武科大機(jī)械專業(yè)英語lesson39-展示頁
2025-02-12 20:01本頁面
【正文】 cheaply so the method is only suitable for long runs with helical gears（斜齒輪的大批量加工） since special cutters and guides must be manufactured for each different helix angle. A great advantage of gear shaping is its ability to cut annular（環(huán)形的，輪狀的） gears such as those required for large epicyclic drives（行星齒輪傳動(dòng)） . Gear Hobbing（滾齒） Gear hobbing， the most used metal cutting method， uses the rack generating principle （齒條展成原理） but avoids slow reciprocation by mounting many “ racks” on a rotating cutter（旋轉(zhuǎn)刀具） . The “ racks” are displaced axially to form a gashed（很深的裂縫） worm（這些“齒條”軸向排布，形成了 有縫 的蝸桿） . Metal removal rates are high since no reciprocation of hob or workpiece（滾刀和工件） is required and so cutting speeds of 40 m/min can be used for conventional hobs（普通滾刀） and up to 150 m/min for carbide hobs（硬質(zhì)合金滾刀） . Typically with a 100mm diameter hob the rotation speed will be 100 rpm and so a twenty tooth workpiece will rotate at 5 rpm. …… ……Each revolution of the workpiece will correspond to mm feed so the hob will advance through the workpiece at about 4 mm per minute. For car production roughing multiple start hobs（多頭粗加工滾刀） can be used with coarse feeds of 3 mm per revolution so that 100 rpm on the cutter, a twostart hob（ 雙頭滾刀） and a 20 tooth gear will give a feed rate of 30 mm/min. Gear Broaching（拉齒） Gear broaching is not usually used for helical gears（ 斜齒輪） but is useful for internal spur gears（ 直齒輪）； the principle use of broaching in this context（在這種情況下） is for internal splines（ 內(nèi)花鍵）which cannot easily be made by any other method. As with all broaching the method is only economic for large quantities since setup costs（設(shè)備的費(fèi)用） are high. Gear Broaching gives high accuracy and low surface roughness（低表面粗糙度） but like all
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