工業(yè)夾緊技術(shù)（中英文）
1 基本原理 / Basic principles
1.1 簡單的液壓夾緊機構(gòu)（圖1）。
A simple hydraulic clamping mechanism (Figure 1).
1.2 術(shù)語和定義 / Terms and definitions
1.2.1 夾緊柱塞 / Clamping Plunger
對工件施加夾緊力的裝置。
A device that applies clamping force to the workpiece.
1.2.2 工件 / Workpiece
需要固定到位的零件或材料。
The part or material that is to be held in place.
1.2.3 壓力活塞 / Pressure Piston
用于向液壓介質(zhì)施加壓力的裝置。
A device used to apply pressure to a hydraulic medium.
1.2.4 液壓介質(zhì) / Hydraulic Medium
用于傳輸通過向壓力活塞施加力而產(chǎn)生的壓力的流體
A fluid used to transmit the pressure created by applying a force to the pressure piston
1.3 液壓夾緊過程 / Hydraulic clamping process
液壓夾緊過程包括正確應(yīng)用液壓夾緊系統(tǒng)產(chǎn)生的力來固定工件。液壓夾緊系統(tǒng)由圖1所示的組件組成，該圖顯示了使用液壓介質(zhì)的基本布置和工作原理。
使用液壓流體用于夾緊目的的任何此類過程可被稱為液壓夾緊系統(tǒng)。夾緊系統(tǒng)中液壓油提供的工作壓力最大可達(dá) 5000 psi (350 bar)，即使在使用緊湊型夾緊缸時也能施加相當(dāng)大的夾緊力。
如果設(shè)計和控制得當(dāng)，液壓夾緊機構(gòu)將防止工件在加工或施加其他力時移動（滑動、扭曲等），但不會導(dǎo)致工件發(fā)生意外的永久變形。
The hydraulic clamping process consists of properly applying the forces created by a hydraulic clamping system to secure a workpiece. A hydraulic clamping system consists of the components illustrated in Figure 1, which shows the basic arrangement and operating principle of the use of hydraulic media.
Any such process using hydraulic fluids for clamping purposes may be referred to as a hydraulic clamping system. The operating pressure provided by hydraulic fluids in clamping systems can reach a maximum of 5000 psi (350 bar), allowing the application of considerable clamping forces even when using compact clamping cylinders.
When properly designed and controlled, the hydraulic clamping mechanism will prevent the workpiece from moving (sliding, twisting, etc.) when machining or other forces are applied, yet will not cause an unexpected permanent distortion to occur in the workpiece.
2 液壓夾緊裝置的裝配 / Assembly of hydraulic clamping devices
2.1 工件的定位、夾緊和支撐 / Locating, clamping, and supporting workpieces
2.1.1 本體的定位 / Locating a Body
術(shù)語“定位”是指將工件定位在夾緊裝置內(nèi)，并將其固定到位以進(jìn)行必要的加工的過程。只有正確固定的工件才能在規(guī)定的公差范圍內(nèi)一致地進(jìn)行加工。
The term “l(fā)ocating” refers to the process of positioning the workpiece inside the clamping device, and holding it in position for the necessary machining. Only workpieces that are correctly held can be consistently machined within specified tolerances.
2.1.2 限制自由度 / Limiting the degrees of freedom
定位和固定工件的過程可以稱為“限制自由度”。工件在任何可能方向上的任何運動都被認(rèn)為代表一個自由度。
因此，三維工件具有六個自由度，如圖 2 所示。這六個自由度由 x、y 和 z 方向上的平移運動“T”以及繞工件轉(zhuǎn)動的旋轉(zhuǎn)運動“R”組成。 x、y 和 z 軸。
可以通過引入穿過任意兩個軸的參考平面來降低給定工件或物體所擁有的自由度。
例如，圖 3a 中的平面限制了沿 x 和 z 方向行進(jìn)的運動以及繞 y 軸的旋轉(zhuǎn)。通過限定該固定平面，工件因此可以被限制或約束到三個自由度。
另外兩個自由度可以通過引入第二參考平面來約束，如圖 3b 所示。該參考平面將運動限制為 x 方向上的平移運動。
約束最后一個自由度可以通過定義第三個參考平面來完成，如圖 3c 所示。
The process of locating and holding a workpiece may be referred to as “l(fā)imiting the degrees of freedom.” Any motion of a workpiece in any possible direction is considered to represent one degree of freedom.
