Automation Technology

How to OptimizeYour Assembly Operations

Type of product

Breakthrough

New

Major revision

Minor revision

0 5 10 15 20 25 30 35 40 45 50

3

Cutting,Forming,

Machining8-30%

Assembly50-75%

Inspection4-15%

Figure 2: Production Labor

The flexibility of your assembly operation canmake the difference in your manufacturing profit

It’s tough to make a buck in manufac-turing today. Rapid change is drivingthe way products are made and eventhe products themselves. Products areincreasingly complex and requiremore assembly steps. But the biggestpressure comes from time, becausewhile product variations expand,product life cycles contract. Thechallenge is to get better products tomarket faster, while maintainingprofit margins and lowering manufac-turing costs (see Figure 1). To dothis, most manufacturers are stayingflexible.

Today’s manufacturing operationspresent both opportunity and chal-lenge for improvement.

To stay ahead of the pack, manufac-turers must seize every opportunity

to increase productivity and through-put, reduce costs, increase productquality and reliability, while manag-ing change on an almost daily basis.Typically, the labor involved in pro-ducing individual components—operations such as metal cutting,forming, and machining or plasticsmolding and finishing—representsbetween 8% and 30% of total manu-facturing costs. The labor involvedin inspection and testing typicallyrepresents between 4% and 15%.But the labor involved with assem-bly can run between 50% and 75% oftotal manufacturing costs (see Figure2). This is clearly where the largestmanufacturing cost savings can beachieved.

While assembly operations may offerthe greatest potential for increasing

efficiency, they also pose severalchallenges. These include:

• Reducing work-in-process (WIP)inventory (the number of pieceparts and materials waiting idly forvalue-added assembly operationsto be carried out).

• Controlling product quality: test andinspection generally take place afterall assembly operations have beencompleted. Rejected assembliesneeding rework increase WIP andcancel previous value-added gains.

• Managing rapid growth: forexample, when customer demand isoutstripping current capacityand/or the product mix is prolifer-ating.

Biggest manufacturing efficiency gains cancome from assembly tasks.

Figure 1: Product Development Time Keeps Shrinking For U.S. Marketers

Time to get to market in months

19921996

19921996

19921996

19921996

Source: Product Development & Management Association

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Old-fashioned assembly methods, like this, are both labor intensive and inefficient.

While agile and lean may bethe ultimate goal for assemblyoperations, achieving that goalis seldom simple.

There are numerous variables involvedin designing the best assembly methodsto move products through a manu-facturing operation. The more com-plex the product, the more extensivethe product mix—the more difficultthe task. Shorter product life cycles alsocomplicate the situation. As productmix or volume increases, traditionalmaterial handling methods (i.e., theuse of plywood pallets and/or rollerconveyor for staging and transferringWIP) may prove inadequate orcounter-productive. Adding more ofthe same is clearly not a long-termsolution.

Additional common assemblychallenges include:

• Numerous parts, components,and/or subassemblies

• Assembly operations requiringprecise, repeatable positioning

• Special environmental provisionssuch as clean rooms, ESD(electrostatic discharge) protection,temperature control, etc.

• Operations to accommodate modelvariations with differing lot sizes

• Products requiring up to 100%inspection

Companies successfully managingthe demands of continued, profitablegrowth have recognized the need fora mechanized solution, i.e., conveyorsystems designed specifically forassembly flexibility. Often, the bestproduct assembly strategy requiresthe right mix of automated and

manual operations—and being able toadjust that mix as necessary. Flexibleassembly conveyors, seamlessly inte-grated into the assembly processesthey support, provide the best solu-tion for today’s complex assemblyconditions.

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Operation

A B C D

FinishedProduct

Figure 3b: Non-Synchronous - Flexible Path, providing variedstation cycle rates.

OperationB

FinishedProduct

Operation A

OperationC

OperationD

Figure 3a: Synchronous - Fixed Path, with no provision forcycle independence.

The fixed path, synchronous system does not provide for cycle independence.Throughput depends on the slowest operation on the assembly line.

Non-synchronous assembly allows buffering in slower task work areas,while maintaining continuous flow on the main production line.

Assembly conveyor systemsare generally classified into twobasic types, each with distinctcharacteristics.

• Synchronous conveyor systemsutilize indexed movement of partsfrom station to station, along afixed path and at a fixed cyclerate. Examples include rotary dialmachines and cam-operated, in-linemachines. Short cycle rates, stan-dardized production, and a highlevel of automation are featuresof the synchronous system. Butsynchronous systems also have theirshortcomings. System throughput,for example, must be geared to theslowest operation on the assemblyline. And there is no provision forcycle independence; all parts of theproduction line move in “lock step.”

• Non-synchronous conveyor systemsprovide independent movementof parts from station to station onan as-needed basis, as they becomeready for the next operation. Workcan be routed independently alonga flexible path. Non-synchronoussystems can accommodate the fullrange of product sizes and weights.Moreover, there are virtually nolimitations on the number orcomplexity of assembly steps withnon-synchronous systems. Manualtasks can be readily integrated withautomated operations, because thesystem allows for varying station

cycle rates. In addition, you caneasily add buffers as needed tobalance assembly line work flow.

Conveyor systems play an increasinglyimportant role in today’s productionoperations. As production levelsincrease, for example, a company

might consider converting from batchto sequential assembly operations orincorporating automated workstationsinto existing sequential manual lines.The challenge will often include theupgrade of an existing facility (retrofit)rather than creation of an entirelynew one.

