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PENN S TATE © T. W. S IMPSON PENN S TATE Timothy W. Simpson Professor of Mechanical & Industrial Engineering and Engineering Design The Pennsylvania State.

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Presentation on theme: "PENN S TATE © T. W. S IMPSON PENN S TATE Timothy W. Simpson Professor of Mechanical & Industrial Engineering and Engineering Design The Pennsylvania State."— Presentation transcript:

1 PENN S TATE © T. W. S IMPSON PENN S TATE Timothy W. Simpson Professor of Mechanical & Industrial Engineering and Engineering Design The Pennsylvania State University University Park, PA USA phone: (814) ME Designing Product Families - IE 546 Commonality in Product Family Design Commonality in Product Family Design © T. W. S IMPSON

2 PENN S TATE © T. W. S IMPSON 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

3 PENN S TATE © T. W. S IMPSON Overview of Todays 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

4 PENN S TATE © T. W. S IMPSON Commonality Much of focus in product family design is to improve commonality and standardization within the family What do we mean by commonality? 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 (McGrath, 1995) Main advantage of commonality within a product family: maintain economies of scale (and scope) in manufacturing and production processes

5 PENN S TATE © T. W. S IMPSON 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 Result: not only a common hinge but also a common door mechanism 777 Passenger Door (Sabbagh, 1996) 98% of all door mechanisms are common

6 PENN S TATE © T. W. S IMPSON Embraer Aircraft Family EMBRAER 190 EMBRAER 195 EMBRAER 170 EMBRAER % Commonality 85% Commonality 95% Commonality 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

7 PENN S TATE © T. W. S IMPSON Airbus Aircraft Family Airbus A3XX Family: common height, width, cockpit The A330 cockpit is common to all other Airbus types while Boeings cockpit is common only with the 757. This enabled the A , a less efficient shrink of a larger aircraft, to outsell Boeings ER, a more efficient stretch design of a smaller aircraft, in 1999 and 2000

8 PENN S TATE © T. W. S IMPSON Boeings Blended-Wing-Body (BWB) Airframe Commonality Scaling in size BWB Family covering passengers with: Identical Wings Identical Cockpit Identical & Similar Bays Source: Boeing

9 PENN S TATE © T. W. S IMPSON Growing a BWB Fuel volume available in wing Adds passengers Adds wing area Adds span ~Balanced Aerodynamically Smooth

10 PENN S TATE © T. W. S IMPSON 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-250s furnishings weight Identical bagracks, seats, crew rest, lavs, galleys, sidewalls, ceilings, floors 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 BWB-450/-250 Common BWB-450/-250 Common BWB-450 T-plug

11 PENN S TATE © T. W. S IMPSON Tanker Global Range Transport/Tanker Bomber C 2 ISR Long-Range Commercial Family 180 Seats Bay Share Common Wing, Cockpit and Centerbody Elements C 2 ISRTankerGlobal Reach Freighter Commercial Family Bomber Representative Cross Sections BWB Common Fleet

12 PENN S TATE © T. W. S IMPSON Commonality Discussion Activity: 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 groups role in product design and realization.

13 PENN S TATE © T. W. S IMPSON Commonality (cont.) 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., McDonalds, 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) 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 companys competitive advantage.

14 PENN S TATE © T. W. S IMPSON 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?

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

16 PENN S TATE © T. W. S IMPSON Common, Variant, & Unique Parts Consider a set of three product variants Variant 1 Variant 2 Variant 3 Common parts are shared by all of the product variants and are identical the platform elements Variant parts are shared by two or more products that differ in one or more aspects (e.g., feature size, color, etc.) Unique parts are used to differentiate a variant from others 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

17 PENN S TATE © T. W. S IMPSON 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 are a variety of metrics available in the literature for measuring commonality of a set of products: Degree of Commonality Index, DCI Total Constant Commonality Index, TCCI Commonality Index, CI Component Part Commonality Index, CI (C) Product Line Commonality Index, PCI Percent Commonality Index, %C Comprehensive Metric for Commonality, CMC

18 PENN S TATE © T. W. S IMPSON Total Constant Commonality Index Modified version of DCI Relative index with absolute boundaries between 0 and 1 Uses same symbol notation as DCI. Commonality Index Modified version of DCI Fixed boundaries: 0 < CI < 1 where: u = number of unique parts p j = number of parts in model j v n = final number of varieties offered 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 where: j = # 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

