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附 錄
附錄1
外文資料
Milling Cutters and Operations
1. Introduction
The two basic cutting tool types used in the metal working industry are of the single point and multi-point design, although they may differ in appearance and in their methods of application. Fundamentally, they are similar in that the action of metal cutting is the same regardless of the type of operation. By grouping a number of single point tools in a circular holder, the familiar milling cutter is created.
Milling is a process of generating machined surfaces by progressively removing a predetermined amount of material or stock from the workpiece witch is advanced at a relatively slow rate of movement or feed to a milling cutter rotating at a comparatively high speed. The characteristic feature of the milling process is that each milling cutter tooth removes its share of the stock in the form of small individual chips. A typical face milling operation is shown in Figure 12.1.
2. Types of Milling Cutters
The variety of milling cutters available for all types of milling machines helps make milling a very versatile machining process. Cutters are made in a large range of sizes and of several different cutting tool materials. Milling cutters are made from High Speed Steel (HSS), others are carbide tipped and many are replaceable or indexable inserts. The three basic milling operations are shown in Figure 12.2. Peripheral and end milling cutters will be discussed below.
A high speed steel (HSS) shell end milling cutter is shown in Figure 12.3 and other common HSS cutters are shown in Figure 12.4 and briefly described below:
2.1 Periphery Milling Cutters
Periphery milling cutters are usually arbor mounted to perform various operations.
Light Duty Plain Mill: This cutter is a general purpose cutter for peripheral milling operations. Narrow cutters have straight teeth, while wide ones have helical teeth.
Heavy Duty Plain Mill: A heavy duty plain mill is similar to the light duty mill except that it is used for higher rates of metal removal. To aid it in this function, the teeth are more widely spaced and the helix angle is increased to about 45 degrees.
Side Milling Cutter: The side milling cutter has a cutting edge on the sides as well as on the periphery. This allows the cutter to mill slots (Fig.12.4b).
Half-Side Milling Cutter: This tool is the same as the one previously described except that cutting edges are provided on a single side. It is used for milling shoulders. Two cutters of this type are often mounted on a single arbor for straddle milling.
Stagger-tooth Side Mill: This cutter is the same as the side milling cutter except that the teeth are staggered so that every other tooth cuts on a given side of the slot. This allows deep, heavy-duty cuts to be taken (12.4a).
Angle Cutters: On angle cutters, the peripheral cutting edges lie on a cone rather than on a cylinder. A single or double angle may be provided (Fig. 12.4d and Fig. 12.4e).
Shell End Mill: The shell end mill has peripheral cutting edges plus face cutting edges on one end. It has a hole through it for a bolt to secure it to the spindle (Fig. 12.3).
Form Mill: A form mill is a peripheral cutter whose edge is shaped to produce a special configuration on the surface. One example of his class of tool is the gear tooth cutter. The exact contour of the cutting edge of a form mill is reproduced on the surface of the workpiece (Fig.12.4f, Fig.12.4g, and Fig.12.4h).
2.2 End Milling Cutters
End mills can be used on vertical and horizontal milling machines for a variety of facing, slotting, and profiling operations. Solid end mills are made from high speed steel or sintered carbide. Other types, such as shell end mills and fly cutters, consist of cutting tools that are bolted or otherwise fastened to adapters.
Solid End Mills: Solid end mills have two, three, four, or more flutes and cutting edges on the end and the periphery. Two flute end mills can be fed directly along their longitudinal axis into solid material because the cutting faces on the end meet. Threeend cutting edge that extends past the center of the cutter can also be fed directly into solid material.
Solid end mills are double or single ended, with straight or tapered shanks. The end mill can be of the stub type, with short cutting flutes, or of the extra long type for reaching into deep cavities. On end mills designed for effective cutting of aluminum, the helix angle is increased for improved shearing action and chip removal, and the flutes may be polished. Various single and double-ended end mills are shown in Figure 12.5a. Various tapered end mills are shown in Figure 12.5b.
