CURRENT RESEARCH IN PRODUCT DESIGN FOR AUTOMATED ASSEMBLY by Mark Jakiela Graduate Student Report No. UM-MEAM-83-16 Research Funded by International Business Machines Corp. Participating Faculty: P. Papalambros A.G. Ulsoy R.A. Volz T.C. Woo Ann Arbor September 1983

ABSTRACT This paper reviews significant work done to date on product design to promote automated assembly. The paper is divided into three main sections: feeding and orienting components, assembly simplification, and parts mating/modification studies.

TABLE OF CONTENTS INTRODUCTION..................... 1 FEEDING AND ORIENTING.................. 2 SIMPLIFICATION.............. 8 PARTS MATING AND MODIFICATION.............. 13 RESEARCH DIRECTIONS............. 20 SUMMARY....... o. o....... ~ ~ ~ ~ ~ ~. 21 APPENDIX 1.......... ~.. 22 APPENDIX 2................. 23 REFERENCES....... o... ~ ~ ~... 24 ii

INTRODUCT I ON The paper is structured to discuss subtopics of product design for automated assembly rather than the work of specific individuals. The three major subtopics are: 1. Feeding and orienting of components prior to assembly. 2. Assembly simplification (reducing the number of parts). 3. Parts mating and modification studies. A large portion of the paper discusses the work of Geoffrey Boothroyd of the University of Massachusetts at Amherst. This seemingly disproportionate emphasis is justified because Boothroyd's work concerns part design more than the work of other researchers. Boothroyd's studies of the economics of automated assembly, however, are not discussed. Two application examples of Boothroyd's "Design for Assembly" method are given in an appendix. Finally, potential research directions are discussed and an extensive list of references is given. 1

2 FEEDING AND ORIENTING Feeding and orienting are the assembly operations prior to mating the parts and fastening them together. Boothroyd has done much to quantify the feeding and orienting properties of parts. His primary motivation is to optimize part design for feeding and orienting in a vibratory bowl feeder (figure (1)). Vibration caused by an oscillating magne t i c Tract_ Outlet \E \ectr-I —ag//te\ Suspensicn Electrorrhc~t-^lU>^^^ ^^ sprigs upport feet Figure (1): Vibratory bowl feeder[2]. field causes the parts to feed up a helix track on the inner wall of the bowl. On this track are the part orienting mechanisms. The left half of figure (2) shows a passive orienting mechanism. Parts that already are correctly oriented are allowed to pass through for assembly; parts that are improperly oriented are forced off the track back into the bowl. An active orienting mechanism (the rail ahown on the right), on the other hand, forcibly orients all the parts approaching it.

3 wiper blade wiper bcde accepts bocks pressure break lying flat or on side bowl wall bowl wall slotted track rail screws rejected unless lyirg on side sidea~~~~~~~~~ ~rail reorients to delivery screws rejected those blocks chute slot in unless in single lying flat on track track to file end-to-end to delivery orient screws or if delivery chute chute is full Figure (2): Passive (left) and active orienting mechanisms[23. Boothroyd quantifies the "feedability" and "orientability" of a part with a five digit code based on the part size, part geometry, and other part properties. An example of this coding system is given below. This code number is essentially a figure of merit for the feeding and orienting properties of the part. The basic part design principles that lead to a desirable code number are actually quite simple: 1. Avoid parts that tangle and nest with each other. 2. Obtain perfect part symmetry if possible. 3. If perfect symmetry is not possible, exaggerate asymmetry. Parts that tangle and nest will be very difficult to seperate from one another and begin on the feeding track. Parts that are symmetric have identical orientations that increase the probability of a correctly oriented part. A strongly asymmetric part facilitates the design of a suitable orienting mechanism. Figure (3), along with the charts in appendix (1), gives an example of the Boothroyd coding system. The "envelope" of the part is the minimal cylinder or rectangular prism that would

13 Part with Feeding and Orienting Code 22400 (OE=0.37, CR =1.5) ^ ^ 20 (dimensions in mm ) Figure(3): Example of Boothroyd coding systeml[]. enclose the part. Because the envelope for this part is a cylinder with a length/diameter ratio of 1.54, we see from Chart (4) that the first digit is "2". The row and column numbers of chart (5) give respectively the second and third digits. Beta symmetry is defined as some symmetry with respect to the major axis of the envelope and alpha symmetry is defined as some symmetry with respect to an axis perpendicular to the major axis. Because this part has a beta symmetric chamfer the second Boothroyd digit is the appropriate row number "2". Because the part has a beta asymmetric projection in both the side and end surfaces, the third digit is found as the column number "4". The fourth and fifth digits describe non-geometric properties of the part. Using chart (7), because the part is non-flexible the fourth digit is the row number "0", and because the part is nonsticky the fifth digit is the column number "O". Hence, the entire Boothroyd code is "22400". Figure (4) shows an enlargement of the box of chart (5) specified by the second and third digits. Here we see the parameters OE (Orienting efficiency) and FC (partial Feeder Cost) highlighted. These two parameters are used in Boothroyd's economic modeling equations. Although a discussion of these equations is not pertinent to this zacpr, it is obvious that the orienting efficiency should be ic>: -: -d and the Dartial feeder cost should be minimized.

