The key technical points of gear hobbing MQL micro lubrication processing

(1) High hobbing speed <br /> Generally, in dry hobbing processing, the linear speed of the coated (TiAlN) high-speed steel hob is required to reach 180m/min or even higher; for the hard alloy steel rolling The cutting speed is required to reach 300 m/min.In order to realize this high-speed hobbing processing, the tool spindle can generally be realized by an electric spindle; for the worktable, a new-designed gear transmission system with automatic clearance elimination is used to replace the traditional worm and worm gear transmission system, LIEBHERR, GLEASON The worktables of high-speed gear hobbing machines of other companies have adopted torque servo motor technology, and the worktable speed can reach more than 800 r/min.
(2) Quick separation of chips <br /> Due to the high temperature, if the chips cannot quickly leave the tool, workpiece and machine tool, it will easily cause thermal deformation and affect the machining accuracy. Therefore, iron chips must be removed quickly and effectively.In dry hobbing, the high-speed hobbing of the hob is generally used to make the iron filings quickly leave the tool and the workpiece.In response to the chip removal problem, many companies have also proposed some machine tool structural improvements, such as using gravity to speed up the removal of iron filings, and avoiding the iron filings from directly falling on the workbench, and then assisting with high-pressure cold air to achieve rapid and effective chip removal.Some companies also use stainless steel heat shields. On the one hand, the surface of stainless steel is smooth, which facilitates the removal of iron filings. On the other hand, the heat conductivity of stainless steel is small, which reduces the heat transfer of iron filings to the workbench and bed.
(3) High-speed hobs <br /> The hob materials for dry hobbing use cemented carbide steel in the early stage of development. However, due to the high cost of cemented carbide steel hobs, the powder metallurgy high-speed steel hobs developed in recent years and TiAlN coated high-speed steel hobs have a tendency to replace hard alloy steel hobs for dry hobbing.In a research report, Liebherr Company has performed the processing of hard alloy hob (Carbide) dry hob, powder metallurgy high-speed steel hob (HSS-PM) and conventional high-speed rigid hob (Conv.HSS). The time and processing cost are compared.The comparative analysis results show that, compared with conventional machining, dry hobbing has shorter processing time and lower cost; the use of powder metallurgy high-speed steel hobs has even better dry hobbing results than the use of cemented carbide steel hobs .

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