Special End Mills: Ball end mills (Fig. 12.6a) are available in diameters ranging from 1/32 to 2 1/2 inches in single and double ended types. Single purpose end mills such as Woodruff key-seat cutters, corner rounding cutters, and dovetail cutters (Fig.12.6b) are used on both vertical and horizontal milling machines. They are usually made of high speed steel and may have straight or tapered shanks.
3. Milling Cutter Nomenclature
As far as metal cutting action is concerned, the pertinent angles on the tooth are those that define the configuration of the cutting edge, the orientation of the tooth face, and the relief to prevent rubbing on the land. The terms defined below and illustrated in Figures 12.7a and 12.7b are important and fundamental to milling cutter configuration.
Outside Diameter: The outside diameter of a milling cutter is the diameter of a circle passing through the peripheral cutting edges. It is the dimension used in conjunction with the spindle speed to find the cutting speed
(SFPM).
Root Diameter: This diameter is measured on a circle passing through the bottom of the fillets of the teeth.
Tooth: The tooth is the part of the cutter starting at the body and ending with the peripheral cutting edge. Replaceable teeth are also called inserts.
Tooth Face: The tooth face is the surface of the tooth between the fillet and the cutting edge, where the chip slides during its formation.
Land: The area behind the cutting edge on the tooth that is relieved to avoid interference is called the land.
Flute: The flute is the space provided for chip flow between the teeth.
Gash Angle: The gash angle is measured between the tooth face and the back of the tooth immediately ahead.
Fillet: The fillet is the radius at the bottom of the flute, provided to allow chip flow and chip curling. The terms defined above apply primarily to milling cutters, particularly to plain milling cutters. In defining the configuration of the teeth on the cutter, the following terms are important.
Peripheral Cutting Edge: The cutting edge aligned principally in the direction of the cutter axis is called the peripheral cutting edge. In peripheral milling, it is this edge that removes the metal
Face Cutting Edge: The face cutting edge is the metal removing edge aligned primarily in a radial direction. In side milling and face milling, this edge actually forms the new surface, although the peripheral cutting edge may still be removing most of the metal. It corresponds to the end cutting edge on single point tools.
Relief Angle: This angle is measured between the land and a tangent to the cutting edge at the periphery.
Clearance Angle: The clearance angle is provided to make room for chips, thus forming the flute. Normally two clearance angles are provided to maintain the strength of the tooth and still provide sufficient chip space.
Radial Rake Angle: The radial rake angle is the angle between the tooth face and a cutter radius, measured in a plane normal to the cutter axis.
Axial Rake Angle: The axial rake angle is measured between the peripheral cutting edge and the axis of the cutter, when looking radially at the point of intersection.
Blade Setting Angle: When a slot is provided in the cutter body for a blade, the angle between the base of the slot and the cutter axis is called the blade setting angle.
4. Indexable Milling Cutters
The three basic types of milling operations were introduced earlier. Figure 12.8 shows a variety of indexable milling cutters used in all three of the basic types of milling operations (Fig. 12.2).
There are a variety of clamping systems for indexable inserts in milling
cutter bodies. The examples shown cover the most popular methods now in
use:
4.1 Wedge Clamping
Milling inserts have been clamped using wedges for many years in the cutting tool industry. This principle is generally applied in one of the following ways: either the wedge is designed and oriented to support the insert as it is clamped, or the wedge clamps on the cutting face of the insert, forcing the insert against the milling body. When the wedge is used to support the insert, the wedge must absorb all of the force generated during the cut. This is why wedge clamping on the cutting face of the insert is preferred, since this method transfers the loads generated by the cut through the insert and into the cutter body. Both of the wedges clamping methods are shown in Figure 12.9. The wedge clamp system however, has two distinct disadvantages. First, the wedge covers almost half of the insert cutting face, thus obstructing normal chip flow while producing premature cutter body wear, and secondly, high clamping forces causing clamping element and cutter body deformation can and often will result. The excessive clamping forces can cause enough cutter body distortion that in some cases when loading inserts into a milling body, the last insert slot will have narrowed to a point where the last insert will not fit into the body. When this occurs, several of the other inserts already loaded in the milling cutter are removed an reset. Wedge clamping can be used to clamp individual inserts (Fig. 12.10a) or indexable and replaceable milling cutter cartridges as shown in Figure 25.10b.
