1、<p><b>　　中文翻譯：</b></p><p>　　制造齒輪，高精密和相對復雜機床是必需的。現有各種各樣類型的機器是努力生產不同幾何形式齒經濟方法的結果。切齒機是由機器元素“齒輪”（如:從機器運動動作的角度)要求的結果,切齒技術可分為如圖9.2所示的成形式和切割(復制)式.</p><p><b>　　齒輪評級流程： </b>&

2、lt;/p><p>　　(a)高幾何精度,盡管形式復雜，但保證必要的運動傳動平穩(wěn);</p><p>　?。╞)高的材料強度,使小型齒輪能傳遞大的扭矩;</p><p>　　（c)設計種類多，特別是針對單個和小批量生產的現像,同時為了優(yōu)化專業(yè)驅動特征。</p><p>　　切齒機是由各種不同的觀點系統分類的。圖9.1對所有的齒輪生產技術作了一個通用

3、的調查并進行了總結。從這里可以看到,粗加工和精加工過程之間分化。按照前面的章節(jié),這項技術將會分為有屑加工和無屑的加工方法。這個有屑加工生產機器是根據切削工具的切削幾何參數進一步細分.</p><p>　　為了達到產量的經濟性,同時也要維持齒輪高精確度的目的,齒輪切削機開始進行具有高的切削速度和快速進給的改進，這是隨后一個整理過程。對于齒輪粗糙的加工過程最廣泛使用的滾齒機、插齒和較大的剃齒機。因為最后精加工的工作,

4、最廣泛使用的技術是磨齒機與剃齒機和精密齒輪滾動,可能用于最后進行過熱處理硬化的齒輪上。</p><p>　　當使用成形式切割方法加工時,輪廓是由工具(銑刀、立銑刀、砂輪)的齒空間完成的。生產齒輪的切削是由每個齒的齒形空間通過一個角度單獨完成進行索引的,,根據加工牙齒的數量允許下一個齒空間(單一索引方法)進行切削。刀具輪廓必須有明確的切削形式所需的齒空間,這意味著,對于加工每個設計不同的齒輪,一個特殊的切割工具是必

5、需的。因此,這種技術是幾乎完全用于專門制造大齒輪的,或在大規(guī)模生產的非常小的齒輪的精密工程行業(yè)。</p><p>　　當使用生成方法加工時，漸開線生成是刀具和被切齒輪相對運動之間的結果。這是通過一個運動之間的耦合,刀具的工作通常在形式是一個封閉的齒輪裙裾。齒側面的形成是由一個切削工具產生獨特形狀造成的輪廓的結果。刀具相對于齒輪的位置由于被切削可能會產生移動增量(指數基因評級技術)或連續(xù)不斷生成技術。刀具本有身直側

6、翼,在切削過程中,可能會將這用于形成一個更廣泛的給定的工作模塊。為了規(guī)范和降低一系列的工具裝備儲備</p><p>　　,基本剖面的直齒圓柱齒輪是由正常段齒條(可能被視為一個外部齒輪與一個放大的齒數,n→∞)和所謂的:面對齒輪(包括直齒圓錐齒輪造成的放大斜角在90°)易用性錐齒輪定義的。</p><p>　　切齒機的進一步細分可以依據齒輪類型,這將在以下部分中討論。各種形式的齒輪

7、見圖9-3所示分類。.切齒機的生產經濟性按照旋轉軸的相對位置和需要特定交配的齒輪。</p><p>　　直齒圓柱齒輪(平行軸的旋轉和滾動動作)可以有外部以及內部的牙齒,這些可能是直的,螺旋或人字形. . </p><p>　　錐齒輪的牙齒可以是直的、斜的或彎曲的。在后者的緩解行兩側牙齒可能基本上遵循作為漸開線或加工延伸外擺線。此外,軸的旋轉被互成直角的可能彼此相交(滾動動作)或他們的軸可