5 Col. 4 0.15 1 Row 2 0.1 1.5 0 137 15 / -T~ OE FC Figure (4): Appropriate box of chart (5)[1]. Figure (5) shows examples of part redesign to imrove the Boothr.oyd code. Unfortunately, this figure is from an earlier Boothroyd publication[2] and these code numbers do not correspond to the charts given in appendix (1). The threaded stud is improved by making it symmetric; the fork gap is widened to prevent tangling; a non-functional hole is added to to the plate to achieve symmetry; and the cone on the pin is made more prominent to to increase orientability. Finally, figure (6) shows examples of non-functional changes to promote feeding and orienting. The upper half of the figure shows how part design changes that prevent tangling increase feedability. The lower half shows how a non-functional change to the geometry of the part can allow easier orienting.

6 Very Difficult to Orient Easy to Orient Code 290 Code 200 Code 904 Code 714 Code 616 Code 600 Code 280 Code 220 Figure (5): Improvements in Boothroyd code[2].

7 Parts will nest Rib in part will stop nesting Straight slot will tangle Crank slot will not tangle Open-ended spring will tangle Closed-ended spring will tangle only under pressure Open spring-lock washer Closed spring-lock washer will tangle will tangle only under pressure Flats on the sides make it Difficult to orient with much easier to orient with respect to small holes respect to the small holes o i r i No feature sufficiently When correctly oriented significant for orientation will hang from rail Triangular shape of Nonfunctional shoulder part makes automatic permits proper orientation hole orientation to be established in a vibratory difficult leeder and maintained in transport rails Figure (6): Nonfunctional changes to promote feeding and orienting[2].

8 SIMPLIFICATION Assembly simplification encompasses two major ideas. First, to reduce the number of parts in the assembly, and second, to optimize the gross motions required to fit the parts together. This gross motion before part insertion is known as "part choreography". Reducing the number of parts is one of the most effective ways to reduce the assembly cost. If the number of parts decreases, the assembly time and therefore the assembly costs also decrease. Reducing the number of parts, however, usually entails making the individual parts more complex. This might require more costly manufacturing operations (e.g. die casting) that nullify any expected savings. Appendix (2) gives an example of an industrial redesign with fewer parts of somewhat increased complexity that still effected a considerable savings. It is interesting to note that most of the parts eliminated were some type of fastener. This hints that the other major problem with reducing the number of parts is decreasing the "repairability" of the assembly. Perhaps in the near future disposable assemblies will become more common if they allow considerable reductions in assembly cost. Screws Slteelt =S^ ~Cover (Steel) Snap on Cover I3 a) o Ad StoodP Ias:~cI So,) ~ sol S'=g, 41e1.tt P#~~~So':0~- -g,$A:ee P'S:o0' v"A" L'- 6p Piston ~Alum.numl Ma-n Block Plasticc (a) ^^?^io~~~ ^^^Ma'r^T>~~~ 6oMaion Llock IF'lastic) Fig 1 Pneumatic piston subassembly Current design (a) has 7 parts. the prroposed design (b) has 4 parts Figure (7): Reducing the number of parts[17].

9 The optimal choreography for most assemblies is to insert every part on the preceding part in a vertically downward direction. This has been called a "pancake structure". Figure (8.) shows an automobile alternator assembled in this manner. There are several reasons why this choreography is favorable. First, gravity is used to secure the parts. This can simplify or eliminate many jigs and fixtures. Also, this choreography facilitates the design of a rotary index table assembly machine. The machine heads are easily designed to be directly above the assembly stations on the rotating table. Figure (9) shows that past practice is evidence of of these reasons. It is seen that direction (1) is the most frequent direction of insertion and that simple peg in hole and screwing insertions are the most common operations in this direction. Figure (10) shows a usual consequence of designing a pancake assembly. A large base part is required to interface with the work carrier and support the rest of the assembly.

10 TOOL' UNLOAD LtST OF TOOLS TOOL. * 17 THREE I 9 1 SMALL THREE-FINGER TOOL TOOL 16 THROUGH a6;]1 BOLTS g 2 SCnEWORIVER 15 BOLTS 3 CONTRACTING COLLET O' 14 REAR 4 ROTOR-NUT TIGHTENER TOOL r' HOUSING 5;. AND 5 LARGE THREE-FINGER TOOL.~ - REAR BEARING G BOLT DRIVER TOOL: (TGHTEN) TOOL t! 13 ROTOR 3 TOOL t' 12 SPACER $..;'.-....:.: -',-~.: ^.... ^i **''.. r *f~w " ^~'.', * *' **.. -: -,... * TRANSFER FRONT SU B TOOL t I | SUBASSEMBLY HOUSING.' SUBASSEMBLY (F' f"~~~~~..r, t...' 5 SPACER, ~'; 3 PULLEY 7 BEARING;; 2 LOCK WASHER <` 6 FRONT.I NUT *3.,s t 1; l4OUS A SCnE i:2 4 FAN SPRING.LOADED I.I HEXAGONAL 3 \J POCKET TOOL FOR NUT TOOL 1 MAIN ASSEMUBLBLY FIXTURE Fic-ure (8):?art -horeography showing pancake structure[5]. 1 NUT ~OUCa> -'::u-e (8)= Pa.~l choreograp~hy s~howing pancske $Lructure[5],

