In plastic injection molding there is ideally no irregular filling in the molded product. Since filling irregularity must be evaluated by the physical characteristics and internal state of the molded product, characteristics that reflect the internal state properly must be measured. In this study to evaluate the uniformity of mold filling patterns with polycarbonate, a transparent resin, we measured the RGB optical density values of light transmitted through a polarizing plate, and compared uniformity of the transmitted density by parameter design techniques, using molding conditions as factors and analyzing the results by the MT method. Evaluation of transmission density through the polarizing plate was able to detect filling irregularities and transmission variations more sensitively than evaluation of transmission density without the polarizing plate.
The impressing of seals is an essential procedure in many fields of business that are based on legal contracts. Verifying seals is also an important art that is practiced particularly frequently in financial institutions. This study is an application of the Taguchi error root mean square, in which the image information pattern of a seal impression was taken as the error variance, the distinguishability of the impression was evaluated by means of the error variance value, and a comparison with the RT method was carried out. Since the measurement data were calibrated with mean values, both positive and negative values appeared, which affected the value of the general mean. Absolute values of the analysis data were therefore taken to improve the effect of the S/N ratio of a nominal-is-best characteristic on the error variance of the general mean. As a result, a correlation coefficient of better than 0.98 was obtained between the RT method and the error root mean square.
The MT system was used to estimate the molding stability of a product produced by an injection molding machine. Initially, dimensional transferability was evaluated by using the injection molding machine to produce a thin-walled S-shaped test piece. The state of the machine when operating was indicated by time-varying process data such as electric power consumed, mold temperature, and internal pressure. The S/N ratio of the transferability was used as a signal factor, and the above process data were used as variables in an equation relating the S/N ratio of the machining capability to the pattern of the process state,by applying the two-sided T method. This made it possible to estimate the S/N ratio of a workpiece from the processing data. The process data items were also diagnosed using an orthogonal array, which showed that hold pressure and mold temperature had large effects.
In this study of a cooling fin, which is a key component of a heat exchanger, we examined the geometric factors that affect radiation performance. It is diffcult to evaluate heat radiation directly. Heat radiation occurs due to the temperature difference between the cooling fin and the ambient air, and the ambient air temperature around a cooling fin is greatly affected by wind velocity. It was therefore thought that heat radiation could be evaluated by using the wind velocity and the temperature difference between the cooling fin and the ambient air as parameters. Since heat is radiated from the fin surface, another evaluation was carried out simultaneously using wind velocity and the heat transfer coefficient with surface area taken into consideration. A linear evaluation was considered applicable in both cases, so the evaluations were performed by use of the zero-point proportional S/N ratio, and the results were used to carry out parameter designs. Evaluation by use of the heat transfer coefficient gave better reproducibility of the gain than did evaluation by use of the temperature difference, and indicated geometric factors affecting radiation performance. This led to the conclusion that to evaluate radiation performance, it is necessary to use the heat transfer coefficient and consider the surface area of the fin where heat exchange occurs.
The stabilization of spindle locking in a machining center with turning function was studied. To lock rotation, a friction brake structure is used: a brake ring is mechanically pressed against the spindle to generate solid friction. The weakness of this structure lies in the conditions of contact between the brake ring and the spindle. When there is water or oil in the contact interface, the friction coefficient drops drastically, resulting in loss of locking performance. The braking structure had been designed using friction coefficients obtained from past experience. In parameter designs of the contact interface carried out in the present study under various design strategies and combinations thereof, the friction coefficient was found to vary greatly, and a stable spindle resistant to external factor effects was successfully developed.