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- Jigs and Fixtures - Mechanical Engineering (MCQ) questions and answers
- Jigs and Fixtures Objective Questions - Fitter (Set-1)
- MCQ's on Jigs & Fixtures.docx
- Jig and fixtures
The basic jig is almost the same for either machining oper- ation. The only difference is in the size of the bushings used. Open jigs are for simple operations where work is done on only one side of the part.
Jigs and Fixtures - Mechanical Engineering (MCQ) questions and answers
Science Research. Abstract: The paper gave a detailed definition of jigs and fixtures, and also identified the numerous advantages that are associated with the use of jigs and fixtures in manufacturing to include: production increase, cost reduction, interchangeability and high accuracy of parts, reduction of the need for inspection and quality control expenses, reduction of accident as safety is improved, automation of machine tool to an appreciable extent, easy machining of complex and heavy components, as well as low variability in dimension which leads to consistent quality of manufactured products.
The work also explained that since the design is dependent on numerous factors which are analyzed to achieve an optimum output, that jigs and fixtures should be made of rigid light materials to facilitate easy handling. For adequate strength and rigidity, a mild steel with 16 millimeters diameter was chosen for the design of a sample jig and fixture. Mild steel which contain about 0. With 1. The Force acting on each of the lips was calculated as N, the Torque M was gotten as N-mm, while the value of the Clamping Force was also calculated as N.
The calculated values confirmed that a 16 millimeter diameter mild will lead to the construction of a rigid and strong jigs and fixtures that will guarantee high machining accuracy, consistent quality of products, and interchangeability.
Finall, the paper advocated that jigs and fixtures must be provided with adequate clearance which should allow for variations in size of components especially during forging, milling, and casting operations. Therefore, to meet up with the high demand, manufacturers have reacted by introducing innovative ways of manufacturing high quality products at a faster rate. The production processes has witnessed numerous changes and evolution with the introduction of numerous innovative manufacturing concepts which include Lean Production System, Cellular Manufacturing, Single Minute Exchange of Dies, as well as Takt Time Analysis.
These creative approaches have necessitated the need for a reliable and cheaper tools and work-holding devices. As the efficient running of a manufacturing company which demands a prompt and simple work positioning strategy for correct operations depends largely on the interchangeability of machine components and work-pieces, to ensure un-complication of assembly, and unit cost reduction, as well as to become competitive, reduce the enormous manufacturing cost, and also increase their profitability, the industry has resorted to streamlining its supply chain in a bid to maintaining a very low amount of inventory.
This has also led to the demand for a better and cost effective work-holding devices which will ensure better quality products, reduce lead time, and also increase throughput.
Also, although some machining operations are so straight-forward, like in turning where the job is secured tightly on the chuck while the turning operations are easily performed, some jobsin other operations may not be easily held on either the three or four jaw chucks, and may also require the tools to be guided by the means of a different device.
This explains the need for production standard work-holding devices to increase the rate of manufacturing. Jig is the device which guides the tool, while fixture is a device that securely holds the job in position during machining operations.
Jigs and Fixtures. Jigs and fixtures are manufacturing tools that are employed to produce interchangeable and identical components. They are unique tool-guiding and work-holding devices designed specifically for machining and assembling large number of parts.
Chennu , listed the following as the purposes of jigs and fixtures reduction of production cost, increase of production rate, high accuracy of products without any manufacturing defects, provision of interchangeability, easy machining of complex shaped parts, reduction of quality control costs, etc.
Jigs and fixtures eliminate the need for a special set up for every work-piece thereby facilitating production and also ensuring that every work piece is manufactured within a predetermined tolerance. According to Meduettaxila , Jigs and fixtures "eliminate the necessity of a special set up for each individual part. Also Mechnol , observed that The main advantages of Jigs and fixtures are "durability, setup reduction, improvement in productivity, reduced decision making in operation selected from the standard components.
The major difference between a jig and a fixture is that jigs guide the cutting tool to its precise position, as well as locating and supporting the work-piece during operations.
