Jig and fixture design edward g hoffman pdf

 
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  2. Jig Fixture Design by Edward Hoffman
  3. Jig and fixture design / Edward G. Hoffman
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Edward Hoffman Jig and Fixture Design, 5E Delmar Learning Drafting (Copyright Cengage Learning. All Rights Reserved. May no). This outstanding Jig And Fixture Design Edward G Hoffman Author is released to give the Get them for file format pdf, word, txt, rar, ppt, zip, and also kindle. Jig And Fixture Design Edward G Hoffman Author. Introduction To Jigs And Fixtures - National Institute Of introduction to jigs and fixtures. introduction a jig.

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Jig And Fixture Design Edward G Hoffman Pdf

Jig and fixture design Edward G Hoffman. This newly revised text presents the basic concepts of the design of workholding devices. Topics covered include the . Download as PDF Print Jig and fixture design / Edward G. Hoffman Send to Email Jig and fixture design / Edward G. Hoffman. keep coming cresalslopebslag.ga you need a jig and fixture design edward g hoffman author, you can download them in pdf format from our cresalslopebslag.ga file format that can.

From simple template and plate-type jigs to complex channel and box-type tooling, this newly revised edition features more than illust By emphasizing similarities among types and styles, "Jig and Fixture Design, Fifth Edition speeds readers to a complete understanding of the why's and how's of designing and building a variety of different workholders for manufacturing. From simple template and plate-type jigs to complex channel and box-type tooling, this newly revised edition features more than illustrations of tools and applications to spur readers to success. All new sections on assembly tools, handling tools, and catalog reading enable readers to develop important skills. Specific examples of various jigs and commercially available fixtures also appear guide readers in developing their understanding of how design principles, as well as the latest design and manufacturing technologies, are being applied in the construction of jigs and fixtures today. As in past editions, heavy emphasis is placed on the economics of jigs and fixtures, including methods and formulas for use in estimating workholder costs. A solid background in industrial processes, as well as machine shop technology, is assumed.

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Industry has responded to this demand with many new and sometimes radical ways of producing products. These changes have created a dire need for more cost-effective and efficient workholding methods and devices.

As more manufacturing companies shift their emphasis toward a zero-parts inventory system to keep costs down and profits up, the need for efficient and cost-effective workholders is becoming increasingly important. Despite the many advancements and changes in cutting tools, machine tools, and production methods, the basic requirement of holding the workpiece has remained constant.

Every part produced must be held while it is machined, joined, or inspected or has any number of other operations performed on it. So, whether the operation requires a simple drill press, a multiple-axes computer, or numerically controlled machining center, the workpiece must be accurately located and securely held throughout the operation.

The part, not the process, is the primary consideration in workholding. Just as no single machine tool will perform every required operation, no individual jig or fixture can possibly hold every part. However, each workholder variation has basic similarities to other types and styles of jigs and fixtures. The subject of this text is these similarities rather than the differences.

This text helps the reader develop a thorough understanding and working knowledge of how and why jigs and fixtures are designed and built as they are. To do this, the discussion starts with the fundamentals of jigs and fixtures and works through the various elements and considerations of design. Throughout the text, two fundamental tool design principles are constantly stressed: simplicity and economy.

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To be effective, a workholder must save money in production. To this end, the construction of the tool must be as cost-effective as possible while ensuring that the tool has the capacity to perform all of the intended functions. The reader becomes familiar with working with part drawings and production plans showing the sequencing of operations in the shop.

The 20 units of this text are divided into four major sections. The first section Units 1—5 gives the reader an overview of the basic types and functions of jigs and fixtures, as well as a detailed description of the way these workholders are designed and built. From the evolution of Com- possibly hold every part. This textIn Time JIT , and Statistical Process Control SPC , helps the reader develop a thorough understandingthe art of manufacturing has undergone many dramat- and working knowledge of how and why jigs and fix-ic changes and advances.

These changes have created tures are designed and built as they are. To do this, thea dire need for more cost-effective and efficient discussion starts with the fundamentals of jigs andworkholding methods and devices. As more manu- fixtures and works through the various elements andfacturing companies shift their emphasis toward a considerations of design.

To be effective, a workholder must save Despite the many advancements and changes in money in production. To this end, the construction ofcutting tools, machine tools, and production methods, the tool must be as cost-effective as possible whilethe basic requirement of holding the workpiece has ensuring that the tool has the capacity to perform allremained constant.

