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stage. Feature-based design essentially involves the feedback to the user which can be on the validity of the designs, design for manufacturability (DFM), and other related factors. Iterative loops between FBDS and the user until the user reaches a satisfactory design are crucial here. It can be considered as a predesign method. Many researchers frequently use the term “feature-based design” to describe post-design modeling methods. (In this chapter, feature-based design denotes the conceptual designing of the part in terms of features). In fact, the characteristic of the feature-based design systems that distinguishes it from other systems is the origin of the model. Other approaches (FRES and FBMS) start with an existing design (a drawing or CAD data) to build the model, whereas this approach solely depends on the imagination and ability of the designer to use the features for designing the part. Hence, FBDS must provide the designer with the tools necessary to carry out the design analysis. These can also be developed using dedicated systems or general purpose CAD systems. This offers the total solution because the part modeling and the design representation match with each other (both are in terms of features) and there will be no special need to carry out part modeling. The design representation can serve the purpose of supplying the required data to the CAPP function. Representation of Technological Details The information pertaining to tolerances and surface finish can be referred to as technological data. Technological data have considerable influence on the determination of machining sequence, manufacturing procedures, machine selection, and chucking positions (Halevi and Weill, 1985; Weill, 1988). To enable the CAPP system to make realistic decisions, it is necessary to include the technological details in the part model. Although representation of technological details is as important as geometrical details, it does not seem that this aspect has enjoyed much interest in the initial stages of CAPP system development. The reason for this may be attributed to the adhoc modeling methods followed when CAD systems are not widely used. In the later stages, CAD systems are used for part modeling. Because of the limitations of CAD systems, FBS has become popular in recent years. In parallel to these developments, issues concerning the representation of technological details in CAD and FBS are addressed by many researchers. Subsequent discussion gives a brief chronological presentation of the work done in this area. In the early stages, a data base management system (DBMS) for storing technological and material information along with information obtained from the geometric modeler was proposed by Iwata and Arai (1983). Representing dimensioning and tolerancing in solid models was studied by Requicha (1983). He proposes a tolerancing theory based on the “variational class” concept. This theory treats tolerances as properties or attributes of an object’s features (surfaces and edges), the variational information is represented by a graph, called Vgraph. Requicha and Chan (1986) also designed a variational graph (Vgraph) to implement this theory in a CSG-based system. As an independent graph, Vgraph stores all the variational information about an object and is attached to a CSG tree through a set of nominal faces (which are indexed through a suitable method) of the object. A number of other schemes have also been developed by other researchers such as Kimura et al. (1986), Suzuki et al. (1988), Ranyak and Fridshal (1988), and Gossard et al. (1988). Faux (1988) classified surface features (of ANSI standard) into resolved primitives (size and form can be separately defined from position and orientation) and unresolved primitives. These primitives are then used for the attachment of geometric tolerances to explicit data, called datum reference frame (DRF). In a recent work, Jasthi et al. (1994) developed a part modeling scheme for rotational parts in which the technological details are divided into two categories: (a) intra-feature data and (b) inter-feature data. In their scheme, feature-specific details are termed intra-feature data (e.g., diametric tolerance, surface finish, circularity, cylindicity, etc.) while inter-feature data denote those tolerances controling a feature
in relation to another feature (e.g., runout, concentricity). This scheme is implemented in developing Turbo-Model, a feature-based part modeling system for rotational parts. Based on the critical study of the published literature in the implementations in several systems, the following conclusions can be drawn: 1. In many representation schemes, the dimensions and tolerances are interpreted as constraints between features. These constraints are also called relationships, links, variations, or lists. It seems that different terms are employed by several researchers to describe the same concept. 2. Tolerance representation schemes are, to a large extent, related to the representation schemes (CSG, B-Rep, Wire frame or hybrid) employed in CAD systems and feature-based systems. 3. The latest works suggest that there is a need to address the issue of representing technological information with reference to the form features in the wake of feature-based systems. 4. To represent dimensions and tolerances, primitive (low-level) features are to be maintained along with the high-level form features. This requirement has led to growing interest in hybrid systems (which can provide multiple abstractions). 5. The primitive features ( cone, cylinder, block, etc. in CSG models; point, line, arc in wire frame models; surfaces in B-rep models) are to be managed throughout the part modeling. The study of the relationship between the form-features and primitive features is a prerequisite to designing the data structures for part representation. 6. Proper indexing (linking or referencing) methods are to be established to access the geometrical entities (or features) of the model for attributing dimensions and tolerances. 7. The features classification in these modeling schemes is influenced not only by the application domain (like design analysis, CAPP, assembly planning, interference checking, etc.) but also by the modeling issues of GD&T. Representation of Global (or General) Details Along with the geometrical and technological data, the part specification also includes certain attributes such as work material, quantity to be produced, etc. These details affect planning decisions such as the process selection and cutting parameter (speed, feed, depth of cut) selection and need to be represented in the part model. Other details, such as the design number, part name, planner’s name, etc. (which normally appear on the drawing and the process plan) can also be included in the part model. This type of data is purely non-geometrical. It can also be seen that the number and variety of geometrical and technological attributes vary from part to part. Hence, complete control should be given to the user in defining these details in a part modeling system. However, in the case of general attributes, there exists a fixed set of details for all parts in a given manufacturing system. Due to this, these details can be easily modeled through predetermined system-user interaction and can be made available to the subsequent CAPP system. Part Modeling for CAPP: A Unified Framework Various part modeling schemes followed in CAPP have been studied in earlier sections and general trends in modeling different types of part details have already been projected. It should be noted, however, that in spite of the numerous part modeling systems reported in literature, a uniform methodology for part modeling is not well established. This is understandable because the selection of a particular modeling scheme and the subsequent system development depends on several factors such as the scope of the CAPP system, part range (rotational, prismatic, etc.), geometrical complexity of the part, the technological details applicable, economics of system development, etc. Each of these factors affects the choice of modeling method in some way. For ex<strong>amp</strong>le, geometrical complexity dictates the feature definition (surface or volume) and representation scheme (wire frame or solid model) while the economics of system development dictates the choice of software (CAD system or programming language) and hardware (PC or workstation) platforms.