4.2 Screw Clamping
This method of clamping is used in conjunction with an insert that has a pressed countersink or counterbore. A torque screw is often used to eccentrically mount and force the insert against the insert pocket walls. This clamping action is a result of either offsetting the centerline of the screw toward the back walls of the insert pocket, or by drilling and tapping the mounting hole at a slight angle, thereby bending the screw to attain the same type of clamping action. The Screw clamping method for indexable inserts is shown in Figure 12.11.
Screw clamping is excellent for small diameter end mills where space is at a premium. It also provides an open unhampered path for chips to flow free of wedges or any other obstructive hardware. Screw clamping produces lower clamping forces than those attained with the wedge clamping system. However, when the cutting edge temperature rises significantly, the insert frequently expands and causes an undes irable retight - ening effect, increasing the torque required to unlock the insert screw. The screw clamping method can be used on indexable ball milling cutters (Fig. 12.12a) or on indexable insert slotting and face milling cutters as shown in Figure 12.12b.
5. Milling Cutter Geometry
There are three industry standard milling cutter geometries: double negative, double positive, and positive/negative. Each cutter geometry type has certain advantages and disadvantages that must be considered when selecting the right milling cutter for the job. Positive rake and negative rake milling cutter geometries are shown in Figure 12.13.
Double Negative Geometry: A double negative milling cutter uses only negative inserts held in a negative pocket. This provides cutting edge strength for roughing and severe interrupted cuts. When choosing a cutter geometry it is important to remember
that a negative insert tends to push the cutter away, exerting considerable force against the workpiece. This could be a problem when machining flimsy or lightly held workpieces, or when using light machines. However, this tendency to push the work down, or push the cutter away from the workpiece may be beneficial in some cases because the force tends to ‘load’ the system, which often reduces chatter.
Double Positive Geometry: Double positive cutters use positive inserts held in positive pockets. This is to provide the proper clearance for cutting. Double positive cutter geometry provides for low force cutting, but the inserts contact the workpiece at their weakest point, the cutting edge. In positive rake milling, the cutting forces tend to lift the workpiece or pull the cutter into the work. The greatest advantage of double posi-tive milling is free cutting. Less force is exerted against the workpiece, so less power is required. This can be especially helpful with machining materials that tend to work harden.
Positive / Negative Geometry: Positive/negative cutter geometry combines positive inserts held in negative pockets. This provides a positive axial rake and a negative radial rake and as with double positive inserts, this provides the proper clearance for cutting. In the case of positive/negative cutters, the workpiece is contacted away from the cutting edge in the radial direction and on the cutting edge in the axial direction. The positive / negative cutter can be considered a low force cutter because it uses a free cutting positive
insert. On the other hand, the positive/ negative cutter provides contact away from the cutting edge in the radial direction, the feed direction of a face mill.
In positive/negative milling, some of the advantages of both positive and negative milling are available. Positive/negative milling combines the free cutting or shearing away of the chip of a positive cutter with some of the edge strength of a negative cutter.
Lead Angle: The lead angle (Fig. 12.14) is the angle between the insert and the axis of the cutter. Several factors must be considered to determine which lead angle is best for a specific operation. First, the lead angle must be small enough to cover the depth of cut. The greater the lead angle, the less the depth of cut that can be taken for a given size insert. In addition, the part being machined may require a small lead angle in order to clear a portion or form a certain shape on the part. As the lead angle increases, the forces change toward the direction of the workpiece. This could cause deflections when machining thin sections of the part.
The lead angle also determines the thickness of the chip. The greater the lead angle for the same feed rate or chip load per tooth, the thinner the chip becomes. As in single point tooling, the depth of cut is distributed over a longer surface of contact. Therefore,
lead angle cutters are recommended when maximum material removal is the objective. Thinning the chip allows the feed rate to be increased or maximized.
Lead angles can range from zero to 85 degrees. The most common lead angles available on standard cutters are 0, 15, 30 and 45 degrees. Lead angles larger than 45 degrees are usually considered special, and are used for very shallow cuts for fine finishing, or for cutting very hard work materials.