A three-dimensional workpiece therefore possesses six degrees of freedom, as shown in Figure 2. These six degrees of freedom consist of the translational motions “T” in x, y, and z direction, and the rotational motions “R” turning about the x, y, and z axes.
The degrees of freedom that a given workpiece or body possesses may be reduced by introducing reference planes that pass through any two axes.
For example, the plane in Figure 3a limits movement to travel in x and z directions and rotation about the y-axis. By defining this fixed plane, the workpiece can thus be limited or constrained to three degrees of freedom.
Another two degrees of freedom may be constrained by introducing a second reference plane, as shown in Figure 3b. This reference plane limits movement to translational motion in the x direction.
Constraining the last degree of freedom can be accomplished by defi ning a third reference plane as shown in Figure 3c.
2.1.3 確定工作地點 / Locating a workplace
定位和保持的過程必然需要消除所有六個自由度的運動，實際應(yīng)用中采用以下三種定位技術(shù)。
圖 4a：半約束工件。工件僅固定在一個平面上（消除三個自由度）。
圖 4b：受約束的工件。工件由兩個平面固定（消除五個自由度）。
圖 4c：完全約束的工件。工件由三個平面固定（消除六個自由度）。
The process of locating and holding a necessarily require the elimination of movement in all six degrees of freedom, the following three locating techniques are used in actual practice.
Figure 4a: Semi-constrained Workpiece. The workpiece is held in one plane only (elimination of three degrees of freedom).
Figure 4b: Constrained Workpiece. The workpiece is held by two planes (elimination of fi ve degrees of freedom).
Figure 4c: Fully-constrained Workpiece. The workpiece is held by three planes (elimination of six degrees of freedom).
2.1.4 避免過度定位 / Avoiding over-location
A. 帶定位平面的工件
b. 工件定位不正確
C. 正確定位工件
當(dāng)對于任何給定的自由度存在多個定位平面或點時，就會發(fā)生工件的過度定位。
a. Workpiece with locating planes
b. Incorrectly located workpiece
c. Correctly located workpiece
Over-location of the workpiece occurs when there is more than one locating plane or point for any given degree of freedom.
為了防止在加工工件時彎曲 bc 肋，引入了第三參考平面 (3)。將工件 (6) 放置在夾緊裝置 (4) 內(nèi)會導(dǎo)致過度定位。由于在該裝置中定位面(1)和(3)之間的距離是恒定的，因此各個工件之間的尺寸c不同。因此，這種過度定位會引起加工誤差。
To prevent bending the b-c rib while machining the piece, a third reference plane (3) is introduced. Placing a workpiece (6) inside the clamping device (4) causes over-location. Since the distance between the locating planes (1) and (3) is constant in this device, the dimension c differs between individual workpieces. This over-location therefore gives rise to machining error.
圖 5c：顯示如何正確定位工件。為了避免工件傾斜，從工件 (5) 傳遞到待加工主體 (6) 的扭矩“M”必須通過適當(dāng)?shù)姆磁ぞ貋砥胶?。該反扭矩由夾緊力“F”產(chǎn)生。
Figure 5c: Shows how to locate a workpiece correctly. To avoid tilting the workpiece, the torque “M” transferred from the workpiece (5) to the body to be machined (6) must be balanced by an appropriate counter-torque. This counter-torque is created by the clamping force “F.”