19 PENN S TATE © T. W. S IMPSON Sample Calculations of DCI, TCCI, & CI Sample calculation of DCI and TCCI: CI sample calculation: Consider family of 6 computer mice, each having 20 parts: Worst case: (no two parts alike) Better case: (70 parts needed to make six mice) 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

20 PENN S TATE © T. W. S IMPSON 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 P j = 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 d j over all the products levels of product i of the family = the total number of applications (repetitions) of a distinct component part d j across all the member products in the family V i = the volume of end product i in the family Q ij = the quantity of distinct component part d j required by the product i

21 PENN S TATE © T. W. S IMPSON Sample Calculation of CI (C) Computation of CI (C) : Example: 3 products 4 assembly levels 12 different parts 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

22 PENN S TATE © T. W. S IMPSON Product Line Commonality Index (cont.) f 1i = part size and shape factor f 2i = materials and manufacturing process factor f 3i = parts assembly and fastening scheme factor f ji = k/n where: k is number of products which share component i n is number of products that have component i e.g., n = 3, k = {1, 2, or 3} PCI = n i x f 1i x f 2i x f 3i - i = 1 P P P n i - i = 1 P 1 ni2ni2 1 ni2ni2 x 100

23 PENN S TATE © T. W. S IMPSON Walkman Example PCI calculation for Sony products (Table 2 in [Kota00]) Sony PCI = 91% RCA PCI = 46.4% RadioShack PCI = 54.6%

24 PENN S TATE © T. W. S IMPSON Drawback of PCI PCI provides a single number to characterize the commonality within a product family 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 are performed on a product by product basis, thereby providing insight into ways to improve commonality of individual products within the family

25 PENN S TATE © T. W. S IMPSON Percent Commonality Index [SD98] 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 = %C x = 100 * common X common X + unique X w c C c + w n C n + w a C a Commonality = c = components n = connections a = assembly workstations w j =weighting factor [SD98] 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, DETC98/DTM-5661.

26 PENN S TATE © T. W. S IMPSON 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 = snaps = solder = wire = prongs = springs = belt = screws = c. strip = plastic Volume Dial Face PanelGear Housing Rear Housing Belt Clip MotorCircuit Board StopRevFF Headphone Connector Radio Tuning Gear Tuning Gear Housing Mode Ctrl Switch Solenoid Super Bass Switch Gear Train Play Battery Coil FWD/REV Switch Radio Ctrl Switch

27 PENN S TATE © T. W. S IMPSON Commonality Viewpoints Why assess commonality of: components? connections? assembly workstations?

28 PENN S TATE © T. W. S IMPSON Selecting a Commonality Index TCCICIPCI%CCI (C) Focus on the number of common components XX Focus on the non- differentiating (non- unique) components X Focus on the number of common connections, and assembly X Focus on the cost of the components X When selecting a commonality index, consider your companys perspective when evaluating the product family 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)

29 PENN S TATE © T. W. S IMPSON Comparison of Commonality Indices DCI, TCCI, CI are the easiest to compute and most repeatable need the same amount of information (parts, number of parts in each product, BOM) %C, PCI are less repeatable (require human intervention) need information subject to variation Ease of computation and repeatability of the CI (C) depends on the data available (simple BOM, component costs, etc.) CI (C) Repeatability Ease of data collection %C PCI DCI TCCI CI 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

30 PENN S TATE © T. W. S IMPSON Using Commonality Indices for Redesign Consider the following six computer mice Phase 1: Data Gathering – we used dissection

31 PENN S TATE © T. W. S IMPSON 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

32 PENN S TATE © T. W. S IMPSON Phases 3: Optimization Results Δ Results from optimization (graphical) Accompanying list of component redesign recommendations and corresponding change in PCI value

33 PENN S TATE © T. W. S IMPSON Phase 4: Recommendations for Redesign Largest PCI by first redesigning receptor in Products 3, 5, 6…

34 PENN S TATE © T. W. S IMPSON 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 [The JSFs 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

35 PENN S TATE © T. W. S IMPSON Commonality within JSF Source:

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

37 PENN S TATE © T. W. S IMPSON 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, 2B, Feb. 22, 2008

38 PENN S TATE © T. W. S IMPSON 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


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