Milling cutters with large lead angles also have greater heat dissipating capacity. Extremely high temperatures are generated at the insert cutting edge while the insert is in the cut. Carbide, as well as other tool materials, often softens when heated, and when a cutting edge is softened it will wear away more easily. However, if more of the tool can be employed in the cut, as in the case of larger lead angles, the tool’s heat dissipating capacity will be improved which, in turn, improves tool life. In addition, as lead angle is increased, axial force is increased and radial force is reduced, an important factor in controlling chatter.
The use of large lead angle cutters is especially beneficial when machining materials with scaly or work hardened surfaces. With a large lead angle, the surface is spread over a larger area of the cutting edge. This reduces the detrimental effect on the inserts, extending tool life. Large lead angles will also reduce burring and breakout at the work- piece edge. The most obvious limitation on lead angle cutters is part configuration. If a square shoulder must be machined on a part, a zero degree lead angle is required. It is impossible to produce a zero degree lead angle milling cutter with square inserts because of the need to provide face clearance. Often a near square shoulder is permissible. In this
case a three degree lead angle cutter may be used.
銑刀和行動
1 。導(dǎo)言
兩個基本類型的刀具所用的金屬業(yè)的工作是單點(diǎn)和多點(diǎn)的設(shè)計,雖然他們可能會有不同的外觀,并在其方法的應(yīng)用。從根本上說,他們是在這類似的行動,金屬切削是一樣的,不論類型的運(yùn)作。分組多項單點(diǎn)工具,在一個通告,持有人,熟悉的銑刀是創(chuàng)建。
銑削的過程,就是一個生成加工表面的逐步取消預(yù)定金額的材料或股票從工件巫婆是先進(jìn)的處于相對的速度緩慢運(yùn)動或飼料,以一銑刀旋轉(zhuǎn)在一個比較高的速度。該特征銑削過程,是每個銑刀的齒刪除其份額的股票,在形式的小型獨(dú)立的芯片。一個典型的面對銑削的運(yùn)作結(jié)果表明,在數(shù)字12.1 。
2 。各類銑刀