如果工件（圖 5）受到太多定位點的限制，也可能會發(fā)生過度定位。沿承載表面引入多于三個定位點、或在引導(dǎo)平面中引入多于兩點、或在支撐平面中引入多于一點可能會導(dǎo)致不期望的工件運動，從而對最終產(chǎn)品的精度產(chǎn)生不利影響。任何額外的支撐點都必須是可調(diào)節(jié)的。
Over-location may also occur if a workpiece (Figure 5) is limited by too many locating points. The introduction of more than three locating points along the bearing surface, or more than two points in the guide plane, or more than one point in the supporting plane may lead to undesirable workpiece motion, and thus adversely affect the precision of the resulting product. Any additional support points must be adjustable.
如果必須支撐待加工的工件以避免偏轉(zhuǎn)，則所有其他支撐點必須定義為變量，并且必須根據(jù)正在加工的工件來確定。
If the workpiece to be machined must be supported to avoid deflection, then all other bearing points must be defined as variables and must be determined in relationship to the workpiece being machined.
選點過程須遵守許多設(shè)計準(zhǔn)則，但也可能有例外。
? 務(wù)必根據(jù)工件的預(yù)加工情況安排定位點。先前加工的點優(yōu)先作為所需的定位點。
? 定位平面上的定位點應(yīng)盡可能遠(yuǎn)離。
? 布置夾緊點，以便在夾緊過程中保留定義的位置。
? 定位點應(yīng)與夾緊點一致，以縮短工件內(nèi)部的力矢量。可以使用三個、兩個甚至一個夾緊來將工件夾緊在定位平面上。
? 精密表面不應(yīng)保持在連續(xù)表面上，這樣可以避免“無限”數(shù)量的接觸點。
The location process is subject to a number of design guidelines, but exceptions are possible.
? Always arrange the location points according to the pre-machined condition of the workpiece. Previously machined points have priority as desirable locating points.
? The locating points on the locating plane should be as far away from each other as possible.
? Arrange the clamping points such that the defined position is retained during clamping.
? The locating points should be in line with the clamping points to shorten the force vectors inside the workpiece. Three, two, or even one clamping point may be used to clamp a workpiece against the locating plane.
? Precision surfaces should not be held on a continuous surface, so that an “infinite” number of contact points can be avoided.
3 夾緊 / Clamping
術(shù)語“夾緊”是指將已定位的工件牢固地緊固在夾緊裝置中以用于加工目的。定位和夾緊可以被視為組合操作。
夾緊總是與通過裝置的力傳遞相關(guān)。力矢量應(yīng)盡可能描述從夾緊力的施加點穿過工件到支承點的直線。
The term “clamping” refers to the secure fastening of an already positioned workpiece in a clamping device for machining purposes. Locating and clamping may be viewed as a combined operation.
Clamping is invariably associated with force transmission through the device. The force vector should, as far as possible, describe a straight line from the application point of the clamping force through the workpiece to the bearing points.
與夾緊一樣，定位也遵循許多設(shè)計準(zhǔn)則，但也可能有例外：
? 保持夾緊力矢量遠(yuǎn)離工件上的關(guān)鍵公差區(qū)域。
? 應(yīng)避免或盡量減少由于夾緊力造成的工件變形和劃痕。
? 應(yīng)選擇工件上的夾緊點，以便無需重新夾緊即可加工工件，或者，如果不可行，則應(yīng)盡量減少重新夾緊。
? 所需的夾緊力應(yīng)通過粗略估計得出。
? 由于加工時產(chǎn)生的熱膨脹和振動，工件的夾緊尺寸可能會發(fā)生變化。
? 僅當(dāng)工件由堅固的支撐點適當(dāng)支撐時，才應(yīng)承受夾緊力，如圖 6 所示。
As with clamping, locating is subject to a number of design guidelines, although exceptions are possible:
? Keep the clamping force vector away from the critical tolerance zones on the workpiece.
? Workpiece deformation and marking due to clamping forces should be avoided or minimized.
