060A4 steel (Chinese standard) is a steel with good machinability, which is very popularly used in mechanical engineering. Therefore, the study of solutions for improvement of quality and productivity when machining this steel type has great technical and economic significance. In this study, the multi-objective optimization process has been performed when milling this steel type on a vertical milling machine. The cutting tool is a face milling cutter made of High Speed Steel (HSS) material. The effect of spindle speed, feed rate, and cutting depth on surface roughness has been found. The combination of the Taguchi method and PSI method has been applied to determine the optimal value of three input parameters to simultaneously ensure the two criteria of the minimum surface roughness and the maximum Material Removal Rate (MRR). The works which will be done by the authors of this article in the near future has also been presented in the last part of this study.
Metal cutting is one of the most important machining processes in manufacturing industry. Thorough understanding of metal cutting process facilitates the optimization in selection of cutting tools and machining parameters. There are several methods used for studying phenomena in metal cutting process. Using a quick-top device is an efficient technique for investigation cutting process in which cutting action is stopped so suddenly that the “froze” specimen called the chip root honestly depicts what happened during cutting action. Design strategies of a quick-stop are accelerating cutting tool away from the workpiece or decelerating the workpiece remaining in engagement with the tool. Operation of a quick-stop device can be either mechanically or by explosive. Quick-stop devices can be utilized for various types of machining processes such as: turning, milling, drilling. This paper described the analysis, fabrication, and testing of a quick-stop device which is used for researching on chip formation in hard turning. This device has simple and safe operation which utilizes spring forces to retract the tool from workpiece during cutting. The results of performance at cutting speed of 283 m/min show that the separation distance is quite small, less than 0.2mm so that the deformations on the root chip are close to that while actual machining process. This indicates that the device has satisfied the requirements of an equipment for studying on chip formation.
This study presents a comprehensive method for designing a multifocal contact lens
(MCL) with Snell’s law and non-uniform rational B-spline (NURBS)
curves. Instead of using thin lens approximation, general mathematical
formulas have been developed to achieve the accurate coordinates of
points on the anterior lens surface profile of the MCL to meet various
given optical power distributions. Then the NURBS curve is adjusted to
fit these data points to obtain the smooth front lens surface profile.
This method not only improves the accuracy of the optical power
profiles of MCLs but also reduces the spherical aberration in
near/distance optical zones. The experimental results show that the
power profiles of soft MCLs agree with those of the simulation results
and original design requirements. The proposed method has been proven
for the MCL design, and it can be feasibly applied in complex optical
lens designs.
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