Commonality in Product Family Design ME 546 Designing

Commonality in Product Family Design ME 546 - Designing Product Families - IE 546 Timothy W. Simpson Professor of Mechanical & Industrial Engineering and Engineering Design The Pennsylvania State University Park, PA 16802 USA phone: (814) 863 -7136 email: tws 8@psu. edu http: //www. mne. psu. edu/simpson/courses/me 546 PENNSTATE © T. W. SIMPSON

Planning Product Platforms • Robertson and Ulrich (1998) advocate a three-step approach: 1) Product plan – which products to offer when 2) Differentiation plan – how products will be differentiated 3) Commonality plan – which components/modules will be shared Source: D. Robertson and K. Ulrich, 1998, "Planning Product Platforms, " Sloan Management Review, 39(4), pp. 19 -31. PENNSTATE © T. W. SIMPSON

Overview of Today’s Lecture • Examples of Commonality in the Aerospace Industry • Discussion: Pros/Cons of Commonality • Metrics for Commonality • Comparison of Commonality Indices • Using Commonality Indices for Redesign/Design PENNSTATE © T. W. SIMPSON

Commonality • Much of focus in product family design is to improve commonality and standardization within the family • What do we mean by commonality? q Possession of common features or attributes in either the product or the manufacturing process for a set of products • A product platform is defined “as the common elements, especially the underlying core technology, implemented across a range of products” (Mc. Grath, 1995) • Main advantage of commonality within a product family: q maintain economies of scale (and scope) in manufacturing and production processes PENNSTATE © T. W. SIMPSON

Boeing 777 Passenger Doors • Each passenger door (8 total) has different sets of parts with subtly different shapes and sizes for its position on the fuselage • Challenge: make the hinge common for all of the doors 777 Passenger Door • Result: not only a common hinge (Sabbagh, 1996) but also a common door mechanism 98% of all door mechanisms are common PENNSTATE © T. W. SIMPSON

Embraer Aircraft Family EMBRAER 170 EMBRAER 175 95% Commonality 85% Commonality EMBRAER 190 95% Commonality EMBRAER 195 PENNSTATE Common pilot type rating 100% commonality in the cockpit High level of commonality in system components 100% flying commonality due to fly-by-wire system © T. W. SIMPSON

Airbus Aircraft Family • Airbus A 3 XX Family: common height, width, cockpit • The A 330 cockpit is common to all other Airbus types while Boeing’s 767 -400 cockpit is common only with the 757. This enabled the A 330 -200, a less efficient “shrink” of a larger aircraft, to outsell Boeing’s 767400 ER, a more efficient “stretch” design of a smaller aircraft, in 1999 and 2000 PENNSTATE © T. W. SIMPSON

Boeing’s Blended-Wing-Body (BWB) Airframe Commonality BWB Family covering 200 -450 passengers with: • Identical Wings • Identical Cockpit • Identical & Similar Bays Scaling in size 200 PENNSTATE 250 300 350 400 450 Source: Boeing © T. W. SIMPSON

Growing a BWB 350 • • • Fuel volume available in wing Adds passengers Adds wing area Adds span ~Balanced Aerodynamically Smooth 450 550 PENNSTATE © T. W. SIMPSON

Payload Commonality • Each bay in the BWB is an identical “cross-section” and thus lends itself to high part/weight commonality amongst the family members • The BWB-450 retains 97% of the BWB-250’s furnishings weight q Identical bagracks, seats, crew rest, lavs, galleys, sidewalls, ceilings, floors BWB-450/-250 Common BWB-450 T-plug BWB-450/-250 Common The BWB has significant benefits over families of tube and wing transports with its ability to cover the large airplane market with ONE cross section PENNSTATE © T. W. SIMPSON

BWB Common Fleet i am ly 7 Bay l. F a i rc 570 me m o C e g on ng a R 6 475 Global Range Transport/Tanker 5 - L 360 4 270 C 2 ISR 3 Tanker 180 Seats Bomber Commercial Family Representative Cross Sections Tanker C 2 ISR Bomber Global Reach Freighter Share Common Wing, Cockpit and Centerbody Elements PENNSTATE © T. W. SIMPSON

