gear hobbing.pptx

This ppt covers the most about gear hobbing but the main contents.

1. GEAR HOBBING Nijerson Jeyaseelan, 2021507030

2. Introduction 01 CONSTRUCTION 02 WORKING 03 DIS/ADVANTAGES 04

3. INTRODUCTION What is a Gear? R otating machine part having cut teeth - Mesh with another toothed part to transmit torque. Gear Cutting: Gear cutting is a specialized job. Gear cutting is any machining process for creating a gear. The most common gear-cutting processes include hobbing , broaching, milling, and grinding. Gear Hobbing:   Continuous gear generation process widely used in the industry for high or low volume production of external cylindrical gears.

4. CONSTRUCTION Hob : R otating cutter - Multipoint cutting tool. It looks like a worm gear having a number of straight flutes all around its periphery parallel to its axis. These flutes are so shaped by giving proper angles to them so that these work as cutting edges. T he hob is rotated at a suitable rpm and simultaneously fed to the gear blank. The gear blank is also kept as revolving. Rpm of both, gear blank and gear hob are so synchronized that F or each revolution of gear bob the gear blank rotates by a distance equal to one pitch distance of the gear to be cut. The motion of both gear blank and hob is maintained continuously and steady.

5. WORKING OF THE MACHINE “ In this process, gear is cut by a generating process by rotating the gear blank and the cutter called a hob at the same time with a fixed gearing ratio between hob and gear blank. T he gear blank is fed towards the rotating hob until the required depth is reached. The hob is fed across the face of the blank until all the teeth are complete. In Hobbing Spur Gear the hob teeth are set parallel to the axis of rotation of the blank. For Helical Teeth Bobbing , the axis of the hob is set over an angle to produce the proper helix. While Worm Gears are produced with the axis of the hob set the right angle to the gear blank.

6. CONVENTIONAL HOBBING TWO TECHNIQUES IN HOBBING PROCESS  In Conventional Hobbing , the direction of feed matches the direction of the cutting motion. In Climb Feeding , the feed is opposite to the direction of the cutting motion. Generally, conventional hobbing produces a better finish, whereas climb hobbing yields better tool life. For either method, the cutting forces of the hob should be directed towards the work spindle and not the tailstock . CLIMB HOBBING

7. PARAMETERS Three important parameters: Indexing movement Feed rate The angle between the axis of gear blank and gear hobbing tool (gear hob).

8. TYPES OF HOBBING PROCESS The hob and gear blanks are set with their axis normal to each other. The rotating hob is fed against the gear blank in radial direction or perpendicular to the axis of gear blank. Used to make the worm wheels. WITH RADIAL FEED The gear hob is fed against the gear blank along the face of the blank and parallel to its axis. Used to make spur and helical gears. WITH AXIAL FEED Used for cutting teeth on the worm wheel. Hob - axis horizontal but at the right angle to the axis of the blank -At full depth of the tooth and then fed forward axially. Then fed tangentially to the face of the gear blank. . WITH TANGENTIAL FEED

9. Fast and continuous process - Economical Lower production cycle time, i.e. faster production rate. Capable to make a wide variety of gears like spur gear, helical gears, worms, splines, sprockets, etc. A special type of gear named herringbone gear cam be generated by gear hobbing exclusively. A wide variety of batch sizes (small to large volume) can be accommodated by this process. Several gear blanks, mounted on the same arbor, can be processed simultaneously. Hob is a multipoint cutting tool having multi cutting teeth or edges at a time few number of cutting edges work so lots of time is available to dissipate the generated heat. There is no overheating and cutting tool. ADVANTAGES OF GEAR HOBBING

10. Not adopted to generate internal gears Restricted adjacent shoulders larger than the root diameter of the gear. Splines and serrations are not suitable for hobbing . DISADVANTAGES OF GEAR HOBBING

11. It is widely used to produce spur, helical gears, worms, and worm wheels. It can also be used for producing internal gears for which the machine should have a facility for fitting a special head. APPLICATION OF GEAR HOBBING

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