İğ sistemlerinin dinamiğinin deneysel incelenmesi

Abstract

ÖZET Tekstil sektöründe ham madde sayılabilecek olan iplik üretiminde karşılaşılan en büyük problemler tüylenme, kop ma ve neticede istenen kalite ve miktarda üretimin sağlana mamasıdır. Bu tür problemler açısından incelenmesi gereken ele man ring iplik makinalarında iğ sistemleri olmaktadır. Çalışmada bu sistemlerin titreşim değerlerinin incelenmesi amacıyla deneysel bir sistem kurulmuştur. Kurulan sistem üzerinden indüktif sensörler yardımı ile değerler okunmuş ve kaydedilmiştir. Sistemden alman değerler çalışma şartlarının titre şimler konusundaki önemini ortaya çıkarmıştır. Daha ile ri çalışmalarda sistem üzerinde daha farklı şartlar ve hız aralıkları ve kurulacak modelle karşılaştırma tarzında baş lıklar düşünülebilir. iv

DYNAMIC ANALYSIS OF RING SPINNING MACHINES SUMMARY In this study, the side effects of vibration of spindels and working conditions of the system on the manu factured yarns are examined, And the experiment based results presented. In order to see how spindles are affected by the amount of the eccentricity, whether the working speed range is far enough from the resonance speed, whether the spindles pass the critical speed fast enough, and whether the spindels are manufactured within the limits of precision or not, an experimental system is carried out and some quantities are recorded. Study consist of two main parts: -Some detailed information about spindles, production phase, main requirements of a spindle, - Test system, measuring system, recorded data under certain conditions and conclusion. A short explanation of these two sections is summarized below. Current discussions on the technology and development of ringspinning are centered around the topics of rationalisa tion and automation. These are important topics, because they are the basis for the future and success of the textile industry. What is undoubtedly to stay is the demand for high yarai. quality. Thus one subject should not be omitted from the discussion: ring spindle. A central component of the ringspinning machine, the running characteristics of which significantly contribute to productivity and yarn quality. At first sight a ring spindle would appear very simple. No electronics, no automation involved, just pure mechanics. However, long years of practical engineering experience have gone into each individual spindle. Each detail has been thought out with the object of ensuring smooth running and a long service life of the spindle.Whether or not a spindle is made to top standarts cannot be seen with the naked eye. Optimum true run, freedom from any unbalance on the spindle, centralisation to the ring, accurate, permanent vertical positioning, long service life, little energy comsumption and smooth run, all these factors are dependent on maximum precision in produc tion. These high demands on precision are decisive for the rate of ends-down, the yarn quality and the consumption of the ring traveller. This is proved by scientific test. These tests are caried out under normal production condi tions. The results show clearly that spindles with a bad true run cause ends-down at a superproportional rate (Fig 3.11.1) Precision spindles with optimum true run thus represent a noticable economic factor in the mill. The carried out prove that the correlation between centricity and rate of ends-down applies to short stable as well as long staple spinning. The test also show for short stable spinning an abvious correlation between centricity and yarn quality. A precision spindle obtains better values for: - The highest tensible force, - Maximum elongation, - Hairynees.' of yarn,. The higher the spindle centricity, the better the spinning run and the better the yarn. It is thus worthwhile for various reasons to constantly check the spindles in the ringgspinning machine and to ensure high precision and quality at the time of the purchase. High performance spindles produce more yarn as well as better yarn, and they reduce production costs by higher productivity. One of the* causes for premature consumption of the ring traveller can be spindle. A lack of centricity leads to increased strain at certain points on the spinning ring. The correlation is shown in Fig. 3. 11.2. The lack of centricity of the spindle to the ring leads to different tension conditions during the run of the traveller, and thus to different spindle speeds together with a different strain on the ring. The consequences are abrupt acceleration and delay in the speed of the traveller, VIand one-sieded wear of the ring. With a well centered spindle, traveller and spindle speeds are constant. As for the production of spindles, there is a mojor producer of spindles so-called SKF. This company produces and develops spindles and spindle bearings for years. Top part of a spindle consists of blade, aluminium cap whorl and cutting device. First of all, the top, which is to become the `small spindle foot` is hammared. This leads to higher density in the material, and the top which is under heavy strain thus obtains the prerequisite for a longer service life. The hardening development which is extended over the comp lete blade is caused by horizontal and radial hardening using a special method of induction. This method hardens largely without distortion and it determines very accurately the degree of hardness of every part throughout the blade. Top and collar bearing receive different hardness. All other parts are specifically kept softer in order to main tain the flexibility of the blade. The required flexibility and break stability are obtained on the principle: hard outside, pliable inside. Then the surface is finished. Repeated rounh-grinding leads to the conical shape of the blade which ensures the correct oil distribution in the finished spindle. During finish-grinding the top and the bearing position for the journal bearing receive their final shape. Then one of the most important part of spindle, the bearing surface superf inished. Superfinish is a technique which renders the material surface exceptionally smooth densifying it one again at the same time. Whorl production phases are drilling, inside and outside turning and knurling. These processes provide the main requirements from the whorl