The application of jigs and fixtures in manufacturing operations lead to the production of faster, more accurate, and reliable products at a reduced cost. A jig is a work-holding device that supports, holds, locates a work-piece and also guides the cutting tool for the desired machining operations. Nanthakumar and Prabakaran , explained that a jig is a type of custom-made tool used for the location and motion of another tool. They observed that the primary purpose of a jig is to provide repeatability, accuracy, and interchangeability in the manufacturing of products.
Although the most common jigs are the drilling and boring jigs, they are all identical except for the shape, type, and the position of the bushings for drilling or boring. Figure 1. A typical Jig. Source: engineeringhut. According to Joshi , Jigs are imparted with tool guiding elements such as drill bushes, which regulate the tool to the right position in the work piece. He observed that they are rarely clamped on the machine table as it is essential to push the jig on the table to align the numerous bushes in the jig with the spindle of the machine.
Thedifferent types of jigs are template jig, drilling jig, open type jig, etc. Fixtures are rigid and sturdy mechanical devices which allow fast and precision machining with reliable quality, interchangeability, and lead time reduction. As a work-holding device, fixtures do not position, guide, and locate the cutting tool, as it is achieved by making necessary adjustments on the machine. Kaija, andHeino , explained that the "main purpose of a fixture is to locate and in some cases hold a work-piece during either a machining operation or some other industrial processes.
Figure 2. A typical fixture: Source: engineeringhut. Fixtures often fastened to the machine table, are made to hold the work piece firmly and in the desired position during machining operations. While fixtures are always identified by the machine tool where they are applied, they have broader applications than jigs, and also manufactured for operations where the cutting tools cannot be easily maneuvered like the drilling or boring tools.
The different types of fixtures are welding fixture, tapping fixture, milling fixture, boring and drilling fixture, milling fixture, turning fixture, etc. Advantages of Jigs and Fixtures. The advantages of jigs and fixtures includebut not limited to the following:.
Elements of Jigs and Fixtures. The Body. As the most outstanding element of jigs and fixtures, the body is constructed by welding of different slabs and metals usually mild steel or by casting of cast iron. After the fabrication, it is often heat-treated for stress reduction as its main objective is to accommodate and support the job.
Channel body type — this is fabricated from the regular steel channel. Box body type — usually made very light, the box type jig body is adopted where a work-piece needs drilling in various parts, hence the jig is fabricated to have a required amount of drill bush plates. Plane body type — this is the most common type of jig body and is often applied when the work-piece requires drilling or boring, hence the provision of drill bushes on it.
Leaf body type — usually made from block of steel as it holds and supports heavy components. Clamping Devices. Without sacrificing efficiency and effectiveness, the clamping devices must be very simple and easy to operate.
Apart from holding the work-piece securelyin place, the strong point of clamping devices is its ability to withhold the strain of the cutting tool during operations. The bench vice is a popular example of a clamping device. The need for clamping the work-piece on the jig or fixture is to apply pressure and press it against the locating components, thereby fastening it in the right position for the cutting tools.
The familiar clamping devices include:. Hook bolt clamp - a simple clamping device generally used where the normal clamping tip cannot fit in. Latch clamp — this is a unique clamp which provides space for the loading and the unloading of a work-piece through its latch or lid.
Other clamping devices are the C — clamp, the Bridge clamp, and the Heel clamp,. Locating Devices. Made with hardened steel and with different designs, the pin is the most popular device applied for the location of work-piece in jigs and fixtures. The locating width of the pin is made bigger than the shank to stop it from being pressed into the jig or fixture body because of the weight of the cutting tools or work-piece.
Locating pins — the locating pins are used for the location of the work-piece when completed or reamed holes have been provided on the work-piece. The two types of locating pins are cylinderical and conical locating pins. Jack pins — jackpins also referred to as spring pins are used for the location of work-piece whose dimension will vary during operation. The pin is designed to rise under spring pressure or in the contrary the weight of the work-piece pushes it down.
As the position of the work-piece is firmly fixed, the locking screw is used to fasten the pin in the desired position. Those with flat heads are often used to provide support and location to machine surface, as more contact area is accessible during location. Because of their stability, the head support locating pins are for supporting coarse or rough surfaces during machining.
