Ultra-High-Speed Performance of Ball Bearings and Annular Seals in Liquid Hydrogen at Up to 3 Million DN (120,000 rpm)©

The ultra-high-speed performance of a hybrid ceramic 25-mm-bore ball bearing, as well as that of floating-ring seals with a sealing diameter of 30 mm, was determined in liquid hydrogen at speeds to 120,000 rpm, 3 million DN, under thrust loads to 3,140 N and sealed pressures to 1.7 MPaG. The bearings had Si₃N₄ balls and a single outer land-guided retainer. The hybrid ceramic bearing exhibited excellent performance at high load, contrasting with the seized all-steel bearing; however, the ceramic balls developed superficial micro-cracks due to frictional heating. Effective cooling of the bearing was achieved by increasing the jet speed through the nozzles. The bearing power loss drastically increased with increasing speed and cooling flow rate. The critical load capacity without bearing damage was also evaluated. Furthermore, the sealing performance of the one-ring seal was superior to that of the two-ring seal in preventing the sealing ring seizure against the runner.     

Design and scheduling for flexible manufacturing cells with automatic set-up equipment

A flexible manufacturing cell (FMC) has become of major interest recently as a new machining unit for low-volume, variety production. However, set-up operations for workpieces have not yet been automated in the usual FMC. In this paper, the design and scheduling problems for FMC with automatic set-up equipment are discussed. The FMC consists of a machining centre, an industrial robot, a loading-unloading station and an index-pallet changer. First, the design and control system of the FMC is explained. Then a scheduling algorithm is developed to achieve the minimum total production time in order to operate the FMC effectively. As this FMC has finite buffer spaces on the index-pallet changer, this model can be regarded as a two-machine flow-shop problem with finite buffer spaces. Next, an algorithm for determining the optimum number of buffer spaces is constructed to design the FMC using the results of scheduling. Finally, a numerical example is given for demonstrating the effectiveness of the proposed algorithms.     

TEXTURAL PROPERTIES OF STARCH GELS FILLED WITH COLLAGEN AND CHITIN

Chitin and collagen powders were added as fillers to various starches (potato, sweet potato, kudzu, corn, wheat, and mung bean), heated at 100C for 10 min with stirring to make a hot paste and allowed to gel quiescently at 5C for 2 h in order to investigate the effects of the filler particle on the texture of the gels. The parameters of hardness, cohesiveness and adhesiveness were determined instrumentally and compared. The filler particles of collagen and chitin were effective in increasing hardness of corn starch gels but had no effects on hardness of the potato, sweet potato, kudzu, wheat and mung bean starch gels except at the lower starch concentrations. Cohesiveness was increased slightly in all starch gels by addition of collagen whereas chitin addition only increased the cohesiveness of sweet potato and mung bean starch gels. Collagen and chitin addition increased adhesiveness all of starch gels, but the intensity of the effect was most remarkable for collagen. The observed differences in effects was apparently due to differences in the interactions between starches and filler particles arising from differences in the surface properties of the filler particles.     

Development of High‐Acceleration Linear Motor to Realize Resource Saving and High Productivity

The use of linear motors has been rapidly increasing in recent years in response to the rising demand for drive mechanisms with higher speed and acceleration to improve the throughput of semiconductor production equipment, machine tools, and so on. In this study, we have developed a new type of linear motor with an opposed magnetic pole structure and twin movers. To achieve higher acceleration of a linear motor, it is necessary to satisfy both large thrust and low inertia. In our proposed new type linear motor, the thrust is improved by increasing the facing area between the permanent magnets and magnetic pole teeth by using multistage movers. Furthermore, the magnetic leakage flux is reduced by multiplexing the magnetic flux path. In a short stroke (approximately 210 mm) drive, the high acceleration of 1670 m/s² and maximum velocity of 14.2 m/s is demonstrated using a prototype linear motor (maximum thrust = 25 kN).     

Design optimization of industrial robots considering the working environment

Industrial robots are being used increasingly in complicated working environments where there are obstacles. Industrial robots most suitable for a given working environment should be designed such that they avoid obstacles while moving in the designated working space. In this paper, a design optimization method is proposed for two-degree-of-freedom rotary angular jointed robots for use in such an obstacle-inclusive working environment. In this method, the lengths of the arms and the directional orientation of the robot installation are theoretically determined. First, the algorithmic procedures of the optimization method are presented. Then analytical procedures for obtaining the feasible set of arm lengths are described. Finally, effectiveness of the method is demonstrated for designing a robot used in a given working environment.