Bottom Roller Research Articles

Numerical analysis of the mechanical behavior of a ring-spinning triangle using the Finite Element Method

The purpose of this study is to investigate the quantitative relationships between the mechanical performance of a ring-spinning triangle and the spinning parameters by using the Finite Element Method (FEM). The constituent fibers in the ring-spinning triangle are considered as three-dimensional elastic beam elements with tensile, compressive, torsional, and bending capabilities. The accuracy of the proposed FEM model in calculating the fiber tension distribution of the spinning triangle has been validated by comparing it with earlier models and experimental data. Compared with the earlier models, some important theoretical factors ignored previously, including the fiber torsional strain and the frictional contact of fibers with the bottom roller, are considered in the current model. With the input of various spinning parameters, some essential factors of the spinning triangle, including the fiber tension distribution and fiber torsion distribution, are numerically examined and their quantitative relationships are discussed in detail.

Precision forming machine with rolling plate cross wedge rolling

Roller cross wedge rolling (CWR) machines have high rigidity, but sector dies are difficult to process. Plate CWR machines have low rigidity and need large floor space, but plate dies are easy to process. Neither roller CWR machine nor plate CWR machine can produce larger workpieces. Based on the above conclusions, this paper presents the mechanical principle of the precision forming machine with rolling plate CWR. Then, its design principle and machine construction are presented. There are a top press roller above the upper sliding plate and a bottom press roller under the lower sliding plate. The press rollers make rolling contact with the sliding plates. The plate dies are mounted on the upper and lower sliding plates, respectively. Furthermore, the axes of both press rollers and centerline of workpiece always keep in the identical vertical plane during forming process. These make the machine retain advantages of high rigidity for roller CWR machine and simpleness of manufacturing dies for plate CWR machine, and abandon defects of poor rigidity for plate CWR machine and difficulty of manufacturing dies for roller CWR machine. Moreover, the machine can produce larger workpieces.

3D modelling and simulation of the filling of cavities by viscoelastic polymer in roll embossing process

The aim of this work is to use numerical simulation to describe the flow of a polymer sheet in compression deformed at a constant temperature. This paper reports on an innovative technique for rapid fabrication of polymer micro- components based on a roll embossing process. In this paper, the numerical studies have been conducted using LSDYNA® software to investigate the filling with amorphous polymer by roll embossing for improving the quality and filling rate in micro cavities of well defined shape. The amorphous polymers sheet (Cyclo Olefin Copolymer - COC) was used as the basic material for experimental tests. In this model, one considers a rigid top roller with micro-cavities and a rigid bottom roller with a smooth surface, with both rollers following an elastic and non-shrinking behaviour. Moreover, in the simulations, the amorphous polymer exhibits a viscoelastic or viscoplastic behaviour depending on the experimental conditions.

Analytical and empirical modeling of top roller position for three-roller cylindrical bending of plates and its experimental verification

Abstract Reported work proposes an analytical and empirical model to estimate the top roller position explicitly as a function of desired (final) radius of curvature for three-roller cylindrical bending of plates, considering the contact point shift at the bottom roller plate interfaces. Effect of initial strain and change of material properties during deformation is neglected. Top roller positions for loaded radius of curvature are plotted for a certain set of data for center distance between bottom rollers and bottom roller radius. Applying the method of least square and method of differential correction to the generated data, a unified correlation is developed for the top roller position, which in turn is verified with the experiments, on a pyramid type three-roller plate-bending machine. Uncertainty analysis of the empirical correlation is reported using the McClintock's method.

Mohair Fibre Drafting in Ring Spinning Part II: Pinned Roller

This paper reports a novel modification to the drafting system of conventional ring spinning. The modification entails the use of a pinned middle bottom roller, together with the conventional double aprons for fibre drafting. The additional pins on the middle bottom roller are intended to improve fibre opening and alignment during fibre drafting. The pinned roller features a combing action coupled with fibre control due to fibre/pin interaction, which is thought to be particularly important for slippery fibres such as mohair. Both mohair and wool yarns were spun with the modified drafting arrangement. The yarn assessment results obtained indicate significant improvement in yarn evenness and imperfections. Yarn hairiness and tensile properties were also improved.