Jig Bushing or Tool Guide. Guiding parts like jig bushings and templates which must be wear resistant, interchangeable, and precise, are used to locate the cutting tool relative to the component being machined.
Jig bushes are applied in drilling and boring, here for the drill to pass through, a bush fits into the hole of the jig. Bushes are mainly made of reliable grade of tool steel in order to ensure hardening at a low temperature and also reduce the risk of fire cracking. Although, hardened steel bushes are preferred for guiding reamers, drills, and taps, the guiding tool bushings can also be made of cast iron. The jig bushings are categorized into three: the linear wearing bushes, press-fit wearing bushes, and renewable wearing bushes.
Selection of Materials. There are a wide range of materials from where jigs and fixtures could be made, to resist tear and wear, the materials are often tempered and hardened. Also, phosphor bronze and other non-ferrous metals, as well as composites, and nylons for wear reduction of the mating parts, and damage prevention to the manufacturing part is also used.
Some of the materials are discussed below:. As the manufacturing of screws is very expensive and also wastes a lot of time, the reduction of their tear and wear is often achieved by using replaceable bronze mating nuts made with phosphor bronze.
When alloyed with vanadium and molybdenum for it to retain toughness at very high temperature, die steels are applied in the fabrication of jigs and fixtures that are used in high temperature work processes which include extrusion, forging, and casting processes.
When tempered, they are applied in the production of jigs and fixtures for reaming, drilling, boring, and cutting operations. Design of Jigs and Fixtures. The design of jigs and fixtures is dependent on numerous factors which are analyzed to achieve an optimum output. Jigs should be made of rigid light materials to facilitate easy handling, as it has to be rotated severally to enable holes to be drilled from different angles. It is recommended that four feet should be provided for jigs that are not bolted on the machine tool, to enable the jig to wobble if not well positioned on the table and thereby alert the operator.
To achieve their expected objectives, jigs and fixtures consist of many elements:. The extent of automation, capacity and type of the machine tool where jigs and fixtures will be employed;. The availability of locating devices in the machine for blank orientation, and suitable positioning;. Figure 3. Major elements of jigs and fixtures. The factors below are to be reflected upon during design, production, and assembly of jigs and fixtures due to the targeted increase in throughput, quality of products, interchangeability, and more accuracy.
Spogel ,advised that the design of jigs and fixtures must be fool-proof so that the tools, bushes, and components cannot be inserted except in the correct way. Apart from ensuring that locating points are made adjustable when the component is a rough casting and may be out of alignment, he admonished that the clamps should be located in the best position in order to resist the cutting tool pressure when at work. A proper design must also incorporate tolerances at the design stage for jig andfixtures components that are standardized.
Jigs and Fixtures Objective Questions - Fitter (Set-1)
Jig and fixtures are made from a variety of the materials. There are times where the metals are hardened to resist wear and tear. From Wikibooks, open books for an open world. Most suitable for most jigs applications as it is the most economical and most widely used material in jigs and fixtures. Carbon Steel Contains carbon 0. Most suitable for workpieces like woodworking tools and hand tools such as files and chisels. It can be hardened to serve as locators and bushings.
The use of jigs and fixtures a Facilitates deployment of less skilled labour for production b Eliminates pre-machining operations like marking, measuring, laying out etc. The following is are the function s of a jig a Holding b Locating c Guiding d All of the above. A fixture does not a Holds the workpiece b Locate the workpiece c Guide the tool d All of the above. Jigs are not used in a Drilling b Reaming c Tapping d Milling. Fixtures are used in a Milling b Shaping c Turning d All of the above. The following holds the workpiece securely in a jig or fixture against the cutting forces a Locating device b Clamping device c Guiding device d Indexing device.
(C) reduced manual handling operations. (D) All of the above. (Ans: D). 3-The following is(are) the function(s) of a jig. (A) Holding. (B) Locating.
MCQ's on Jigs & Fixtures.docx
IT HAS BEEN stated many times that jig and tool design is a difficult subject to teach because the design of such equipment rarely has a mathematical basis. Few will disagree with the latter part of the statement, but the implications of the first part must be examined carefully. Walker, W.