8、能相對移動(斜角蝸桿傳動)。錐齒輪主要通過是擠壓和研磨然后進行后熱處理。</p><p>　　圓柱斜齒輪是交配的圓柱螺旋齒輪,與軸線交叉形成不同螺旋角。兩齒輪螺旋角的角度總和確定了軸的交叉方向。他們的制造工藝不同于的直齒圓柱齒輪。</p><p>　　為了獲得高齒輪比率使軸躺成相互直角可以運用圓柱蝸桿和蝸輪傳動。</p><p><b>　　蝸輪蝸桿驅動應

9、用：</b></p><p>　　9.1切削成形齒輪刀具與切削刃使用的關鍵幾何因素</p><p>　　9.1.1齒輪滑行機</p><p>　　9.1.1.1直齒圓柱齒輪</p><p>　　當應用到生產直齒圓柱齒輪中時,齒輪滑行機按照索引生成原理在半連續(xù)工藝(圖9.4)中操作,這意味著為了產生特定長度(齒數)的切割變形,生成幾

10、個齒空間之前,索引是必要的。切割架提供了切削運動,而工作臺通常使產生進給運動。有一部份齒被切完后,工作臺就開始脫離,搬回到開始位置并重新切削后面的牙齒。</p><p>　　刀具由直齒或螺旋齒齒條與寬慰側翼(切削后角)組成。當與其它方法相比,刀具相對容易改變。在高磨損條件(如生產大型齒輪由高強度合金)下,切割架可以變換位置工作才能完成,并且沒有影響工作的質量。</p><p>　　完整的齒

11、輪滑行機的傳動系統如示意圖9.5。主傳動(1)的切割架(3)通過一個曲柄安裝、連接到減速齒輪機構(2)上,用于設置沖程率。該系統是通過驅動曲柄滑塊改變齒輪機構(8)和導螺桿(10)和箴見線性組件產生運動;工作表是安裝在提供機構評級塊，生成旋轉運動來驅動齒輪系(7)得到示數變化,傳送到一個伸縮軸和一個蝸輪蝸桿傳動機構中。剩下的輔助驅動是用來設置齒根圓半徑與電動機或手輪(26)數值,變化徑向深度切削運動使用齒輪機構(27)和床主軸(11),

12、以及參與反向自由扭轉運動(12、16和18),直到評級機構顯示已經到達行程盡頭。 圖9.6給出了機械結構原理圖。刀軸與刀架(尖瘦地調為螺旋齒)是固定在機床上的。旋轉的工作表是一個協調滑用于徑向切削深度在橫向切削進給評級行動。大型機器,徑向切削深度,橫向進給是由一個滑動柱提供的。圖9.7顯示了一個齒輪滑行機的一個前視圖 。</p><p><b>　　9.1.1.2齒輪</b></p&g

13、t;<p>　　生產錐齒輪有些相似于直齒圓柱齒輪的制造。代替架形成切削刀具,刀具采用的形式是一個面齒輪,原理如圖9.8所示。由于生成運動的面齒輪(切割輪直站,齒條式剖面)和齒輪毛坯傾斜的斜面角δ之間,兩翼之間產生齒側面，切割運動方向產生牙齒的長度。 </p><p>　　錐齒輪滑行機、直、斜齒,工作在索引生成原理的基礎上。他們的驅動機制是類似齒輪滑行的機器。取而代之的是線性運動的切削機架、切割鼓轉動

14、和旋轉刨刀(面齒輪),從而產生其切削運動。圖9.9說明了這樣一個錐齒輪滑行機的工作原理。</p><p>　　另一種方法的錐齒輪滑行它必須被定義為一個錐齒輪滑行過程模板技術形式。刀具是由模板來生成所需的齒廓。該方法是用于專門制造非常大的錐齒輪,切削力會高于傳統機器但是生產力相當差。</p><p><b>　　9.1.2插齒機</b></p><p