which are maximum preci sion of belt running contact and blade pasition. Then yarn cutter is mounted by automatic machines. After all, the circular blade, springs and lockring are mounted onto the grooved baker. Aluminium cap has the production processes as dirilling VIIreaming of the conical blade seat, facing and centering,, pressing in of blade and whorl, turning of the top, milling of the seats for the 3-point clutches, accurate straigh tening and smooting and polishing. As an example, the tolerance for the true run of the complete top is max-3/ 100 mm. Spindle base can be called as bearing system. The blank, a part manufactured by extrusion moulding, has almost tha shape of end product. The coller is turned and initially facet, the seat of the bearring reamed, the screw rolled up the contact surface to the spindle rail rough- turned, the roller bearring oiled and pressed in. Finally, completing these things is an operation which guarantees the absulately vertical positioning of the spindle in the spindle rail ; The contact. surface of the base is faced at an angle of exactly 90 degrees. The maximum tolerance here is under2/ 100 mm. The way in which a spindle is technically constructed depends on its purpose. Distinction is made between light spindles for short and long staple spinning and heavy spind les for twisting and draw-twisting spinning in the man-made fiber section. Main criteria are tube dimensions and cops weights. The higher the cop weigth, the heavier and sturdier the spindle construction. Fig. 3. 2.2. Illustrates the some kind of spindles, from left to rigth: Short staple* long staple, twisting and draw-twisting spindles. The type of the braking system to be used depends on the spindle drive which will be discussed later, on the weigth to be braked, and on the question of how long the spindle is to be stopped for. Spindles in short and long staple spinning are generally used. In the case of particularly high cops weights and spindle speed pneumatic outer brake shoes are used. For the tybe of draw-twisting spindles the electro-stop brake is used. This tybe of brake can also be used for spindles with individual motor drive on draw-twisting and glass fiber machines. As for the drive systems for the spindles, there are various types of drive systems that can be used which are given as following: VIII- Individual drive, which may be, for example, a helical gear drive or a tape drive. - Group drive, of which the four spindle tape drive is an example, - Tangential belt drive which may have a separate driving belt for the spindles on each side of one beld for driving all the spindles of the machine. The use of individual drives has been almost wholly abandoned in modern textile machine designs.- Four-spindle tape drive is given at Fig. 3. 7.1. Some developed details are as following: - The full-length drive cylinder was eliminated and by using. individual drive pulleys instead, a reduction of the rotating mass was achieved. - Synthetic tapes were introduced. - The tension pulley arrangement was improved. Tangential belt drive as shown in Fig. 3. 7. 2. Its advantages are these: - Speed variation between the individual spindles, which is 2-4% in four spindle tape drive, is as little 1-2% in tangential belt drive. - Less servicing is required than in other drive sys tems, as the belt will usually not require repla cement before completion of several years of service while a four spindle tape drive involves a frequent necessity for replacing a number of tapes, which means frequent machine stoppage. - The speed of spindle is not influenced by stopping the adjacent spindle. - The absence of a drive cylinder means less machine vibration. - Formed drive elements are eliminated and free space is thus obtained inside the machine. The use of this drive became possible with the develop ment of suitable multiple-ply belts having several super posed high-tensility plies of polyamide or polyester and, firmly bonded to these, special running plise with a high friction factor. IXAny power consumption data obtained for a spindle have validity only for the given application with its given operating conditions and materials. Power consumption measurements on a machine have shown that by reducing the wharve diameter from 30 mm to 23 mm. with all other operating data remaining unchanged, a power saving in the order of 7- 8% may be obtained. This is due to less driving speed being required for the same spindle. The rate of power saved by reducing the whare size becomes less with each reduction. The spindle blade is a body presenting rotation sym metry and can be regarded as a shaft having a circular cross section and being supported in two bearings. The inevitable tolerances in its manufacture and the unbalance of the bobbin are bound the cause tne center of gravity *of the rotating parts to lie away from the axis of rotation, deviating from this axis by distance `e`. This eccentricity of the centre of mass is bound to produce a centrifugal force exerting a pull at the free top end of the blade. It is possible to determine the rigidity of a spindle blade assembly, but a rigidity calculation for the whole spindle is an extremely complicated matter, since the influences of the blade, the centring element and the dam ping system would have to be included and the influence of the speed. To make this kind of calculation for spin dles in the critical speed range would involve unjustifi able complications, apart from the that such calculated.. results fail to correspond adequately with those obtained in practice. Experiment system consists of some supporting elements an asyncron electric motor, a spindle and measuring elements Speed is increased by a frame from 1500 rpm to 9500 rpm. It was intended to realise this experiment with a d.c. motor, since it makes possible to change speed from a mini mum to a maximum, but no d.c. motor was avaliable in the University. The drawings of the system is given in Appendix A-l. Measuring system consists of two inductive sensors, a dynamical bridge, an amplificator and a paper record machine Three types of test conditions a.re examined which are given as follows. - unloaded spindle - Loaded spindle X- Loaded and eccentric spindle The results of the are given in Appendix A-2 XI