A System for Automated Fixture Planning with Modular Fixtures

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1.3. Effect of Fixture Plans on Cost Effective Setup Planning 4 previous researdl relared to setup plaooing typicaUy has consfdered feam geomeq without fully considering cutting plans or fixmre pians Mayes 911 Wau 87l. This mearch either considers C&g sequence in a swlp or assumes thata fixture plan exism for each seutp. As a nsalt setup plans and heir sequence may not be validifacuttingplao or a fixaae plan does not exis1 for a setup. Assembly of the fixture typidy takes a much longer time compared wih the time spent for other processes. Tie spent for the assembly ofa fixMe plan ranges from several minutes for a simple setup m several hours for a complex setup WoIofFman 87. Thus, the reduction of fixm assembly time is often critical in increasing the producti3ty and m 0primiZing.pancOst The quality of a fixnue. plan can be measlned by the time necessary for awmbly if the partac~uracy is ensured durjngmachinhg. A typical fixture plan consiscr of locams, suppons. and clamps. In general, clamps are the mm time colwming fixme cDmponenti draiag assembly relative m lhe assembly time for suppons and locators. The assembly time of clamps p mptidy inness*l with the. nnmba of clamps in a fyture plan. Tbw itisdcsirable to use the mrmallestnumbaof clamps h a fixture plan can exmadequate. clamping force to bold the pw. Thus, - In metal cutting, many quire mole than one setup due to limimious in eithercutfing tools or tixtures. In gencraL as the number of setups inaeaseS, tbe cost and time to m b l e the fxtures and machine the pw also inaeases, and the put’s accumcy tends m it is desirable to geneme tbe minimum number of serups. ’Ihe numb of semp aod their squmce may be detanined cmly by cMlsidering rhe geuneey aod Orientarioaofrhe feaaacsaad/opthe macbinc roals‘ camhg~ticrwithoutcorrpidering detailalfixnIIe plans Wyes 911. Ifa ffxttueplan cDoldbc gcncrad farah serup, saup plana and rheir sequence would be successfully nsed fa acaral machining process. Howew. when a Eume plan is wt available for a semp due m Limited fixturing capgbiliries or other reasom tbe setup should be divided mu, muitiple Sub-setups. Funrre plaos with a small number of clamps an o h uncial to achieve the minimum number of setups and redm the OvePBu fixture assanbly he. m various semps. Thc numkof damps io a fixnue plan is determined bycoosidaing cutting forasand a clamp‘s maximum damping force. Howcver, it is not easy to accurately estirmue the clamping force because& magnitudcanddirection Macutting Swce is difficult m measlac. In cader to.- rty: rigidity ia-pm/iimm assslnbly ELning maphining. a mol designer often P-- ‘vc fixture pleas mat require molr: elamps with a largcrclamping 6mce than actually quid. Clamp Locarions are spreadapt tom- the ability to offset maments creared by cuuiog tools from various dhwions. This wcuid not only inexease the. time to assemble clamping componeats, but also w w inaease the danger of pan deflecrion in a thin part due to a largu damping force. Moreover, the hmrt plan may not be. successful due m interference among clamps. This will increase the number of setups andresult in a much long semp time.
5 By &mating the necessary clamping force m m accurately and placing clamps at pmper locations, it is often possible to use smaller number of clamp to hold the part than the number of clamps in a fixture plan generated by a human expen with a conservative es4imation. 1.4. Objective The objective of this thesis is to deveiop a system timl advances tke automation of generaring cost- gectiwfurure plans with momtlarf7xwes for a given metat cutting setup. Future planning will consida the following: Automated .dection of fixture components from a data beae a Autoolated detarmnan ’ ‘on of future componenrs’ locations Automated estimation of the clamping force Automared generation of Iixture plans with aminimum n umb of clamps 15. Domain In a modular fixturing system, various clamping components exist: ovwhead clamps, side clamps, and a movable vise jaw. Overhed clamps apply their damping fime perpendicular to a fixm base plate, and side damps apply meir clamping farce pakl to a fizlnre base plate. A movable vise jaw can be considered as a side clamp since it applies dampmg f m paraUei to a fixtllre base plate. Depcndiog on what clamping components are u& a fixture plan may vary signifkanrly from one to another due to the different constraims The mcwt popular fixme plans in practice are made with either overbeadclamps OT a vise. A v k is d y the mostoost4ktive workholding tool for arectangular parts due m its fast and rigid holding capability, and thus it has bcen widely used in practice. However, tinle memh b been co~~I~~ted w automate the fim plaaning pra%ss with a vise. In this thesis, we cmsider aullrmatkn of fixture plarmmg wih ovahead clamps OT a vise. 1.6. Summary ’This thesis describes a system that automarically generates practical fixture plans with modular fmture components. The system consists of two algcuithms developed to aukmate fixture planning with overhead clamps and a vise, respectively. The system considers the geometry and limitations of each fixture component m the fixture library m order to &ect necessary components and determine their location and the clampjng f m Future compoaents’ dimensions and timitarions are parameterized and stored m a data base. A fmture component’s geomeiry can be dynamically constructed from its parameters and represented mnd the pan when its position and orientath are specified m the part coordinate.
