... He describes a top-down design methodology to systematically translate key characteristics to critical features on parts and choose consistent assembly ... Wang and Ozsoy [24] provided a method for automatically generating tolerance... more
... He describes a top-down design methodology to systematically translate key characteristics to critical features on parts and choose consistent assembly ... Wang and Ozsoy [24] provided a method for automatically generating tolerance chains based on assembly fea ...
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Presents a state transition model of assembly and concepts from control theory to model variation propagation and control during assembly. The assembly process is modeled as a multi-stage linear dynamic system. Two types of assemblies are... more
Presents a state transition model of assembly and concepts from control theory to model variation propagation and control during assembly. The assembly process is modeled as a multi-stage linear dynamic system. Two types of assemblies are addressed: Type-1 where the assembly puts together parts at their pre-fabricated mating features, and Type-2 where the assembly process can incorporate in-process adjustments to redistribute variation. The model builds on the concept of the datum flow chain. Algorithms are developed to determine and control variation in final assembly propagated through the combined effect of individual part variations and choice of assembly methods. An optimal control problem is formulated to develop a scientific approach to designing assembly features
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Complex mechanical products, such as automobiles and airplanes, must satisfy many customer requirements, commonly called Key Characteristics (KCs). Such products have many separate parts, all of which must cooperate to deliver these... more
Complex mechanical products, such as automobiles and airplanes, must satisfy many customer requirements, commonly called Key Characteristics (KCs). Such products have many separate parts, all of which must cooperate to deliver these requirements. In many cases there are more requirements than degrees of freedom available to meet them all independently, requiring prioritization. This problem is called KC conflict. In a highly complex product, such conflicts can be difficult to detect during design. This paper defines this problem and shows how screw theory can be used to detect and potentially correct it.
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Research Interests: Engineering and ROBOT
... want to access the data for non-engineering reasons such as cost analysis, documentation, etc. ... A detailed study of the product development process and supporting IT tools for this system ... context, the DSM greatly enhances the... more
... want to access the data for non-engineering reasons such as cost analysis, documentation, etc. ... A detailed study of the product development process and supporting IT tools for this system ... context, the DSM greatly enhances the value of the existing documented knowledge base ...
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Research Interests: Engineering and Symbiosis
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... Cambridge, MA 02139 ABSTRACT mis presentation combines historical line-age, assessment of the state of the art, and repre-sentative videotapes on robot force control. The ... inertias strategy forcing of a events related geometry to... more
... Cambridge, MA 02139 ABSTRACT mis presentation combines historical line-age, assessment of the state of the art, and repre-sentative videotapes on robot force control. The ... inertias strategy forcing of a events related geometry to task sequence of ector or ...
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One of the most difficult problems which designers of complex mechanical assemblies face routinely is not to be aware of when they are committing mistakes. More and more dependence of designers on CAD systems further aggravates the... more
One of the most difficult problems which designers of complex mechanical assemblies face routinely is not to be aware of when they are committing mistakes. More and more dependence of designers on CAD systems further aggravates the problem of committing the mistake of not giving proper attention to the kinematic structure of the assembly. This article presents design phases for assemblies according to a top-down design process and the generic steps that constitute different design phases. A comprehensive classification of mechanical assemblies follows the outline of the steps of the design process. This classification also defines the characteristics of different types of assemblies and most importantly it identifies the possible mistakes that designers may commit. A separate classification of different procedures for meeting assembly tolerances is also presented. This article will not only talk about the classifications but it will also enlist information about various techniques that can be used to analyze different types of assemblies. Together, these sets of classifications outline a comprehensive design procedure that will help designers of assemblies in making sure that they justify their design decisions. This paper also links the steps in the design process to specific tools developed in previous papers.
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Assembly research comprises the definitive description of how parts interact during assembly (called Part Mating Science), and the collection of part mating processes into systems that assemble products. Products can be assembled by four... more
Assembly research comprises the definitive description of how parts interact during assembly (called Part Mating Science), and the collection of part mating processes into systems that assemble products. Products can be assembled by four techniques: manual labor, special purpose machines, programmable systems (a new type of interest in mid volume production), or hybrids of the above. Programmable systems promise to exhibit some of the adaptability of manual labor plus the repeatibility of special machines, a good combination where parts variation and market uncertainties are present.
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In this paper, we consider the problem of accelerating commercial product development by overlapping adjacent functions. We formulate an approach, called iterative overlapping, in which downstream development activities start with... more
In this paper, we consider the problem of accelerating commercial product development by overlapping adjacent functions. We formulate an approach, called iterative overlapping, in which downstream development activities start with preliminary design information and incorporate upstream design changes in subsequent iterations. In the absence of careful control, iterative overlapping could cause excessive downstream rework and result in an increase in development time. We develop models of iterations and design change to help decide when upstream design information should be committed for downstream iterations. When applied to an automobile door panel development process at a US automaker, the models suggest improvements that would reduce development time by 27%.
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... and R represents terms we omit from the true solution. Then, defining the propagated integration error as E, = x(t,) - xk = true value -.computed value, we have from [4] a difference equation for ck : E,+, = eAhgk + Rx, ... DANIEL E.... more
... and R represents terms we omit from the true solution. Then, defining the propagated integration error as E, = x(t,) - xk = true value -.computed value, we have from [4] a difference equation for ck : E,+, = eAhgk + Rx, ... DANIEL E. WHITNEY Dept. of Mech. Engrg. Mass. Inst. Tech. ...