15、>　　插齒機不斷基因評級切齒機,可以從圖9.10看到。切割輪有一個線性中風運動(切削運動)和齒輪毛坯的同時旋轉。先進的機器使用這種方法獲得的切削速度超過100米每分鐘，結果導致的高雙作用沖擊率。</p><p>　　刀具擁有一個齒輪形式與鏟齒、漸開線形齒側翼。制造螺旋齒輪的牙齒,合適的螺旋齒切割車輪必須雇用。如圖9.10所示軸有一個旋轉運動在其行程上,由螺旋鉛套引導。這樣一個螺旋鉛套,結合不同的切割輪,可以

16、用于一個特定范圍的螺旋角。作為切削工具有一個有限的應用范圍,齒輪機成形主要用于生產內圈齒輪和齒輪的制造與一個小自由軸向空間,如人字,尤其是人字齒(圖9.11),以及切割齒輪的集群等。</p><p>　　圖9.12顯示了按照圖式驅動的齒輪成形機。為了獲得機構評級切削行動,四個主要運動是必需的。扶輪的運動是切割輪生產的芯片運動,并持續(xù)工作至行程和回程。電力傳輸是直接從主電動機中風的機制。作為中風運動是由一個曲柄運動

17、,切削速度不恒定在整個長度的</p><p>　　沖程。在回程中有一個緩沖運動，否則由于連續(xù)旋轉動作,一個齒輪毛坯和刀具之間的干擾將導致摩擦的發(fā)生。旋轉進給運動是產生于主傳動通過進刀機構變速齒輪。該評級運動即協調旋轉的工具和齒輪毛坯的運動,是由傳感器輪系和傳播到隨機存取存儲器主軸通過上層蝸輪管理,工作表通過降低蝸輪管理。在一開始的工作周期,工作表產生額外的徑向運動,因此得到所需的深度削減。建設插齒機如圖9.13所

18、示。</p><p>　　9.1.3齒輪擴孔機</p><p>　　齒輪擴孔機(有時稱為形式塑造機器)利用形式切割或復制行動沒有任何基因評級運動。刀具的形狀根據所需的齒空間輪廓。拉削的漸開線齒輪的牙齒主要用于大批量生產工作,由于高加工成本和相對高的生產力。機器結構及其運動學在很大程度上類似于那些傳統的擴孔機,即生產問題和準確度依賴于施工的工具。</p><p>　　

19、9.1.3.1直齒圓柱齒輪</p><p>　　該工具為粗擴內部齒輪，通常由一個圓刀架包含拉削刀具,研磨到所需的漸開線形狀和夾緊的楔形。刀具的數量在周邊通常是所切削牙齒數目的一半。內部剖面產生兩個沖程。一個組件夾具持有齒輪毛坯,讓它通過一個齒距。這種技術可以降低成本,還降低了工具的切削力。</p><p>　　圖9.14(左)顯示了一個示例的粗擴孔的大批量生產行星環(huán)形齒輪,該工具包括一個熱

20、處理主體與螺紋在柄和結束切削部分。準確的槽是在主體切削刀具中插入,由優(yōu)質工具鋼組成,是固定的。</p><p>　　由于大型軸向深度削減和高切削力的作用,要求的齒輪的齒精度通常不是這樣的工具可以實現的。這個工作是粗糙的加工，然后對尺寸而言,在第二次操作中,完成鉆孔與分段完成拉削,如圖9.14(右)。</p><p>　　基本上,有兩種方法用于擴外部齒輪齒的孔;速度剪切技術和管擴孔技術。在速