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COMPUTER-AIDED DESIGN, ENGINEERING,
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Library of Congress Cataloging-in-P
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Editor Cornelius T. Leondes, B.S.,
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Chapter 1 Chapter 2 Chapter 3 Chapt
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the implementation of the IPD syste
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In our IPD system implementations,
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2. Specification of analysis-specif
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FIGURE 1.2 base or the design insta
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FIGURE 1.4 System architecture of t
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of a beam is considered for FEA. Th
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FIGURE 1.7 through the control expe
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2. machining facility (e.g., gang m
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from the FBDS. The user also specif
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Depending on the type of feature to
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TABLE 1.6 Tolerance synthesis is de
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FIGURE 1.12 Display of the NC tool
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component geometric entities and va
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FIGURE 1.14 The system architecture
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TABLE 1.10 User Input for the Toler
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TABLE 1.11 Tolerance Specifications
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7. Z. Young and I. R. Groose. A rul
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FIGURE 2.1 Tool paths generated for
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FIGURE 2.2 sented by instances of f
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TABLE 2.1 A CAD-Generated Hole Conf
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FIGURE 2.6 mounted on the rotary ta
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FIGURE 2.8 fixture for the machinin
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FIGURE 2.10 or best-fit, or the cur
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FIGURE 2.11 Linear approximation of
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FIGURE 2.13 Circular approximation
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FIGURE 2.14(b) Circular approximati
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FIGURE 2.16 Types of biarcs. FIGURE
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FIGURE 2.18 Approximation of scanne
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FIGURE 2.20 A touch trigger probe c
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TABLE 2.4 Substitute Elements in CM
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FIGURE 2.21 CMM planning requiremen
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Product Model Representation for Co
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© 2001 by CRC Press LLC TABLE 2.5
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TABLE 2.7 Partial Listing of Dimens
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24. Makinouchi, S., Okamoto, M., an
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Bijan Shirinzadeh Monash University
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FIGURE 3.1 Trends in flexible manuf
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FIGURE 3.3 and constrain different
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Other Fixturing Techniques There ar
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FIGURE 3.6 contact point. The geome
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FIGURE 3.8 The vertical support fix
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and moments about the contact point
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een identified, the normals are use
Page 95 and 96: one of choosing the variables: such
Page 97 and 98: Fixture Module Location An importan
Page 99 and 100: FIGURE 3.15 Illustration of functio
Page 101 and 102: FIGURE 3.18 Minimum separation test
Page 103 and 104: direction) the face, respectively.
Page 105 and 106: FIGURE 3.21 Software structure for
Page 107 and 108: 3.8 Conclusion A reconfigurable fix
Page 109 and 110: Heui Jae Pahk Seoul National Univer
Page 111 and 112: FIGURE 4.1(b) Conceptual framework
Page 113 and 114: 4.3 Measurement Points Sampling and
Page 115 and 116: Surface S2 Measurement Path FIGURE
Page 117 and 118: FIGURE 4.4 Rough phase alignment ba
Page 119 and 120: deviation between the nominal CAD d
Page 121 and 122: FIGURE 4.6(a) Sum of squares distan
Page 123 and 124: FIGURE 4.7(c) Trailing edge. (c) th
Page 125 and 126: FIGURE 4.8(a) Profile tolerance of
Page 127 and 128: The calculated minimum form error i
Page 129 and 130: FIGURE 4.11(a) A typical mold havin
Page 131 and 132: FIGURE 4.11(d) Inspection results f
Page 133 and 134: FIGURE 4.12(c) Maximum deviation (p
Page 135 and 136: 5.1 Introduction Developments in th
Page 137 and 138: process plan for a part (Figure 5.3
Page 139 and 140: FIGURE 5.5 leading to the developme
Page 141 and 142: the previously stored process plan
Page 143 and 144: FIGURE 5.7 Techniques of defining a
Page 145: Feature Recognition and Extraction
Page 149 and 150: FIGURE 5.9 Framework for building a
Page 151 and 152: FIGURE 5.10 Process plan content.