Page 1: A System for Automated Fixture Plan
Page 5: Abstract This thesir desribes a sys
Page 9: Acknowledgements First of all, I wo
Page 12 and 13: 4.7.1. Position and Orientation of
Page 15 and 16: List of Figures Figure 1-1: A modul
Page 17: Figure 6-26: A force model to estim
Page 20 and 21: describes how the pan is held on .t
Page 24 and 25: 6 New and existiog analytical mls a
Page 27 and 28: Chapter 2 Literature review Two maj
Page 29 and 30: 11 Inim 2-2: A fixnae plan by C~OU
Page 31 and 32: 13 Thaoreridy, grasp planning and f
Page 33 and 34: 3.1. Introduction 15 Chapter 3 Nece
Page 35 and 36: Y A A x . X mul max 17 - x P i e 3-
Page 37 and 38: 19 are projected onto the same plan
Page 39 and 40: Z X 21 Wrenches from bodom referenc
Page 41 and 42: For toque: For thrust M Kp]8d1.8A T
Page 43 and 44: 2s The equation (3.5) conservativel
Page 45 and 46: n @ friction force _.. .- normal I
Page 47 and 48: Minimize N1 -p - N
Page 49 and 50: 31 area is 1 square inch. the stres
Page 51 and 52: 4.1. Introduction 33 Chapter 4 A Sy
Page 53 and 54: 35 checking part deflection and sel
Page 55 and 56: 4.4. Assumptions 37 The future plan
Page 57 and 58: 39 A touch probe should be used to
Page 59 and 60: 4.6.2. Cutting plan 41 1 major refe
Page 61 and 62: Cutting force and direction 43 Chap
Page 63 and 64: Clamp bar 45 , .....-, . strap clam
Page 65 and 66: aata base for supports> Type No. R
Page 67 and 68: 49 thickness. If the part is suppor
Page 69 and 70: 51 While the z coordinate of the pa
Page 71 and 72: 5.1. Introduction 53 Chapter 5 Fixt
Page 73 and 74:
55 Because the goal is to generate
Page 75 and 76:
Accessible edge 57 Inaccessible edg
Page 77 and 78:
clamps are oriented so that they am
Page 79 and 80:
61 unacceptable part deflection due
Page 81 and 82:
Enlarged f I ! 63 Y 4 Figure 5-9: E
Page 83 and 84:
clamp location I 65 Pipre 5-11: par
Page 85 and 86:
67 desirable contact area Y Zt X
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69 When every candidate plan genera
Page 89 and 90:
71 5.9.1. Generation of Candidate L
Page 91 and 92:
73 Egure 5-20 shows the actual loca
Page 93 and 94:
5.10. Rating Fixture Plans 75 Typic
Page 95:
n not be possible to install a clam
Page 98 and 99:
L jaw geometry in the local c odite
Page 100 and 101:
m = no. of contact planes for a mov
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84 The following rearming is used m
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86 F i €4 shows obstacles mapped
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88 In our reasoning. each pan face
Page 108 and 109:
i obstacles Figure 6-11: Globally f
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7 obstacles I case 3: If xiax < 92
Page 112 and 113:
6.7. Determining the loeation of vi
Page 114 and 115:
xo Case 1 96 X common contact area
Page 116 and 117:
98 Obr Option 1: adjust the jaw loc
Page 118 and 119:
100 Parallel bars should be placed
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When LCfc Lbor+ 2 d Case 1: When %=
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movable jaw 1W . . . . . . There is
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X m Pigore 6-28 Invalid fume plans
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planner getg cutting plans for a se
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0.150 110 ; IMW Teat Part 2 -- boon
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112 For a clamp libmy, we have cons
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114 *** Plan with clamp type with 5
Page 134 and 135:
116 II II Fipre 7-6: F m plans with
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118 77 1 Y II’ .- Figure 7-7: Fut
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120 I i Figum 7-9 Fuhue plans with
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The system has generated multiple f
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,170 Chamfered hole 124 Chamfer 1 C
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I1 i Figure 7-14: Fixture plans for
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I 0.150 - 2582 - 7.7.1. Speed of Fi
Page 148 and 149:
130 Figure 7-18: F’art geometry o
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134 8.1.1. Fixfure Planning with Ov
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for holding rectangular parts due t
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138 series of fixture plans fm each
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the fixture plan viokea any fixture
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142
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144 Ohwovoride [Ohwovoriole 801 app
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[Ahmad 871 t m 851 [Goldman 561 Ref
Page 164 and 165:
Menassa, R. J. and Devries, W. R. O
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A System for Automated Fixture Planning with Modular Fixtures

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