The flexible factory: case studies Technology is making that seeming oxymoron, custom mass production, a reality. Today factories are coming on line that are agile at tailoring goods to a customer’s requirements, without halting production for a tooling change. In one such factory-Motorola Inc.’s Fusion facility-the product and manufacturing

ertwined that a product is manufactured virtually ( in the technical sense) while the order is taken.

Some companies, like National Bicycle Industrial Co. and Applied Digital Data Systems Inc., blended

elligence of people with the tireless perfectionism of robots in order to make better products economically. Yet at the Charles Stark Draper Laboratory Inc., the extreme precision needed could be achieved only through automation.

A common theme among the case studies in this section is how companies have benefited from the risk of developing flexible manufacturing facilities. Nowhere is this clearer than in the case of Allen- Bradley Co., whose flexible eight-year-old contactor line continues producing profits.

manufacturing are learning how to rapidly prototype products, not merely to evaluate the product itself, but also to smooth the way to agile manufacturing. Industry is on the brink of the virtual factory-a place where the product manufactured depends solely on the imagination of the designer, and the variety of models produced (always with maximum economy) depends only on the whims of the market.

Companies at the forefront of

A guick luuk at rapid prototyping ____. ~~

Richard Comerford Senior Editor

Today, businesses are deploying several techniques for accelerating design and pro- duction. Among those that have already aroused much interest are concurrent engi- neering and just-in-time manufacturing, as well as electronic design automation tools such as logic synthesis. Thanks to these techniques, electronic components may be produced in just weeks.

Until recently, however, the housings and

To check out stereolithography (SLN and selective laser sintering (SLS) processes, Sandiu National Laboratories, Albuquerque, NM, created a bicycle crank arm. From the computer- aided design file seen on the screen, the labs’ rapid prototyping group made an SLA model lleftlto see how the arm would fit with other parts. Then, they made an SLS model [center1 from which a mold for the final part [right] was made.

the electromechanical parts also needed for electronic systems took many months to fabricate. Further, if those parts did not mate properly or function correctly, the extra tooling-fabrication cycle could give competitors just the break they needed to get to market first.

No wonder, then, that companies today are excited about the swiftly progressing field of rapid prototyping. In a paper de- livered last May at the Rapid Prototyping and Manufacturing ’93 Conference in Dearborn, MI, authors Clinton L. Atwood, Gerald D. McCarty, and Brian T. Pardo of Sandia National Laboratories’ Rapid Proto- typing Laboratory, Albuquerque, NM, stated: “The introduction of rapid proto- typing machines into the marketplace promises to revolutionize the process of producing prototype parts with production- like quality.” CRANKING UP. The excitement of the Sandia researchers was fanned by recent experi- ences with modern rapid prototyping sys- tems. To establish benchmark data, the

group used stereolithography and selective laser sintering equipment as part of a tech- nology-transfer program to produce a bicycle crank arm for a local bike shop. The geometry of the crank arm was of average complexity [see photo above].

Stereolithography (SLA), the most popular technique for rapidly producing pro- totypes, was invented in 1982 by Charles Hull, now president of 3D Systems Inc., Valencia, CA, which first commercialized the method in 1986. A stereolithographic system takes information about the object to be modeled directly from a computer- aided design database and builds a solid version of it out of liquid photopolymer. The system’s laser sketches a cross section of the product on the liquid, simultaneously curing it. By piling up successive cross sections, the system creates the final, solid form. Sandia used the resultant prototype, built on an SLA-250 from 3D Systems, for fit checking (that is, verifymg dimensional accuracy) and proof of design.

To make a prototype part out of the same

28 0018-9235/93/$3 00- 1993 IEEh IEEE SPECTRUM SEPTEMBER 199

material as the final production versions, in a way that replicates an investment-casting (lost-wax) production process, Sandia first builds a wax model with selective laser sin- tering (SLS).

Following data from slightly modified SLA files, the sintering creates a model by fusing wax powder with a laser. The wax models are then fitted with wax gates and vents, and the resulting assembly is re- peatedly dipped into a binder and a ceramic powder to build a ceramic shell. Once the shell is complete, the wax is melted out, leaving a mold for molten metal.

