GY01-154@机床夹具柔性化技术研究及设计
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GY01-154@机床夹具柔性化技术研究及设计,机械毕业设计全套
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第 2章 夹具的类型与功能 学习目标 学习完该章后，学生应具备下述能力： 分清夹具的种类 分清夹具的类型 根据典型零件的 特定工序，选择夹具的种类和类型 JIGS 与 FIXTURES 夹具是批量生产零件时使用的工件夹持装置。通过夹具，刀具或其它工具与工件的正确相对位置得以确定。要做到这一点，夹具需要对每一个被加工工件进行夹持、支承及定位，以使其被加工后都能达到规定的精度。 Jigs 与 fixtures 的关系是如此密切，以至于从术语上经常造成混淆及交替使用。这二者之间的区别，在于刀具导向的方式。 Jig 是夹持、支承或固定于被加工工件上的专用装置。它是一种生产工艺装备。它不仅对工件进行定位和夹紧，而且在加工过程中对刀具进行导向。 Jig 一般都配有淬硬钢制作的导向套，来对钻头或其它刀具进行导向。见图 2-1A。 一般说来，小的钻模不固定在钻床的工作台上。然而， 当被加工孔的尺寸大于 .25英寸时，则必须将其可靠地固定在机床工作台上。 Fixture 是一种对被加工工件进行可靠的定位、夹持和支承的生产工艺装备，其作用是使所需加工工序得以正常进行。对刀块、塞尺、厚薄规在该类夹具上被用来确定刀具与工件的正确相对位置。见图 2-1B。 Fixture必须很牢靠地固定于机床工作台上。 Fixture主要应用于铣床。为了完成各种不同的工序加工，其它大多数通用机 床上也使用Fixture。 Fixture 可以是一个极为简单的工具，也可能是一种非常昂贵、复杂的装置。在专用机床上，也利用 Fixture来简化金属加工工序。 JIGS的类型 Jigs可大体上分为二大类：镗模和钻模。当孔的直径太大不能钻削，或加工不能用标准钻头加工的特殊尺寸孔时，需要采用镗模。见图 2-2。钻模用来钻孔、铰孔、功丝、锪倒角、锪沉孔、锪锥孔、反向锪锥孔及反向锪台阶孔。见图 2-3。镗模和钻模的基本形式几乎是相同的，其区别仅在于所采用的导向套尺寸有所不同而已。 钻模可分为两种类型：开式与闭式。开式钻模用于仅从工件的一个方向进行加工的简 UNIT 2 Types and Functions of Jigs and Fixtures OBJECTIVES After completing this unit, the student should be able to: Identify the classes of jigs and fixtures. Identify the types of s jigs and fixtures. Choose a class and type of jigs and fixture for selected operations on sample parts. JIGS AND FIXTURES Jigs and fixtures are production-workholding devices used to manufacture duplicate parts accurately. The correct relationship and alignment between the cutter, or other tool, and the workpiece must be maintained. To do this, a jig or fixture is designed and built to hold, support, and locate every part to insure that each is drilled or machined within the specified limits. Jigs and fixtures are so closely related that the terms are sometimes confused or used interchangeably. The difference is in the way the tool is guided to the workpiece. A jig is a special device that holds, supports, or is placed on a part to be machined. It is a production tool made so that it not only locates and holds the workpiece but also guides the cutting tool as the operation is performed. Jigs are usually fitted with hardened steel bushings for guiding drills or other cutting tools, Figure 2-1A. As a rule, small jigs are not fastened to the drill press table. If, however, holes above .25 inch in diameter are to be drilled, it is usually necessary to fasten the jig to the table securely. A fixture is a production tool that locates, holds, and supports the work securely so the required machining operations can be performed. Set blocks and feeler or thickness gauges are used with fixture to reference the cutter to the workpiece, Figure 2-1B. A fixture should be securely fastened to the table of the