Commonality Discussion Activity: q q Count off 1, 2, 3, 4, 5, 6 and form groups (5 -6 people/group): 1. Marketing 2. Engineering 3. Manufacturing 4. Sales & Distribution 5. Service 6. Customers In your group, take ~10 minutes to discuss (and take notes): – – when and why is commonality good? when and why is commonality bad? based on your group’s role in product design and realization. PENNSTATE © T. W. SIMPSON

Commonality (cont. ) q Within your group, count off A, B, C, D, E, F and re-group into: A. An automobile company (e. g. , Ford, Chrysler, Toyota) B. A software company (e. g. , Microsoft, Adobe, Corel) C. A fast food chain (e. g. , Mc. Donalds, Burger King, Subway) D. A computer manufacturer (e. g. , Dell, Gateway, IBM, HP) E. A furniture company (e. g. , Herman Miller, Steelcase, IKEA) F. A telecommunications company (e. g. , Verizon, AT&T) q In your group, take ~10 minutes to discuss (and take notes): – what do you want to make common within your company and the products that you offer? – what do you want to make distinct within your company and the products that you offer? in order to maintain your company’s competitive advantage. PENNSTATE © T. W. SIMPSON

Advantages of Commonality • Decrease lead times (and risk) in product development • Reduce product line complexity • Reduce set-up and retooling time • Fewer components in inventory • Fewer parts need to be tested and qualified Other advantages? • • • PENNSTATE © T. W. SIMPSON

Disadvantages of Commonality • Hinder innovation and creativity • Compromise product performance Other disadvantages? • • • PENNSTATE Performance • Lack of distinctiveness Individually Optimized Designs Poor Designs Best Designs Based on Common Platform Degree of Commonality Despite disadvantages of commonality, it does provide a useful metric for assessing families of products. © T. W. SIMPSON

Common, Variant, & Unique Parts • Consider a set of three product variants Variant parts are shared by two or more products that differ in one or more aspects (e. g. , feature size, color, etc. ) Common parts are shared by all of the product variants and are identical the platform elements Variant 1 Variant 3 Variant 2 Unique parts are used to differentiate a variant from others PENNSTATE When designing a product family, the goal is to: • maximize the number of common parts, • minimize the number of unique parts, and • use the cheapest variant parts possible © T. W. SIMPSON

Commonality Indices • Commonality indices provide a surrogate measure for estimating the benefits of a product family when production cost information is not readily available • There a variety of metrics available in the literature for measuring commonality of a set of products: Degree of Commonality Index, DCI q Total Constant Commonality Index, TCCI q Commonality Index, CI q Component Part Commonality Index, CI(C) q Product Line Commonality Index, PCI q Percent Commonality Index, %C q Comprehensive Metric for Commonality, CMC q PENNSTATE © T. W. SIMPSON

Definitions of DCI, TCCI, & CI Degree of Commonality Index • Most traditional measure of component part standardization • Reflects the average number of common parent items per average distinct component part Total Constant Commonality Index • Modified version of DCI • Relative index with absolute boundaries between 0 and 1 Uses same symbol notation as DCI. where: Fj = # of immediate parents component j has over a set of end items d = total # of distinct components in the set of end items i = the total # of end items or the total # of highest level parent items for the product structure level(s) Component item = any inventory item other than an end item that goes into higher level items End item = finished product or major subassembly subject to a customer order or sales forecast Parent item = any inventory item that has component parts PENNSTATE Commonality Index • Modified version of DCI • Fixed boundaries: 0 < CI < 1 where: u = number of unique parts pj = number of parts in model j vn = final number of varieties offered © T. W. SIMPSON

Sample Calculations of DCI, TCCI, & CI • Sample calculation of DCI and TCCI: Source: Wacker, J. G. and Trelevan, M. , 1986, “Component Part Standardization: An Analysis of Commonality Sources and Indices, ” Journal of Operations Management, 6(2), pp. 219 -244. • CI sample calculation: q Consider family of 6 computer mice, each having 20 parts: Worst case: (no two parts alike) PENNSTATE Better case: (70 parts needed to make six mice) © T. W. SIMPSON