21、度剪切技術中工件是通過固定刀頭向上推(拉削運動)。在刀頭(見圖9.15,一個刀片)里面,異形鋼的速度剪切刀片是固定的徑向主軸齒輪毛坯,這樣所有的牙空間同時削減。徑向位置的葉片是由兩個相互作用的錐形環(huán)接觸向導的面孔葉片鉗,在圖9.16可以看到在剖視圖的銑頭。</p><p>　　在每一個沖程工作中,錐形環(huán)產生一個小的上升運動,這樣的外殼內部錐形環(huán)允許刀片從工件在回程收回。在每個新的工作行程,錐形環(huán)的移動與一個額外的

22、沖程運動在一個向下的方向,所以,內殼層外錐形環(huán)使間隙距離被取消了。此外,這個動作是使所有葉片進一步向工件所需深度的沖程。圖9.17顯示了工作區(qū)域,這樣一個拉床與卡盤、齒輪毛坯和銑頭。</p><p>　　該技術只有對大量生產具有經濟性,作為一個新的刀頭是需要每個空白直徑。在特殊情況下,使用此方法可以產生內部齒輪。</p><p>　　當管拉削工作,對于速度剪切的技術,是安裝在芯棒和向上推到

23、工具管的中空拉刀。在管擴孔工具,使徑向切削刀具被安裝與進步的高度增加和固定。在插入時,指引線是提供給控制工件安裝頭在拉削過程。</p><p>　　9.1.3.2錐齒輪</p><p>　　傘齒輪擴孔機工作通常按照“Relevancy“單一索引過程,只能被認為是用在大批量生產領域。在圖9.18中,當擴孔車輪轉動后，鉸孔(類似于一個拉刀)、粗、精加工刀具被依次錄用后，就會生產完成齒空間。當切

24、削時,拉削輪子的中心按指定安排好的順序平行移動到根齒。在一個齒空間完成后,齒輪毛坯的清除是從刀具的拉削車輪到索引一個齒的空間。</p><p><b>　　9.1.4滾齒機</b></p><p>　　9.1.4.1直齒圓柱齒輪</p><p>　　齒輪滾刀機器操作一個連續(xù)運動的齒輪滾刀作為切削工具。齒輪滾刀的主體是一個圓柱漸開線蝸桿。一個刀具

25、是源自蝸桿。由于蝸桿螺旋被凹槽中斷與，兩側翼合成的切削齒是鏟齒，允許自由切割。</p><p>　　為了有助于基因的評級動作的理解,一個與齒輪滑行和齒輪成形原理相似的簡圖如圖9.19。在基因評級運動、齒輪滾刀和齒輪毛坯旋轉像一個蝸輪蝸桿的傳動。旋轉滾刀的切削運動也被包含在里面。如圖9.20,齒輪的生產可以通過幾種不同的動作組合。</p><p>　　當侵蝕滾齒滾刀下切,切屑厚度在初剪時是很

26、大的;實際輪廓成形于剛剛結束的單切。這可能,在某些情況下,由于“組合”的邊緣導致質量問題。在切滾刀易用性上,剖面形狀立即反映在開始的切削的過程中,結果小切屑片卷產生初始摩擦或壓縮,并可能在切削時產生阻力。</p><p>　　對于徑向軸向滾壓易用性,滾刀是首先徑向進入齒輪毛坯進入到所需的齒槽深度,然后滾銑或者使用上切或下切侵蝕的動作。在一個給定數量的齒空間已加工的齒輪或毛胚,滾刀是由給定數據直接地移動，為了使用所

27、有的齒滾刀同時工作。這個動作,有時被稱為“轉移”,不斷發(fā)生在對角擠壓方法中,在這一個沖程中由一個軸向和切向分量</p><p>　　滾刀的主要尺寸.時間和設置值如圖9.21所示，滾刀實際切割位置，滾刀角設置(入射角,η)依賴于螺旋的方向和價值。角β的牙被削掉(如果有的話).</p><p>　　這個螺旋角γ的蝸桿在滾刀架上。對于任何一個滾刀，齒輪給定的任何齒數和螺旋齒角,以及各種各樣的齒廓

