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Workpieces with a globoid shape have been used extensively in industry. However, its hourglass shape increases machining difficulty and requires exact accuracy during manufacturing. The issues could be remedied using a different manufacturing procedure to minimize machining difficulties. As a result, our research developed a way to reduce machining challenges. The novelty of the study is the general mathematical model for machining the globoid screw rotor surface. The machining process on both flank surfaces of the workpiece is conducted simultaneously using a disk-type cutting tool. Analytical and virtual cutting simulations on globoid screw rotor surface machining are investigated. The machine setting and the coordinate system are proposed. A mathematical model for the surface of the tool and workpiece is presented. The generation of the workpiece surface on the offered machine is investigated. The machining process simulation of the globoid screw rotor surface by the disk-type cutting tool is performed. The numerical solution of cutting points and the normal deviation of the globoid rotor surface are solved. Sensitivity analysis, additional movements, cutting tool assembly error, and the numerical solution for machine-axis settings using the Levenberg–Marquardt algorithm are conducted. Virtual cutting simulation is presented using VERICUT. Verification of mathematical modeling is performed. The hourglass worm and the roller-gear cam are taken as numerical examples. Results from the machining examples are presented to verify the advantages of manufacturing the globoid rotor surfaces in the proposed method. [ABSTRACT FROM AUTHOR]

The whirl-machining process is a precise, efficient, and promising machine process for manufacturing workpieces over the milling process. At the same time, the roller-gear cam has advantages over the other cam-follower system. However, the whirl-machining process has not been applied to manufacture the roller-gear cam. Therefore, this paper proposes a novel method for roller-gear cam manufacturing using a whirl-machining process. Mathematical modeling is described for generating the roller-gear cam, roller, and whirl-milling tool surface. A novel CNC machine and its coordinate system are proposed. Cutting simulations for obtaining the surface topologies and normal deviations are conducted. Globoidal cam with different cylindrical rollers, globoidal cam with a conical roller, and cylindrical cam with a conical roller are taken as case studies, and results are discussed. A virtual cutting simulation was conducted using VERICUT. Some machining examples are shown to verify the benefits of the proposed method in roller-gear cam manufacturing. [ABSTRACT FROM AUTHOR]

• A novel method for machining double-enveloping worms is proposed. • The whirl-machining tool is generated using a straight-lined blade. • Normal deviations in surface topology are investigated. • Virtual cutting simulation on worm machining is conducted. • The generated worm gear drive is achieved through the proposed process. Double-enveloping worms (DEWs) are widely used in many applications, especially in space-saving and high-reduction ratio equipment. DEWs have a higher transmission efficiency and contact ratio than non-enveloping worms. In this study, a general method to manufacture enveloping worms using a whirl-machining process is proposed. The whirl-machining tool profile is provided from a straight-lined blade, which is tilted with an angle the same as the lead angle of the worm. The whirl-machining model is developed by a relative-motion coordinate system of a proposed CNC machining machine. The cutting simulations, surface topologies, and normal deviations for worms are demonstrated with different pitch radius of gear, lead angles, and cylindrical worms. In order to determine the practicability and accuracy of the developed model, six numerical examples are performed. A virtual cutting simulation was conducted on the worm using VERICUT. The results verify the benefits of the proposed method in DEW manufacturing. [ABSTRACT FROM AUTHOR]

In order to improve the understanding of transient behavior of gas-liquid plug two-phase flow in a horizontal pipe, CFD simulations and experimental studies on the relevant phenomena were carried-out. The pipe diameter and pipe length were 26 and 9.5 m respectively. The transient calculations were carried out using a Volume of Fluid (VoF) multiphase flow model of the commercial CFD code of FLUENT 6.3. The corresponding CFD solution has been obtained by using the Best Practice Guidelines of CFD for thermal engineering purposes. In the present works, the series of high quality experimental data was used to validate the CFD calculations in terms of time and space. A comparison with the high-speed video observations shows a good qualitative agreement. The results indicate also a quantitative agreement between calculations and experimental data for the elongated bubble length and the time variation of the liquid hold-up. [ABSTRACT FROM AUTHOR]

A robust design of a disk-type milling cutter involving multiple inserted blades is required in screw rotor milling since it significantly influences the machining precision. Hence, it is essential to discover a prediction model for rapidly simulating rotor profiles and cutting marks to evaluate the cutter design to enhance the cost-time savings in cutter manufacturing. This study proposes an insert-cutting trajectory (ICT) method that is resolved by considering the cutting-edge form of each insert type and cutting conditions. In addition, the ICT method's accuracy is determined according to the number of points on the insert cutting-edge length and the number of grids on the tooth profile length. The result confirms that the rotor profile and the surface cutting marks were successfully generated by applying both disk-type milling cutters with standard and special inserts. The profile results indicate that the special insert can achieve smoother than the round-standard insert. The ICT method relied on the screw rotor milling with distinction cutting conditions utilizing the special inserts. Finally, an experimental result verified that the ICT method is reliable and practicable. [ABSTRACT FROM AUTHOR]

A vacuum pump mainly consists of intermeshing screw rotors, which apply a cycloid profile to enhance the operating performance. However, it yields a concave rotor profile, increases the machining difficulty, and requires precision accuracy in the manufacturing process. This study proposes an analytical design of a particular whirling cutter and the rotor cutting method considering double tilt angles and assembly offset setting. The cutting simulation is demonstrated in analytical methods and virtual machining for various vacuum pump screw rotors. The analytical cutting result indicates that the overall lengthwise rotor profile deviation is identical. Besides, the virtual machining result indicates that the tooth surface topology is smooth and uniform, and the maximum profile deviation is still much more undersized than the grinding allowance. Moreover, the proposed method is still reliable for various vacuum pump rotors of Kashiyama type, Quimby type, Hanbell Precise Machinery P series, and Hanbell Precise Machinery P series with clearance design, where their delta deviations consistently tinier than 0.1 mm. Finally, it verifies that the proposed analytical design of the whirling cutter design, utilization of double tilt angles, and assembly offset setting are reliable for various vacuum pump rotors applying whirling milling machining. [ABSTRACT FROM AUTHOR]

• The unique inserts cutting-edge are generated considering the cutter curve curvature. • A modified cutter coordinate system is constructed with a revolve angle to arrange the insert. • Both cutters with special and round-standard inserts are compared. • A cutting simulation and experimental verification are performed. • Rotor profile and surface topography are investigated to evaluate the cutter design. A milling cutter with inserted blades is designed for each screw rotor since the geometry profile is unique, corresponding to its purposes and function. Correctness in cutter design, including the cutting-edge insert profile, is necessary to achieve a precise rotor profile; therefore, it is essential to introduce an enhanced cutter design. This study proposes a design of a disk-type milling cutter with special inserts. The insert cutting edge was generated on the axial plane considering the cutter curve curvature and then positioned onto the cutter body according to the modified coordinate system with a revolve angle. The analytical cutting result indicates that the simulated profile is relatively even along the gear tooth profile and the normal deviation is significantly tinier than the insert arrangement area. In addition, the cutter design applying special inserts acquires better results than standard inserts. Finally, the experimental result, including the rotor surface topography, confirms that the proposed cutter design is reliable and realistic in CNC screw rotor milling. [Display omitted] [ABSTRACT FROM AUTHOR]