machine upon which the work is done. Though largely used on milling machines, fixture are also designed to hold work for various operations on most of the standard machine tools. Fixtures vary in design from relatively simple tools to expensive, complicated devices. Fixtures also help to simplify metalworking operations performed on special equipment. TYPES OF JIGS Jigs may be divided into two general classes: boring and drill jigs. Boring jigs are used to bore holes that either are too large to drill or must be made an odd size, Figure 2-2. Drill jigs are used to drill, ream, tap, chamfer, counterbore, countersink, reverse spotface, or reverse countersink, Figure 2-3. The basic jig is almost the same for either machining operation. The only difference is in the size of the bushing used. Drill jigs may be divided into two general types., open and closed. Open jigs are for simple operations where work is done on only one side of the part. Closed, or box, jigs are 2-1 ntsFigure 2-1 Referencing the tool to the work 图 2-1 夹具、刀具与工件相对位置的确定 REFERENCE EDGES FOR FEELER GAUGE 安放塞尺的基准面 SET BLOCK 对刀块 DRILL BUSHING 钻套 单工序。闭式钻模，或称箱式钻模，则用于至少要从多于一个方向进行加工的工件。人们经常可以通过钻模的名称，来判断其制造方式。 盖板式钻模 通常用来保证工件的精度，而不是提高其加工效率。这种钻模安装在工件上，一般也不进行夹紧。见图 2-4。盖板式钻模是目前使用的最为经济和简单的钻模。它们可能带有钻套，也可能没有钻套。不用钻套时，钻模板一般要整体淬硬。 板式钻模 与盖板式钻模类似，见图 2-5。其区别在于板式钻模具有工件夹紧装置。板式钻模也可带或不带钻套，这取决于所加工零件的数量。为了加工大的工件，有时会给板式钻模安上支承柱，以使钻模板离开钻床工作台一定高度。这种类型的钻模被称为桌式钻模。 used for part that must be machined on more than one side. The name used to identify these jigs refer to the way the tool is built. Template jigs are normally used for accuracy rather than speed. This type of jig fits over, on， or into the work and is not usually clamped, Figure 2-4. Templates are the least expensive and simplest type of jig to use. They may or may not have bushings. When bushings are not used, the whole jig plate is normally hardened. Plate jigs are similar to the templates, Figure 2-5. The only difference is that plate jigs have built-in clamps to hold the work. These jigs can also be made with or without bushings, depending on the number of parts to be made. Plate jigs are sometimes made with legs to raise the jig off the table for large work. This style is called a table jig, Figure 2-6. BUSHINGS 镗套 BORING BAR 镗杆 TOOL BODY 夹具体 MACHINE SPINDLE 机床主轴 WORKPIECE 工件 Figure 2-2 Boring jig 图 2-2 镗模 2-2 nts DRILL REAM TAP CHAMFER COUNTERBORE COUNTERSINK 钻孔 铰孔 攻丝 锪倒角 锪台阶 孔 锪锥孔 REVERSE REVERSE COUNTERSINK COUNTERBORE 反锪锥孔 反锪台阶孔 Figure 2-3 Operations common to a drill jig (在钻模上进行的一般加工工序 ) Figure 2-4 Template jigs(盖板式钻模 ) 夹层式钻模 是板式钻模的一种，其特点是在工件被加工面的背面另有一块支承板。见图 2-7。这种钻模对装夹软材质或容易变形翘曲的工件，较其它类型的钻模要理想的多 。需要再次提及的是，是否采用钻套仍决定于工件的数量。 