A jig is a work-holding device that holds, supports, and locates the workpiece and guides the one or more tools to perform a specific operation. Fixtures are the work holding devices, which holds, supports and locates the workpiece but not guides the cutting tool to perform a specific operation. Fixture is used for the convenience of fabrication of a job by welding which is set in this device so that it can be swiveled around Degree as per requirement.
Science Research. Abstract: The paper gave a detailed definition of jigs and fixtures, and also identified the numerous advantages that are associated with the use of jigs and fixtures in manufacturing to include: production increase, cost reduction, interchangeability and high accuracy of parts, reduction of the need for inspection and quality control expenses, reduction of accident as safety is improved, automation of machine tool to an appreciable extent, easy machining of complex and heavy components, as well as low variability in dimension which leads to consistent quality of manufactured products. The work also explained that since the design is dependent on numerous factors which are analyzed to achieve an optimum output, that jigs and fixtures should be made of rigid light materials to facilitate easy handling.
Беккер спустился вниз, постоял, глядя на самолет, потом опустил глаза на пачку денег в руке.
Jig and fixtures
Но я хочу иметь копию. Я хочу открыть этот проклятый файл и ознакомиться с созданной Танкадо программой. Сьюзан была столь же любопытна, как и ее шеф, но чутье подсказывало ей, что расшифровка алгоритма Цифровой крепости неразумна, какой бы интерес это ни представляло. В данный момент эта чертова программа надежно зашифрована и абсолютно безопасна.
Вот почему мы внесены в телефонный справочник. Мы занимаемся легальным бизнесом. А вы ищете проститутку. - Слово прозвучало как удар хлыста. - Но мой брат… - Сэр, если ваш брат целый день целовался в парке с девчонкой, то это значит, что она работает не в нашем агентстве.
Теперь все умолкло, так что можно было различить облегченный вздох раненого чудовища - ТРАНСТЕКСТА, постепенно стихающее шипение и посвистывание, сопутствующие медленному охлаждению. Сьюзан закрыла глаза и начала молиться за Дэвида. Ее молитва была проста: она просила Бога защитить любимого человека. Не будучи религиозной, она не рассчитывала услышать ответ на свою молитву, но вдруг почувствовала внезапную вибрацию на груди и испуганно подскочила, однако тут же поняла: вибрация вовсе не была рукой Божьей - она исходила из кармана стратморовского пиджака. На своем Скайпейджере он установил режим вибрации без звонка, значит, кто-то прислал коммандеру сообщение. Шестью этажами ниже Стратмор стоял возле рубильника. В служебных помещениях ТРАНСТЕКСТА было черно как глубокой ночью.
Повинуясь инстинкту, он резко нажал на тормоза, но мотоцикл не остановился на скользком от машинного масла полу. Веспу понесло. Рядом раздался оглушающий визг тормозов такси, его лысая резина заскользила по полу. Машина завертелась в облаке выхлопных газов совсем рядом с мотоциклом Беккера. Теперь обе машины, потеряв управление, неслись к стене ангара. Беккер отчаянно давил на тормоз, но покрышки потеряли всякое сцепление с полом.
Она превозмогала боль сколько могла, но ее силы иссякли. Она сказала ему, что их брак исчерпал себя, что она не собирается до конца дней жить в тени другой женщины. Вой сирен вывел его из задумчивости. Его аналитический ум искал выход из создавшегося положения. Сознание нехотя подтверждало то, о чем говорили чувства.
Должен быть какой-то другой выход. - Решайте! - крикнул Хейл и потащил Сьюзан к лестнице.
Если он скажет да, его подвергнут большому штрафу, да к тому же заставят предоставить одну из лучших сопровождающих полицейскому комиссару на весь уик-энд за здорово живешь. Когда Ролдан заговорил, голос его звучал уже не так любезно, как прежде: - Сэр, это Агентство услуг сопровождения Белен. Могу я поинтересоваться, кто со мной говорит.
Так вот почему Дэвид отложил поездку в Стоун-Мэнор. - Сегодня утром я послал за ним машину. Он сказал, что позвонит тебе перед вылетом.