Hiroshi Gunbara

Manufacturing method of double-helical gears using CNC machining center

Double-helical gears are usually manufactured using special type of machine tools, such as gear hobbing and shaping machines. In this paper, a manufacturing method of double-helical gears using a CNC machining center instead of the special type of machine tools is proposed. This manufacturing method has the following advantages: (i) the tooth surfaces can be modified arbitrarily, (ii) all we have to do in gear machining is only one machine setting, (iii) the hole and blank diameter and so on except the tooth surface can be also machined, and (iv) the auxiliary apparatus, special type of tools, and special type of machine tools are not needed. For this study, first the tooth profiles of the double-helical gear were modelled using a 3D computer-aided design system and the gear was machined using a CNC machining center based on a computer-aided manufacturing system. Next, the profile deviations, helix deviations, pitch deviations, and surface roughnesses of the manufactured double-helical gears were measured. Afterwards, the relationship between the tool wear and life time of the end mill were made clear. Finally, this manufacturing method was applied to the gears for a double-helical gear pump. As a result, the validity and effectiveness of the manufacturing method of double-helical gears using a CNC machining center were confirmed.

Machining and Running Test of High-Performance Face Gear Set

The purpose of this research is to develop a high-performance face gear set for aircraft. The geometrical design method of the face gear has already been proposed, and how to decide an effective engagement area under the design parameter has been clarified. A numerical example is presented based on the proposed method. Before machining test, the modified-tooth was decided by the developed Tooth Contact Analysis (TCA) program in order to control the tooth contact pattern. The influence of alignment error of each axis of gear was investigated using TCA. The designed modified-tooth was processed by the Multi-Tasking machine. Finally, running test was performed at a pinion rotating speed of 970 rpm. The face gear set can be operated continuously at an maximum load torque 1390 N · m, without any trouble. The transmission efficiency reached 98.9% under maximum load torque. This cutting method of the face gear introduces a new degree of freedom for defining optional shapes of tooth modification.© 2011 ASME

Tooth Contact Analysis and Manufacture on Multi-Tasking Machine of Large-Sized Straight Bevel Gears

Straight bevel gears are widely used in the plant of large-sized power generation when the gears have large size. The purpose of this study is to manufacture the large-sized straight bevel gears with equi-depth on multi-tasking machine. The manufacturing method has the advantages of arbitrary modification of the tooth surface and machining of the part without the tooth surface. For this study, first the mathematical model of straight bevel gears by complementary crown gears considering manufacture on multi-tasking machine is proposed, and the tooth contact pattern and transmission errors of these straight bevel gears with modified tooth surfaces are analyzed in order to clarify the meshing and contact of these gears. Next, the numerical coordinates on the tooth surfaces of the bevel gears are calculated and the tooth profiles are modeled using a 3D-CAD system. 5-axis control machines were utilized. The gear-work was machining by a swarf cutting using a coated carbide end mill. After rough cutting, the gear-work was heat-treated, and it was finished based on a CAM process through the calculated numerical coordinates. The pinion was also machined similarly. The real tooth surfaces were measured using a coordinate measuring machine and the tooth flank form errors were detected using the measured coordinates. As a result, the obtained tooth flank form errors were small. In addition, the tooth contact pattern of the manufactured large-sized straight bevel gears was compared with those of tooth contact analysis. As a result, there was good agreement.Copyright

Hourglass Worm Gears Designed to Concentrate Surface Normals. Manufacturing and Experimental Investigation on Tooth Bearing.

To avoid the influence from the small displacement of gear axes under load, the authors propose that all contact normals of a tooth surface be at right angles to the direction of the small displacement induced at each contact point under load. On the basis of this state of surface normals, a few methods for tooth surface generation have been devised for realizing this concept. In this research, an hourglass worm gear having the above geometrical characteristics was made using the conventional methods of tooth surface generation and tooth bearing of the worm gear was experimentally tested. As a result, the validity of this design concept was proven.