Principles Of Jig And Fixture Design PdfBy Nholarutus In and pdf 18.05.2021 at 21:33 4 min read
File Name: principles of jig and fixture design .zip
- Workpiece Fixture & Design Principles
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- TEACHING TOPICS: The Teaching of Jig and Tool Design
- Jig and Fixture Design
Workpiece Fixture & Design Principles
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View our Full Privacy Statement. Locating and clamping are the critical functions of any workholder. As such, the fundamental principles of locating and clamping, as well as the numerous standard components available for these operations, must be thoroughly understood.
To perform properly, workholders must accurately and consistently position the workpiece relative to the cutting tool, part after part. To accomplish this, the locators must ensure that the workpiece is properly referenced and the process is repeatable.
Referencing and Repeatability "Referencing" is a dual process of positioning the workpiece relative to the workholder, and the workholder relative to the cutting tool. Referencing the workholder to the cutting tool is performed by the guiding or setting devices. With drill jigs, referencing is accomplished using drill bushings. Referencing the workpiece to the workholder, on the other hand, is done with locators. If a part is incorrectly placed in a workholder, proper location of the workpiece is not achieved and the part will be machined incorrectly.
Likewise, if a cutter is improperly positioned relative to the fixture, the machined detail is also improperly located. So, in the design of a workholder, referencing of both the workpiece and the cutter must be considered and simultaneously maintained.
The location of the workpiece relative to the tool and of the tool to the cutter must be consistent. If the jig or fixture is to maintain desired repeatability, the workholder must be designed to accommodate the workpiece's locating surfaces.
The ideal locating point on a workpiece is a machined surface. Machined surfaces permit location from a consistent reference point.
Cast, forged, sheared, or sawed surfaces can vary greatly from part to part, and will affect the accuracy of the location. The Mechanics of Locating A workpiece free in space can move in an infinite number of directions. For analysis, this motion can be broken down into twelve directional movements, or "degrees of freedom.
As shown in Figure , the twelve degrees of freedom all relate to the central axes of the workpiece. Notice the six axial degrees of freedom and six radial degrees of freedom.
The axial degrees of freedom permit straight-line movement in both directions along the three principal axes, shown as x, y, and z. The radial degrees of freedom permit rotational movement, in both clockwise and counterclockwise radial directions, around the same three axes. Figure The twelve degrees of freedom.
The devices that restrict a workpiece's movement are the locators. The locators , therefore, must be strong enough to maintain the position of the workpiece and to resist the cutting forces. This fact also points out a crucial element in workholder design: locators , not clamps , must hold the workpiece against the cutting forces. Locators provide a positive stop for the workpiece.
Placed against the stop, the workpiece cannot move. Clamps , on the other hand, rely only upon friction between the clamp and the clamped surface to hold the workpiece. Sufficient force could move the workpiece.
Clamps are only intended to hold the workpiece against the locators. Forms of Location There are three general forms of location: plane, concentric, and radial.
Plane locators locate a workpiece from any surface. The surface may be flat, curved, or have an irregular contour. In most applications, plane-locating devices locate a part by its external surfaces, Figure a. Concentric locators , for the most part, locate a workpiece from a central axis. This axis may or may not be in the center of the workpiece.
The most-common type of concentric location is a locating pin placed in a hole. Some workpieces, however, might have a cylindrical projection that requires a locating hole in the fixture, as shown in Figure b.
The third type of location is radial. Radial locators restrict the movement of a workpiece around a concentric locator , Figure c. In many cases, locating is performed by a combination of the three locational methods.
The three forms of location: plane, concentric, and radial. Locating from External Surfaces Flat surfaces are common workpiece features used for location. Locating from a flat surface is a form of plane location. Supports are the principal devices used for this location. The three major forms of supports are solid, adjustable, and equalizing, Figure Solid, adjustable, and equalizing supports locate a workpiece from a flat surface. Solid Supports are fixed-height locators.
They precisely locate a surface in one axis. Though solid supports may be machined directly into a tool body, a more-economical method is using installed supports, such as rest buttons.
Adjustable supports are variable-height locators. Like solid supports, they will also precisely locate a surface in one axis. These supports are used where workpiece variations require adjustable support to suit different heights.
These supports are used mainly for cast or forged workpieces that have uneven or irregular mounting surfaces. Equalizing supports are a form of adjustable support used when a compensating support is required.
Although these supports can be fixed in position, in most cases equalizing supports float to accommodate workpiece variations. As one side of the equalizing support is depressed, the other side raises the same amount to maintain part contact. In most cases adjustable and equalizing supports are used along with solid supports. Locating a workpiece from its external edges is the most-common locating method. The bottom, or primary, locating surface is positioned on three supports, based on the geometry principle that three points are needed to fully define a plane.