SI:MPLE PEG HOLE I I PUSH AND TWIST_ MULTIPLE PEG HOLE INSERT PEG AND RETAINER E F G I H -' - ~ S --- - -- ------- ----- --- -------- ---- ~~-~ —-^ —- — ^i.^ ---- M~i.^- | _., o ti 11........... *.........' SCREVWS I I FORCE FIT ) | REMOVE LOCATING PIN FLIP PART OVER -— ~r. >.'.,,~'4"X'i<) 1PROVIDE TEMPORARY SUPPORT CRIMP SHEET METAL REMOVE TEMPORARY SUPPORT WELD OR SOLDER 40 30 DIRECTION I ~ ".;.*=[ O1RECT;.O:.N 20'....- Dti' T~O Ih1jI Z3 DIRECTION 2 10t I0-. AB C D E F I J K L A B C DE F I K A C DE F G H I K A-C DE F I J KL AB C E F G H IK L DIRF.C;r.ON D IRECTION 2 DIRECTiON 3 ALL OrtEtR DIRECT'IO.S SUMMARY Figure (9): Evidence of pancake structure[5].

12 A' —- ^ fi~(b) iWork carrier Figure (10): Large base part for pancake structure[2].

13 PARTS kATING AND MODIFICATION Parts mating and modification studies concern how parts contact, fit, and fasten together. The term "mating" refers to the way two parts interface and the term "modification" refers to part redesign to optimize this interfacing. What is called "insertion" is actually made up of two phases: location and insertion. "Location" is the process of aligning the parts within tolerable limits that will allow them to be moved to their final positions. The most common part design feature that promotes location is the ordinary chamfer. Figure (11) shows the simple function of the chamfer. In the upper sketch, insertion is impossible because of the lateral misalignment. In the lower sketch, on the other hand, the same misalignment is tolerable because of the chamfer. The net effect is to make the pins seem smaller during initial insertion, relying on some compliance in the system as the insertion is completed. Looking even more closely at the interface between a peg and hole yields further, more specific, information. Figure (12) presents the definations of "wedging" and "jamming" derived by S. Simunovic of the Charles Stark Draper Laboratory. Both definitions depend upon angular misalignment. "Wedging" is defined as angular misalignment impeding insertion when the ratio L/D is less than the coefficient of friction of the interface. Further force applied anywhere on the end of the peg will only deform the peg or the hole or both. "Jamming" is defined as angular misalignment impeding insertion when the ratio L/D is greater than the coefficient of friction. Further force applied in the proper location will cause the insertion to continue. The upper row of figure (13) shows some important effects related to these definitions. On the left it is seen how a lateral misalignment becomes an angular misalignment: the peg co;n;acts the chamfer of the part and the compliance of the tool:.':_g the peg allcws it to tilt as it slides down the chamfer.

I i.... I; —l --- ---! IX i I I__ Ad E I ~____^-I I I Figure (11): Function of a chamfer.

15 aP- -) az 4 ( Wn n n Figure (12): Wedging and jamming.

16 Vve;nual1y, the opposite side of the peg touches the opposite side of the hole causing two-point contact and possible wedging or jamming. In figure (d) of the top row is shown the resulting insertion "funnel". This can be defined as the locus of allowable angular misalignment as a function of the depth of the start of two-point contact. The center row of figure (13) shows the forces that arise as the insertion takes place. The bottom row shows the compliance required of the gripper and the force it puts on the part (a,b). In (c,d) it is seen that if the force was applied in the proper location it would promote insertion: (c) suggests that a good way of applying the contact force would be to pull the peg into the hole, allowing it to rotate about this lower point as the insertion proceeds. This idea lead to the development, at the Charles Stark Draper Laboratory, of the Remote Center Compliance end effector (RCC) shown in figure (14). The device consists of cascaded independent translational and rotational compliance mechanisms. Lateral error or angular error or combinations of both can be tolerated. The effect is the desired result described above. The peg behaves as if it the force is applied at the pulling point, or "remote center". This idea of cascaded compliances is common to many end effectors, both instrumented and noninstrumented. Counterweights are added to the device to allow insertions not from directly above. Finally, a brief example is given of a parts modification to promote assembly. Figure (15) shows a nonfunctional boss incorporated into the design to interface with the "V" jaws of the gripper. This allows a very simple gripper to handle both the pillars and boss/plate parts.

17 )X { I f1 do / i 7 JJ tSERTION4 CHAMFER b FU\NEEL 3NE-POINT TWO.POINT ONTACT CONTACT AXIAL FORCE f-thCTtOM:XIAL FRICTION I ORCE ORCE \ FORCE oc I_ _ b \ c d d CONTACT \FRICTION _r- W CONTACT FOR-CE~"~ CONTACT Y FoRcE NTACT cc 0 FORCE I CACT ORCE FORCE | F LLE MOMENT FORCE.l - 1 5; r IC |MOMENT CONTACT FORCE *.....,, Figure (113): Insertion funnel and compliance[5].