Every part produced must be held of the intended functions. The reader becomes familiar with requirements of industry for years to come. Finally, aworking with part drawings and production plans unit on tooling materials covers the properties ofshowing the sequencing of operations in the shop. The 20 units of this text are divided into fourmajor sections. The first section Units 1—5 gives the A glossary is provided for ready reference and asreader an overview of the basic types and functions of an aid to the reader in mastering the terminology ofjigs and fixtures, as well as a detailed description of workholder design.

The reader learns the basic elements of supporting, FEATURESlocating, and clamping the part and then is introducedto the basic principles of workholder construction. This edition includes a more integrated approach toThis section provides the background information for the global nature that challenges the tool designer. Concepts include the use of design teams in accom- plishing the task of competitively delivering good The second section Units 6—8 introduces the design in a time efficient manner.

This requires the usereader to the primary considerations of design eco- of CAD as a universal language that crosses bound-nomics and the basic methods used to initiate and aries and languages, and yet provides an ergonomi-prepare the design drawings.

In keeping with the cally designed tool capable of passing the test ofworldwide standard of measurement and modern OSHA standards. Vendor supplied libraries of toolingdrafting practices, the SI system International Sys- components have allowed the design process to pro-tem of Units is introduced and explained. New material covering the applications of Com- rent engineering. Communicating as part of theputer Aided Design CAD and how it is applied to design team may require good computer skills andjig and fixture design has also been added to this sec- video conferencing capabilities, since the end func-tion to inform the reader of the developments in this tion of the tooling may be half way around the world.

The design team may be comprised of individuals from more than one country. This is a departure from The third section Units 9—14 introduces and the traditional methods that were used when globalexplains the processes involved in designing and con- partnerships were not as predominant. Many areasstructing the basic types and forms of jigs and still work through the tool design process in veryfixtures. From simple template and plate-type work- familiar fashion; however, the trend toward concur-holders to more detailed and complex channel and rent engineering is used in many industry areas wherebox-type tooling, each basic style is thoroughly outsourcing is very common.

Covering power work- trations and many new photographs showing theholding methods and equipment, modular workhold- variety of tools and workholders available as welling systems and low-cost tooling practices, and as typical applications. Numerous examples are included, as well as applications in the review portion of the unit. Hoffman holds a B. Mike has taught at the college since fixtures describing many new and innovative and is a Tool and Die Maker, having completed products useful for reducing quantity production his apprenticeship in He has developed and con- runs and one-of-a-kind machining.

Mike is a member of the Administrative Circle at production. Hawkeye Community College and serves as the pro- gram chair of skilled trades. Program , a school to work program. Process Engineer. She assisted students in chartering The guide contains the answers to the reviews at a student chapter of the Society of Manufacturing the end of each unit of the text.

Engineers at HCC. Edward G. He script:has written 17 books on tool and manufacturing engi-neering subjects and currently writes 40 magazine Clyde Avery, Carritos College, Norwalk, CAcolumns per year for several trade journals. His experience also includes 10years of teaching and lecturing for colleges, technicalsocieties, and trade schools. He has helped thousands Copyright Cengage Learning. Con-turing costs while maintaining quality and increased current engineering is a process that allows theproduction.

To accomplish this, the tool designer must design team to be involved in a comprehensive plansatisfy the following objectives: for product design and production. Concurrent engi- neering allows the tool design team member to be involved in product design and production where their knowledge of fixtures and manufacturing processes will result in fewer design errors.

Concur- rent engineering teams consist of product designers, process planning engineers, tool designers, quality control engineers, production management, and 1 Copyright Cengage Learning. Companies may vary job may include a solid model. The solid model allows thetitles and team compositions to suit their internal designer to view the three-dimensional part geometry.

The task of tool design begins with a more complete understanding of the part. A prototype, or a single Team members contribute based on their area of manufactured part used for evaluation purposes, can beexpertise. The product, a method for manufacturing, made available. A prototype goes one more steptooling concepts, and a quality plan are developed that beyond the solid computer model.

The prototype, asuits the selected manufacturing facility. In this way, single physical part provided prior to formal produc-problems are not discovered on the production floor, tion, is a valuable tool for understanding more com-but are corrected early in the concurrent process. This plex part geometries. Prototypes are manufacturedultimately saves time and money while speeding up using conventional Computer Numerical Controlthe process of getting product to market earlier.