各種銑刀適用于所有類型的銑床有助于使銑削一個非常靈活的加工過程。刀是在一個大范圍的大小和幾種不同的刀具材料。銑刀是由高速鋼(高速鋼) ,其他是硬質(zhì)合金打破許多人或更換刀片。這三個基本銑削行動顯示在圖12.2 。周邊和頭銑刀,將在下文討論。
1高速鋼(高速鋼)殼端銑刀是在數(shù)字顯示, 3月12日和其他共同高速鋼刀具的顯示在圖12.4和簡要說明如下:
2.1周邊銑刀
周邊銑刀通常喬木展開,以執(zhí)行各種業(yè)務(wù)。
輕型平原軋機(jī):這刀是一個普遍的目的,刀周邊銑削行動。狹隘的刀具有直齒,而廣泛的有螺旋牙齒。
重型平原軋機(jī):重型平原軋機(jī)是類似的向輕型磨除,這是用于較高的金屬去除。以援助,它在這方面的功能,牙齒更廣泛地間距和螺旋角增加至約45度。
方銑刀:側(cè)銑刀有一個尖端對雙方以及對周邊地區(qū)。這使得刀磨插槽( fig.12.4b ) 。
半方銑刀:這個工具是一樣的一個先前所描述的除外前沿提供一個單一的一面。這是用于銑削的肩膀上。 2刀具的這種類型的往往是裝在一個單一的喬木,為跨越銑削。
錯開齒側(cè)磨:這刀是一樣的一側(cè)銑刀,除了牙齒交錯,使每其他牙齒削減對某一方面的插槽。這使得深,重型削減將要采取的( 12.4a ) 。
刀具的角度:對角切割器,周邊前沿躺在一張錐,而不是一缸。一單人或雙人的角度也可提供(圖12.4d和圖。 12.4e ) 。
蜆殼立銑刀:蜆殼立銑刀已周邊前沿再加上面對的前沿上一年底。它有一個洞,通過它一個螺栓,以確保它主軸(圖12.3 ) 。
軋機(jī)形式:一種形式軋機(jī)是一個周邊刀具,其優(yōu)勢是各種形狀,以產(chǎn)生一個特殊的配置,在表面上。其中一個例子,他類的工具,是齒刀。確切的輪廓前沿的一種形式軋機(jī)轉(zhuǎn)載表面上的工件( fig.12.4f , fig.12.4g , fig.12.4h ) 。
2.2頭銑刀
銑刀,可用于對縱向和橫向銑床為各種所面臨的,開槽,剖面和行動。固體銑刀是由高速鋼或燒結(jié)碳化物。其他類型,如殼銑刀及蒼蠅刀具,構(gòu)成刀具是螺栓或以其他方式固定,以適配器。
固體銑刀:固體銑刀有兩個,三個,四個,或者更多的長笛和前沿對年底及周邊。二長笛銑刀可以美聯(lián)儲直接沿其長軸成堅實的物質(zhì),因為切割面臨的年底滿足。 threeend尖端延伸過去的中心,刀具也可以直接進(jìn)入美聯(lián)儲堅實的物質(zhì)。
固體銑刀是雙重或單一的結(jié)束,直或圓錐??怂?。年底軋機(jī)可以的存根型,短切長笛,或該超長型為達(dá)到進(jìn)入深腔。對銑刀的設(shè)計有效的切割鋁,螺旋角是上升,升幅為改善剪切行動和芯片搬遷,和長笛,可拋光。各種單和雙結(jié)束銑刀顯示在數(shù)字12.5a 。各種錐形銑刀顯示在圖12.5b 。
特別銑刀:球銑刀(圖12.6a ) ,現(xiàn)已在直徑介乎1 / 32至2 1 / 2英寸,在單,雙結(jié)束類型。單一的目的,銑刀等伍德拉夫的關(guān)鍵議席刀具,刀具四舍五入角落,并配合刀具( fig.12.6b )是用在縱向和橫向銑床。它們通常高速鋼,并可能直接或圓錐??怂?。
3 。銑刀名稱
據(jù)金屬切削行動而言,相關(guān)的角度,對牙齒的,是那些界定的配置前沿,方向的齒面,及救濟(jì),以防止擦在那片土地上。條款以下定義和說明,在數(shù)字12.7a和12.7b是重要的和根本的銑刀配置。
外徑:外徑一個銑刀是直徑為一循環(huán),通過周邊前沿。這是維一起使用,與主軸轉(zhuǎn)速找到切削速度
( sfpm ) 。
根直徑:直徑,這是衡量一個圓圈,通過底部的魚片的牙齒。
牙齒:齒是部分的刀具開始在身體和結(jié)束與周邊前沿。更換牙齒也稱為插入。
齒面:齒面是表面的牙之間的圓角和前沿,那里的芯片幻燈片,在其形成的。
土地:面積背后的尖端對牙齒是紓緩,以避免干擾,是所謂的土地。
長笛:長笛是所提供的空間內(nèi)為芯片流之間的牙齒。
伽什角度:加什的角度來衡量之間的齒面和背面的牙齒,立即提前。
圓角:圓角半徑是在底部的長笛,提供了讓芯片流和芯片冰壺。該條款所界定的上述主要適用于銑刀,尤其是平原銑刀。在界定的配置,牙齒就刀具,下列條款是很重要的。