18'!.,........................ ~ 1.1 I I~eel OF RODS flODS CO aINATION /,,,.,...... *~V~ ~LI:; I' CEENTE R OF MOTION O DEFORMABLE OF RODS A RODS a e CENTER OF MOTION ---- OF WIRES Figure (14): Remote center compliance device[5].

19 Figure 2. V jaw tpe gripper. I 1- E A PILLARS r.... —--- BOSS c',h I A \ T VtIEW CC Figure (15): Part modification to promote parts mating ] igue adi Figure (15): Part modification to promote parts mating[19]1

20 RESEARCH DIRECTIONS One of the areas the author is now investigating is the use of the Boothroyd data in a knowledge-based consulting system. The hope is that such a system would allow a designer to achieve a part with desirable assembly properties with a single design synthesis effort. This is in contrast to the more traditional iterative method of design, followed by Boothroyd analysis, followed by redesign. Other areas include integrating the Boothroyd data into a group technology data base, the relationship of the Boothroyd data to a high level automated assembly programming language (such as IBM'S AUTOPASS), and part design to promote insertion (part design rather than end effector design).

21 SUMMARY This paper has discussed product design to promote automated assembly. A strong foundation of research experience and experimental results has been created. Others must draw upon this knowledge to solve the problems that will arise as assembly is automated to a higher degree.

22 APPENDI X 1 Boothroyd Coding System for Automatic Handling and Assembly On the following pages are reproductions of the Boothroyd automatic handling and assembly coding charts[1].

AUTOMATIC HANDLING FIRST DIGIT _~ DISCS UD < 0.8 0 -a (2) Z SHORT CYLINDERS 0 1 0.8 UD a1.5 (2) LONG CYLINDERS " 2 L/D > 1.5 (2) ^A/B s 3 Z FLAT A/C >4 (3) 6 LONG A/B>3 (3) 7 0 C AO s 4(3) o CUBIC AJB 3 8 z A/C 4 (3) NOTES 1. A part whose basic shape is a cylinder or regular prism whose cross-section is a regular polygon of five or more sides is called a rotational part. In addition, triangular or square parts that repeat their orientation when rotated about their principle axis through angles of 120~ or 90~ respectively are rotational parts. 2. L is the length and D is the diameter of the smallest cylinder than can completely enclose the part. 3. A is the length of the longest side, C is the length of the shortest side and B is the length of the intermediate side of the smallest rectangular prism that can completely enclose the part. 1'~82 loothroyd & Dewhhurst CHART 4

AUTOMATIC HANDLING -DATA FOR ROTATIONAL PARTS KEY: OE FC (first digit 0, 1 or 2) V V I 0 > 0.3 1 first \ digit 1 15 part is not BETA symmetric (code the main feature or features (~ 2~ > ~ 5 requiring orientation about the principal axis).2 > 0.45 1.5.0 BT slightly D <4l BETA asymmetric projections, asymmetric <O \-^ steps, or chamfers BETA asymmetric grooves or flats or small L u 3 (can be seen in silhouette) (can be seen in silhouette) features less >^.O N ^ ^^~ ____________________________________than D/10' and L/10 XE > ^ through through groove an SIDE > —.. > on both groove can be seen in holes or reSURFACE \ ^? on side on end side and or flat side view cesses which PvO /surface surface(s) only only* end can be:annot be L E-: only only surface(s) seen in on end on side seen in oute SURCT Q ICFACES "^ ______________ end vievw surface surface e of ~~~~_ _ __SURFACES _ _ _ _ _ _ _ _ ___silhouette ~'~~ _0 2 3 4 5 6 7 8 part is ALPHA 0.7 1 0.3 1 0.5 1 0.3 1 0.35 1 0.2 1 0.5 1 symmetric 0 0.7 1 0.15 1 0.2 1 0.15 1 0.2 1 0.2 1 0.2 1 (see note 1) 0.9 1 0.45 1 0.9 2 0.45 1 0.9 1 0.9 2 0.9 2 part can be fed in a slot supported by large end or 0.4 1 0.2 1 0.25 1. 0.2 1 0.2 1 0.1 1 0.25.1 protruding flange with 1 0.3 1 0.1 1 0.1 1 0.1 1 0.1 1 0.1 1 0.1 1 center of mass below sup-! center of mass below sup 0.9 1. 0.45 1 0.9 2 0.45 1 0.9 1 0.9 2' 0.9 2 porting surfaces BETA symmetric steps or 0.4 1 0.15 1 0.25 1 0.15 1 0.35 1 0.1 1 0.25 1 chamfers on 5 external surfaces 2 0.3 1 0.1 1.5 0.1 1.5 0.1 1.5 0.2 1.5 0.05 1.5 0.1 1.5 (see note 3) 0.75 1 0.37 1.5 0.25 3 0.37 1.5 0.5 1 0.5 3 0.5 2. o~ on both 0.5 1 0.15 1 0.25 1 0.15 10.2 1 0.1 1 0.25 1 Ci sd a nd 3 0.2 1 0.1 1.5 0.1 1.5 0.1 1.5 0.1 1.5 0.05 1.5 0.1 1.5 " end surface(s) 0.85 1 0.43 1.5 0.25 2 0.43 1.5 0.5 1 0.5 2 0.5 2,;:-.^ BETA. symmetric * X smometr on side 0.5 1 0.15 1 0.25 1 0.15 1 0.2 1 0.1 1 0.25 1 holes or surface 4 0.1 1 0.1 1.5 0.1 1.5 0.1 1.5 0.1 1.5 0.05 1.5 0.1 1.5 s:.. ho recesses only0.85 1 0.43 1.5 0.25 2 0.43 1.5 0.5 1 0.5 2 0.5 2.,3.= (see note 3) on end 0.5 1 0.15 1 0.25 1 0.15 1 0.2 1 0.1 1 0.25 1 >'- surface(s) 5 0.2 1 0.1 1.5 0.1.1.5 0.1 1.5 0.1 1.5 0.05 1.5. 0.1 1.5:',..' < only 0.6 1 0.27 1.5 0.25 2 0.27 1.5 0.45 1 0.45 2 0.45 2:;"^ < ~ BETA symmetric hidden........*f...r.'-'*'5 -..-,, c ^ features with no cor......;-...;;:-:'".'. responding exposed 6.. * ^'XK -eatures (see note 4) 0.6 1 0.27 1.5 0.25 2 0.27 1.5 0.45 1 0.45 2 0.45 2. s ":.-..-.....*....:^.,....-.v:. BETA asymmetric 025 1 0.1 1 01 1 0.25 1'. features on side or 7. 0.1 1.5 0.05 1.5 - -. 0.05 1.5 0.1 1.5,.nd surface(s) 0.27 2 0.25 3 0.27: 2 0.1 3 0.5 3 0.5 3., - Sl,,;tfl v asymmetric....'...'...,. otr,rm.ill features;' ",..,i,,Lunt of asymmetry or 8 — MANUAL HANDLING REQUIRED —'. "'.ir.itrc ~~ie less thanI 1i [)', ),nd l.'10 I" j.__....______..._ ____ -_ __ _'C. 1ti/') I;[u'tla r~irl R rv,... k f'4ART ^

