Experimental determinations concerning the weaving machine vibrations.

Vigaru, Cosmina ; Luca, Gheorghe ; Rusu, Lucian 等

1. INTRODUCTION

In the case of weaving machine it is difficult to identify each source of vibration. In weaving process all mechanisms are working simultaneously and generate vibrations having different amplitudes and directions. There are many theoretical studies regarding the influence of the vibrations on the weaving process (Reicher & Dragoi, 1985), (Demeulare, 2004), but few experimental results. Most of the studies consider only one mechanism of the machine or vibrations on a single direction in space. The used methods for these studies are based on the classical vibration theory or finite element method (Deger, 2000).

The aim of the whole study was to experimentally evaluate the resultant vibrations of a weaving machine on a set of points and each direction. Based on the experimental results the final goal is to reduce the vibrations level. In the framework of the performed experimental study of vibration influence, the measurements were effectuated by placing the transducer on different elements of the machine, to record longitudinal, transversal and vertical vibrations. The paper presents only the vertical vibrations obtained from the transducer fixed on the launch box.

2. THEORETICAL AND EXPERIMENTAL STUDY

The most important sources of vibrations for the weaving process are: the slay mechanism, the launching mechanism, the shedding mechanism and the warp regulator.

For the experimental study of vibrations, the measurements were effectuated by placing a Bruel&Kjaer accelerometer on different elements of the machine, to record longitudinal, transversal and vertical vibrations. The experimental data were analyzed following the cyclical diagram for the most important mechanism for the weaving process (Stefanuta, 1997).

2.1 Cyclical diagram for the shedding mechanism

During the weaving process, the cycle of shedding mechanism motion corresponds to two complete rotations of the main shaft.

The time interval corresponding to shedding mechanism motion was determinate based on the main shaft rotations: [[alpha].sub.1]--the rotation angle of main shaft, corresponding to warp thread lifting; [[alpha].sub.2]--the rotation angle of main shaft, corresponding to the upper shedding mechanism stationary position; [alpha]3--the rotation angle of main shaft, corresponding to warp thread during the descending motion; [[alpha].sub.4]--the rotation angle of main shaft, corresponding to the lower stationary position of the shedding mechanism.

Considering that the angular velocity of main shaft is constant it can be written:

[[alpha].sub.1] + [[alpha].sub.2] + [[alpha].sub.3] + [[alpha].sub.4] = [720.sup.0] (1) [t.sub.1] + [t.sub.2] + [t.sub.3] + [t.sub.4] = T

where: [[alpha].sub.1], [[alpha].sub.2], [[alpha].sub.3], [[alpha].sub.4]--represent the main shaft rotation angles corresponding to each phase; [t.sub.1], [t.sub.2], [t.sub.3], and [t.sub.4] represents the corresponding time intervals, for each phase; T--represents the total duration of two rotations of the main shaft.

During the movement of the shedding mechanism, the main shaft rotation angles corresponding to the warp thread lifting and descent are equals: [[alpha].sub.1] = [[alpha].sub.3] = [180.sup.0]; also, the angles of stationary shedding mechanism in superior and inferior positions [[alpha].sub.2] = [[alpha].sub.4] = [40.sup.0] are equals.

The obtained values of the considered time intervals are: [t.sub.1] = [t.sub.3] = 0.120s; [t.sub.2] = t4 = 0.027 s.

2.2 Cyclical diagram for the warp regulator

In the case of warp regulator the cyclogram is given by the angle of the main shaft rotation: [[alpha].sub.1] = [215.sup.0]--the main shaft rotation angle of the weaving machine corresponding to warp regulator which released the necessary amount of warp; [[alpha].sub.2] = [85.sup.0]--the main shaft rotation angle of the weaving machine corresponding to return of warp regulator; [[alpha].sub.3] = [290.sup.0]--the main shaft rotation angle of the weaving machine corresponding to stationary warp regulator.

2.3 Cyclical diagram for the slay mechanism

For the Sulzer weaving machine the cyclogram of the slay mechanism is given by the following angles: [[alpha].sub.1] = [70.sup.0]--the rotation angle of main shaft, corresponding to the moment when the slay is moving in extreme frontal position; [[alpha].sub.2] = [70.sup.0] the rotation angle of main shaft, corresponding to the moment when the slay is moving in extreme posterior position; a3 = [220.sup.0]--the rotation angle of main shaft, corresponding to the moment when the slay is in extreme posterior position.

