Product Design for Manufacture and Assembly- Third Edition by Geoffrey Boothroyd- Peter Dewhurst- Winston a. Knight - Download as PDF File .pdf), Text File. Product Design for Manufacture and Assembly, Third Edition (Manufacturing Engineering and Materials Processing): Free PDF Download. Publication Date: December 8, ISBN ISBN Edition: 3. Product design for manufacture and assembly Geoffrey Boothroyd Design is the first step in manufacturing, and it is where most of the important decis.
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that automation could only account for one-third of the total difference in productivity Product design for manufacture and assembly: G Boothroyd. Productivity. Product Design for Manufacture and Assembly by Geoffrey Boothroyd, In addition to the expected updating of data in all chapters, this third edition has been. Booktopia has Product Design for Manufacture and Assembly, Third Edition by Geoffrey Boothroyd. download a discounted PDF of Product Design.
Bookmark it to easily review again before an exam. The best part? As a Chegg Study subscriber, you can view available interactive solutions manuals for each of your classes for one low monthly price. Why download extra books when you can get all the homework help you need in one place? Can I get help with questions outside of textbook solution manuals? You bet! Fred W. Hugh J. Nello Zeuch. Youngseog Lee. Home Contact us Help Free delivery worldwide.
Free delivery worldwide. Bestselling Series. Harry Potter. Popular Features. New in Classical Mechanics Engineering: Product Design for Manufacture and Assembly. Description Hailed as a groundbreaking and important textbook upon its initial publication, the latest iteration of Product Design for Manufacture and Assembly does not rest on those laurels.
In addition to the expected updating of data in all chapters, this third edition has been revised to provide a top-notch textbook for university-level courses in product design and manufacturing design. The authors have added a comprehensive set of problems and student assignments to each chapter, making the new edition substantially more useful.
See what's in the Third Edition: Updated case studies on the application of DFMA techniques Extended versions of the classification schemes of the features of products that influence the difficulty of handling and insertion for manual, high-speed automatic, and robot assembly Discussions of changes in the industry such as increased emphasis on the use of surface mount devices New data on basic manufacturing processes Coverage of powder injection molding Recognized as international experts on the re-engineering of electro-mechanical products, the methods and guidelines developed by Boothroyd, Dewhurst, and Knight have been documented to provide significant savings in the product development process.
Often attributed with creating a revolution in product design, the authors have been working in product design manufacture and assembly for more than 25 years. A review of published case histories emphasizes the enormous advantages to be gained by adopting this relatively new approach as the major tool in concurrent and simultaneous engineering. Finally, a discussion of the various roadblocks affecting DFMA implementation is followed by a discussion of current developments, which include product design for disassembly, service and recycling.
Those who complacently say that the USA is changing to a service economy may eventually find that they no longer have the means to download these services. Competitiveness has been lost in many areas, most notably, as can be seen in Figure 1, in automobile manufacture. The study attempted to explain the wide variations in automobile assembly-plant productivity throughout the world.
However, it was found that automation could only account for one-third of the total difference in productivity between plants, and that, at any level of automation, the difference between the most and least efficient plants is enormous. The question is that of whether manufacturability and ease of assembly are more important than automation in improving productivity.
The authors of the study conclude that no improvements in operation can make a plant fully competitive if the product design is defective. However, they fail to make a direct connection between product design and productivity, and an attempt is made in this paper to show that there is now overwhelming evidence to support the view that product design for manufacture and assembly can be the key to high productivity in all manufacturing industries.
US- and Japanese-owned plants in Europe, 1 t: European-owned plants in Europe, NIC: Mexico, Brazil, Taiwan and Korea. International Motor Vehicle Program Study. These drawings arc then passed to the manufacturing and assembly engineers.
Frequently, it is at this stage that manufacturing and assembly problems arc encountered and requests are made for design changes. Sometimes, these design changes result in considerable delays in the final product release. As an example, the Ingersoll Rand Company reported: In addition. Development started in June , and the new design went into full production in February Traditionally, the attitude of designers has been "we design it, you build it'.
Product Design for Manufacture and Assembly
One means of overcoming this problem is to consult the mam, facturing engineers at the design stage. The resulting teamwork avoids many of the problems that arise. G Boothroyd attached to screw drive part must be examined as it is added to the product during assembly: The motor must be fully enclosed for aesthetic reasons, and have a removable cover for access so that the position sensor can be adjusted.
The principal requirements are a rigid base that is designed to slide up and down the guiderails, and that supports the m o t o r and sensor. The motor and sensor have wires that connect them to a power supply and a control unit, respectively. A proposed solution is shown in Figure 6. The base is provided with two bushes to provide suitable friction and wear characteristics. The motor is secured to the base with two motor screws, and a hole in the base accepts the cylindrical sensor, which is held in place with a set screw.