AUTOMATIC HANDLINGDATA FOR NON-ROTATIONAL PARTS (first digit 6, 7 or 8) A 1.1B or B 1.1C (code the main feature or features which distinguish the adjacent surfaces having similar dimensions) OE FC v V > 1~18 steps or chamfers (2) through grooves (2) otherb > 0.7 1 and parallel to - parallel to - holes or including recesses slight > 0.45 1.5 > 0.1 B asymmetry X axis Y axis Z axis X axis Y axis Z axis (cannot (3), fea> 03 3 2 and and and and and and be seen tures too > 0.1C > 0.1C > 0.18 > 0.1C > 0.1C > 0.1 B in silhouette] small etc. 0 1 2 3 4 5 6 7 8 part has 1800~ 0.8 1 0.8 1 0.2 1 0.5 1 0.75 1 0.25 1 0.5 1.5 0.25 2 symmetrvy MANUAL about all 0 0.9 1 0.9 1 0.5 2 0.5s 05 -5 HANNC three axes (1) 0.6 1 0.5 1 0.15 2 0.15 1.5 0.5 1 0.15 1 0.15 1.5 0.15 2 REQUIRED B'" p. code the main feature, or if orientation is defined by more than one feature, then code the feature that gives the e ^^S,.^ ~ Blargest third digit steps or chamfers (2) through grooves (2) other parallel to. parallel to- holes or including recesses slight, ________ —- --- -------------- > 0.1 B asymmetry cannot (3), fea"-,4A X axis Y axis Z axis X is Y X axis Y axis Z axistoo and and and and and and > 01C > 0.1C > 0.1B > 0.1C > 0.1C > 0.18 in silhouett small etc. 0 1 2 3 4 5 6 7 0.4 1 0.6 1 0.4' 1.5 0.4: 1 0.3'1 0.7 1 0.4-. 2 about Xaxis 1 0.5.. 1 0.5 5 10.225 10.25 1.5 0.25 3 0.4 1 0.6 1 0.4 2 0.2 0.2 0.3 1 0.15 1 0.1 2 0.4 1 0.3 1 0.4.1.5 0.5 1 0.3 1 0.4 10.4' 2 ab out 2 20.4 1 0.2 1 0.25,:'2 0.4. 1 0.25. 1 0.25 1 0.25 2 Y axis 0.5 1 0.15 1 0.5 2 0.2 1 0.15 1 0.15 2 0.15 2 or'entation 0.4 1 0.3 10.4'.5 0.4 10.3 1 0.4 1.5 0.4 2 S about WA Zaxis 3 0.3 1 0.2 1 0.25 2 0.3 1 0.25 1 0.25 2 0.25 2; 0.4 1 0.2 1 0.4. 2 0.2 1 0.15 1 0.15 2 0.15 2' ~'orientation 1 I ^ i entair1 1" (0.25 0.15 15.0.1.1 015 2I 0.1. 0.1 Z defined by'one main feature 0.15 1 0.14 1 0.15 1 0.1 1 0.05 1 0.1 1.5 0.08 2: - ()rientation defined rintationdefined 0.2 2 0.15n. 2 0.1 2.5 0.1 2 0.15 2 0.1 2.5 0.1 3 by two main i.atures and one,is 6( 0.1 3 0.1 3.5 0.1 4 0.1 3 0.1 3.5 0.1 4 0.1 5 "tI 1'). I hanif.r or': 4:.-,,V(. 0.05 2 0.05 2 0.05 2.5 0.05 2 0.05 2 0.05 2.5 0.05 3:clin: M (ludn.'. MANUAL HANDLINC REQUIRED digll asym. *. n,,lrV (J) etc -.....,..|.',Itt li,,i<.(~,~,,,, t I)., husl, CHART 6