角铁式钻模 用来装夹被加工孔的轴线与 Sandwich jigs are a form of plate jig with a back plate, Figure 2-7. This type of jig is ideal for thin or soft parts that could bend or warp in another style of jig. Here again, the use of bushing is determined by the number of parts to be made. Angle-plate jigs are used to hold parts that are machined at right angles to their mounting locators, Figure 2-8. Pulleys, collars, and gears are some of the parts that use this type of 2-3 ntsFigure 2-10 Box or tumble jig（箱式或翻转式钻模） Figure 2-8 Angle-plate jig(角铁式钻模 ) 图 2-9 Modified angle-plate jig(变形角铁式钻模 ) Figure 2-7 Angle-plate jig(夹层板式钻模 ) BACK PLATE 背面板 LOCATING PINS 定位销 Figure 2-6 Table jig(桌式钻模 ) Figure 2-5 Plate jig(板式钻模 ) QUICK-ACTING KNOB 快速旋钮 REMOVABLE BUSHING 活动钻套 2-4 QUARTER-TURN SCREW 1/4 转螺钉 SOLID LOCATOR LEAF 固定支承 铰链钻模板 THUMB SCREW 蝶式螺母 DRILL BUSHING 钻套 THUMB SCREW 蝶式螺母 BOX JIG （ TOP REMOVED） 箱式钻模（去掉顶部） JIG TEET 钻模支脚 BOX JIG （ TOP REMOVED） 箱式钻模（去掉侧面） DRILL BUSHING 钻套 THUMB SCREW 蝶式螺母 nts jig. A variation is the modified angle-plate jig, which is used for machining angles other than 90 degrees, Figure 2-9. Box jigs, or tumble jigs, usually totally surround the part, Figure 2-10. This style of jig allows the part to be completely machined on every surface without the need to reposition the work in the jig. Channel jigs are the simplest form of box jig, Figure 2-11. The work is held between two side and machined from the third. In some cases, where jig feet are used, the work can be machined on three sides. Leaf jigs are small box jigs with a hinged leaf to allow for easier loading and unloading, Figure 2-12. The main differences between leaf and box jigs are size and part location. Leaf jigs are normally smaller than box jigs and are sometimes made so that they do not completely surround the part. They are usually equipped with a handle for easier movement. Indexing jigs are used to accurately space holes or other machined areas around a part. To do this, the jig uses either the part itself or a reference plate and a plunger, Figure 2-13. Larger indexing jigs are called rotary jigs. Trunnion jigs are a form of rotary jig for very large or odd-shaped parts, Figure 2-14. The part is first put into a box-type carrier and then loaded on the trunnion. This jig is well suited for large, heavy parts that must be machined with several separate plate-type jigs. Pump jigs are commercially made jigs that must be adapted by the user., Figure 2-15. The lever-activated plate makes this tool very fast to load and unload. Since the tool is already made and only needs to be modified, a great deal of time is saved by using this jig. Multistation jigs are made in any of the forms already discussed, Figure 2-16. The main feature of this jig is the way it locates the work. While one part is