Definition of CI(C) Component Part Commonality Index • Extended version of the DCI • Takes into account production volume, quantity per operation, and the cost of component part • Does not have fixed boundaries: d = total # distinct component parts used in all the product structures of a product family j = the index of each distinct component part Pj = the price of each type of purchased parts or the estimated cost of each internally made component part m = the total number of end products in a product family i = the index of each member product of a product family = the number of immediate parents for each distinct component part dj over all the products levels of product i of the family = the total number of applications (repetitions) of a distinct component part dj across all the member products in the family Vi = the volume of end product i in the family Qij = the quantity of distinct component part dj required by the product i PENNSTATE © T. W. SIMPSON

Sample Calculation of CI(C) Example: • 3 products • 4 assembly levels • 12 different parts Computation of CI(C): Source: Jiao, J. and Tseng, M. M. , 2000, “Understanding Product Family for Mass Customization by Developing Commonality Indices, ” Journal of Engineering Design, 11(3), pp. 225 -243. PENNSTATE © T. W. SIMPSON

Product Line Commonality Index (cont. ) P S PCI = i = 1 P ni x f 1 i x f 2 i x f 3 i - P S i = 1 ni - P S i = 1 1 n i 2 x 100 1 n i 2 • f 1 i = part size and shape factor • f 2 i = materials and manufacturing process factor • f 3 i = parts assembly and fastening scheme factor • fji = k/n where: q k is number of products which share component i q n is number of products that have component i q e. g. , n = 3, k = {1, 2, or 3} PENNSTATE © T. W. SIMPSON

Walkman Example • PCI calculation for Sony products (Table 2 in [Kota 00]) • Sony PCI = 91% • RCA PCI = 46. 4% • Radio. Shack PCI = 54. 6% PENNSTATE © T. W. SIMPSON

Drawback of PCI • PCI provides a single number to characterize the commonality within a product family q PCI measure by itself does not yield insight into ways to improve commonality of individual products within family • Siddique and Rosen (1998) developed percent commonality indices which: quantify commonality of components, connections, and/or assembly stations q are performed on a product by product basis, thereby providing insight into ways to improve commonality of individual products within the family q PENNSTATE © T. W. SIMPSON

Percent Commonality Index [SD 98] % Commonality = %Cx = q q 100 * common X + unique X where X can be components, connections, or assembly workstations % commonality can be calculated for each X, then combined to form an overall commonality measure for the product family Commonality = wc. Cc + wn. Cn + wa. Ca c = components n = connections a = assembly workstations wj =weighting factor [SD 98] Siddique, Z. and Rosen, D. W. , 1998, September 13 -16, "On the Applicability of Product Variety Design Concepts to Automotive Platform Commonality, " Design Theory and Methodology - DTM'98, Atlanta, GA, ASME, DETC 98/DTM-5661. PENNSTATE © T. W. SIMPSON

Assembly Graphs for Commonality Assessment • Graph helps assess commonality of connections (and assembly workstations) within a product family • Typically drawn at the sub-assembly and (major) component level Volume Dial Super Bass Switch FWD/REV Switch Face Panel Gear Housing Rear Housing Belt Clip = snaps = wire = c. strip = solder = prongs = screws = springs = belt = plastic PENNSTATE Gear Train Stop Radio Ctrl Switch Play Rev Motor FF Mode Ctrl Switch Circuit Board Headphone Connector Radio Solenoid Tuning Gear Housing Battery Coil Tuning Gear © T. W. SIMPSON

Commonality Viewpoints • Why assess commonality of: q components? q connections? q assembly workstations? PENNSTATE © T. W. SIMPSON

Selecting a Commonality Index • When selecting a commonality index, consider your company’s perspective when evaluating the product family TCCI CI PCI %C CI(C) X X Focus on the number of common connections, and assembly X Focus on the cost of the components X Focus on the number of common components Focus on the nondifferentiating (nonunique) components • We do not recommend using DCI since it does not have fixed boundaries, making comparisons difficult; same for CI(C), but no other metrics include cost explicitly (we are working to fix that) PENNSTATE © T. W. SIMPSON