AUTOMATIC HANDLING-ADDITIONAL FEEDER COSTS, DC parts will not tangle or nest tangle or nest but not severely FIGURES TO BE -I ADDED TO FC, not light light not light light' 2. ____.....> >c OBTAINED FROM >- ~ not not not not C=, CHARTS 5 OR 6 sticky sticky sticky sticky sticky sticky stick y sticky 0 1 2 3 4 5 6 7 8 9 I —- - - mm -~: mmI mm; mm Im mm- IT- 11 I, - 1 non- " | - -' t | flexible 0 3; 3 3 7' |.... _: -: i _ _- ~'::.-<3: ^:: ^ r -~;':'::?:.:.".'..:'....._-__-: ~e -.,-a~ ~,-.. -.::. |> -r S flexible 1 5 O 4N 6g r^.- Y'-i- 7 flexible r-~ =~ ~ I " n:, 2 * I r * |-:* *s i' 6 - | - 5'i- -|5" X *^ |.: flexible | 7:.-':. -^.. 4 - ~i;~~3 flexible 35..4 -..,,... 6-4f:~' very small parts large parts rotational non-rotational rotational non-rotational L/DS1.5 L/D>15 > A/b > 3 LID/ 1.5L/D>1.5 > A/B> 3^ fleible...:..2. 3: 4 " - 5 -.6 7,4 8 9' ar~ are very small or 8 | 2 - 2small parts large parts'''r parts will not severely tangle or nest orientation defined by orienton, 6 e ometrc features geometricfeatures -' | -6 | 6c non-flexible. | O C o. |onverlap overlap | ovexrlap. overlap c..:-: _. |. _ | V. | 4___0_1__0 1 2 3 4 5 1 6'7 "8 " 9,~ ~~ d n. _ -e f le xb oel _ a. |! >t larts [|97 2 | 4 | 4 1 % t. 9 | 4 |: - 1t82 3oothrod,& )ehurst CHART 7

AU I UMA IL IN3tK I IUNRELATIVE WORKHEAD COST, WC after assembly no holding down required to holding down required during subsequent process(es) to maintain orientation and maintain orientation and location (5) location an not easy to align or not easy to align or easy to align position (no features easy to align position (no features and position (6) provided for the and position (6) provided for the purpose)__ purpose) no no no no Ke: resistance resistance resistance resistance resistance resistance resistance resistance to to to to to to. to to WII |PART ADDED insertion insertion (7) insertion insertion (7) insertion insertion (7) insertion insertion(7) but............__ I.__ INOT SECURED 0 1 2 3 6 7 8 9 t 1 1.5 1.5 2.3 1.3 2 2 3 from;,'Ivraboely 1 1.2 1 6 1.6 2.5 1.6 2.1 2.1 3.3 above 2.:= i- 2 2 3 3 4.6 2.7 4 4 6.1'" not trom _______ __________?._ _.. J vertically,= p J above (3) ___iI___ _ii iII i - 5 -- ---- n/ o screwing opera,- pplastic deformation immediately after insertion'- rS / tion or plastic scr:= ~- ~......... screwing - o nsertio n not deformation g n inserptic bending rivetting or similar immediately straight line i/mmediately after plastic bendng plastic deforation after motion (4) insertion (snap or..... rnt n(|press fits, etc.) "not easy to align not easy to align insertion -___ ~ n~,..___'_~ ^ or position (no or position (no _ c features provided S features provided _ PAR S EU.C for the purpose) | g for the purpose) = PART SECURED c O' c o " - _ 3 3 CtC C 0 " K CO IMMEDIA TELY = C.0 C lo w.. o,' — __tI1 M~DMTi'_.,ij|7..-__! u,, 0 C p W I —-oo —- ~"Oi' " I from \ l.,-', -.-'-.l... 6 fvertically. C..... CC... S... v i.... f iabove l \ 0 1 2 3 4 5 6 7 8 9' Un U....... i n s3 1.2 1.9. 1.6-: ^2*:4; 3.6 1 0:9 | 1.4 |2.1 o'0.8:;-|"'1 -8 ~ ~ fro m "... ~.'.~,..:. ~.;,'-. ~;...,.. - ~......j,., ~ W Wo from 1 r to vertically 4.1.3 2 2'4.8,1.5 2.3., 2:_. straight line / (parts already in pla ce) in placce) processes none or localized metallurgical, plastic deformation C __| _ processes C, M,1"'above-':::""2'3" additional6 7';;:,,!,, *" | 9 |:..6~ ~ 9. |. 1.6 0.9 0. 1.2 1 1 1 0.8 1.5 insertion not straight line mcotio~n (4)'' non'mechanical tasteninE mechanical fastening processes Irnon-f astening (parts already in place) inp cs ar l d processes none'or localized metallurgical,1 plastic deformation p S,r,! w C.h I.1 1.:'E'"' C. — ell >, 0) ~'~ I............C lh~ ~ "''"..."''I I ~!~~1o~Io~I....~....

