Manufacturingputsa new spin on design

The design-for­manufacturingphilosophy isgaInIngmomentumas more

.companIesdiscover itproducesbetter productsin less time.

To Detroit, low-volumeproduction means anythingbelowa million autos. But forbuilders of the Panoz Roadsterin Atlanta, Ga., low volumemeans about 50 cars each year.For such small quantities,DFM principles suggestedthat Panoz engineers usesuperplastic forming to shapealuminum bodypanels,including hoods and fenders.Alternatives would have beenexpensive stampings orfiberglass.

PAUL DVORAKSenior Editor

W hen the Coors Ceramics Co.bought a new hermetic packageproduct line, it didn't take man­

agers there long to realize they had bigproblems. Detailed design and process ca­pability was almost completely lacking.The result: "We couldn't predictably run theplant or make products of the right quality,"explains Coors Production Manager JimBachman.

Today, such travails are a dimming mem­ory. Through an arrangement with IBM,Coors went under the temporary tutelage oftwo IBM systems engineers who conducteda workshop in design-for-manufacturing(DFM). The experience let Coors dramati­cally improve production yield, quality, anddelivery. Moreover, application of DFMprinciples helped it reduce the cost of mak­ing the packages by a factor of four.

Word is spreading throughout industryabout how DFM can bring successes similarto those at Coors. Numerous organizationsare taking up the DFM banner. The U.S.Department of Commerce, for one, has

started DFM projects at six of their regionalmanufacturing centers. General Motors hasrelied on DFM to power its concurrent-en­gineering efforts with startling response:It's saving 20% of the total car cost of the1992 models on which it was applied. DFMand designing-for-assembly concepts havealready worked wonders trimming materialand manufacturing costs from a range ofproducts. Now new ideas are infiltrating thediscipline.

New ideasDFM pertains to more than just designing

parts. "Its getting the product in its least­cost configuration while maintaining fit,form, function, and service," says CliffMerkley, senior consultant with IBM."Even the process of assigning costs shouldcome under scrutiny." In some cases, manu­facturers may be forced to change their ac­counting practices to really see the benefitsof the DFM approach. To understand why,consider a part having a 4-sec production­cycle time and 16 hr of setup. With conven­tional bookkeeping, the 16 hr are charged asgeneral overhead. Now suppose a re­designed version of the part requires the

FEA proved its accuracy during a recent deflection test, says Soroka.The deflection analysis simulates a drilling load of 2,200 lb applied to ahead stock. When physical testing finished, a comparison to the FEA re­sults showed only a 2% difference.

Most companies already have the expertise in-house to start a DFM pro­gram - with the right mind set and a few organizational changes. DanielSoroka, director of research with Hardinge Brothers Inc., a machine-toolmanufacturer in Elmira, N.Y., was instrumental in establishing that firm'sDFM program. He offers these first steps.

• Tear down the department walls. "There can be no barriers betweendesign, manufacturing, purchasing, or service," says Soroka. If teammembers talk to each other about designs at hand, you've won thebiggest battle to improving manufacturability.

• Give the team the right tools. "A CAD system generates informationthat is useful throughout the organization," he adds. CAD drawingsshould serve several purposes. They help communicate technical infor­mation to manufacturing people and serve as a focal point for technicaldocumentation. For example, the assembly drawing database atSoroka's facility also drives all part lists.

• Learn to use finite-element analysis. "It lets teams predict behavior ­stress, deflection, vibration, and thermal response - of product proto­types so well that only one prototype is needed." The benefit of athorough analysis is fewer nasty surprises in the physical testing.

same cycle time but only an hour ofsetup. If recorded using ordinarypractices, the manufacturing cost ofthe two parts would be identical.The only impact of the redesignwould be a slight dip in general fac­tory overhead. By contrast, an activ­ity-based costing scheme would morelikely make the reduced setup cost evident.This is because activity-based costingtracks overhead activities more closely withthe operations that really use them.