To provide the required covers, an end plate is secured by two end-plate screws to two standoffs, which are, in turn, screwed into the base. This end plate is fitted with a plastic bush through which the connecting wires pass. Finally, a box-shaped cover slides over the whole assembly from below the base, and is held in place by four cover screws, two passing into the base, and two into the end cover. Two subassemblies are required, the motor and the sensor, and, in this initial design, there are eight additional main parts, and nine screws, making a total of 19 items to be assembled.
When D F M A began to be taken seriously in the early s, and the consequent benefits were appreciated, it became apparent that the greatest improvements arose from simplification of the product by reduction of the number of separate parts.
To give guidance to the designer in reducing the part court, the D F M A methodology 3 provides three criteria against which each During the operation of the product, does the part move relative to all the other parts already assembled?
Only gross motion should be considered; small motions that can be accommodated by integral elastic elements, for example, are not sufficient for a positive answer. Must the part be of a material that is different from those of all the other parts already assembled, or must it be isolated from these?
Only fundamental reasons relating to materials properties are acceptable.
Must the part be separate from all the other parts already assembled because necessary assembly or disassembly of other separate parts would otherwise be impossible? The two bushes do not satisfy the criteria, and can theoretically be integral with the base.
The motor is a standard subassembly of parts which is a downloadd item. Thus, the criteria cannot be applied unless the assembly of the motor itself is considered as part of the analysis. In this example, we assume that the motor and sensor are not to be analysed. Invariably, separate fasteners such as the two motor screws do not meet the criteria, because an integral fastening arrangement is always theoretically possible. The sensor is a downloadd item. The set screw is theoretically not necessary.
The two standoffs do not meet the criteria; they could be incorporated into the base. The end plate must be separate for reasons of assembly. The two end-plate screws are theoretically not necessary. The plastic bush can be of the same material as, and therefore combined with, the end plate. The cover can also be combined with the end plate.
Finally, the four cover screws are theoretically not necesary. From this analysis, it can be seen that, if the m o t o r and sensor subassemblies can be arranged to snap or screw into the base, and a plastic cover can be designed to snap on, only four separate items will be needed, instead of These four items represent the theoretical minimum number needed to satisfy the constraints of the product design without consideration of the practical limitations.
It is now necessary for the designer or design team to justify the existence of those parts that have not satisfied the criteria. Justification may arise from practical, technical or economic considerations. In this example, it can be argued that two m o t o r screws are needed to secure the motor, and one set screw is needed to hold the sensor, because any alternatives would be impractical for a low-volume product such as this. It can be argued that the two powder metal bushes are unnecessary, because the base could be machined Computer-Aided Design Volume 26 Number 7 July Product design for manufacture and assembly: G Boothroyd a v o i d s the need for a reorientation.
Finally, Table 3 c o m p a r e s the cost of the p a r t s for the two designs. Finally, it is very difficult to justify the s e p a r a t e standoffs, end plate, cover, plastic bush a n d a s s o c i a t e d six screws. Now, before an alternative design can be considered, it is necessary to have estimates of the a s s e m b l y times and costs, so that a n y possible savings can be t a k e n into account when considering design alternatives.
The theoretical m i n i m u m n u m b e r of parts is four, as e x p l a i n e d above, and, if these parts were easy to assemble, they w o u l d t a k e 3 s each to assemble on average.
Here, the bushes are c o m b i n e d with the base, a n d the standoffs, end plate, cover, plastic bush a n d six associated screws are replaced by one s n a p - o n plastic cover. The new cover takes only 4 s to assemble, a n d it Figure 7 Redesign of motor-drive assembly following design-forassembly analysis Table 1 Results of DFA analysis for initial design of motor-drive assembly Item Number Theoretical part count Assembly time, s Assembly cost, US cents 1 2 1 2 1! downloadd motor and sensor subassemblies not included.
Figure 8 Typical steps taken in simultaneous engineering study using DFMA It can be noted that the redesign suggestions arose through the application of the minimum part-count criteria during the design-for-assembly analysis; the final cost comparison was made after assembly-cost and parts-cost estimates were considered.
Figure 8 summarizes the steps taken when using DFMA during design. The design-for-assembly DFA analysis is conducted first, leading to a simplification of the product structure.
Product Design for Manufacture and Assembly, Third Edition
Then, early cost estimates for the parts are obtained for both the original design and the new design in order to make tradeoff decisions. During this process, the best materials and processes to be used for the various parts are considered.
