Research On Machining Non-Orthogonal Face Gears By Power Skiving With Tooth Flank Modification Based On Six-Axis Machine Tool

To solve the manufacturing difficulties of non-orthogonal face gear, an efficient gear machining method referred to as power skiving is proposed. The machining principle of the power skiving and the relative position between the cutter tool and the workpiece are analyzed. Then, the mathematical model of machining non-orthogonal face gears by power skiving is established and the tooth flank equation is obtained. The installation and movement mode of non-orthogonal face gears on six-axis machine tool are analyzed and the machining parameters are calculated precisely. A method of tooth flank modification on the six-axis machine tool is presented by changing the machining parameters. The meshing performance of the obtained non-orthogonal face gear is analyzed by an example. Finally, the processing test and the tooth flank measurement are carried out. The experimental results show that the non-orthogonal face gear can be machined and modified by power skiving on the proposed six-axis machine tool.

Research on the profile modification of power skiving tool for internal gears

Power skiving provides an effective solution and considerable machining efficiency for the machining of internal gears. The tool profile design and the reusability after resharpening is critical in gear machining. In this paper, a tool profile correction method based on the error inverse complement of involute profile is proposed. The mathematical model of involute cutter with rake angle and relief angle is established, and the profile error relative to the target gear is calculated by using the tool of this mathematical model. The distribution of gear profile error is fitted by fifth-order multinomial, and the multinomial function of fitting was attached to the cutter profile. The theoretical error of the target gear profile is in 10e-7mm order of magnitude through the calculation of fewer iterations. The distribution of the coefficient of the error multinomial along the resharpening direction is obtained by linear programming. The result shows that the tool designed by this method has almost negligible error accuracy and good repeatability.

Predictions of Cutting Force and Tool Wear in Gear Power Skiving

Power skiving is a promising method that can enhance the efficiency of gear machining. The machining mechanism is complicated due to several factors, such as the continuous variation in the rake angle and undeformed chip thickness. The tool wear process is also difficult to be evaluated due to the constantly varying in cutting conditions. Hence, to make a comprehensive understanding of the cutting process, we proposed a parametric modeling process based on the kinematics of power skiving. In this model, the undeformed cutting chip was calculated in each pass and shows the consistency with deformed cutting chip in experiments. The effective rake angle and undeformed cutting chip thickness were defined, calculated, and displayed on undeformed cutting chip for a better understanding of the cutting process. The cutting force and tool crater wear were calculated by estimating the distribution of the stress and temperature on the rake face of the cutting tool. Multiple radial-feed experimental evaluations were conducted with the gears of construction vehicles. In the results, the predicted margin of the absolute error of the normal force on the rake face was under 5% in every pass. The wear distribution on the rake face is consistent with the superimposed tool-chip contact area. The results show high potential for the optimization of the cutting tool or cutting conditions in gear power skiving.

The Effect of Chip Binding on the Parameters of the Case-Hardened Layer of Tooth Surfaces for AMS 6308 Steel Gears Processed by Thermochemical Treatment

The following article describes influence of pressure welded or bound chips to the gear tooth flank and/or the tooth root on a carburized case and surface layer hardness of Pyrowear 53 steel gears, machined by Power Skiving method. This paper is focused only on one factor, the chips generated while forming gear teeth by power skiving, which could result in local changes in the carburized case parameters as a negatively affecting point of mechanical performance of the carburized case. The chips, due to the specifics of the power skiving process and the kinematics of tooth forming, could be subject to the phenomena of pressure welding or binding of chips to the tooth. During the carburizing stage of the downstream manufacturing processes, the chips form a diffusion barrier, which ultimately could result in localized changes in the carburized case. This work was an attempt to answer the question of how and to what extent the chips affect the case hardening. Performed simulations of chips by a generating cupper “spots”, mentioned in the study, represent a new approach in connection with minimization of errors, which could appear during carbon case depth and case hardness analysis for typical chips, generated during the machining process—assurance that a complete chip was bound to the surface. Hardness correlation for zones, where the chip appears with areas free of chips, gives simple techniques for assessment. Performed tests increased the knowledge about the critical size of the chip—1.5 mm, which could affect the case hardening. Obtained experimental test results showed that the appearance of chip phenomena on the gear tooth might have a negative impact on a carburized case depth and hardened layer.

Mathematical Modelling of Power Skiving for General Profile based on Numerical Enveloping

Power skiving is an effective generating machining method for internal parts like gears with respect its high productivity. The general mathematic modelling for power skiving is the basis for cutting tools design, machining precision evaluation, and machining process optimization. Currently, mainly studies are focus on the involute gear machining with adopting the analytical enveloping equation. However, these analytical methods have failed to deal with overcutting for general profile skiving tasks. Moreover, little attention has been devoted to investigate the power skiving process with taking variable configuration parameters, which is significant to control the machined surface topography. Herein, we introduce a mathematic modelling method for power skiving with general profile based on the numerical discrete enveloping. Firstly, the basic mathematic model of power skiving is established, in which the center distance is formulated as polynomial of time. With transforming the power skiving into a forming machining of the swept volume of cutting edge, a numerical algorithm is designed to distinguish the machined transverse profile via the discrete enveloping ideology. Especially, the precise instant contact curve is extracted according to the feed motion speed inversely. Finally, simulations for involute gear and cycloid wheel are carried out to verify the effectiveness of this method and investigate the influence of variable radial motions on the machined slot surface topography. The results show this method is capable to simulate the dynamic power skiving process with general profiles and to evaluate the machined results.

Temperaturverteilung beim Wälzschälen/Temperature distribution during power skiving

Innenverzahnungen, die aufgrund der Elektromobilität zunehmend im Fokus stehen, lassen sich mithilfe des Wälzschälens produktiv herstellen. Um diese Produktivität weiter zu steigern, müssen die wirkenden Verschleißmechanismen untersucht und verstanden werden. Der Beitrag behandelt die experimentelle Temperaturuntersuchung des Wälzschälens mit anschließender Modellierung der Wärmeverteilung, welche als erster Schritt zum Mechanismenverständnis angesehen werden kann.   Internal gears, which are increasingly in focus due to electromobility, can be manufactured productively with the help of power skiving. In order to further increase the productivity, the wear mechanisms have to be investigated and understood. This paper discusses the experimental temperature analysis of power skiving by subsequently modelling the heat distribution. This process can be seen as a first step towards understanding the underlying mechanisms.