There are other nontechnical obstacles toDFM besides questionable bookkeeping.Among the biggest is lack of an open mindand resistance to change on the part of engi­neers. Relates Sandy Munro, president ofMunro & Associates Inc., "Just getting peo­ple to try new manufacturing processes is achallenge. They often convince themselvesuntried developments can't work." Munrospeaks from experience. He cites the trialsof an aircraft manufacturer struggling with apart that elongated excessively while oper­ating. One solution suggested by an outsiderwas to spray on ceramic that could insulatethe part and control its thermal growth. Butengineers close to the project dismissed thisas unworkable. "When we suggested that ithas worked in similar applications, they be­gan to doubt themselves and allowed a brieftest," says Munro. The engineers eventuallyconvinced themselves that the ceramic wastheir own idea. And that's OK, says Munro,because it got new technology into use.

Another facet of DFM gives designers abigger role in estimating costs. They arealso assuming more responsibility for judg­ing the accuracy of bids from vendors. Inone instance, a telephone-equipment manu­facturer in the UK began evaluating produc­tion costs for metal enclosures rather thanwait two weeks for estimates from vendors.What made these home-grown cost esti­mates possible was DFM software. Newprograms in this area give estimates in min­utes and make it possible to evaluate a widescope of design alternatives for costs anddelivery times.

"Software increasingly lets users almostpeek in the books of competitors to see whatthey're paying for injection molds, diecases, and machined components," saysMiles Parker, a spokesman for BoothroydDewhurst Inc. BDI markets its own brand ofdesign-for-manufacturing and assemblysoftware that facilitates such cost estimates.In one case, Polaroid used BDI software toquestion a vendor about some expensive

molds. When con­fronted with Polaroid's detailed cost calcu­lations for the proposed work, the vendorcut its price by $5,000 on each of fourmolds.

Research is also paving the way for morecreative manufacturing processes and novelengineering materials. "Composite struc­tures, for one, have not grown into wideruse because they are difficult to designwithout considering how they'll be manu­factured," says Jami Shah, professor of en­gineering at Arizona State University.

One of Shah's recent projects dealt with

DO·IT·YOURSELF DFM

Engineers with HendryTelephone Products say SheetAdvisor and ME30 software,both from Hewlett·Packard,let them simulate sheet-metalmanufacturing and assemblecomponents before production.The orange strip at the bottomwarns the designer that therequested hole may bedeformed after the bendoperation.

as few components as possible. The idea isto minimize assembly time and give theproduct reliability by using fewer parts. Oneproblem, however, is that combining toomany functions into one part can increasemanufacturing costs. DFM lets engineersbetter spot the hazy divide between practi­cal and prohibitively expensive designs.

But engineers shouldn't get carried awaywith fancy software alone, suggests JohnFedor, president of Masco Machine inCleveland, Ohio. "Smart management canbe just as beneficial as sophisticated soft­ware. A little common sense and experiencegoes a long way," he adds. "For instance,when several designers work on the samejob, keep them close and talking to eachother." Another effective tactic is to stan­dardize on vendors and parts. Each designermight prefer a different bearing type andmanufacturer, for example. But agreeing ona single manufacturer and a few key sizeshelps cut design complexity.

"The same goes for fasteners," says Fe­dor. The general rule is to settle on as fewkinds of fasteners as possible. "When youmanufacture the parts, you won't be huntingfor different drills and taps. Minimizing fas­teners saves more than just the componentcosts," he says.

Simulating manufacturingEven product lines made mostly of bent

sheet metal increasingly benefit from theprinciples of DFM. One force driving suchbenefits are the constant requests for de­signs that differ slightly from those in thecatalog. To fill this niche, expert metal ben­ders have developed several packages thatteach engineers about designing sheetmetal. In fact, this smart software lets de­signers simulate manufacturing while theydesign.

In a program called Sheet Advisor, for in­stance, once an engineer defines the mate­rial and its thickness, the software can act asmentor by presenting a list of the acceptablepunching tools. Should the designer requestan inappropriate feature, such as trying tobend X-in. sheet into a YJ6-in. radius, the soft­ware issues a warning that the tight radiuswill fracture the material.

"The software technology database alsolets us add rules," says Chris Chapa, systemadministrator of CAD services with HendryTelephone Co. in Santa Barbara, Calif., anda Sheet Advisor user. "For example, we'vewritten manufacturing conditions intomacros that describe deformation zones on

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defining manufacturability guidelines forfiber-reinforced composite parts. "The ma­terial has limits from fracturing and delami­nation, so manufacturing methods cannotbe ignored," he adds.

