As the market for minimally invasive procedures developed rapidly, there was an increase in the demand for high-precision, high-performance catheter fabrication technology. Sheath and dilator tubes are essential intervention devices for procedures, in which catheters are used and require precise dimensional accuracy, and uniform roundness and surface roughness. Polyethylene is used in sheath and dilator limitation for processability, which causes low melt flow index and side effects. Therefore, in the extrusion process using polyethylene, it is important to study the manufacturing of tubes with improved roundness and surface roughness. In this study, we proposed a calibrator for precise production with an aim to manufacture 5Fr micro-puncture tubes, and studied the changes in the roundness and surface roughness of tubes by changing the cooling water temperature and water disk thickness. As a result, it was found that the cooling water temperature and wafer disk thickness had an effect on the roundness and surface roughness, and the roundness had an effect on the formation of the wall thickness. Therefore, these experimental results were used as a study for the production of improved Sheath and Dilator tubes.

In this paper, when the finishing process is performed on the additive by FDM type, the optimal parameter set of the additive-finishing design parameters to improve the surface quality and the verification of the finishing effect are described. Additive design parameters such as nozzle diameter and layer height and finishing design parameters such as depth of cut and feed rate have a significant influence on the printing time and surface roughness of the sculpture. So, we define the major additive-finishing design parameters expected to affect the results. So, we define the major additive-finishing design variables that expected to affect the experimental results. And to confirm how much they affect the results with the minimum number of experiments, the sensitivity analysis of the design parameters was performed through the level average analysis of the Taguchi method. As a result, compared to the surface roughness and additive time when only high-quality sculpture was performed, and it was confirmed that the printing time improved up to 70% and the surface roughness improved up to 87% for the additive-finishing sculpture performed with the optimal combination of design parameters.

Compacted graphite iron (CGI) has been widely used in the automobile industry because of its good mechanical properties. CGI has better strength as compared to grey iron due to its internal structure. It includes graphite particles, which enhance the adhesion between graphite and iron. However, the material characteristics can negatively affect the machinability. In this study, cryogenic milling was performed for CGI450. It is well known that cryogenic machining is effective in improving the machinability. The process included spraying liquid nitrogen as a cryogenic coolant, and the influences on machinability were experimentally investigated with a focus on the cutting force and surface roughness. When liquid nitrogen was sprayed, the cutting force was slightly increased due to the cold-strengthening effect. On the other hand, surface roughness was dramatically decreased by 44.7% as compared to dry milling because brittleness of work material was increased by cryogenic coolant spraying.

The objective of the present study was to investigate the relationship between surface roughness and touch perception of surfaces with randomly spaced, irregular features. Two sets of specimens with top surfaces consisting of triangular peaks and valleys were modeled and 3D-Printed by varying the height of the peak, the depth of the valley, and the width between two intersections of the peak or valley with the center line. For one set of specimens, values of these variables were kept constant within a specimen but varied across specimens. For the other set of specimens, values of these variables were randomly selected in given ranges within a specimen while ranges were varied across specimens. The level of touch perception of each specimen was then measured using a questionnaire consisting of 16 adjectives related to touch perception and a 7-point Likert scale. Measured data were statistically analyzed and compared between different sets of specimens. Results indicated that it was inappropriate to directly apply findings of the previous studies for surfaces with regularly spaced, geometrically well-defined features to surfaces with randomly spaced, irregular features.