? The clamping points on the workpiece should be selected so that the piece can be machined without reclamping or, if this is not feasible, with a minimum of reclamping.
? The required clamping forces should be approximated by rough estimations.
? The clamping dimensions of the workpiece may change due to thermal expansion and vibration resulting from machining.
? The workpiece should only be exposed to a clamping force if it is appropriately supported by a solid bearing point, as illustrated in Figure 6.
由于振動和熱膨脹的影響，夾緊工件的尺寸可能會發(fā)生變化。兩種類型的夾緊可以補償這些變化。
? 機械夾緊
? 液壓夾緊
The dimensions of clamped workpieces may change due to vibrations and the effects of thermal expansion. Two types of clamping may compensate for these changes.
? Mechanical Clamping
? Hydraulic Clamping
圖 7（機械夾緊）中的插圖表明，隨著夾緊區(qū)域中工件尺寸的變化，張力會得到緩解。
在液壓夾緊中，夾緊工件的夾緊元件會根據(jù)變化進(jìn)行調(diào)整，同時保持恒定的夾緊力。如圖 8 所示，其中工件由于加工過程中溫度升高而被拉長。
The illustration in Figure 7 (mechanical clamping) demonstrates that tension is relieved as the dimensions of the workpiece in the clamping area change.
In hydraulic clamping, the clamping elements gripping the workpiece adjust to changes while maintaining a constant clamping force. This is illustrated in Figure 8, where the workpiece is elongated due to temperature increases during machining.
機械夾緊是通過使用以下機械夾緊元件來完成的：
? 夾緊桿
? 夾緊彈簧
? 夾緊螺母
? 夾緊螺栓（圖 7）
Mechanical clamping is accomplished by using the following mechanical clamping elements:
? Clamping Bars
? Clamping Springs
? Clamping Nuts
? Clamping Bolts (Figure 7)
液壓夾緊是通過以下方式實現(xiàn)的：
? 彈性介質(zhì)
? 空氣夾緊（氣動夾緊）
? 液體夾緊（液壓夾緊）
Hydraulic clamping is achieved by:
? Elastometric media
? Clamping with air (pneumatic clamping)
? Clamping with liquids (hydraulic clamping)
機械夾緊元件通常用于簡單的夾緊裝置。然而，通過在夾緊元件和工件之間插入氣缸，可以將機械夾緊元件轉(zhuǎn)換為液壓夾緊元件。此外，機械元件也可以與液壓夾緊元件相結(jié)合。
夾緊可能會出現(xiàn)誤差，導(dǎo)致被夾緊的工件變形。由于此類變形不得影響工件的功能，因此應(yīng)考慮所有可想到的定位和支撐技術(shù)，以及夾緊力通過工件的最佳可能定向傳遞。
建議估算夾緊力，以防止夾緊力過高和工件可能變形。還可以通過為夾緊點和定位點選擇合適的形狀（例如球形）來避免工件的變形。
Mechanical clamping elements are usually used for simple clamping devices. However, mechanical clamping elements may be converted to hydraulic ones by inserting cylinders between the clamping element and the workpiece. In addition, mechanical elements may also be combined with hydraulic clamping elements.
Clamping may be subject to errors that cause deformation of the clamped workpiece. Since such deformations must not affect the function of the workpiece, all conceivable locating and supporting techniques, as well as the best possible directed transmission of the clamping force through the workpiece, should be considered.
It is recommended that clamping forces be estimated to prevent excessively high clamping forces and possible deformation of the workpiece. Deformation of the workpiece may also be avoided by selecting a suitable shape (for example, a sphere) for the clamping points and the locating points.