23 APPENDIX 2 Application Examples of Boothroyd's Design for Assembly System The first example[1] shows a redesign and the associated reduction in assembly costs. Note that assembly costs were cut by approximately a factor of nine but manufacturing costs were not considered. The second example[18] shows an actual industrial application of the Design for Assembly System. Here it is important to note that the total product cost was reduced by 36%.

First example[13 1- complete assembly 2- screw(2) (mild steel) _ 8 16 3- bearing housing (mild steel) 4- plate (spring steel) 5- washer (2) (mild steel) II 4 6- nut (2) (mild steel) Qf' Figure 10 Diaphragm Assembly ( dimensions in mm ).S1

0 II I s u | O | I I LO | I _a - - —.X0-ii - N w e " d OJ__ _ tr_',. — ~.=~~~~_ 0~ln zozo uo ii o; saii ii i IKZ L () () xa | | I N' Jed jad uo asu!i.:)ewomne;o )SO' 0 0 O Ia -Uo!iasuiL |e!eUoa)ne Jol s a C " n _."". =, ~.).. ^ r ~ apoD uo-i asul | ||O O wflwuE 3i)ouwoine p!8ip^om | 0 0 | ~ C4 ~ | 10 x 9'o = D 0 jl'Ou1oDPue4 6 | P zs! uo!iado 6 6' C 6 c) Wj'alei paaj Ln C V -l _....D o,qwnuix.. mI i l -Wi, i I 0 I 0 0 10 UO!aJoL0i0 o 0 o o euwoFneuP 1 1 Wp-aAe No Dh A ss e mI ~,O' o ~ - ewo~ne Ji )jp-do 0 L0 cI I:~!edmne 2U!jpUL( 0 00 seou ne JO )SO C FigureA 11 Worksh-e- f - AsN 52I ON -a-l lied %.D L p 30'A~uapeJ p r4 -- D + o =o CY paiiJJLr Li uoirPJ)do e4 N - c4

II slJed wnw!u!w o spu s I I I u I ~ I |z I I | o 1! I..nue.!!P |o -..., 1Jed UJnadu o^ jee)lajoaq) Jo 2 uollPawiS9 jo; sajnli; slua:'-j0o3 uoi)Jeado 4 awu! uo!ipasu! lenuewu jC3~~C p!() po: s! uo!lJadosu le Figure2 Manuual Assembly of Diapragm Plate HJLed *jd 056 56

2- plate (spring steel) -- 3- bearing housing (plastic) Figure 13 Re-design of Diaphragm Assembly

C*~~~~0 0 O _ C II -I -' A0-).:= ~s c,, _D D-.uo!eWQO. -.JO 5 O Os O'ted jd uoniasuij - ea313Joa o _ -. CJ uo_!eu!nsa J sajn _ _ _ [((L) + (9] x (Z) o" c.4 m a e I I I I jaJ 10 x g0'0 = 13 T Ir II'3Jed Jad uo!3jasu! - "' "':!aPuw one jo D so~ 0 0 0 p0 ouolJasu! 0W I pewone!lpOmJ I 0 0I I: peqvd j. d Su._IPea4 _ C ^ apol uoijasui O O 3R 5 JO x ~0'0 = J3 c.4 O; co';Jpd jad Su!lpueq "c - = 3!)ewo0ne o Iso3 0 | I I I I I uIPu4 uL N.,3pu0wwone jo) 0O Supp AiIn3ip! c i l _ V A Wj'aje paad cc _. ~ JOieq unuixPu e n U' s f- -3 wo _ _Jj _r'c ~ V Sa + 3= r *3'so 0 N t jonpaa aAliP|aJ p- - al. S| squiiguaJ!o 0 6 I o-t o o N Figure 14 Worksheet for Re-design of Diaphragm Assembly 60

becona exampleL ioj N ".x I Q t -~~-.. "........,,.., <..... ~.-e' of Xex.,c, th. Pat Sy s.t Theoretica Mins^; Nme of Parts Il 0 u Estimated Assembly Time (Min.) 6 90 1.48 5J42 L 9\g_ ~- "'"'"a)'1 b) Fig. 1. Latch Mechanism: (a) existing design. (b) proposed re-design for ease of assembly. Table 1 Redesign of Xerox Latch Using the UMass System ~~...~~.........Old New'1, Design Design Savings Change Manual Assembly Efficiency *.8', 22.5.: Estimated Parts Cost S9.80 7.44 S2.36 24% Total Product Cost S12:56 S8 03 S4.53 36%