Shah helped develop DFM software thatlets designers consider composite-partformability, die design, and structural de­sign together. It works like this: A designerfirst describes each feature to the software.The program then runs through its rules todetermine whether or not it's possible tomake the feature. The program keeps trackof features that are expensive to make andlater suggests how to redesign them. Thedesigner can accept or disregard the sugges­tions. With each change, the software alsorecalculates manufacturing costs.

The basicsThe philosophy of designing for easy as­

sembly suggests combining functions into

The sheet-metal module in theMatra Datavision Euclidprogram lets designers withMiddleby Cooking Systemssimulate the manufacturing ofcooking equipment, such asthe rendered toaster. The solidmodeler lets them assembleproducts and look for interfer­ence and other assemblyproblems before cuttingsheet metal.

An integrated DFAand DFM systemfrom Lucas Ltd. letsusers analyze a partsix different waysfor manufacturabil­ity in areas thatinclude plasticmolding, stamping,sintered metal, andsheet metal. Afterdescribing the partto the system, userscall up the differentmanufacturingmodules for a quickanalysis. The system may prompt users to consider building a complex part in twopieces, as a less-expensive alternative.

TAKE AFEW TIPS FROM OUTSIDERSThere are potentially.dozens of different ways to make any given part, yet most engi­n~ers can p!obably thmk of only a few. "People in every discipline get stuck in a small~Ir~le of fnends and suffer from what I call engineering incest," says Sandy Munro.Airplane people only talk to each other, auto people only talk to each other, and medi­

cal people only talk to each other. Tlte result is that eventually most products begin tolook and function alike," he says. '. The solutio~, says M~nro, is to exam~n~ manufacturing developments outside yourmdu~try. Fo~ Illstance, high-spee~ mach~Dlng comes from the auto industry and super­plastI.c formmg comes from the aIrcraft mdustry, but each has applications in other in­dustnes.

Such observations can pay big dividends. Munro cites two examples. An aircraft man­ufacturer wanted to apply DFM rules to a complex bulkhead made with over 10 000?arts a~d op~rations. (To understand the complexity of the problem, consider that ~Iac­mg a ~mgle nvet takes about 30 separ~teoperations.) Following the DFA philosophy ofreducmg part counts as much as pOSSIble, Munro proposed a monolithic structure cutfro~ a single bloc~ of aluminum. The airplane designers' response: "Impossible. HighreSIdual stresses will cause cracking."

.However, experie~ce from other industries indicated that machining the structureWIth a 60,000-rpm spIndle removes metal fast enough to prevent residual stresses. Afterovercoming their initial. reservations, the designers applied the concept to produce abUI~e~d stronger and lIghter than the previous design without residual stresses. Thispart IS In production and on flying aircraft today.

The second example comes from the auto industry where most manufacturers thinkone way - big stampings. The approach is logical for cars built in the millions and formodel runs lasting many years. But stampings are prohibitively expensive for the nichema~kets that are the new focus for automakers in the 1990s, where production runs tend to?e In the thousands rather than the millions. A better alternative comes from the aircraftI.?du~try. Manufacturers there use a process called superplastic forming that is cost effec­tIve III low volumes. In this method, l20-psi air is used to press hot aluminum sheet overa mold. Parts cost a bit more, but tooling costs are minimal and the process produces moreaccurate contours. In all, the process is a good fit for low-volume vehicle production.

The moral ?f the s.tory,.says MU~ro: looking beyond your own industry for new ap­proaches aVOIds engIneenng myopIa. One way is to keep your eye on industry eventsand developments at trade shows you don't usually attend.

~ stamping," he says. Should a designer, formstance, place a dimple in a deformationzone, the dimple might not perform its in­tended function. To prevent this, the systemgenerates a detailed warning message.

The rules that Chapa and others mentionare usually well established and can befound in thick volumes of machining hand­books. The software complements thehandbooks because it can recall thousandsof rules, particularly those preferred by ashop for manufacturing its specialty.

Chapa also says that describing sheet­metal parts as solids models in CAD pack­ages can yield manufacturing advantages."We can build an entire assembly, up to 200parts, in the computer. This lets us uncoverthe assembly problems and fix them beforepunching a single piece," he says.