28、的修改,可能會產生不同通過不同的機器設置,提供了牙齒的相同模塊和壓力角。任何限制僅僅是由于機器的工作能力。</p><p>　　一個簡化布局的驅動的滾齒機如圖9.22所示。主電機直接驅動滾刀，而工作表通過側速變速齒輪機構中間伸縮蝸輪蝸桿傳動。選擇傳感器在改變齒輪系坐標的旋轉工具和工作比例,這是依賴于被切削牙齒數目和滾刀的螺旋。蝸桿傳動驅動進給改變齒輪機構,如圖9.。22。旋轉的軸向主軸通過無級變速。制造螺旋齒和對

29、角滾齒機、齒輪毛坯切受到額外的旋轉運動</p><p>　　相對于滾刀進給,由差分驅動提供。微分籠被釋放并設置成運動的微分改變齒輪機構,并且選擇適當的齒輪。圖9.23是一個詳細的表示這樣的滾齒機運動學的原理圖,這也顯示了軸獲得旋轉運動的徑向進給。</p><p>　　圖9.24顯示了一個通用滾齒機的圖片。在傳統的機器,圓柱是連接到機器床上的。這個工作主軸滑動及其支持中心是由徑向進給軸和橫向

30、移動獲得徑向進給。可以移動的滾刀主軸沿擠壓滑動通過切向驅動器和一個切向軸,也可以是有角度地調整以適應設置所需的螺旋角的齒輪被削減。鐵架驅動和進給驅動位于圓柱。</p><p>　　在一個機器最初的設計,工作臺是固定和圓柱沿床身打滑。只有主驅動軸和進給軸在圓柱上。為了提高散熱所有其他驅動元素是在一個單獨的傳動箱左側機。</p><p>　　為了提供反向自由驅動器,現代機器都為軸裝有預緊聯結在

31、一起,傳遞球螺母。表驅動可以反向自由通過兩個軸向預應力螺旋或反對使用所謂的“雙蝸桿”,有一個稍微不同的傾斜在它的左右兩翼,使其調整的方向稍微厚螺旋線當磨損發(fā)生時。圖9.25顯示了這樣的建筑設備剖視圖一個十字架。</p><p><b>　　英文翻譯原文</b></p><p>　　GEAR-CUTTING MACHINES</p><p>　　

32、For the manufacture of gear wheels, comparatively complicated and highly precise machine tools are required. The wide variety of existing types of machines is the result of the effort made to find economic production met

33、hods for the geometrically diverse gear-tooth forms. The requirements of a gear-cutting machine result from the demands that are made by the machine element 'gear wheel', e.g.:</p><p>　　(a) high geom

34、etric accuracy, notwithstanding the complicated form necessary for the smooth transmission of motion;</p><p>　　(b) high material strength to enable the transmission of large torques with small-sized wheels;

35、 (c) large varieties of design, particularly in the field of small-batch and 'one .off' production, in order to optimize specialized drive characteristics.</p><p>　　Systematic classifications of gea

36、r-cutting machines can be made from a variety of different standpoints. As a general survey, all techniques for the production of gear wheels are summarized in Fig. 9.1. From the aspect of the qualities obtainable, diffe

37、rentiation may be made between roughing and fine-finishing processes. In line with the previous chapters, the techniques will be divided into chip-producing and chipless production methods. The chip-producing machines ar

38、e further subdivided accord</p><p>　　In order to achieve an economic production rate, whilst at the same time maintaining a high degree of accuracy of the gears produced, gear cutting is commenced with a hig

39、h cutting speed and fast feed rates. This is then followed with a finishing process. For rough gear cutting, the processes most widely used are those of hobbing, gear shaping and for larger gear wheels, gear planing; for

40、 finishing work, the most widely used technique is that of gear grinding which, in contrast to gear shaving an</p><p>　　From the point of view of the kinematic action of the machine, gear-cutting techniques