Creating a wax model in this way takes only five days, versus several months by tra- ditional methods, and reduces the cost of obtaining prototypes by as much as 90 percent. As a bonus, the technique also elec- tronically documents the entire process, from design through production. POWER TOOL. Sundstrand Aerospace’s Elec- tric Power Systems Division in Lima, OH, first worked with rapid prototyping in June 1991, for part of an aircraft’s variable-speed, constant-frequency electric system. The customer had encountered field problems with a current-transformer/electromagnet- ic-interference module and wanted them corrected in just four months.

A month after starting the project, the group had a prototype mock-up. Engineers fabricated detailed polyurethane parts using stereolithography and silicone rubber molds. Printed-circuit boards were made from glass epoxy sheets, and interconnecting flex circuits were simulated with folded paper. The mock-up, built in just a week’s time, won the customer over.

Rapid prototyping has dramatically changed the way the company works, said Rchard Gee, manager of mechanical design and development. Gee called the technique “not just a technology by itself, but a process that extends into every aspect of the devel- opment cycle.”

Pocket pagers in lots of one Russ Strobel and Andy Johnson Motorola Inc __

During the 1980s, Motorola Inc. started ag- gressive programs to reduce cycle time and improve quality. Its highly regarded Six Sig- ma program for reducing defects to 3.4 per million parts [see p. 431 has inspired a num- ber of manufacturing innovations. Among them is the new Fusion program at its Paging Products Group in Boynton Beach, FL.

The evolution of computer-integrated manufacturing KIM) at this group began in the mid-’SOs as a competitive response to comparable but cheaper products from off-

Hotline Credit verification Order entry node

Electronically speak- ing, Motorola’s Fu- swn process makes the distance between the

Customer order system (On-line database)

customer and manu- facturang extremely small. A customer can

“Explode” bill of matenal order a pager over a Set line rate Traceorders “hotlane” phonelane, Schedule choosang features by

descrabang them an blaan Endash. The

Verify orders

----- Check invenloE - - Evaluate matenal available Download to CIM

Y

order can then be au-

into the data the fac-

Factory orders expressed as station and bin locatfons

tory needs, checked Factory CIM system out by theoretically

Map processes Build virtual product

bualdang zt on a com- puter, and sent to the factory poor for fabra- cation-whale the cus- tomer is still on the lane.

Consolidate and s h i J d

shore firms. At that time, Motorola decided to change its manufacturing strategies.

The earlier Motorola prescription had been to assemble products offshore, re- trieving populated printed-circuit boards from plants in Singapore, Puerto Rico, and the South Pacific. Manufacturing costs were lowered, but the cumbersome process was not fast enough to respond to customer re- quirements or, in the long term, the compe- tition. So in 1985, Motorola began planning to automate the manufacture of one of its upcoming paging products, Bravo, at its Boynton Beach facility.

Development of the product was well under way. Nevertheless, the so-called Bandit project was chartered to create a fully automated system to manufacture Bravo pagers domestically for less than tra- ditional methods could. A small team of process, product, automation, and computer engineers was charged with creating the line in 18 months; by 1987, the line was working and demonstrating that advanced CIM was truly cost competitive.

In the six years since then, Motorola has advanced to the Fusion manufacturing system that is bolstered by easy customer access [see above figure]. Fusion had its genesis in the desire to introduce the most advanced new family of paging products in the world. The product family, code-named Fusion, was revolutionary enough to require a specially designed CIM factory. The factory envisioned would also enable ad-

vanced product development and distri- bution. Since the word “fusion” signdies uni- fication and integration, it was chosen as the name for the product, the process, the factory, and the team’s philosophy.

Fusion’s CIM and automated assembly system can manufacture a wide variety of different products. The factory’s computer system processes each order and relays it to the factory floor, where the machinery

Defining terms Aglle inwfaCtvtln# symfn: a system that can fabricate different objects simultaneously, without having to be shut down for retooling. Cyberspace: a hypothetical area in which elec- tronic information, as well as objects and events simulated by computers, are imagined to exist. Cell c”lbr a computer system used to control a group, or cell, of computers in a factory and is itself controlled by a higher-level computer. Inlectlm molding: a process for producing highly accurate objects in which the material used to form them is injected into a mold under high pressure to ensure that it solidly fills the mold. Une cwboller: a computer that is ultimately re- sponsible for the operation of an assembly line. 8trtion contrdkn: a computer usually dedicated to the control of a single manufacturing operation at one particular work site. Vlftual: an adjective used to describe the use of computers to realistically create, manipulate, and display objects or events.

Strobel and Johnson-Pocket pagers m lots of one

I i

29