drilled, another can be reamed and a third counterbored. The final station is used for unloding the finished parts and loading fresh parts. This jig is commonly used on multiple-spindle machines. It could also work on single spindle models. There are several other jigs that are combinations of the types described. These complex jigs are often so specialized that they cannot be classified. Regardless of the jig selected, it must suit the part, perform the operation accurately, and be simple and safe to operate. 定位元件轴线成正交的工件，见图 2-8。使用该类钻模时，要用到滑轮 、 collars与 gears。这种钻模的变形钻模可用来加工非正交孔，如图 2-9。 箱式钻模 ，亦称 翻转钻模 ，通常是在哥哥方向上将工件包围起来，如图 2-10。适用这种钻模，可在一次定位夹紧的条件下，完成对工件所有表面的加工。 槽式钻模 是最简单的箱式钻模，如图 2-11。工件被夹紧在槽的二侧面之间，从另外一个方向对工件进行加工。在某些情况下，可以给槽式钻模安装支脚，以便能从三个方向对工件进行加工。 铰链式钻模 是一种较小的箱式钻模。它有一个铰接式的钻模板，以便于工件的装卸，如图 2-12。铰链式钻模与箱式钻模的主要区别在于尺寸及工件的定位方式。铰链式钻模一般小于箱式钻模，而且大都不将工件全方位包围起来。为便于搬运，铰链式钻模通常具有一个手柄。 分度钻模 用来加工零件圆周上的精密分度孔或其它表面。为了做到这一点，需要利用零件本身的基准面，或另外的基准板，以及一个定位栓，见图 2-13。大型的分度钻模被称为回转钻模。 轴耳式钻模 是一种用于装夹特大型工件或特殊形状工件的回转钻模，见图 2-14。工件首先在一个箱式器具中被定位夹紧，然后以其装到耳轴上。对于大型及重型工件，这一套钻模的功能相当于好几套分离式的钻模。 滑柱式钻模是一种商品 化的钻模，如图 2-15。杠杆驱动的钻模板使得工件的装卸极为快捷。由于这种钻模是预制好的，仅需要进行改装，所以能节省大量时间。 多工位钻模 可以制成上述任一钻模型式，如图 2-16。这种钻模的特点在于其对工件进行定位的方式。当一个工件在进行钻孔时，另一个可进行铰孔，第三个则可进行扩孔。最后一个工位则用于装卸工件。这种钻模既可用于多轴钻床，也可用于单轴钻床。 还有几种钻模，它们在结构上是上述某几种钻模的复合。这些复合钻模是极专门化的，以至于难以分类。无论选择何种类型的钻模，它必须适应工件特点，保证工序精度，且操作简 单，安全可靠。 2-5 Figure 2-11 Channel jig(槽式钻模 ) Figure 2-11 Leaf jig(铰链式钻模 ) DRILL BUSHING 钻套 LOCATORS 定位元件 CAM LO CK 自锁凸轮 ntsFigure 2-13 Indexing jig(分度式钻模 ) DIRECTION OF ROTARY 旋转方向 SPRING PLUNGER 弹簧式定位器 KNURLED KNOB 滚花螺母 Figure 2-14 Trunnion jig(轴耳式钻模 ) TRUNNION 轴耳 INDEXING LOCK PIN 分度锁紧销 TRUNNION 轴耳 Figure 2-15 Pump jig(滑柱式钻模 ) INDEXING LOCK PIN 分度锁紧销 INDEXING HOLES 分度孔 REAM 铰孔 DRILL 钻孔 CBORE 扩孔 LOAD-UNLOAD 工件装卸 Figure 2-16 Multistation jig(多工位钻模 ) HAND KNOB 手动旋钮 2-6 nts FIXTURES的类型 各种不同类型的 fixtures的名称，主要取决于它是如何制造的。仅就定位元件与装置来说，Jigs 与 fixtures 的区别很小。主要区别在于他们的结构重量。用于同一个工件的 fixtures所需要的夹紧力，一般要比 jigs 为大，所以fixtures 的结构强度和重量要大于相应的jigs。 基础板式夹具 是最为简单的夹具，如图 2-17。这种基本夹具有一块基础平板，上面配置有各种定位及夹紧元件，以完成对工件进行定位及夹紧。简约而且适应性强，使得这种夹具在绝大多数机械加工工序得到了广泛 应用。 角板式夹具 是基础板式夹具的一个变种，如图 2-18。在这种夹具上，通常是从工件的支承定位元件的正交方向来对工件进行加工。由于大多数角板式夹具是制造成 90的，所以在某些需要非 90夹具的场合，就需要采用如图 2-19所示的改良型角板式夹具。 虎钳爪改装夹具 用于加工小型零件，如图2-20。在这种夹具上，标准的虎钳爪被适应工件形状的专用虎钳爪所代替。虎钳爪改装夹具是制造成本最低的夹具，其应用范围仅受标准虎钳尺寸规格的限制。 分度夹具 与分度钻模极为相似，如图 2-21。使用这种夹具所加工的工件，一定具有需要加工 的间隔角度一定的等分表面。图 2-22所示的零件是一些用分度夹具加工的典型例子。 多工位夹具 主要用于加工循环需要连续进行的高效率、大批量生产工艺中。只有两个工位的双工位夹具是最为简单的多工位夹具，如图 2-23。这种夹具允许装卸工件与加工过程同时进行。例如，一旦加工工序在工位 1完成以后，转动夹具 使工位 2处于加工位置并进行加工，与此同时，在工位 1 上可卸下加工完毕的工件，并装上新的工件。 靠模夹具 用来引导刀具对一般机床运动无能为力的内部或外部成形轮廓进行加工。遇有刀具与夹具靠模始终接触，所加工工件的轮廓几乎不可能 出差错。图 2-24表示的是一个凸轮轮廓被精确加工的情形。由图中可见，套于刀具上的轴承始终与夹具靠模相接触。在这里轴承是一个必须要有的重要元件。 FIXTURES的分类 夹具一般依照其所依附的机床种类而进行分类。同时也可根据工序类型再进行细分。