• DCI, TCCI, CI are the easiest to compute and most repeatable q need the same amount of information (parts, number of parts in each product, BOM) • %C, PCI are less repeatable (require human intervention) q need information subject to variation • Ease of computation and repeatability of the CI(C) depends on the data available (simple BOM, component costs, etc. ) Ease of data collection Comparison of Commonality Indices DCI TCCI CI CI(C) %C PCI Repeatability • For a detailed comparison and pros/cons of each, see: Thevenot, H. J. and Simpson, T. W. (2005) “Commonality Indices for Assessing Product Families, ” Product Platform and Product Family Design: Methods and Applications (Simpson, T. W. , Siddique, Z, and Jiao, J. , eds. ), Springer, New York, pp. 107 -129. PENNSTATE © T. W. SIMPSON

Using Commonality Indices for Redesign • Consider the following six computer mice Phase 1: Data Gathering – we used dissection PENNSTATE © T. W. SIMPSON

Phases 2 & 3: Commonality and Optimization • Phase 2: Commonality Assessment – PCI chosen to consider changes in size/shape, material, manf, and assembly • Phase 3: Optimize Family – GA runs to determine parameter settings for problem PENNSTATE © T. W. SIMPSON

Phases 3: Optimization Results from optimization (graphical) Accompanying list of component redesign recommendations and corresponding change in PCI value Δ • • • PENNSTATE • • • • • • © T. W. SIMPSON

Phase 4: Recommendations for Redesign • Largest DPCI by first redesigning receptor in Products 3, 5, 6… PENNSTATE © T. W. SIMPSON

Using Commonality Indices for Design • Military had a goal to create three variants – the CTOL, CV and STOVL aircraft – of the F-35 Joint Strike Fighter (JSF), the 5 th generation, single-engine, single-seat aircraft with supersonic dash capability and some degree of stealth (http: //www. jsf. mil/) • To reduce development, production, and operation and support costs, component commonality targets of 70 -90% were set to maximize commonality in the airframe, engine, and avionics components and save an estimated $15 billion q “[The JSF’s unique development approach] avoids the three parallel development programs for service-unique aircraft that would have otherwise been necessary” (Letter from Secretary of Defense William S. Cohen to Rep. Jerry Lewis, June 22, 2000) • Unfortunately, as the project progressed, the actual commonality within the family of three aircraft fell far short of these targets, with final values in the 30 -40% range PENNSTATE © T. W. SIMPSON

Commonality within JSF Source: http: //www. jsf. mil/ PENNSTATE © T. W. SIMPSON

Cousin Parts? • Commonality indices such as PCI (Product Line Commonality Index) differentiate parts based on: q Size & Shape q Materials & Manufacturing q Assembly & Fastening PENNSTATE These can be used to define part commonality as follows: © T. W. SIMPSON

2008 Saturn Vue • The 2008 Saturn Vue SUV, a full redesign, is nearly identical to the German Opel Antara model that General Motors, parent to both brands, sells in Europe. Saturn is trying to morph from GM's touchy-feely brand to its Euro marque, so it kept as much German feel as possible. GM is trying to cut costs by sharing development and components rather than starting from scratch on each new vehicle. Besides being a near-twin of Antara, including visually, Vue shares some underpinnings with GM's Chevrolet Equinox and Pontiac Torrent, and with GM affiliate Suzuki's XL-7, but shares no body parts. "Call them 'cousins, ' not 'siblings, '" says Saturn's Mike Morrissey. There's an art to this commonality. How much do you keep for the sake of low cost? How much do you change to appeal to buyers in a specific market -- America, for example? GM's last try to hew so tightly to an Opel design resulted in a U. S. minivan line so bad it drove GM from the minivan market. - J. R. Healey, USA Today, 2 B, Feb. 22, 2008 PENNSTATE © T. W. SIMPSON

Closing Remarks • Commonality indices are to product family redesign what DFMA is to product redesign • Commonality indices can provide useful information regarding the extent of similar and unique components within a family • The computation of many of these metrics can be automated if necessary information (e. g. , BOM) is readily available • Methods to support product family redesign based on improving commonality have great potential • More comprehensive metrics for commonality and commonality/diversity are being developed PENNSTATE © T. W. SIMPSON