For example, would it be better to manufacture the cover in the new design from sheet metal? Once the materials and processes have been finally selected, a more thorough analysis for design for manufacture DFM can be carried out for the detail design of the parts. In this, manufacturing data was accumulated into one large reference volume, with the idea that designers would have, at their fingertips, the manufacturing knowledge necessary for efficient design.
However, the emphasis was on the design of individual parts for 'producibility', and little attention was given to the assembly process. This approach led, for example, to the curious recommendation shown in Figure 9: In fact, when one considers the means whereby the separate simple parts in Figure 9 might be secured, one can see that the total cost of this recommended design would be far greater than that of the single part.
It has now become clear that the objective should be to simplify the product structure to reduce assembly cost and reduce the total parts cost.
In fact, design for assembly DFA should always be the first consideration. Perhaps one of Significant benefits derived from the use of DFA were not realized until systematic-analysis tools became available around The reason was that design guidelines, even if they provide sound recommendations, do not help the designer any more than by saying 'try to Computer-Aided Design Volume 26 Number 7 July Product design for manufacture and assembly: G Boothroyd design so that the product is easy to assemble'.
Examples of changes made to simplify assembly in other products never seem to apply to the product under consideration, and, in order to cover a reasonable proportion of possible design changes, the design-guideline handbook would be huge, leaving the designer to thumb through numerous examples with little chance of success in the end.
Interestingly, most of the first efforts to develop systematic procedures for assembly analysis concentrated on product design for ease of automatic assembly. This emphasis arose from the fact that, when a company desired to automate the assembly of a product, it was forced to reconsider its design.
There are many examples of products for which automatic assembly is simply not feasible without redesign, but none where manual assembly is not feasible. Also, when redesign for automatic assembly was undertaken, it was frequently found that the resulting product was so easy to assemble manually that automatic assembly could no longer be justified.
It is now the application of design for manual assembly that is resulting in staggering cost savings in many products, because of the resulting simplification of the product and the reductions in total manufacturing and assembly costs.
As with the method just described, the idea behind most systematic DFA methods is to consider each part in turn as it is inserted into the product, gauge the difficulty of the assembly process, and then sum the results to obtain a numerical rating of assembly difficulty.
Ideally, different individuals analysing the same product will obtain similar ratings, thus providing the means for independent evaluation of a design. Examples of the symbols and penalty scores 8 are given in Figure 10, and examples of their application are given in Figure By , more than engineers at Hitachi had been trained to use this method, and it was claimed that the method was saving tens of millions of dollars annually.
In the process of developing this system, the product design was considered carefully using the Assembly Evaluation Method developed at Hitachi. This method is based on the principle of 'one motion for one part'. For more complicated motions, a point-loss standard is used, and the assemblability of the whole product is evaluated by subtracting points lost.
The AEM method, described in by Miyakawa and Ohashi 5, uses two indices at the earliest possible stage of design, namely the assembly-evaluation score E, which is used to assess the design quality or the difficulty of assembly, and the assembly-cost ratio K, which is used to project assembly costs relative to current assembly costs.
The method does not distinguish between manual, robot or automatic assembly, because, Myakawa and Ohashi believe, there is a strong correlation between the degrees of assembly difficulty using these three methods. In the AEM, approximately 20 symbols represent the various assembly operations. These handbooks included analysis methods and databases for both manual and high-speed automatic assembly.
For each process, the handling of the parts and their insertion were considered separately. The original procedure for design for automatic assembly was the result of collaboration between the author of this paper and A H Redford and K G Swift in Salford.
In , a new handbook, based on the lessons learned in implementing DFA in industry, was introduced, and, since then, design for robot assembly and PCB assembly have been added 3. Product design for manufacture and assembly: Thus, both assembly difficulty and functional value are evaluated, and a combined rating is given. This means that parts which have little functional value such as separate fasteners and that are difficult to assemble are given the lowest ratings.
These ratings are then used as guides to redesign see Figure In the Lucas method, the three steps are as follows: The authors emphasize assembly-cost reduction and parts-count reduction, and include the use of the Boothroyd Dewhurst minimum-parts criteria in a 'truth' table to assist in part-count reduction.
A handling and feeding analysis is carried out in which the parts are scored on the basis of three areas: A target of 2.We did a search for other eBooks with a similar title, however there were no matches.
Design for X
Here, the bushes are c o m b i n e d with the base, a n d the standoffs, end plate, cover, plastic bush a n d six associated screws are replaced by one s n a p - o n plastic cover. Yiming Kevin Rong. Learn more about site Prime. In each case, a considerable reduction in part count has been achieved, resulting in a simpler product.
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