Besides simulating produc-tion, good DFM softwareshould accommodate engi­neering design preferences."For instance, you might pre­fer starting with a blank andforming it knowing bend radiiand material thickness," saysHector Gonzalez, network ad­ministrator with MiddlebyCooking Systems Group inElgin, Ill. "Or you may preferto shape a block in the pro­gram to get the required partwith volume and materialthickness. Or maybe just weldpieces together like a con­struction set," he says. Then,the touch of a button shouldunfold the part.

Gonzalez uses DFM sheet­metal software in the EuclidCAD program from MatraDatavision. It contains a rulebase to warn users when theyviolate metal-forming guide­lines. A database of tools han­dles preferences for makingslots and holes. "We estimatethe software saves 40 to 50%of the time otherwise neededto make a part," he says.

Features designed to easethe milling process have cometo be categorized as DFM aswell. For some time, mostCAM milling packages haveincluded cutting-time genera­tors that give manufacturingengineers an idea of part pro-

The Titan CNC horizontalmachining cell from JohnFedor's Masco Machine cutsmetal andgraphite on largecylindrical bodies. Thesemachining modules arestandard Masco horizontalspindle units each equippedwith a #50 taper and20-slottoolchanger. Fedor designedand built the machine applyingDFMprinciples within a qualityprogram supported by theAssociation ofManufacturingTechnology. "DFM shouldn'tstand alone, " he says. "Itshould be part ofa total qualityimplementation and continuousimprovement process. "

Copyright © 1994 by Penton Publishing, Inc., Cleveland, Ohio 44114

Close proximity ofparts and inventory in the assemblyarea help make for efficientproduction of HP's Multimeter. The assembly area occupies less than 300 sq ft.Furthermore, where manufacturers may keep 60 to 75 days worth of componentinventory, HP keeps only two to four days worth for the 34401A.

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Mu n PO

&Ass 0 cia te s, Inc.

900 Wd,hipe Dpive, Suite 301TP04, Michigan 48084

(810) 362-5110

"" Computerized competitive analysis

"" Product design/re-design services

"" Project management engineering

"" Facilitation of hands-on DFM workshops

"" On-going DFM implementation consultation

"" Trainingftmplementation support forDFM software .

Munro & AssociatesServices & Capabilities

"" Design for serviceability/recycling assistance

"" Competitive benchmarking

"" Executive management briefings on DFM

"" Plant layout analysis and manufacturingmethod evaluation

times, and the final-cycle time, so users cancompare machines. The information letsmanufacturing engineers pinpoint the bestmachine for running a part when several areavailable. It also gives designers a good ideaof production costs.

The influence these simple DFM systemsexert extends beyond design departments.In one application, a sales engineer with analuminum manufacturer shows customershow a new, easily machined aluminum al­loy speeds cycle times and extends tool life.The company simulates operating figuresfor the new aluminum on customer ma­chines and then compares them to figuresgenerated for standard aluminum. •

duction time. "The timecalculator lets users evalu­ate, say, three differen tways to cut a pocket," saysBill Burd, senior CADICAM scientist with Manu­facturing Consulting Ser­vices. "Or they could NCprogram a series of cutsand make trade-offs to finda least-time and least-costmanufacturing method."

Accountant on a diskSoftware can now pro­

vide unbiased figures for production costsand times. For instance, "Machine-tool esti­mating packages can produce times and costfigures that are within 2% of actual," saysCraig Hoffman, system manager with Mi­cro Estimating Systems Inc.

These packages usually hold machineperformance data in a database. "They storeinformation such as turret-indexing time, arange of rapid-travel speeds, and how fast itramps to speed," says Hoffman. Lathes canbe described with about 50 parameters.

To use the software, engineers need onlyonce define the process for making a part.The software then recalculates cycle timefor any number of machine tools. The soft­ware gives a full process layout, details ev­ery operation, feeds, speeds, cut times, idle

Hewlett-Packard engineersdeveloped the 34401A Multime­ter using Boothroyd Dewhurst'sDFMA package as part of astrategy for cutting time andcosts. Project goals includedbuilding the performance of a$3,000 instrument in a $1,000unit. Now one person assemblesthe meter in just over 6 min,compared to 20 min for theprevious unit.