24 REFERENCES 1. Boothroyd, G., Design for Assembly-A Designer's Handbook, The University of Massachusetts at Amherst, 1981. 2. Boothroyd, G., Murch, L., Poli, C., Automatic Assembly, New York and Basel, Marcel Dekker Inc., 1982, (EngineeringTransportation Library call # TJ1317.B661). 3. den Hamer, H.E., Interordering-A New Method of Component Orientation, New York, Elsevier Scientific Publishing Co., 1980, (Engineering-Transportation Library call # TJ1317.5.H351). 4. Esken, R., "Automatic Assembly," Mechanical Enqineering, 1960, V. 82, No. 5, pps. 40-42, (Engineering-Transportation Library call # TJ1.M49). 5. Whitney, D.E., Nevins, J.L., "Computer-Controlled Assembly," Scientific American, V. 238, No. 2, pps. 62-74, (EngineeringTransportation Library call # T1.S415). 6. McCalloin,H., Alexander, K.V., Pham, D.T., "Aids for Automatic Assembly," Proc. First International Conference on Assembly Automation, IFS (Publications) Ltd., 35-39 High St., Kempston, Bedford, England, 1980, pps. 313-323, (EngineeringTransportation Library call # TJ1317.I581). 7. Reuleaux, F., Kinematics of Machinery, Dover, New York, 1963, pps. 96-114, (Engineering-Transportation Library call # TJ175.R443). 8. Whitney, D.E.,"Discrete Parts Assembly Automation-An Overview," ASME, New York, Paper 78-WA/DSC-11, 1978. 9. Engleberger, J.F., "Robot Arms for Assembly," ASME, New York, Paper 78-WA/DSC-37 1978. 10. Boothroyd, G., Ho, C., "Natural Resting Aspects of Parts for Automatic Handling." ASME, New York, Paper 76-WA/Prod-40, 1S76.

25 11. Rozen, C., Nitsan, D., "Some Developments in Programmable Automation," Manufacturing Engineering, Sept. 1975, pps. 26-30, (Engineering-Transportation Library call TJ1180.A1 T67B). 12. Takeyasu, K., Goto, T., Inoyama, T., "Precision Insert Control Robot and Its Application," ASME, New York, Paper 76-Det-50, 1976. 13. Lynch, P.M., "An Economic Guideline for the Design of Programmable Assembly Machines," ASME, New York, Paper 77WA/Aut-2, 1977. 14. Kondoleon, A.S., "Results of Programmable Assembly Machine Configuration," SME, Dearborn, Michigan, Paper MS77-753, (Engineering-Transportation Library call # TS176.S68. 15. Lieberman, L.I., Wesley, M.A., "The Design of a Geometric Data Base for Mechanical Assembly," IBM Research Report RC-5489, June 1975, (Available in CRIM Robot Systems Library). 16. Wesley, M.A., "Robotics and Geometric Modeling," Yorktown Heights, New York, 10598, IBM T.J. Watson Research Center,Computer Sciences Dept., (Available in CRIM Robot. Systems Library). 17. Boothroyd, G., "Design for Producibility-The Road to Higher Productivity," Assembly Engineering, March 1982. 18. Boothroyd, G., Dewhurst, P., "Computer-Aided Design for Assembly," Assembl Engineering, Feb. 1983. 19. Heginbotham, W.B., Tewari, N.K., "A mechanized assembly system-Its influence on component design and tolerances," International Journal of Production Research, V. 16, No. 1, 1978, pps. 77-85, (Engineering-Transportation Library call # TS155.A1 162). 20. Watson, P., "A Multidemensional System Analysis of the Assermbly Process as Performed by a Manr.pulator." SME

26 Technical Paper MR76-613, 1976, (Engineering-Transportation Library call # TS176.S68). 21. Abraham, R.G., Stewart, R.J.S., Shum, L.Y., "State of the Art in Asaptable-Programmable Assembly Systems," SME Technical Paper MS77-757, 1977, (Engineering-Transportation Library call # TS176.S68). 22. Hill, J.W., "Force Controlled Assembler," SME Technical Paper MS77-749, 1977, (Engineering-Transportation Library call # TS176.S68). 23. Nevins, J.L., Whitney, D.E., et. al., "What is Remote Center Compliance and What Can It Do?," Charles Stark Draper Laboratory Report P-728, November 1978, (Available in CRIM Robot Systems Library). 24. Nevins, J.L., DeFazio, T.L., "Industrial Assembly PartMating Studies," Charles Stark Draper Laboratory Report P-919, September 1979, (Available in CRIM Robot Systems Library). 25. DeFazio, T.L., "Displacement State Monitoring for the Remote Center Compliance-Realizations and Applications," Charles Stark Draper Laboratory Report P-948, 1979, (Available in CRIM Robot Systems Library). 26. Miaw, D.C., Wilson, W.R.D., "Use of Figures of Merit in Computer-Aided Process Selection," ASME, New York, Paper 81DET=103, 1981.