Two adjacent edges, usually perpendicular to each other, are then used to complete the location. The most-common way to locate a workpiece from its external profile is the , or six-point, locational method. With this method, six individual locators reference and restrict the workpiece. As shown in Figure , three locators , or supports , are placed under the workpiece. The three locators are usually positioned on the primary locating surface.
This restricts axial movement downward, along the -z axis 6 and radially about the x 7 and 8 and y 9 and 10 axes. Together, the three locators restrict five degrees of freedom. Three supports on the primary locating surface restrict five degrees of freedom. The next two locators are normally placed on the secondary locating surface, as shown in Figure Adding two locators on a side restricts eight degrees of freedom.
The final locator, shown in Figure , is positioned at the end of the part. It restricts the axial movement in one direction along the -x axis. Together, these six locators restrict a total of nine degrees of freedom. The remaining three degrees of freedom 1, 4, and 5 will be restricted by the clamps.
Adding a final locator to another side restricts nine degrees of freedom, completing the location. Although cylindrical rest buttons are the most-common way of locating a workpiece from its external profile, there are also other devices used for this purpose.
These devices include flat-sided locators, vee locators, nest locators and adjustable locators. Locating from Internal Surfaces Locating a workpiece from an internal diameter is the most-efficient form of location.
The primary features used for this form of location are individual holes or hole patterns.
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Till now, we know that jigs and fixtures are the devices which help in the machining of jobs and reducing the human efforts required for producing these parts. Specific tools are necessary for producing these objects in identical shapes and sizes on a mass scale, by holding and locating tasks to minimize the repetition work. That is when various types jigs and fixtures come into play. Considering the variety in the nature of jobs to be machined, the quality, and the associated functions, the type of jig and fixture varies as well. Following are the various kinds of jigs and fixtures. Template Jig: The template jig is the simplest of all the models.
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Jigs and fixtures are devices used to facilitate production work, clamp jig is a design for drilling holes that are all the same size—for example, the stud holes in a a jig hole. The same general principles concerning clamping, support while.
TEACHING TOPICS: The Teaching of Jig and Tool Design
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Post a Comment. Jigs and Fixtures improve productivity of process, equipment and operators.
Jig and Fixture Design
Show all documents It is not important neither the design of jig and fixture is simple nor complex but the most important thing is the design follow the specification which is the milling machine needed. Besides, this project shall concern with the basic rules for locating, such as positioning the locators, part tolerance, fool proofing and duplicate location.
Jigs and Fixtures are critical to repeated manufacturing to with high degrees of accuracy and precision. Jigs and Fixtures hold one or multiple parts in one or multiple machine centers to provide stability and repeatable alignment of the part. A Fixture is a special workholding device that holds work during machining or assembly operations and establishes size dimensions General purpose clamps and chucks are not fixtures or jigs. The location principle is used to ensure that every part placed in the device occupies the same position with respect to the cutting tools. And finally locating the part relative to the first two planes by establishing a third plane perpendicular to the first two planes using a single point. Clamping should be designed such that the cutting forces work against the fixed portion of the clamp, not the movable portion.
assembly part for this design also are more simple. 8. Basic Design Principle for Jig and Fixture. Basic principle while designing of.
Are you looking for the notes on Jigs and Fixture s? Yap, you are landed in the right destination. A jig is a work-holding devic e that holds, supports, and locates the workpiece and guides the one or more tools to perform a specific operation. In other words, this can also be defined as, used for holding the tools and also guiding the cutting tools. Both the jigs and the fixtures are used to reduce the nonproductive time of any mass production process. The jig is used for guiding the cutting tool like a drill bit , and for doing so, jigs have components like a bush, which comes in contact with the cutting tool. Fixtures assure the position and alignment of the workpieces for getting the required machining operation done.
Сьюзан, в свою очередь, удивил ответ шефа. - Но ведь у нас есть ТРАНСТЕКСТ, почему бы его не расшифровать? - Но, увидев выражение лица Стратмора, она поняла, что правила игры изменились. - О Боже, - проговорила Сьюзан, сообразив, в чем дело, - Цифровая крепость зашифровала самое. Стратмор невесело улыбнулся: - Наконец ты поняла. Формула Цифровой крепости зашифрована с помощью Цифровой крепости.
Наверное, Испания напомнила мне о том, что по-настоящему важно. - Помогать вскрывать шифры? - Она чмокнула его в щеку.
Они, не замечая Халохота, шли своей дорогой, напоминая черный шуршащий ручеек. С пистолетом в руке он рвался вперед, к тупику. Но Беккера там не оказалось, и он тихо застонал от злости. Беккер, спотыкаясь и кидаясь то вправо, то влево, продирался сквозь толпу. Надо идти за ними, думал .
Халохот оглядел дворик.