2.4 Cyclical diagram for the launching mechanism

The cyclical diagram of the launching mechanism is obtained following the four phases of a complete rotation of the main shaft. A complete cycle for the launching mechanism is characterized by the phase angles:

[[alpha].sub.1] + [[alpha].sub.2] + [[alpha].sub.3] + [[alpha].sub.4] = [360.sup.0] (2)

where:

--[[alpha].sub.1] = [306.sup.0]--the rotation angle of the main shaft, corresponding to energy potential stored by the torsion bar;

--[[alpha].sub.2] = [45.sup.0]--the rotation angle of the main shaft, corresponding to projectile lifting on carrier;

--[[alpha].sub.3] = [1.sup.0]--the rotation angle of the main shaft, corresponding to the launching mechanism;

--[[alpha].sub.4] = [8.sup.0]--the rotation angle of the main shaft, corresponding to projectile launching.

In this experimental study of the weaving machine vibrations, the amplitudines of accelerations were analyzed as function of time. This study was realized taking into account the movement of each mechanism for only one rotation of the main shaft.

The functioning of each mechanism and the way of vibration transmission to the whole machine were analysed. The following aspects were observed:

* slay generates vibrations on vertical and longitudinal directions;

* shedding mechanism generates vibrations on vertical and longitudinal directions;

* warp regulator generates vibrations on longitudinal and vertical directions;

* launching mechanism generates vibrations on vertical an transversal directions.

Since weaving machine represents an assembly of many mechanisms, the resulting vibrations are transmitted to the frame and to the other machine elements.

There were setted up the following directions:

* longitudinal direction corresponds to the sense of the warp threads;

* transversal direction coincides with the shaft machine direction;

* vertical direction is perpendicular to the floor.

3. RESULTS AND DISCUSSIONS

The experimental measurements were performed in an educational laboratory. The weaving machine under study was a Sulzer model (Luca&Vigaru, 2009).

The elaborated study was focused on the vibration evaluation based on measurements on an old weaving machine.

The transducer positioning on the vertical direction is presented in figure 1.

In the case of vertical vibration the recorded signal is presented in figure 2. The maximum value of acceleration a= 0.9m/[s.sup.2] was obtained for t = 0.350 s.

By applying the Fourier Transform, it results the vibration amplitudes as a function of frequencies (figure 3).

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

[FIGURE 4 OMITTED]

The spectrum representation of acceleration amplitudes as function of frequency (figure 3), do not offer information about the time period corresponding to each maximum amplitude.

In order to obtain the maximum value of acceleration amplitude and the corresponding moment, shown in figure 4, the amplitude was represented as function of time. The maximum value was correlated with the functioning of mechanism during the (0 - 0.1) s interval.

Analyzing the mentioned graphics it is observed that in (0.01-0.02) s interval appears a peak value for acceleration a = 75 m/[s.sup.2]. The mechanisms that transmit vertical vibration are: the shedding mechanism in t = (0-0.12) s and the slay mechanism moving in extreme frontal position in t=(0-0.046) s.

4. CONCLUSION

The experimental study allowed to evaluate the vibration amplitudes and each mechanism influence on the general vibrations acting on the Sulzer weaving machine, but do not offer information for identifying the vibration source of the mechanism.

The launching mechanism does not transmit the vibration on vertical direction on the launch box. The peak amplitude is mainly due to the shedding mechanism and slay mechanism in the moment when starts the movement toward extreme frontal position.

5. REFERENCES

Deger, Y., (2000). Structural dynamics of weaving machines: combined use of experimental modal analysis and FE simulation as an optimization tool. International Conference on Noise &Vibration Engineering, 13-15 September, Leuven, Belgium

Demeulenare B., (2004). Dynamic balancing of reciprocating machinery with application to weaving machines International Conference on Noise & Vibration Engineering, 20-22 September, Leuven, Belgium

Luca, Gh. &Vigaru C., (2009). Weaving machines, Editura Politehnica Timisoara, ISBN 9789736268183, Timisoara

Reicher F. & Dragoi L., (1985). Basic design of weaving machines, Polytechnic Institut, Iasi

Stefanuta I., (1997). Weaving technology, The Editure of Lucian Blaga University, Sibiu