Con- CNC machine tools or some of the newer technolo-current engineering allows a company to have a dis- gies such as stereolithography or a layered object man-tinct economic advantage in a global market. Both the stereolithography and LOM develop the part The tool designer develops a plan for maintain- geometry using a system of layering the medium anding the concepts developed by the team with respect solidifying or cutting out that layer with a laser.

Theto economic guidelines. Expert computer systems result is a solid object made one layer at a time whereare now part of the design environment, and they the layers may be no more than. Whethersupport an integrated approach for tracking time and analyzing the prototype and the part drawing or justmoney allocated for the project and provide imme- the part drawing, the designer must consider the fol-diate information at any point in the concurrent lowing factors that directly influence the design choic-process.

This istime wisely spent and results in an efficient and cost- Production Planeffective tool design. The design process is not as lin-ear as it used to be. Communication models between The production plan Figure 1—2 is an itemized list ofteam members include e-mail and electronic transfer the manufacturing operations and the sequence of theof materials and may make use of sophisticated tech- operations chosen by the process planning engineer. Team members The production plan can take many forms, dependingmay consist of customers, designers, and builders in on the needs of each company.

At the least, it shoulddifferent locations that may take them halfway include a brief description of each machining operationaround the world. Part Drawings The tool designer also uses this plan to assist in the design. The production plan can include the following:The tool designer receives a duplicate of the part geom-etry that will be used to make the part Figure 1—1. Using check each operation?

Answering these questions and others related to the specific task, the tool designer develops alternative solu-Alternatives tions. From these alternative solutions, the most effi- cient, dependable, and cost-effective design is chosen. One of the first steps in problem solving is determiningthe alternative solutions. Duringthis phase of the design, the tool designer must analyze The tool designer has many manufacturing responsi-all important information in order to answer the follow- bilities.

In addition to technical design duties, the tooling questions: designer may be responsible for obtaining materials, toolroom supervision, and tool inspection. UNIT I Pupose of Tool Design 5Design designer possesses, these skilled toolmakers can often see solutions that may not be obvious to theIn this phase, the tool designer is responsible for designer. For this reason, it is always a good idea todeveloping the drawings and sketches of the tool build a good working relationship with your toolmak-design ideas.

Design drawings are usually subject to ers. In tool design, a cooperative relationship betweenapproval by a chief designer. However, in smaller the designer and the toolmakers is essential. Not onlycompanies, the tool designer often makes the tooling does working together make the task at hand easier,decisions.

Often a tool designer is responsible for obtaining theSupervision for a single section, such as design or materials to make the tool. In either supply materials and parts that meet the design speci-case, the ability to lead others is helpful. When selecting a vendor, a good practice is to choose the company that offers the most service to One resource a tool designer may often use to its customers.

Services such as design assistance andhelp resolve design problems is the group of skilled problem solving, where their product is involved, arepeople in the toolroom. The toolroom is the area in a important factors to consider before making a finalshop where the machine tools and the skilled work- selection. Another point to consider is whether theforce are found. In this way, single physical part provided prior to formal produc-problems are not discovered on the production floor, tion, is a valuable tool for understanding more com-but are corrected early in the concurrent process.

This plex part geometries. Prototypes are manufacturedultimately saves time and money while speeding up using conventional Computer Numerical Controlthe process of getting product to market earlier. Con- CNC machine tools or some of the newer technolo-current engineering allows a company to have a dis- gies such as stereolithography or a layered object man-tinct economic advantage in a global market.

Both the stereolithography and LOM develop the part The tool designer develops a plan for maintain- geometry using a system of layering the medium anding the concepts developed by the team with respect solidifying or cutting out that layer with a laser.

Theto economic guidelines. Expert computer systems result is a solid object made one layer at a time whereare now part of the design environment, and they the layers may be no more than. Whethersupport an integrated approach for tracking time and analyzing the prototype and the part drawing or justmoney allocated for the project and provide imme- the part drawing, the designer must consider the fol-diate information at any point in the concurrent lowing factors that directly influence the design choic-process.

These factors are: This istime wisely spent and results in an efficient and cost- Production Planeffective tool design. The design process is not as lin-ear as it used to be. Communication models between The production plan Figure 1—2 is an itemized list ofteam members include e-mail and electronic transfer the manufacturing operations and the sequence of theof materials and may make use of sophisticated tech- operations chosen by the process planning engineer.