Page 153 and 154: FIGURE 5.12 Schematic sketch of the
Page 155 and 156: Several techniques of defining a fe
Page 157 and 158: TABLE 5.1 Data Structure for Repres
Page 159 and 160: FIGURE 5.16 Classification of the t
Page 161 and 162: system to ensure that the part bein
Page 163 and 164: FIGURE 5.19 Graphical model of the
Page 165 and 166: TABLE 5.4 Data Structure for Repres
Page 167 and 168: FIGURE 5.20 Mapping between machini
Page 169 and 170: algorithms. (Some details of the pr
Page 171 and 172: FIGURE 5.24 An example rotational p
Page 173 and 174: FIGURE 5.26 Down_face-turn-up_face
Page 175 and 176: FIGURE 5.27 Procedure for machine t
Page 177 and 178: FIGURE 5.28 Determining the number
Page 179 and 180: DL is needed to be set only if the
Page 181 and 182: FIGURE 5.31 Operation sequencing co
Page 183 and 184: Cutting Tool Selection Selection of
Page 185 and 186: 1. A tool is searched for in the da
Page 187 and 188: FIGURE 5.32 Inputs to optimization
Page 189 and 190: When these values are substituted,
Page 191 and 192: Usually, maximum and minimum speed
Page 193 and 194: FIGURE 5.33 Solution methodology.
Page 195 and 196: TABLE 5.6 Process Plan Internal Rep
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In a strict theoretical perspective
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18. Domazet, D. S. and Lu, S. C. Y,
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63. Prasad, A. V. S. R. K., Rao, P.
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CAD systems. The sample consists of
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learn to master the new system. An
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Although researchers appear to agre
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Link and Zmud28 found that organic
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Informal Training Informal CAD trai
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informal training programs, felt th
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6. C. A. Beatty, Tall Tales and Rea
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A.Y.C. Nee National University of S
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FIGURE 7.1 Planning, design, and ma
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A metal stamping can have the follo
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FIGURE 7.3 Strips used to notch out
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A Skeletal Approach for the Recogni
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These findings can be used to devel
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Semi-Direct Piloting In cases where
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a larger value, the die operations
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FIGURE 7.9 Symbolic relationship be
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FIGURE 7.11 The shape of the envelo
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TABLE 7.1 Schema for the Generation
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strong reasons to support a move to
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FIGURE 7.16 3-D CAD model of a part
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References Cheok, B.T. et al. (1994
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include the once forbidden generati
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A temporal matrix (T-Matrix) is pro
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FIGURE 8.1 A basic process. (From R
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FIGURE 8.4(a) Generate a new IG usi
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Note if the pair of nodes are both
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TABLE 8.1 Summary of the Rules Cond
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The correctness of these rules is e
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needs to show that after each full
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ule is violated, a warning should b
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Π1 Π3 Π4 FIGURE 8.8(a) After add
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
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A ik � ‘U’ and is in a cycle
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FIGURE 8.12(a) Add [p2 t7 p7 t8 p4]
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FIGURE 8.12(c) Add a token to p8 vi
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FIGURE 8.12(e) Add [p8 t9 p14 t10 p
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FIGURE 8.13 An example of rule TT.0
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FIGURE 8.14 A GPN model of a machin
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FIGURE 8.15(b) The first exclusive
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FIGURE 8.15(d) The last exclusive T
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FIGURE 8.15(f) After entering the a
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FIGURE 8.15(h) Completion of Compon
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FIGURE 8.15(j) Two PP-generations:
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FIGURE 8.15(l) The last exclusive T
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t1 t5 p1 p5 t6 (a) t2 t3 t4 2 2 p2
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FIGURE 8.17 An example of partial f
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Theorem 10: If pi → pk in a synth
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Note that control transitions are o
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t j than the lower at , it indicate
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• Programming logic and VLSI arra
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7. Chao, D. Y. and D. T. Wang, Appl
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53. Villaroel, J. L., J. Martinez,
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q u : the numerator of the least ra
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geometric modeling, engineering ana
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In dimension driven or parametric d
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FIGURE 9.3 configuration of bodies
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FIGURE 9.6 FIGURE 9.7 Geometric Int
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FIGURE 9.8 Intersection of degrees
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will introduce a way to propagate p
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Completeness of Dimensions Complete
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FIGURE 9.12 3-D constraints. © 200
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The distance constraint from pt �
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therefore: Now merge the lists and
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Quantity analysis methods have the
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y a revolute joint. By selecting al
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