CN102896557B - 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 scientific and technical fast development, the Digit Control Machine Tool with turnning and milling complex function becomes the very fast machine of development in recent years because having the features such as the complicated processing of adaptation and production high efficiency.This lathe can adopt kinds of processes processing method to complex surface machining simultaneously, and the war products such as Aeronautics and Astronautics are produced and particularly needed.But due to current shortage abroad can reference technical data, make 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, China is developed to this type of high-grade, digitally controlled machine tools equipment significant.

In 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 on turn-milling complex machining center, can not be arranged on knife rest as turning processing, can not be arranged on workbench as Milling Process, therefore use the actual uplink of dynamometer measurement turnning and milling Compound Machining cutting force obstructed.

Retrieval domestic and foreign literature is known, there is no so far good method for turnning and milling Compound Machining cutting force measurement, and this is a technical barrier of this field further investigation of puzzlement.

CN101804584A patent application specification discloses a kind of three-way cutting force measurement instrument for turning and milling processing.This measuring instrument adopts, on the seat of milling cutter rear end, 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, after being processed, obtains three-dimensional cutting force data by computer.This measuring instrument not only complex structure, to manufacture cost high, and signal collecting element and milling cutter directly join, and under high-speed cutting processing environment, adds various external disturbance, makes the accuracy of measurement result be difficult to guarantee.

Summary of the invention

The problem that the object of the invention is to exist for above-mentioned prior art provides a kind of turnning and milling Compound Machining cutting force measurement method, 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 small echo signal processing method, noise signal in process is removed, then convert time domain displacement signal to frequency domain shift signal; Utilize the transfer function of milling cutter and workpiece, obtain the function of frequency domain cutting force, finally convert frequency-region signal to time-domain signal again, obtain the size of cutting force.

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

1) with cutter spindle in vertical left and right and former and later two directions and workpiece bottom, with the above-below direction of milling cutter axially parallel on respectively with fixture fixed installation triple channel displacement transducer, displacement transducer is joined with computer respectively, the various holding wires and the data wire that utilize aluminium-foil paper that displacement transducer is connected to computer wrap, 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 turnning and milling composite processing machine tool, cutting revolving body workpieces, measure respectively the milling cutter displacement variable signal that under respective sensor location point time domain condition, distortion produces in three directions by three displacement transducers, be then 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:

$x^{\&prime;}\left(t\right)=\frac{{\mathrm{<figure-callout\; id="2"\; label="Fl"\; filenames="HDA00002149042100011.png,HDA00002149042100021.png"\; state="\{\{state\}\}">Fl</figure-callout>}}^2}{6\mathrm{EI}}(3L-l)---\left(1\right)$

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

In 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 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):

$x\left(t\right)=\frac{x^{\&prime;}\left(t\right)\&CenterDot;3L^3}{(3L-l)\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="l"\; filenames="HDA00002149042100011.png,HDA00002149042100021.png"\; state="\{\{state\}\}">l</figure-callout>}}^2}$

Utilize low pass filter that upper rheme time domain displacement variable outside high-frequency signals (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 party's cutting force upwards;

7) obtain the cutting force on front and back, upper and lower both direction by above-mentioned same procedure.

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

Beneficial effect of the present invention:

1, measuring method is simple, in experiment, only need displacement transducer install and adjust be put in place with fixture, and remaining data is extracted and processed and completes 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 processing environment, the turnning and milling drawing processing cutting force result reliability is high, can be and discloses turnning and milling Compound Machining mechanism, research processing flutter provides reference frame.

Accompanying drawing explanation

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

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 the milling cutter respective sensor location point that records of sensor on left and right directions;

Fig. 5 is the change in displacement discharge curve that adopts the point of a knife point obtaining after 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.

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

The specific embodiment

Take rapidoprint steel 1018(American Standard in 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 first arranged on handle of a knife 1 with milling cutter 2(milling cutter) axially in vertical left and right and former and later two directions, with fixture A3 and B5, triple channel displacement transducer A4 and B6 are installed respectively; The bottom of workpiece 9, with the above-below direction of milling cutter axially parallel on triple channel displacement transducer C8 is installed with fixture C7, each displacement transducer is connected with computer system by wire, utilize aluminium-foil paper is connected each sensor various holding wires and data wire with computer to wrap, 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 computer; Open turn-milling complex machining center, cutting revolving body workpieces, goes out the milling cutter displacement variable signal that the distortion of respective sensor location point produces in three directions by three displacement sensors, is transferred to computer, machine processing as calculated, obtains the cutting force in three directions of milling cutter.

Take the cutting force on milling cutter left and right directions as example, each variable quantity curve is shown in Fig. 4 to Fig. 9.Wherein Fig. 4 is the change in displacement discharge curve of the milling cutter respective sensor location point that records of sensor on left and right directions; Fig. 5 is the change in displacement discharge curve that adopts the point of a knife point obtaining after 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. a turnning and milling Compound Machining cutting force measurement method, is characterized in that comprising the following steps:

1) with cutter spindle in vertical left and right and former and later two directions and workpiece bottom, with the above-below direction of milling cutter axially parallel on respectively with fixture fixed installation triple channel displacement transducer, displacement transducer is joined with computer respectively, the various holding wires and the data wire that utilize aluminium-foil paper that displacement transducer is connected to computer wrap, 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 turnning and milling composite processing machine tool, cutting revolving body workpieces, measure respectively the milling cutter displacement variable signal that under respective sensor location point time domain condition, distortion produces in three directions by three displacement transducers, be then 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 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 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 party's cutting force upwards;

7) obtain the cutting force on front and back, upper and lower both direction by above-mentioned same procedure.

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