41、may </p><p>　　be classified as shown in Fig. 9.2 into form cutting (copying) and gene rating processes.</p><p>　　When using the form-cutting processes, the tool (milling cutter, end mill, grindi

42、ng wheel) is made with the contour of the finished tooth space. Each tooth space is individually finished and the gear wheel being cut is then indexed through an angle, depending on the number of teeth to be produced, to

43、 allow the next tooth space to be out (single-indexing method). The cutter profile must be of the exact form of the required tooth space, which means that for every set-up of a different gear wheel t</p><p>

44、　　9.1 Chip-forming gear-cutting machines using cutters with cutting edges of a critical geometry</p><p>　　9.1.1 Gear-planing machines</p><p>　　9.1.1.1 Spur gears</p><p>　　When appli

45、ed to the production of spur gears, gear-planing machines operate in accordance with the indexing-generation principle in a semi-continuous technique (Fig. 9.4); this means that as a result of the particular length (numb

46、er of teeth) of the cutting rack, several tooth spaces are generated before indexing is necessary. The cutting rack provides the cutting movement, while the work blank generally makes the generating action. After a numbe

47、r of teeth have been cut, the work blank is diseng</p><p>　　Fig. 9.4 Principles of gear planing</p><p>　　The cutting tool consists of a straight or helical tooth rack with relieved flanks (cutti

48、ng clearance angle). When compared with other methods, the cutting tool is comparatively easily changed. Under high wear conditions (e.g. the production of large gear wheels made from high-tensile alloys), the cutting ra

49、ck may be exchanged before the work is completed, without a detrimental effect on the quality of the work.The complete drive system of a gear-planing machine is shown schematically in Fig. 9.</p><p>　　9.1.1.

50、2 Bevel gears</p><p>　　The production of bevel gears has some similarities with the manufacture of spur gears. In place of the rack-formed cutting tool, the cutter takes the form of a face gear, the principl

51、e of which is shown in Fig. 9.8. As a result of the generating motion between the face gear (cutting wheel with a straight sided, rack-type profile) and the gear blank inclined at the bevel angle δ, the gear-tooth flanks

52、 are produced. The cutting motion is in the direction of the length of the teeth.Bevel-gear-plan</p><p>　　9.1.2 Gear-shaping machines</p><p>　　Gear-shaping machines are continuously gene rating

53、gear-cutting machines, as may be seen from Fig. 9.10. The cutting wheel has a linear stroke movement (cutting movement) and simultaneously rotates with the gear blank. Advanced machines using this method obtain cutting s

54、peeds in excess of 100 m.min-l as a result of the application of high double-acting stroke rates.</p><p>　　The cutting tool has the form of a gear wheel with form-relieved, involute-shaped tooth flanks. For

55、the manufacture of helical gear teeth, suitable helical-toothed cutting wheels must be employed, as shown in Fig. 9.10. The ram spindle has a rotary motion during its stroke, guided by a helical lead sleeve. Such a helic

56、al lead sleeve, in combination with different cutting wheels, may be used for a specific range of helix angles. As the cutting tools have a limited range of application, gear shapi</p><p>　　Figure 9.12 shows

57、 schematically the drive of a gear-shaping machine. To obtain the gene rating cutting action, four main movements are required. The rotary action of the cutting wheel is the chip-producing motion, and continues through t

58、he working stroke and the return stroke. The power transmission is direct from the main motor to the stroke mechanism. As the stroke movement is produced by a crank motion, the cutting speed is not constant throughout th

59、e length of the stroke. During the return s</p><p>　　9.1.3.1 Spur gears</p><p>　　The tool for rough-broaching internal gear wheels usually consists of a round tool-holder containing the broachin

60、g cutters, which are ground to the required involute form and are clamped with wedges. The number of cutters around the periphery is normally half that of the number of teeth to be cut. The internal profile is produced i

