Design for assembly (DFA) is a process by which products are designed with ease of assembly in mind. If a product contains fewer parts it will take less time to assemble, thereby reducing assembly costs. In addition, if the parts are provided with features which make it easier to grasp, move, orient and insert them, this will also reduce assembly time and assembly costs. The reduction of the number of parts in an assembly has the added benefit of generally reducing the total cost of parts in the assembly. This is usually where the major cost benefits of the application of design for assembly occur.
Design for assembly can take different forms. In the 1960s and 1970s various rules and recommendations were proposed in order to help designers consider assembly problems during the design process. Many of these rules and recommendations were presented together with practical examples showing how assembly difficulty could be improved. However, it was not until the 1970s that numerical evaluation methods were developed to allow design for assembly studies to be carried out on existing and proposed designs.
The first evaluation method was developed at Hitachi and was called the Assembly Evaluation Method (AEM).[1] 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 ease of assembly of the whole product is evaluated by subtracting points lost. The method was originally developed in order to rate assemblies for ease of automatic assembly.
Starting in 1977, Geoff Boothroyd, supported by an NSF grant at the University of Massachusetts Amherst, developed the Design for Assembly method (DFA), which could be used to estimate the time for manual assembly of a product and the cost of assembling the product on an automatic assembly machine.[2] Recognizing that the most important factor in reducing assembly costs was the minimization of the number of separate parts in a product, he introduced three simple criteria which could be used to determine theoretically whether any of the parts in the product could be eliminated or combined with other parts. These criteria, together with tables relating assembly time to various design factors influencing part grasping, orientation and insertion, could be used to estimate total assembly time and to rate the quality of a product design from an assembly viewpoint. For automatic assembly, tables of factors could be used to estimate the cost of automatic feeding and orienting and automatic insertion of the parts on an assembly machine.
In the 1980s and 1990s, variations of the AEM and DFA methods have been proposed, namely: the GE Hitachi method which is based on the AEM and DFA; the Lucas method, the Westinghouse method and several others which were based on the original DFA method. All methods are now referred to as design for assembly methods.
Implementationedit
Most products are assembled manually and the original DFA method for manual assembly is the most widely used method and has had the greatest industrial impact throughout the world.
The DFA method, like the AEM method, was originally made available in the form of a handbook where the user would enter data on worksheets to obtain a rating for the ease of assembly of a product. Starting in 1981, Geoffrey Boothroyd and Peter Dewhurst developed a computerized version of the DFA method which allowed its implementation in a broad range of companies. For this work they were presented with many awards including the National Medal of Technology. There are many published examples of significant savings obtained through the application of DFA. For example, in 1981, Sidney Liebson, manager of manufacturing engineering for Xerox, estimated that his company would save hundreds of millions of dollars through the application of DFA.[3] In 1988, Ford Motor Company credited the software with overall savings approaching $1 billion.[4] In many companies DFA is a corporate requirement and DFA software is continually being adopted by companies attempting to obtain greater control over their manufacturing costs. There are many key principles in design for assembly.[5][6][7][8][9]
Notable examplesedit
Two notable examples of good design for assembly are the Sony Walkman and the Swatch watch. Both were designed for fully automated assembly. The Walkman line was designed for "vertical assembly", in which parts are inserted in straight-down moves only. The Sony SMART assembly system, used to assemble Walkman-type products, is a robotic system for assembling small devices designed for vertical assembly.[citation needed]
The IBM Proprinter used design for automated assembly (DFAA) rules. These DFAA rules help design a product that can be assembled automatically by robots, but they are useful even with products assembled by manual assembly.[10]
^Miyakawa, S. and Ohashi, T., "The Hitachi Assembly Evaluation Method (AEM)," Proc. International Conference on Product Design for Assembly, Newport, Rhode Island, April 15–17, 1986.
^Boothroyd, G., "Design for Assembly – A Designer's Handbook", Department of Mechanical Engineering, University of Massachusetts, Amherst, Nov. 1980.
^Boothroyd, G., "Design for assembly: The Road to Higher productivity", Assembly Engineering, March, 1982.
^Assembly Automation and Product Design G. Boothroyd, Marcell Dekker, Inc. 1992
^Product Design for Manufacture and Assembly G. Boothroyd and P. Dewhurst, Boothroyd Dewhurst, Inc. 1989 Marcell Dekker, Inc. 1994
^Design and Analysis of Manufacturing Systems Rajan Suri University of Wisconsin 1995
^Product Design for Assembly: The Methodology Applied G. Lewis and H. Connelly
^Simultaneous Engineering Study of Phase II Injector Assembly line Giddings & Lewis 1997
^"IBM Proprinter Case Study". Engineering Systems Research Center. University of California at Berkeley [1] 2010-07-05 at the Wayback Machine[2] 2006-06-21 at the Wayback Machine
Further informationedit
For more information on Design for Assembly and the subject of Design for Manufacture and Assembly see:
Boothroyd, G. "Assembly Automation and Product Design, 2nd Edition", Taylor and Francis, Boca Raton, Florida, 2005.
Boothroyd, G., Dewhurst, P. and Knight, W., "Product Design for Manufacture and Assembly, 2nd Edition", Marcel Dekker, New York, 2002.