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Abstract Manufacturing is one of the most complex things that people do collectively. Consideration of advanced or automated manufacturing systems means not merely mechanizing today's processes and methods. It really means addressing... more
Abstract Manufacturing is one of the most complex things that people do collectively. Consideration of advanced or automated manufacturing systems means not merely mechanizing today's processes and methods. It really means addressing the entire functional way that manufacturing is carried out and addressing it with new methods and new kinds of systems. This paper will outline some of the issues and techniques associated with four manufacturing areas. The areas chosen to illustrate these issues are a) materials, b) process control, c) inspection, and d) assembly
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This paper describes a method for finishing cast iron stamping dies. The task is to remove tool marks in the form of grooves and cusps left by a ball-end milling tool. The bottoms of the grooves represent the desired final surface... more
This paper describes a method for finishing cast iron stamping dies. The task is to remove tool marks in the form of grooves and cusps left by a ball-end milling tool. The bottoms of the grooves represent the desired final surface profile. The method consists of using a closed-loop force-controlled robot with a flexible grinding disk coupled to a means for measuring the height of the partially ground cusps. Measurement is particularly easy, accurate, and sensitive if the tops of the partially ground cusps are flat, a condition that is not easy to obtain; otherwise accurate measurement is a chore. The Taguchi method is used to determine process parameters (grinding grit size, feed speed, disk speed, disk inclination angle, etc.) that yield flat tops. This grinding strategy has proven successful. A smooth, regular, and accurate final shape is obtained in spite of the relatively poor position accuracy of the robot. The measurement strategy has not been implemented yet but it appears feasible based on preliminary experiments.
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A static and dynamic analysis is carried out for spherical hydrostatic bearings under conditions of incompressible flow. The usual static theory is shown to need the addition of quadratic loss effects in order to agree with experiments.... more
A static and dynamic analysis is carried out for spherical hydrostatic bearings under conditions of incompressible flow. The usual static theory is shown to need the addition of quadratic loss effects in order to agree with experiments. Computer models of static and dynamic behavior agree well with experimental data. Procedures for estimating stiffness and damping are presented taking the extra quadratic losses into account. Comparison with circular recess bearings shows that spherical bearings appear capable of higher damping ratio for the same size bearing.
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The unique strength of this book lies in the fact that Whitney grounds the topic of assemblies and assembly operations in the context of product design, beginning with a discussion of functional requirements and design constraints. He... more
The unique strength of this book lies in the fact that Whitney grounds the topic of assemblies and assembly operations in the context of product design, beginning with a discussion of functional requirements and design constraints. He then carries the concepts through the entire ...
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Hierarchy is a generic structure in which levels are asymmetrically ordered. In an industry setting, classic supply chains display strict hierarchy, whereas clusters of firms have linkages going in many different directions. Previous... more
Hierarchy is a generic structure in which levels are asymmetrically ordered. In an industry setting, classic supply chains display strict hierarchy, whereas clusters of firms have linkages going in many different directions. Previous theory has often assumed the existence of the hierarchical relationships among firms and empirical work has focused on a single level of an industry or bilateral relationships. However, quantitative evidence on the deep hierarchy in large industrial sectors is lacking. In this paper, we develop metrics and methods to define and measure the degree of hierarchy in transactional relationships among firms, and apply the methods to two large industrial sectors in Japan: automotive and electronics. We compiled the networks of firms connected by transactional relationships. Our empirical analysis shows that the automotive sector exhibits a higher degree of hierarchy than the electronics sector. We further analyze the differences in hierarchy using a simulation model based on transaction breadth and transaction specificity. The empirical measurement and model analysis together indicate that it is the low transaction specificity that drives down the degree of hierarchy in the electronics sector. Differences in transaction patterns in turn may result from the differences in the power level of underlying technologies, which affect product specificity and asset specificity. Thus, the degree of hierarchy in an industry sector may be traced back to fundamental properties of the underlying technologies
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Research Interests: Business, Computer Science, Decomposition, Engineering Design, Local Development, and 12 moreNew Product Development, Social Science Research Network, Design process, Asynchronous Communication, Information Exchange, Information Hiding, Product Development, Oscillations, Schedule, System performance, dynamic model, and Model Design
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ABSTRACT
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A math programming model is formulated for selecting assembly stations and assigning operations to these stations so as to satisfy a production volume requirement at minimum system cost. A branch-and-bound algorithm, coupled with a... more
A math programming model is formulated for selecting assembly stations and assigning operations to these stations so as to satisfy a production volume requirement at minimum system cost. A branch-and-bound algorithm, coupled with a subgradient optimization procedure, is proposed. The model and algorithm are demonstrated by example on a system design problem for assembling automobile alternators. The model is applicable
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A stati space approach is taken to vehicle merging on high speed highways. The vehicles ate assumed to be traveling in equal sized "slots" which move at the group velocity. At points where two or more lanes merge, some vehicles must be... more
A stati space approach is taken to vehicle merging on high speed highways. The vehicles ate assumed to be traveling in equal sized "slots" which move at the group velocity. At points where two or more lanes merge, some vehicles must be moved forward or backward to other slots to accomplish the merge. The state of a group of vehicles to be merged is defined in terms of the slots occupied at any time. A finite set of admissible terminal stales, representing possible merged configurations, is easily determined. The sequence of moves required to obtain a merge is found as a shortest path in the space of all states, running from the initial state to the terminal manifold. Various costs may be applied to moves in this space, such as time consumed, or number of vehicles being moved simultaneously. Costs may also be assigned to the terminal arrangements, reflecting, for example, the size of platoons in the resulting merge. Estimates are made of required computing load and the method is compared with other approaches.