61、n two strokes. A component fixture holds the gear blank, and rotates it through one circular pitch. This technique reduces tool costs and also lowers the cutting force</p><p>　　Figure 9.14 (left) shows an ex

62、ample of rough broaching for the mass production of planetary annular gears, in which the tool consists of a heat-treated main body with a screwed-on shank and end section. Accurate grooves are ground in the body into wh

63、ich the cutting inserts, made of high-quality tool steel, are fixed.</p><p>　　Owing to the large axial depths of cut and the high cutting forces involved, the required gear--tooth accuracies are normally not

64、 achievable with such tools. The work is rough-broached, dimensionally under-size, and then, in a second operation, finish-broached with a segmented finishing broach, as shown in Fig. 9.14 (right).</p><p>　　

65、Fundamentally, there are two techniques available for the broaching of external gear teeth; the Shear-Speed technique and the tube-broaching technique. In the Shear-Speed technique the workpiece is pushed upwards through

66、 a fixed cutter head (broaching movement). Inside the cutter head (which is illustrated in Fig. 9.15, with a single cutting blade), the profiled steel 'Shear-Speed blades' are fixed radially to the axis of the ge

67、ar blank so that all its tooth spaces are simultaneously cut. The ra</p><p>　　Fig. 9.17 External broaching of involute gear teeth using the Shear-Speed techniqueThe technique is only economic for large-quant

68、ity production, as a new cutter head is required for each blank diameter. In special cases, it is possible to produce internal gear wheels with this method.</p><p>　　When tube broaching, the work, as in the

69、case of the Shear-Speed technique, is mounted on a mandrel and pushed upwards into the tool tube of a hollow broach. Within the tube-broaching tool, radial cutting inserts are arranged with progressive height increases a

70、nd fixed. Between the inserts, guides are provided to control the workpiece mounting head during the broaching process.</p><p>　　9.1.3.2 Bevel gears</p><p>　　Bevel-gear-broaching machines usuall

71、y work in accordance with the 'Revacycle' single-indexing process, which can only be considered for use in the mass-production field. As may be seen in Fig. 9.18, during the rotation of the broaching wheel (simil

72、ar to a broach), roughing and finishing cutters are employed behind each other, and produce a finished tooth space. While cutting, the centre of the broaching wheel moves parallel to the root of the tooth being cut in th

73、e order indicated. After a tooth</p><p>　　9.1.4 Gear-hobbing machines</p><p>　　9.1.4.1 Spur gears</p><p>　　Spur-gear-hobbing machines operate a continuous-generating action with a g

74、ear hob as cutting tool. The body of the gear hob is a cylindrical involute worm. A cutting tool is derivece the worm helix is interrupted with grooves and the flanks of the resultant cutting teeth are form-relieved to p

75、ermit free cutting.</p><p>　　In order to aid the understanding of the gene rating action, a comparison with gear planing and gear shaping is given in Fig. 9.19. During the gene rating motion, the gear hob an

76、d the gear blank rotate like a worm and worm wheel. The hob rotation also provides the cutting motion. As shown in Fig. 9.20, the production of a gear can be achieved through several different combinations of movements.&

77、lt;/p><p>　　When downcut hobbing, the chip thickness is large at the beginning of the cut; the actual profile takes shape only just before the end of a single cut. This can, under certain circumstances, lead to

78、 quality problems as a result of 'built up' edges. In the ease of upcut hobbing, the profile is shaped immediately up on the beginning of the cut; the resulting small chip volumes introduce initial rubbing or com

79、pression and may cause a resistance at the beginning of the cut.</p><p>　　In the ease of radial-axial hobbing, the hob is first fed radially into the gear blank to the desired tooth depth, and then hobbed us

80、ing either upcut or downcut motions. After a given number of tooth spaces or gear blanks have been machined, the hob is moved tangentially by a given amount in order to use all the teeth of the hob equally. This action,

