducers and be out of shape the displacement variable signal that produces under respective sensor location point time domain condition on three directions, then be transferred to computer system, computer is pressed following routine processes:

As an example of left and right directions example (front and back are identical with above-below direction), the displacement variable of establishing distortion generation under corresponding this direction sensing station point time domain condition of milling cutter that displacement transducer records is x'(t).

3) utilize similar cantilever beam formula:

$x^{\&prime;}\left(t\right)=\frac{{\mathrm{<figure-callout\; id="2"\; label="Fl"\; filenames="HDA00002149042100011.png"\; state="\{\{state\}\}">Fl</figure-callout>}}^2}{6\mathrm{EI}}(3L-l)---\left(1\right)$

$x\left(t\right)=\frac{{\mathrm{<figure-callout\; id="3"\; label="FL"\; filenames="HDA00002149042100011.png"\; state="\{\{state\}\}">FL</figure-callout>}}^3}{2\mathrm{EI}}---\left(2\right)$

In the formula:

X'(t)---the milling cutter respective sensor location point time domain displacement variable that displacement transducer records;

F---suffered external force (cutting force) on direction of measurement;

L---milling cutter length;

L---measurement point to milling cutter cutter root distance from;

L-l---measurement point to the milling cutter point width from;

E---elastic modelling quantity;

I---the moment of inertia;

Draw point of a knife time domain displacement variable by formula (1) and (2):

$x\left(t\right)=\frac{x^{\&prime;}\left(t\right)\&CenterDot;3L^3}{(3L-l)\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="l"\; filenames="HDA00002149042100011.png"\; state="\{\{state\}\}">l</figure-callout>}}^2}$

Utilize low pass filter that upper rheme time domain displacement variable outside high-frequency signals (such as noise etc.) is filtered out, to improve signal quality;

4) utilize Laplace transform to convert above-mentioned time domain displacement variable x (t) to frequency domain shift variable quantity X (S);

5) utilize the transfer function on left and right directions to convert above-mentioned frequency domain shift variable quantity X (S) to frequency domain power variable quantity F (S);

6) utilize anti-Laplace transform to convert above-mentioned frequency domain power variable quantity F (S) to time domain power variable quantity f (t), i.e. the cutting force that makes progress of the party;

7) obtain by above-mentioned same procedure before and after, the cutting force on the both direction up and down.

Various variable quantities on above-mentioned three directions can be shown and printed by computer system.

Beneficial effect of the present invention:

1, measuring method is simple, only needs in the experiment with anchor clamps the displacement transducer install and adjust to be put in place, and remaining data is extracted and processed and finish by computer.

2, measurement equipment therefor structure is relatively simple, and cost is relatively cheap.

3, displacement signal is directly obtained by displacement transducer, adopt low pass filter technology and correlation theory computing, got rid of the disturbing factor in the processing environment, the turnning and milling that draws processing cutting force result reliability is high, can be and discloses turnning and milling Compound Machining mechanism, research processing flutter provides reference frame.

Description of drawings

Fig. 1 is that front view on the fore-and-aft direction is arranged in displacement transducer and milling cutter and workpiece space in the measuring method of the present invention;

Fig. 2 is the upward view of Fig. 1;

Fig. 3 is the right view of Fig. 1;

Fig. 4 is the change in displacement discharge curve of milling cutter respective sensor location point on left and right directions that sensor records;

Fig. 5 is for adopting the change in displacement discharge curve of the point of a knife point that obtains after the low pass filter filtering;

Fig. 6 is frequency domain shift variable quantity curve;

Fig. 7 is the point of a knife point transfer function real part on left and right directions;

Fig. 8 is the point of a knife point transfer function imaginary part on left and right directions;

Fig. 9 is frequency domain power variable quantity curve;

Figure 10 is time domain power variable quantity curve.