例如，一个设计用在铣床的夹具称为铣床夹具；但若该夹具是用于跨铣加工，则它又被称为跨铣夹具。利用同一原理对车床夹具分类， TYPES OF FIXTURES The name used to describe the various types of fixtures are determined mainly by how the tool is built. jigs and fixtures are made basically the same way as far as locators and positioners are concerned. The main construction difference is mass. Because of the increased tool forces, fixtures are built stronger and heavier than a jig would be for the same part. Plate fixture are the simplest form of fixtures, Figure 2-17. The basic fixture is made from a flat plate that has a variety of clamps and locators to hold and locate the part. The simplicity of this fixture makes it useful for most machining operations. Its adaptability makes it popular. The angle-plate fixture is a variation of the plate fixture, Figure 2-18. With this tool, the part is normally machined at a right angle to its locator. While most angle-plate fixture are made at 90 degrees, there are times when other angles are needed. In these cases, a modified angleplate fixture can be used, Figure 2-19. Vise-jaw fixtures are used for machining small parts., Figure 2-20. With this type of tool, the standard vise jaws are replaced with jaws that are formed to fit the part. Vise-jaw fixture are the least expensive type of fixture to make. Their use is limited only by the size of the vises available. Indexing fixture are very similar to indexing jigs, Figure 2-21. These fixtures are used for machining parts that must have machined details evenly spaced. The parts shown in Figure 2-22, are examples of the uses of an indexing fixture. Multistation fixtures are used primarily for high-speed, high-volume production runs, where the machine cycle must be continuous. Duplex fixtures are the simplest form of multistation fixture, using only two stations, Figure 2-23. This form allows the loading and unloading operations to be performed while the machining operation is in progress. For example, once the machining operation is complete at station1, the tool is revolved and the cycle repeated at station 2. At the same time, the part is unloaded at station 1 and a fresh part loaded. Profiling fixture are used to guide tools for machining contours that the machine cannot normally follow. These contours can be either internal or external. Since the fixture continuously contacts the tool, an incorrectly cut shape is almost impossible. The operation in Figure 2-24 shows how the cam is accurately cut by maintaining contact between the fixture and the bearing on the milling cutter. This bearing is an important part of the tool and must always be used. CLASSFICATION OF FIXTURES Fixture are normally classified by the type of machine on which they are used. Fixtures can also be identified by a subclassification. For example, if a fixture is designed to be used on a milling machine, it is called milling fixture. If the task it is intended to perform is straddle milling, it is called a straddle-milling fixture. 