External linksedit
"Successful Design for Assembly" - February 26, 2007 article from Assembly Magazine
November 23, 2023
design, assembly, process, which, products, designed, with, ease, assembly, mind, product, contains, fewer, parts, will, take, less, time, assemble, thereby, reducing, assembly, costs, addition, parts, provided, with, features, which, make, easier, grasp, move. Design for assembly DFA is a process by which products are designed with ease of assembly in mind If a product contains fewer parts it will take less time to assemble thereby reducing assembly costs In addition if the parts are provided with features which make it easier to grasp move orient and insert them this will also reduce assembly time and assembly costs The reduction of the number of parts in an assembly has the added benefit of generally reducing the total cost of parts in the assembly This is usually where the major cost benefits of the application of design for assembly occur Contents 1 Approaches 2 Implementation 3 Notable examples 4 See also 5 Notes 6 Further information 7 External linksApproaches editDesign for assembly can take different forms In the 1960s and 1970s various rules and recommendations were proposed in order to help designers consider assembly problems during the design process Many of these rules and recommendations were presented together with practical examples showing how assembly difficulty could be improved However it was not until the 1970s that numerical evaluation methods were developed to allow design for assembly studies to be carried out on existing and proposed designs The first evaluation method was developed at Hitachi and was called the Assembly Evaluation Method AEM 1 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 ease of assembly of the whole product is evaluated by subtracting points lost The method was originally developed in order to rate assemblies for ease of automatic assembly Starting in 1977 Geoff Boothroyd supported by an NSF grant at the University of Massachusetts Amherst developed the Design for Assembly method DFA which could be used to estimate the time for manual assembly of a product and the cost of assembling the product on an automatic assembly machine 2 Recognizing that the most important factor in reducing assembly costs was the minimization of the number of separate parts in a product he introduced three simple criteria which could be used to determine theoretically whether any of the parts in the product could be eliminated or combined with other parts These criteria together with tables relating assembly time to various design factors influencing part grasping orientation and insertion could be used to estimate total assembly time and to rate the quality of a product design from an assembly viewpoint For automatic assembly tables of factors could be used to estimate the cost of automatic feeding and orienting and automatic insertion of the parts on an assembly machine In the 1980s and 1990s variations of the AEM and DFA methods have been proposed namely the GE Hitachi method which is based on the AEM and DFA the Lucas method the Westinghouse method and several others which were based on the original DFA method All methods are now referred to as design for assembly methods Implementation editMost products are assembled manually and the original DFA method for manual assembly is the most widely used method and has had the greatest industrial impact throughout the world The DFA method like the AEM method was originally made available in the form of a handbook where the user would enter data on worksheets to obtain a rating for the ease of assembly of a product Starting in 1981 Geoffrey Boothroyd and Peter Dewhurst developed a computerized version of the DFA method which allowed its implementation in a broad range of companies For this work they were presented with many awards including the National Medal of Technology There are many published examples of significant savings obtained through the application of DFA For example in 1981 Sidney Liebson manager of manufacturing engineering for Xerox estimated that his company would save hundreds of millions of dollars through the application of DFA 3 In 1988 Ford Motor Company credited the software with overall savings approaching 1 billion 4 In many companies DFA is a corporate requirement and DFA software is continually being adopted by companies attempting to obtain greater control over their manufacturing costs There are many key principles in design for assembly 5 6 7 8 9 Notable examples editTwo notable examples of good design for assembly are the Sony Walkman and the Swatch watch Both were designed for fully automated assembly The Walkman line was designed for vertical assembly in which parts are inserted in straight down moves only The Sony SMART assembly system used to assemble Walkman type products is a robotic system for assembling small devices designed for vertical assembly citation needed The IBM Proprinter used design for automated assembly DFAA rules These DFAA rules help design a product that can be assembled automatically by robots but they are useful even with products assembled by manual assembly 10 See also editDesign for inspection Design for manufacturability Design for X Design for verification DFMANotes edit Miyakawa S and Ohashi T The Hitachi Assembly Evaluation Method AEM Proc International Conference on Product Design for Assembly Newport Rhode Island April 15 17 1986 Boothroyd G Design for Assembly A Designer s Handbook Department of Mechanical Engineering University of Massachusetts Amherst Nov 1980 Boothroyd G Design for assembly The Road to Higher productivity Assembly Engineering March 1982 Henchy L W American Manufacturing Fights Back Business Solutions Feb 22 1988 p 10 Assembly Automation and Product Design G Boothroyd Marcell Dekker Inc 1992 Product Design for Manufacture and Assembly G Boothroyd and P Dewhurst Boothroyd Dewhurst Inc 1989 Marcell Dekker Inc 1994 Design and Analysis of Manufacturing Systems Rajan Suri University of Wisconsin 1995 Product Design for Assembly The Methodology Applied G Lewis and H Connelly Simultaneous Engineering Study of Phase II Injector Assembly line Giddings amp Lewis 1997 IBM Proprinter Case Study Engineering Systems Research Center University of California at Berkeley 1 Archived 2010 07 05 at the Wayback Machine 2 Archived 2006 06 21 at the Wayback MachineFurther information editFor more information on Design for Assembly and the subject of Design for Manufacture and Assembly see Boothroyd G Assembly Automation and Product Design 2nd Edition Taylor and Francis Boca Raton Florida 2005 Boothroyd G Dewhurst P and Knight W Product Design for Manufacture and Assembly 2nd Edition Marcel Dekker New York 2002 External links edit Successful Design for Assembly February 26 2007 article from Assembly Magazine Retrieved from https en wikipedia org w index php title Design for assembly amp oldid 1177768544, wikipedia, wiki, book, books, library,