Among the figure: 1-handle of a knife, 2-milling cutter, 3-anchor clamps A, 4-displacement transducer A, 5-anchor clamps B, 6-displacement transducer B, 7-anchor clamps C, 8-displacement transducer C, 9-workpiece;

The specific embodiment

Take rapidoprint steel 1018(American Standard on the gloomy smart machine NT3150 turning milling center of MORISEIKI) revolving body is as example.Machining condition is: milling cutter rotating speed 2000rpm, workpiece rotational frequency 10rpm, feed speed 0.2mm/s, cutting depth 0.5mm.Adopt the inventive method to measure its cutting force, with reference to Fig. 1, Fig. 2 and Fig. 3, be installed on the handle of a knife 1 with milling cutter 2(milling cutter first) axially vertical about and with anchor clamps A3 and B5 triple channel displacement transducer A4 and B6 are installed respectively on former and later two directions; In the bottom of workpiece 9, with anchor clamps C7 triple channel displacement transducer C8 is installed with the above-below direction of milling cutter axially parallel, each displacement transducer is connected with computer system by wire, utilize aluminium-foil paper that various holding wires and the data wire that each sensor is connected with computer wrapped, to prevent from cutting the damage sensor that splashes, adjust the distance between each sensor and milling cutter and workpiece, make it to reach sensor instructions for use value; The operation program of above-mentioned cutting force is enrolled in the computer; Open turn-milling complex machining center, the cutting revolving body workpieces goes out the milling cutter displacement variable signal that the distortion of respective sensor location point produces on three directions by three displacement sensors, is transferred to computer, machine is processed as calculated, obtains the cutting force on three directions of milling cutter.

Cutting force on the milling cutter left and right directions is as example, and each variable quantity curve is seen Fig. 4 to Fig. 9.Wherein Fig. 4 is the change in displacement discharge curve of milling cutter respective sensor location point on left and right directions that sensor records; Fig. 5 is for adopting the change in displacement discharge curve of the point of a knife point that obtains after the low pass filter filtering; Fig. 6 is frequency domain shift variable quantity curve; Fig. 7 and Fig. 8 are respectively point of a knife point transfer function real part and the imaginary part on left and right directions; Fig. 9 is frequency domain power variable quantity curve; Figure 10 is time domain power variable quantity curve.

Claims (1)

1. turnning and milling Compound Machining cutting force measurement method is characterized in that may further comprise the steps:

1) with cutter spindle about vertical and on former and later two directions and workpiece bottom, with the above-below direction of milling cutter axially parallel on respectively with anchor clamps fixed installation triple channel displacement transducer, displacement transducer is joined with computer respectively, utilize aluminium-foil paper that various holding wires and the data wire that displacement transducer connects computer wrapped, prevent the smear metal damage sensor that splashes, adjust the distance between sensor and milling cutter and workpiece, make it to reach the instructions for use of displacement transducer;

2) open the turnning and milling composite processing machine tool, the cutting revolving body workpieces, measure respectively milling cutter by three displacement transducers and be out of shape the displacement variable signal that produces under respective sensor location point time domain condition on three directions, then be transferred to computer system, computer is pressed following routine processes:

Take left and right directions as example, the displacement variable of establishing distortion generation under corresponding this direction sensing station point time domain condition of milling cutter that displacement transducer records is x'(t);

3) utilize similar cantilever beam formula:

$x^{\&prime;}\left(t\right)=\frac{{\mathrm{Fl}}^2}{6\mathrm{EI}}(3L-l)---\left(1\right)$

$x\left(t\right)=\frac{{\mathrm{FL}}^3}{2\mathrm{EI}}---\left(2\right)$

In the formula:

X'(t)---the milling cutter respective sensor location point time domain displacement variable that displacement transducer records;

F---suffered external force on direction of measurement;

L---milling cutter length;

L---measurement point to milling cutter cutter root distance from;

L-l---measurement point to the milling cutter point width from;

E---elastic modelling quantity;

I---the moment of inertia;

Draw point of a knife time domain displacement variable by formula (1) and (2):

$x\left(t\right)=\frac{x^{\&prime;}\left(t\right)\&CenterDot;3L^3}{(3L-l)\&CenterDot;l^2}$

Utilize low pass filter that upper rheme time domain displacement variable outside high-frequency signals is filtered out, to improve signal quality;

4) utilize Laplace transform to convert above-mentioned time domain displacement variable x (t) to frequency domain shift variable quantity X (S);

5) utilize the transfer function on left and right directions to convert above-mentioned frequency domain shift variable quantity X (S) to frequency domain power variable quantity F (S);

6) utilize anti-Laplace transform to convert above-mentioned frequency domain power variable quantity F (S) to time domain power variable quantity f (t), i.e. the cutting force that makes progress of the party;

7) obtain by above-mentioned same procedure before and after, the cutting force on the both direction up and down.

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