VIBRATION RESISTANCE AT PROCESSING BY END MILLS WITH VARIABLE PITCH

In this work there is carried out an investigation of tooth different pitches with the purpose to increase a technological system vibration resistance at processing by end mills with a variable pitch and using elements of an operation modal analysis (OMA). An experiment is carried out in the course of which there are performed tests for the level definition of vibrations and resonance frequencies of technological system oscillations at cutting by an end mill with a constant and varied pitch. The work results show that the average level of vibrations at the work with a mill with a constant pitch is higher than at the work with a mill with a varied one. The existence of some own frequencies in one direction for a mill with a constant pitch of teeth is defined that is possible in the systems with a great number of degrees of mobility. At the same time for a mill with a varied pitch the oscillations were observed only at one frequency of own oscillations in one direction. In this connection a possibility of resonance oscillations decreases. During the work of the mill with a varied pitch the vibration waves with different length appear on the surfaces of cutting. A developed physical model of a technological system oscillation process at the work with a mill with a varied pitch shows that with the increase of a circular pitch the resultant oscillation displacements decrease.

Cylindrical Gears with Changing Ratio

Changing ratio gears are noncircular. It means that if they are combined with a conventional cylindrical gear a changing axis distance will be given. Changing axis distance can generate a lot of difficulties and additional costs in the construction. Our goal was to create changing ratio gears that have cylindrical geometry and interlock with conventional cylindrical gears at a constant axis distance. This can be achieved by applying continuously changing profile shift. Profile shift modifies the diameter of the gears, however it does not have any effect on the ratio; regardless if that is constant or changing. The point of our calculation is that some gears with noncircular rolling curves can have circular pitch curve with the help of changing profile shift.

Instantaneous Circular Pitch Cyclic Power (ICPCP) – A Tool for Diagnosis of Planetary Gearboxes

The process of monitoring and diagnosis of planetary gearboxes is currently one of the most significant topics for vibroanalysis. The reason for ubiquitous research activities on the topic arises form a shortage of efficient method for a non-destructive thorough vibration analysis of planetary gearboxes, especially working under low speeds. On the other hand, the number of high-value planetary gearboxes working in industry rises rapidly, mainly due to expansion of wind farms. In the paper, the authors present a novel method for the assessment of the technical state of planetary gearboxes with a vibration sensor mounted on the casing, and without a planets position sensor. The method is based on the calculation of cyclic energy of gearbox teeth contact within consecutive carrier revolutions. The methods performance is illustrated on a real data from a wind turbine.

Design of Third-Order Non-Circular Planetary Gear

The design of the third-order non-circular planetary gear is presented. In order to design the third-order non-circular planetary gear, the pitch of those gears is needed. Firstly theory and composition of the third-order non-circular planetary gear mechanism is introduced. Then according to the two conditions that the pitch should meet, the non-circular pitch formulas of the third-order non-circular planetary gear mechanism is given. Finally an application case of the center distance 3-4 type planetary gear mechanism was calculated by using the designed MATLAB program and created high-order elliptic curve. The design of the third-order non-circular planetary gear is achieved.

Flowrate formulation and displacement analyses for deviation function-based gerotor pumps

This article presents a research on the flowrate formulation and displacement analysis of gerotor pumps. The flowrate formula is based on the deviation function and is applicable to gerotors with any pitch curves and generating curves that are either circular or non-circular. For gerotors with the circular pitch curves and generating curves, the derivation of the formula proposed here is much simpler than the current available one. Two dimensionless parameters, the lobe non-circularity and the pitch non-circularity, are then introduced so that gerotor performance can be analysed systematically. As examples, the specific flowrate and displacement curves with the combinations of sinusoidal and polynomial pitch curves and deviation functions are illustrated. Based on these case studies, it is found that in general the specific displacement increases according to the lobe non-circularity, whereas the pitch non-circularity has only the minimum effects on the performance of pumping displacement. The results of the given case studies also show that the pumps with less lobe numbers are capable to have relatively larger specific displacements.

A Novel Harmonic Drive With Pure Involute Tooth Gear Pair

Consider commercially available “harmonic drives” or “strain wave gearings” (all patented designs). The tooth profiles of the mating pairs of teeth of the noncircular (pitch curve) flex gear and circular (pitch circle) ring gears are nearly conjugate and noninvolute. Evidently none of them offers ideal gear kinematics. In this paper, we propose a new wave generator (or cam) to drive flex gears of harmonic drives with fully conjugate gear pairs of purely involute profiles. The cam profile is made of circular arcs at the two diametrically opposite contact zones and shifted elliptical curves for the other two zones. The geometric construction is done in such a way that tip interference is properly avoided for both engagement and disengagement with nominally stubbed or full depth tooth involute gears. We develop the theory of geometric and gearing conditions. We have also built a physical model in order to verify the geometry of tooth interference and other relevant gearing kinematics.

Perceptual Dynamics of Circular Pitch

The convention of representing pitch and key relations within a geometric scheme has a long history. Such schemes often emphasize perceptual similarities or differences among tones or keys. In the present work, we focus on the dynamics of perception of pitch movement, within the framework of geometric models. In the first two experiments, perception of the pitch pattern of pairs of Shepard tones (R. N. Shepard, 1964) is examined in three different orderings: (1) random permutation of tone pairs, (2) sequential increases in the frequency components of the second tone of each pair, and (3) sequential decreases in the second tone's frequency components. Consistent with previous reports, when tone pairs are randomly permuted, the pitch pattern is equally likely to be judged as ascending or descending as the frequency difference between tones nears the half-octave. In the ordered conditions, the boundary between ascending and descending pitch is sensitive to the direction of frequency change such that hysteresis, or perceptual assimilation, is observed. In Experiment 3, we obtain pitch judgments of all two-tone permutations of Shepard tones of the chromatic scale, then map the judgments onto a toroidal stimulus space formed by the product of two pitch circles. Perceptual dynamics are explored by systematic excursions through the stimulus space. The results indicate that spatial models of pitch provide an incomplete description of the higher than/lower than pitch relationship in Shepard tones; also crucial is the path taken through the space defined by the stimuli.