Team members The production plan can take many forms, dependingmay consist of customers, designers, and builders in on the needs of each company. At the least, it shoulddifferent locations that may take them halfway include a brief description of each machining operationaround the world. Part Drawings The tool designer also uses this plan to assist in the design.

The production plan can include the following: The tool designer receives a duplicate of the part geom-etry that will be used to make the part Figure 1—1. Using check each operation?

Jig Fixture Design by Edward Hoffman

Answering these questions and others related to the specific task, the tool designer develops alternative solu-Alternatives tions. From these alternative solutions, the most effi- cient, dependable, and cost-effective design is chosen. One of the first steps in problem solving is determiningthe alternative solutions. Duringthis phase of the design, the tool designer must analyze The tool designer has many manufacturing responsi-all important information in order to answer the follow- bilities.

In addition to technical design duties, the tooling questions: UNIT I Pupose of Tool Design 5Design designer possesses, these skilled toolmakers can often see solutions that may not be obvious to theIn this phase, the tool designer is responsible for designer.

For this reason, it is always a good idea todeveloping the drawings and sketches of the tool build a good working relationship with your toolmak-design ideas. Design drawings are usually subject to ers. In tool design, a cooperative relationship betweenapproval by a chief designer. However, in smaller the designer and the toolmakers is essential.

Not onlycompanies, the tool designer often makes the tooling does working together make the task at hand easier,decisions.

Often a tool designer is responsible for obtaining theSupervision for a single section, such as design or materials to make the tool.

In either supply materials and parts that meet the design speci-case, the ability to lead others is helpful. When selecting a vendor, a good practice is to choose the company that offers the most service to One resource a tool designer may often use to its customers.

Services such as design assistance andhelp resolve design problems is the group of skilled problem solving, where their product is involved, arepeople in the toolroom. The toolroom is the area in a important factors to consider before making a finalshop where the machine tools and the skilled work- selection. Another point to consider is whether theforce are found. These skilled trades employees are vendor can supply special parts or components whencapable of taking the prints for the individual compo- necessary.

Jig and fixture design / Edward G. Hoffman

Generally, the specialty vendors can fur-nents of a tool and manufacturing them, assembling nish special items for much less than those items costthe parts, and verifying their accuracy.

A variety of to make in-house. Regardless of the level of skill aImage not available due to copyright restrictions Copyright Cengage Learning. First, the tool itself is inspectedfor compliance with the tool drawing. Second, several The following important concepts were presented intest parts are produced with the tool and are carefully this unit: List the seven objectives of tool design. Determine the source of the following data by indicating 1 for the part drawing, 2 for the pro- duction plan, and 3 for additional instructions.

Time allocation b. Overall size and shape of the part c. Required accuracy d. Sequence of operations e. Type and size of machines used f. Money available Copyright Cengage Learning. Number of pieces 3. What does the term concurrent mean and how ish. Previous machining it applied to the design of tooling?

Locating surfacesj. Material specifications 4. Describe a toolroom. Type of cutters needed 5. List the skills of a tool designer.

Type of machining required Copyright Cengage Learning. Jigs are usually fitted with hard- ened steel bushings for guiding drills or other cuttingAfter completing this unit, the student should be tools Figure 2—1A.

If, however, holes above. Set blocks and feeler or thickness gauges are used with fixturesJigs and fixtures are production-workholding devices to reference the cutter to the workpiece Figure 2—1B. The A fixture should be securely fastened to the table ofcorrect relationship and alignment between the cutter, the machine upon which the work is done. Thoughor other tool, and the workpiece must be maintained.

Fixtures vary in design from relatively simple Jigs and fixtures are so closely related that the tools to expensive, complicated devices. Fixtures alsoterms are sometimes confused or used interchangeably. It is a production Jigs may be divided into two general classes: Boring jigs are used to bore holesworkpiece but also guides the cutting tool as the oper- that either are too large to drill or must be made an odd size Figure 2—2.

Drill jigs are used to drill, 8 Copyright Cengage Learning. The more than one side. The names used to identify thesebasic jig is almost the same for either machining oper- jigs refer to how the tool is built.

The only difference is in the size of the bushingsused. Template jigs are normally used for accuracy rather than speed.

Templates are the least expensive and simplest type of jig to use. TheyDrill jigs may be divided into two general types, open may or may not have bushings. When bushings are notand closed. Open jigs are for simple operations where used, the whole jig plate is normally hardened.