Dynamic Measurements of Mechanical Errors in Sliver-drawing

An investigation is reported in which the lifts of the roller necks of the upper of each of the sets of drafting rollers in a drawframe were measured. Data expressed in the frequency domain showed that roller errors could be clearly seen at the fundamental frequencies of the various rollers when the error and the measurements related to the same set of rollers. Some harmonics were also visible. When errors were in one set of rollers and the measurements were made down the fibre-flow line, the sharpness of the peaks was greatly reduced by drafting waves in the fibres flowing through the system. It was deduced that drafting waves dispersed the singular frequencies produced. An absolute encoder was used on a bottom roller to average out asynchronous signal components and random errors. The averaged data demonstrated the roller shape under dynamic conditions even when the error was small. It was possible to use a ratio technique to produce a virtual encoder for the top roller. At start-up, the viscoelastic properties of the rubber covering, the distance apart of the rollers, and the error levels changed as the rubber warmed up. The dynamic shape of the roller could be determined, and the result was repeatable.

Hydraulic jump in trapezoidal channel

The internal flow features of hydraulic jumps in trapezoidal channels are explored. Based on 3-D observations, it is shown that the flow phenomena significantly differ from the classical hydraulic jump. This is particularly attributed to the presence of a bottom roller. The main flow properties such as the sequent depths, the spatial extension of the bottom roller, and the length characteristics are analysed. Further, typical jump instabilities are discussed. Finally, some design recommendations are presented.

Spectral Analysis of Yarn irregularity and Its Relationship to Other Yarn Characteristics

Spectral analysis was used to break up the yarn irregularity into periodic, quasiperiodic, and random components for three different counts, namely 20 tex (30s Ne), 9.9 tex (60s Ne), 5.9 tex (100s Ne), spun at three different levels of drafts and four levels of top and bottom roller eccentricities, and their combinations. The periodic component increases nonlinearly at higher eccentricities and higher drafts and there is also an increase in quasiperiods. This behavior contradicts the commonly accepted theory of linear increase put forward by Foster. The thin and thick places in yarn increase nonlinearly, whereas single thread strength drops rapidly at higher levels of eccentricity and draft. Yam appearance grades deteriorate, particularly with increase in the periodic component. At comparable levels of irregularity, periodic component leads to a diamond barring effect, whereas existence of higher quasiperiods dampens the diamond bars by confounding the periodic component.

Abrasive damage of the concrete of the overflow dam of the ust'-Kamenogorsk hydroelectric station

1. The presence of fragmental rock and deposits of coarse alluvium (gravel, pebbles) in the lower pool of an overflow dam can be the cause of abrasion of the concrete of the spillways and apron if, during discharge, conditions are created for the cyclic movement of abrasive material and its entry into the roller zone or other zones with a high turbulence, for example, whirlpool zones near piers, walls, etc. The intensity of the destructive process under especially unfavorable conditions can be quite high even with small specific discharges over the spillways. 2. The movement of abrasive material toward places where it performs destructive work can be accomplished by bottom currents, occurring under certain conditions, which pass under the nappes of the spillways. The direction of these currents on the whole is opposite to the main flow, and their velocities are sufficient to transport coarse alluvium. 3. Construction on the spillway of a deflector creating a hydraulic regime with a bottom roller in the lower pool can promote damage of the deflector concrete and of portions of the piers and apron adjacent to the deflector if during flow over the spillway the possibility of the entry of abrasive material (alluvium, construction trash) into the zone of the bottom roller is not eliminated. 4. If the abrasive process is the determining factor in damaging the concrete surfaces of the spillways and apron, then the radical step of removal of the abrasive material is the only recourse, since just filling the caverns is ineffective.

24—Short-Wave Variation in Cotton Rovings Caused by Machinery Defects in the Speed Frames

AbstractUneven rotation of the bottom middle roller is identified as the primary mechanical cause of irregular drafting in cotton speed frames. The defect Produced has an abnormally short wavelength, between one-third and two-thirds of an inch, and is not apparent as a thickness variation in the roving, being hidden by the overlap of the fibres. The fault is only developed as a thickness variation at the next stage of drafting, when the period length becomes long compared with the length of the fibres.The main cause of uneven rotation of the roller arises from lack of rigid support of the back roller shaft; secondary causes are rubbing of the draft gear teeth against obstructions and deep setting of the carrier pinion. Defective drafting due to these causes may occur in any of the speed frames, but is most objectionable at the intermediate frame since the equivalent length of the period in weft yarn is then such as to give rise to diamond pattern barring in cloth. The remedies in the majority of cases are...