2-7 nts 则设计用于径向车削的夹具称为径向车削车床夹具。 下面是使用夹具的部分生产工艺： 装配 热处理 牛头刨 镗削 珩磨 冲压 拉削 检查 攻螺纹 钻削 研磨 试验 成形加工 铣削 车削 测量 龙门刨 焊接 磨削 锯切 The same principle applies to a lathe fixture that is designed to machine radii. It is called a lathe-radius fixture. The following is a partial list of production operations that use fixtures: Assembling Heat treating Shaping Boring Honing Stamping Broaching Inspecting Tapping Drilling Lapping Testing Forming Milling Turning Gauging Planing Welding Grinding Sawing LOCATOR PINS 定位销 Figure 2-17 Plate fixture(基础板式夹具 ) SET BLOCK 对刀块 SUPPORTS 支承元件 STRAP CLAMPS 压板 Figure 2-18 Angle-plate fixture(角板式夹具 ) STRAP 压板 KNURLED NUT 滚花螺母 SET BLOCK 对刀块 LOCATOR PINS 定位销 SET BLOCK对刀块 C WASHER C形垫圈 HEX NUT 六角螺母 Figure 2-19 Modified angle-plate fixture(改良型角板式夹具 ) 2-8 nts Figure 2-20 Vise-jaw fixture(虎钳爪改装夹具 ) JAWS FORMED TO FIT PART 适应工件形状的钳爪 SET BLOCK对刀块 VISE BODY 虎钳本体 2 CLAMPS 二只压板 INDEXING PLUNGER 分度插销 INDEXING PLUNGER分度插销 LOCK KNOB 锁紧螺母 BINDER KNOB 接合螺钉 PLUNGER分度插销 24 HOLE CIRCLE 24只圆周分布孔 SECTION A-A A- A 剖面 Figure 2-21 Indexing fixture(分度夹具 ) HEXGON SQUARE GEAR SPLINE KEYWAYS Figure 2-22 Parts machined with an indexing fixture(用分度夹具加工的零件 ) 六角形 正方形 齿轮 花键 键槽 Figure 2-23 Duplex fixture (双工位夹具 ) INDEXING PLUNGER 换位插销 ROTATION 旋转 Figure 2-24 Profiling Fixture 分度夹具 BALL BEARING球轴承 END MILL 立铣刀 PROFILING FIXTURE 夹具靠模 2-9 nts 总结 本节介绍了下述重要概念： 夹具是用来对工件进行定位、支承和固定的生产工艺装置。 - A jig利用导向套对刀具进行导向。 - A fixture利用对刀块及塞尺、厚薄规、量具来确 定刀具的相对位置。 Jigs可大致上分为二大类：钻模和镗模。 Jigs的类型由其结构所决定，有开式和闭式两种。 - 盖板式、板式、夹板式、角板式均属于开式 jigs。 - 箱、槽式、铰链式属于闭式 jigs。 - 其它演绎型式的 jigs，如分度、旋转、轴耳、滑柱与多工位式的，即可制造成开式的，也可制造成开式的 jig。 Fixtures 的类型取决于其结构。最常用的类型是基础板式、角板式、虎钳爪改装式、分度式及多工位式。 Fixtures 的分类一般取决于其所依附的机床，有时也根据其所应用的工序分类。一个用于跨铣加工工序的夹具可归类为铣床夹具，也可归类为跨铣夹具。 复习 1. Jig and a fixture的区别何在？ 2. 一般怎样区分 Jig与 Fixture？ 3. 对刀块的用途何在？ 4. 扩孔通常用开式还是闭式钻模？ 5. 组合铣削夹具实际上是哪一大类的夹具？ 6. 分析下列零件图纸及相应待完成工序，并为其选择最好的夹具。 A. 图 2-25，铣 .250 .250 英寸槽。 (1)箱式夹具 (2)双工位夹具 (3) 虎钳爪改装夹具 B: 图 2-26，钻 4-.500英寸直径孔。 (1)板式钻 模 (2)角板式钻模 (3)槽式钻模 SUMMARY The following important concepts were presented in this unit: Jigs and fixtures are production workholding devices designed to hold, support, and locate a workpiece. - A jig guides the cutting tool with a drill bushing. - A fixture references the cutting tool with a set block and feeler, or thickness, gauges. Jigs are divided into two general classes: drill jigs and boring jigs. The type of jig is determined by the way it is built. The two types of jigs are open and closed. - Temp
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