4 支撐工件 / Supporting the workpiece
4.1 支撐工件 / Supported workpiece
工件需要支撐以確保刀具、工件和夾緊裝置之間的功能性力傳遞，和/或保護(hù)工件免受由于加工力、重力而變形（例如在薄橫截面的點處的偏轉(zhuǎn)）和夾緊力。工件支撐還可以消除由此產(chǎn)生的加工誤差（圖 9）。
此外，通過使用更佳的支撐機構(gòu)，可以提高表面質(zhì)量并延長工具的使用壽命。然而，工件的三維位置不應(yīng)由其支撐來定義。它依次位于定位進(jìn)程之前，并且優(yōu)先級也較低。
The workpiece requires support to ensure functional force transmission between the tool, the workpiece, and the clamping device, and/or to protect the workpiece from deformation (such as deflection at points with a thin cross-section) due to machining forces, gravitational forces, and clamping forces. Workpiece support also acts to eliminate the resulting machining errors (Figure 9).
In addition, surface quality may be improved and the service life of the tool prolonged with the use of an optimum supporting mechanism. The three-dimensional position of a workpiece, however, should not be defined by its support. It is preceded sequentially by the locating process and also has a lower priority.
4.2 彎曲工件的支撐選項 / Supporting options for bent workpieces
a. 未夾緊的工件
b. 夾緊工件
c. 加工工件
a. Unclamped workpiece
b. Clamped workpiece
c. Machined workpiece
即使工件必須由超過理論定位點數(shù)量的頻繁移動和可變元件支撐，工件也被認(rèn)為是受到支撐的。一個例子是容易振動的不穩(wěn)定工件。
當(dāng)變形工件必須在所有三個平面上保持和夾緊而不改變其形狀時，可以使用涉及自調(diào)節(jié)球面的技術(shù)。在這種情況下，軸承表面、緊公差螺栓、限位器以及可垂直調(diào)節(jié)的支撐和夾緊元件必須配備球面。
A workpiece is considered to be supported even if it must be supported by frequently mobile and variable elements surpassing the theoretical maximum number of locating points. An example of this would be an unstable workpiece that easily vibrates.
When a deformed workpiece must be held and clamped in all three planes without altering its shape, it is possible to use a technique involving selfadjusting spherical surfaces. In this case the bearing surfaces, the close-tolerance bolts, the limit stops, and the vertically adjustable supporting and clamping elements must be equipped with spherical surfaces.
圖 10 中的圖示說明了兩種不同的夾緊方法。它顯示了傳統(tǒng)夾緊引起的工件變形（圖 10a）。由于這種變形，工件的表面區(qū)域在松開時表現(xiàn)出更大程度的變形。
The illustrations in Figure 10 illustrate two different clamping methods. It shows deformation of a workpiece caused by conventional clamping (Figure 10a). As a result of this deformation, the surface area of the workpiece exhibits a greater degree of deformation when unclamped.
這種凸形變形可能是由于一旦夾緊壓力釋放，工件就呈現(xiàn)其原始變形形狀（c）。
This deformation, which is convex in shape, may be attributed to the fact that the workpiece assumes its original, deformed shape (c), as soon as the clamping pressure is released.
圖 10b 所示的夾緊點呈球形，因此可以很大程度上適應(yīng)工件曲率 (b)。因此，加工表面是平坦的，工件僅承受可能通過加工釋放的內(nèi)應(yīng)力。
The clamping points illustrated in Figure 10b are spherically shaped, and can therefore largely adapt to the workpiece curvatures (b). The machined surface is therefore fl at, and the workpiece is only exposed to possible internal stresses that may be released by machining.
4.3 鎖模力的確定 / Determination of the clamping force
重要的是要確保夾緊在設(shè)備內(nèi)的工件不會因夾緊力和隨后的切削力作用而從其位置移動。通過向設(shè)備的實心軸承表面施加夾緊力，可以較大限度地減少這種移動風(fēng)險（圖 11）。
It is important to ensure that a workpiece that is clamped inside a device is not moved from its position by the clamping force and the subsequent action of the cutting force. This risk of movement may be minimized by applying the clamping force to the solid bearing surfaces of the device (Figure 11).
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