81、sometimes referred to as 'shifting', occurs continuously in the diagonal-hobbing method, as here the feed consists of an axial and tangential compo</p><p>　　The leading dimension s and setting values

82、 of a hob are shown in Fig. 9.21 in which the hob is shown in the actual cutting position. The angular setting (angle of incidence, η) of the hob is dependent upon the direction and value of the helix angle β of the toot

83、h to be cut (if any) andthe helix angle γ of the worm on the hob. With any one hob, gears of any given number of teeth and helical tooth angle, as well as all kinds of tooth profile modifications, may be produced by diff

84、ering machine sett</p><p>　　A simplified layout of the drive of a hobbing machine is shown in Fig. 9.22. The main motor drives the hob directly and also the work table through the pick-off change gear train

85、and the intermediate telescopic worm and worm wheel drive. The choice of ratio in the pick-off change gear train co-ordinates the rotations of the tool and work, which are dependent upon the number of teeth to be cut on

86、the gear and the number of start s of the helix on the hob. The worm drive drives the feed-change gea</p><p>　　Figure 9.24 shows a general picture of a hobbing machine. On conventional machines, the column i

87、s bolted on to the machine bed. The work-spindle slide and its support centre are driven by the radial-feed spindle and moved horizontally to obtain a radial feed. The hob spindle can be moved along the hobbing slide thr

88、ough a tangential drive and a tangential spindle, and may also be angularly adjusted to accommodate the setting of the required helix angle for the gear to be cut. The hob drive and th</p><p>　　On a machine

89、of recent design, the table is stationary and the column slides along the machine bed. Only the main drive shaft and the feed shaft are in the column. All other drive elements are in a separate drive box on the left side

90、 of the machine in order to improve heat dissipation.</p><p>　　In order to provide backlash-free drives, modem machines have all feed shafts fitted with preloaded, re-circulating ball nuts. The table drive m

91、ay be made backlash-free either by the employment of two axially opposed pre-stressed worms or by the use of a so called 'double worm' which has a slightly different pitch on its right and left flanks, enabling i

92、t to be adjusted in the direction of the slightly thicker helix when wear has taken place. Figure 9.25 shows a cross--sectional view of such a c</p><p>　　9.1.4.2 Bevel gears</p><p>　　Contrary to

93、 the exclusively continuous mode of the hobbing of spur wheels, bevel gear-hobbing machines can operate either continuously or with an indexing action. The cutting tools are side-and face-type milling cutters, inserted-t

94、ooth cutters or bevel gear hobs.</p><p>　　Bevel-gear index-hobbing machines usually employ two large cog-type, interlocking, radial-inserted tooth-cutter heads, with easily interchangeable cutter tips. The c

95、utting edges of all the cutters represent a tooth of a given crown wheel against which the gear blank to be cut is rolled. Figure 9.26 pictures the working area of such a machine with both work stations and the interlock

96、ing cutter heads. For small module s up to m = 6 mm, the two cutters first sink a slot into the stationary gear bla</p><p>　　The cutters of the cutter head are very largely universal. Within a certain range

97、of modules,</p><p>　　the same set of cutters may be used, which enables these machines to be economically employed even for small-scale production.</p><p>　　On a different construction of machin

98、e for index-hobbing of bevel gears, the cutter takes the form of a face-milling cutter head, which permits the manufacture of curved-toothed bevel gears. In this variation of the technique, the cutting edges of all the c

99、utters again represent one tooth of the 'idea!' crown wheel. The gear blank makes a generating motion against the rolling plane of the crown wheel, from which the tooth profile develops. The possible movements of

100、 such an inserted tooth-cutter </p><p>　　The generating motion during the process is executed about the axes of the gene rating drum (rocker) (2) and the gear blank (1); the cutting action occurs about the c

101、utter head axis (4). The plunge movement is obtained through the movement of the slide (8). Adjustments on the cutter-head slide (3) enable the setting of the cutting angle which is dependent on the diameter of the cutte