Closed, or Figure 2—2 Boring jig. Figure 2—4 Template jigs. Plate jigs are similar to templates Figure 2—5. Figure 2—6 Table jig. The only difference is that plate jigs have built-inclamps to hold the work. These jigs can also be madewith or without bushings, depending on the numberof parts to be made.

Plate jigs are sometimes madewith legs to raise the jig off the table for large work.

This style is called a table jig Figure 2—6. Sandwich jigs are a form of plate jig with a backplate Figure 2—7. This type of jig is ideal for thin orsoft parts that could bend or warp in another style ofjig. Here again, the use of bushings is determined bythe number of parts to be made. Angle-plate jigs are used to hold parts that aremachined at right angles to their mounting locators Figure 2—8.

Pulleys, collars, and gears are some ofthe parts that use this type of jig. A variation is themodified angle-plate jig, which is used for machiningangles other than 90 degrees Figure 2—9. Both ofthese examples have clearance problems with the cut-ting tool. As the drill exits the product being drilled,it has little or no room for the drill point to clear theproduct completely, produce a round hole all the waythrough the part wall, and avoid drilling the part loca-tor. This is most noticeable in Figure 2—9, where anangled hole requires additional clearance to therelieved portion of the part locator.

Additional clear-ance here would allow the drill to complete the holeand avoid drilling the relieved portion of the locator. The part locator will most likely be hardened and the Copyright Cengage Learning.

Figure 2—8 Angle-plate jig. Figure 2—9 Modified angle-plate jig. Channel jigs are the simplest form of box jig FigureAdditional clearance on the relieved diameter of the 2— The work is held between two sides andpart locator may be possible. A larger clearance hole machined from the third side. In some cases, where jigin the locator could also be added if the relieved feet are used, the work can be machined on three sides. The additional designconsideration added to the locator would include the Leaf jigs are small box jigs with a hinged leaf tofeature to provide the correct orientation of this clear- allow for easier loading and unloading Figure 2— Leaf jigs are normally smaller than box jigs and are sometimes made so that Box jigs, or tumble jigs, usually totally surround they do not completely surround the part.

They arethe part Figure 2— This style of jig allows the 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 Copyright Cengage Learning. Figure 2—11 Channel jig. The final station is used for unloading the fin- ished 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 opera- tion accurately, and be simple and safe to operate. Larger indexing jigs are calledrotary jigs. The names used to describe the various types of fix- tures are determined mainly by how the tool is built.

Trunnion jigs are a form of rotary jig for very Jigs and fixtures are made basically the same way aslarge or odd-shaped parts Figure 2— The part is far as locators and positioners are concerned.

Thefirst put into a box-type carrier and then loaded on the main construction difference is mass. Because of thetrunnion. This jig is well suited for large, heavy parts increased tool forces, fixtures are built stronger andthat must be machined with several separate plate- heavier than a jig would be for the same part.

Plate fixtures are the simplest form of fixture Pump jigs are commercially made jigs that must be Figure 2— The basic fixture is made from a flatadapted by the user Figure 2— The lever-activated plate that has a variety of clamps and locators to holdplate makes this tool very fast to load and unload.

Since and locate the part. The simplicity of this fixturethe tool is already made and only needs to be modified, makes it useful for most machining operations. Itsa great deal of time is saved by using this jig. Multistation jigs are made in any of the forms The angle-plate fixture is a variation of the platealready discussed Figure 2— The main feature of fixture Figure 2— With this tool, the part is nor-this jig is how it locates the work.

While one part is mally machined at a right angle to its locator. While Copyright Cengage Learning. Figure 2—13 Indexing jig. In parts Figure 2— With this type of tool, the stan-these cases, a modified angle-plate fixture can be dard vise jaws are replaced with jaws that are formedused Figure 2— Vise-jaw fixtures are the least expen- Copyright Cengage Learning.

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Figure 2—15 Pump jig. The parts shown in Figure 2—22 are examples of the uses of an indexing fixture. Their use is limited onlyby the sizes of the vises available. Multistation fixtures are used primarily for high- speed, high-volume production runs, where the Indexing fixtures are very similar to indexing jigs machining cycle must be continuous. Duplex fixtures Figure 2— These fixtures are used for machining are the simplest form of multistation fixture, usingparts that must have machined details evenly spaced.

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 station 1, the tool is revolved and the cycle is repeated at station 2. At the same time, the part is unloaded at station 1 and a fresh part is loaded.

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