周邊前沿:前沿不結(jié)盟主要是在方向刀具軸是所謂的周邊前沿。在周邊銑削,正是這個優(yōu)勢,消除金屬
面對前沿:面對前沿,是金屬去除邊緣不結(jié)盟主要是在徑向方向。在側(cè)銑和面對銑削,這優(yōu)勢,其實形式新,表面上雖然周邊尖端仍可能消除大部分的金屬。它對應(yīng)到年底,尖端單點(diǎn)工具。
救濟(jì)角度:這個角度來衡量之間的土地和相切的前沿,在周邊。
關(guān)角:清拆的角度提供,以騰出空間給芯片,從而形成長笛。通常兩關(guān)的角度,提供以保持實力,牙齒和仍然提供足夠的芯片空間。
徑向前角:徑向前角是角之間的齒面和刀具半徑,測量在飛機(jī)正常的刀具軸。
軸向前角:軸向前角是衡量之間的周邊前沿和主軸的刀具看時,徑向在點(diǎn)相交。
葉片設(shè)置的角度:當(dāng)一個插槽是所提供的刀具機(jī)構(gòu)的刀片,之間的夾角基地插槽和刀軸是所謂的刀片設(shè)置的角度。
4 。索引銑刀
該三種基本類型的銑削行動年初推出。 8月12日的數(shù)字顯示,各種索引銑刀的使用在所有這三個基本類型的銑削行動(圖12.2 ) 。
有各種各樣的夾緊系統(tǒng)的刀片在銑削
刀機(jī)構(gòu)。的例子顯示,包括最流行的方法,現(xiàn)在在
使用說明:
4.1楔夾緊
銑削插入已鉗位用挖起桿多年來在刀具業(yè)。這個原則是普遍適用于下列方式之一:要么楔形的設(shè)計和面向支持插入,因為這是鉗制,或楔形夾具對切削面對插入,迫使插入對銑削機(jī)構(gòu)。當(dāng)楔是用來支持插入,楔,必須吸收所有的力量中產(chǎn)生的削減。這就是為什么楔夾緊對切削面插入是首選,因為這種方法轉(zhuǎn)移負(fù)荷所產(chǎn)生的削減,通過插入到刀體。雙方的挖起桿夾緊方法顯示在圖12.9 。楔形夾具系統(tǒng),但有兩個明顯的缺點(diǎn)。首先,楔涵蓋幾乎一半的插入切割面,從而阻礙了正常的芯片流的同時,生產(chǎn)刀具的身體過早磨損,其次是高鎖模力造成夾緊元件和刀體變形可以,而且往往會導(dǎo)致。過度鎖模力可造成足夠的刀體失真,在某些情況下,當(dāng)加載插入到銑削機(jī)構(gòu),最后插入插槽將有收窄至1點(diǎn),最后插入不適合進(jìn)入人體。發(fā)生這種情況時,幾個其他插入已經(jīng)加載,在銑刀被刪除一重置。楔夾緊,可以用來打擊個別插入(圖12.10a )或索引和更換銑刀墨盒顯示,在數(shù)字25.10b 。
4.2螺桿夾緊
這種方法的夾緊是用在與一插入了一個壓countersink或counterbore 。扭矩螺桿通常被用來偏心山,并迫使插入對插入口袋的墻壁。這夾緊行動是一種結(jié)果,要么抵銷了中線的螺桿對回堵墻插入口袋,或由鉆井和挖掘安裝孔在一個輕微的角度,從而彎曲的螺絲,以達(dá)到同一類型的夾緊行動。螺絲夾緊方法,刀片是在數(shù)字顯示, 11月12日。
螺桿夾緊,是優(yōu)良的為小直徑銑刀的空間,是一個溢價。它還提供了一個開放的不受阻礙的路徑芯片流免費(fèi)的挖起桿或其他任何阻塞的硬件。螺桿夾緊產(chǎn)生較低的鎖模力比達(dá)到與楔夾緊系統(tǒng)。然而,當(dāng)尖端溫度的升高而顯著,插入經(jīng)常擴(kuò)大和原因一undes irable retight -e ning的效果,增加扭矩要求解鎖插入螺絲釘。螺絲夾緊方法可用于對索引的球銑刀(圖12.12a )或?qū)λ饕牟迦氩迕鎸︺姷讹@示,在數(shù)字12.12b 。
5 。銑刀幾何
有三個行業(yè)標(biāo)準(zhǔn)銑刀的幾何構(gòu)型:雙重否定的,雙陽性,正/負(fù)。每個刀具幾何類型,具有一定的優(yōu)勢和劣勢時,必須考慮選擇正確的銑刀的工作。正面和負(fù)面的耙耙銑刀幾何形狀的顯示在數(shù)字12.13 。
雙重否定幾何:一個雙重否定銑刀只使用負(fù)面插入關(guān)押在一個負(fù)面的口袋中。這提供了尖端的實力和粗嚴(yán)重中斷的削減。當(dāng)選擇刀具的幾何形狀,這是重要的是要記