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1、Gear manufacturing methodsAbstract This paper deals with the production process of the chain wheel. It Detailed description of gear planning ,gear shaping, gear hobbing, gear broaching , gear shaving ,gear grinding, and introduce the teeth of the production of a variety of methods and the used occas
2、ions. Key Words gear planning ,gear shaping, gear hobbing, gear broaching , gear shaving ,gear grinding, Gear Planing the shape of the space between gear teeth is complex and varies with the number of the gear as well as tooth module, so most gear manufacturing methods generate the tooth flank inste
3、ad of forming .Gear planing uses a reciprocating racks, stroking in the direction of the helix on agear with a gradual generation of from as the rack effectively rolls round the gear blank . The rack is relieved out of contact for the return stroke as in normal shaping or planning .It has the great
4、advantage that the cutting tools is a sampling rack with (nearing) straight sided teeth which can easily be ground accurately .This method is little used for high production because it is relatively slow in operation due to the high tool and slide mass; for jobbing purpose the slow stroking rate doe
5、s not matter and low tool cost give an advantage where unusual sizes or profile modification are required .Gear shaping gear shaping is inherently similar to gear planning but uses a circular cutter instead of a rack and the resulting reduction in the reciprocating inertia allows much higher strokin
6、g speed ;modern gear shapers cutting car gears can run at 2000 cutting strokes per minute .The shape of the cutter is roughly the same as an involute gear but the tips of the teeth are rounded .The generating drive between cutter and workpiece does not involve a rack or leadscrew since only circular
7、 motion is involve a rack or leadscrew since only circular motion is involved . The tool and workpiece move tangentially typically 0.5 mm for each stroke of the cutter .on the return stroke the cutter must be retracted about 1mm to give clearance otherwise tool rub occurs on the backstroke and failu
8、re is rapid.The advantage of gear shaping are that production rates are relatively high and that is the possible to cut right up to a shoulder .Unfortunately , for helical gears ,a helical guide is required to impose a rotational motion on the stroking motion ;such helical guides cannot be produced
9、easily or cheaply so the method is only suitable for long runs with helical gears since special cutter and guides must be manufactured for each each different helix angle .a great advantage of gear shaping is its ability to cut annular gears such as those required for large epicyclic drives.Gear Hob
10、bing gear hobbing , the most used metal cutting method , uses the rack generating principle but avoids slow reciprocation by mounting mangy “racks” on a rotating cutter .the “racks” are displaced axially to from a gashed worm.Metal removal rates are high since no reciprocation of hob or workpiece is
11、 required and so cutting speeds 40 m/min can be used for conventional hobs and up to 150m/min for carbide hobs . Typically with a 100mm diameter hob the rotation speed will be 100rpm and so a twenty tooth workpiece will rotate at 5 rpm. Each revolution of the workpiece will correspond to 0.75mm feed
12、 so the hob will advance through the workpiece at about 4mm per minute .for car production roughing multiple start hobs can be used with coarse feed of 3 mm per revolution so that 100rpm on the cutter ,a two-start hob and 20 tooth gear will give a feed rate of 30 mm/minute .Gear Broaching Gear broac
13、hing is not usually used for helical gears but is used for internal sour gears ;the principle used of broaching in the context is for internal splines which cannot easily de made by any other method .As with all broaching the method is only economic for large quantities since setup costs are high .G
14、ear broaching give high accuracy and low surface roughness but like all cutting processes is limited to “soft ” materials which must be subsequently case-hardened or haet treated ,giving distortion .Gear Shaving Gear shaving is used as finishing processes for gears in the “soft ” state .The objectiv
15、e is to improve surface roughness and profile by mating the roughed-out gear with a “cutter” which will improve form .A gear shaving cutter looks like a gear which has extra clearance at the root (for swarf and coolant removal) and whose tooth flanks have been grooved to give cutting edges. It is ru
16、n mesh with the rough gear with crossed axes so that there is in theory point contact with a relative velocity along the teeth giving scraping action .The gear shaving cutter tooth are relatively flexible in bending and so will only operate effectively when they are in double contact between two gear teeth. The gear and cutter operate at high rotation speeds with traversing of the workface and about 100 micron of machine