Positioning UnitProvides precise pallet

positioning for assembly operations

Lift Transverse UnitLifts and transfers the

workpiece pallet at right angles over the

conveyor section to an adjacent line

Drive UnitPowers the belt or

chain to move pallets through the

system

Transverse ConveyorTransfers pallets

between two lines

Return UnitReturns the belt or

chain to the drive unit

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Figure 4: A typical non-synchronous, pallet-based conveyor system is made up oFor increasing numbers of manufac-turers the use of non-synchronous,pallet-based modular conveyors is anideal solution to their assembly sys-tem requirements. Non-synchronousassembly conveyors typically incorpo-rate a continuously moving belt orchain with pallets and pallet compo-nents, which move with the conveyorunless held by a stop. Modular con-veyor components and accessoriesease assembly and future reconfigura-tion or expansion as conditionswarrant.

Stop GatesStandard stops halt

pallet travel. Cushioned stops reduce pallet

impact force for transport of sensitive

components

Rockers and StopsDetect workpiece

pallets and also provide a stop at the end of a Lift-Transverse Unit

Coding SystemsRead/Write pallet coding system enables proper workpiece pallet

routing and data collection to optimize manufacturing flexibility

and control

Modular ConstructionUse of standard

structural components allows flexibility when

reconfiguring a system

Workpiece PalletSizes from 80 x 80 mm to

1200 x 1200 mm

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When to consider pallet-basedmodular conveyors

While some product assemblyoperations may not call for anon-synchronous, pallet-basedmodular conveyor system, it couldbe the ideal solution when:

• Multiple product modelsminimize productionchangeover time.

• Changes to product designand corresponding assemblyoperations are frequent.

• Product delivery lead-timesare shrinking.

• Introducing automated assemblyoperations is essential to improveproductivity.

• Material flow paths must bereconfigured.

• Precision assembly tasks arerequired.

• Line balancing is a crucialelement of production efficiency.

• Space is at a premium.

of modular components.

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The benefits of modularitymesh with today’s assemblyenvironment.

Based on a “building block” concept,modular, non-synchronous conveyorsystems provide an unmatched levelof flexibility because the conveyorcomponents can be quickly configuredto provide required functional char-acteristics. They can be reconfiguredwhen production requirementschange, and their availability asoff-the-shelf modules can dramaticallyspeed project implementation. Systempayback (ROI) is another advantagefor using non-synchronous systems.Compared to heavily automatedsystems, payback on a flexible assem-bly conveyor occurs sooner because:

• Start-up costs are lower

• There is a shorter debug time

• Reuse reduces later capitalinvestments

The flexibility of modular, non-synchronous, pallet-based conveyorsystems provides a long list ofbenefits that mesh ideally withtoday’s assembly environment.

These include:

1. Phased implementation –Stand-alone assembly tasks, forexample, can be moved on-lineto increase productivity; later,manual stations can be replacedwith automated stations asrequired. See Figure 5.

2. Integration of automatedprocesses – Many factors drivethe need to introduce, or increasethe level of automated processesto the assembly function. Theseinclude incorporation of new man-ufacturing technology, changesin product design, an increase inproduct mix, the need to lowerunit costs, or any combinationof these. Using conveyor modules,the task of integrating automatedprocesses such as screwdriving,ultrasonic welding, or testing intowhat may have been completelymanual assembly operations canreadily be accomplished.

3. Line balancing flexibility –Balancing work load is a primarygoal for assembly operations.Without the flexibility to respondeffectively to changing productionrequirements, the ability to main-tain optimal line balance may beseriously compromised. However,the line routing flexibility of mod-ular systems allows parallel spursto be added for balancing of cyclerates between slow and fast work-station tasks or the routing ofreject parts off-line and reworkedparts back on-line.

4. Integration of test functions –As assembly operations becomeboth more complex and efficient,test and/or inspection functionsare being incorporated as anintegral part of the process.Retrofitting these functions intoan existing system may poseinsurmountable obstacles unlessthe system is modular and affordsthe flexibility for reconfiguration.

Reworking stations

Automatic stations

Manual workstations

Workpiece- pallet circulation

Figure 5: Line balancing through automated/manual operations on thesame assembly line.

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5. Implementation of processcontrol(s) – The ability to fitpallets with read/write devicespermits each workpiece to beuniquely identified. This in turn,allows the control system to trackthe status and control the move-ment of units through automatedworkstations and provides a wayof collecting data for statisticalprocess control (SPC). Such aprocess control system allows fortwo or more models of a productto be assembled on the same lineand provides for product reworkas necessary.

6. Material flow options –Material flow through anassembly facility can be affectedby changes in any facet of theassembly operations. These caninclude the replacement of man-ual workstations with automatedworkstations, a product designchange that requires a modifica-tion to assembly procedures, orthe introduction of new models.An existing modular conveyorline can easily allow materialflow patterns to be modifiedor reconfigured. See Figure 6.

Yesterday

Today

Tomorrow

Figure 6: A system that expands with your needs

7. Reduced WIP – Reducing thelevel of WIP can have a majorimpact on lowering assembly costs.Non-synchronous, pallet-based con-veyor systems, by their very nature,focus on keeping work moving, notpiled in stacks on the productionfloor. Thus, a transition from batchto progressive, sequential assemblycan pave the way to reduced in-process inventories necessary forjust-in-time (JIT) manufacturingoperations.

8. Improved ergonomics – There is growing evidence thatsound ergonomics goes hand-in-hand with improved productivity.The pallet positioning and orien-tation modules available withthese modular conveyor systemsare designed to reduce wastedmotion and fatigue of a worker bypresenting the workpiece properlypositioned for the required assemblytask. Moreover, compared withalternative systems such as rollerconveyor, these modular assemblyconveyors are basically quiet inoperation. Low ambient noiselevel is another important elementin the overall ergonomic scenario.

9. Reduced footprint –The variety of conveyor typesand modules are geared forsystem designs that conservespace and accommodate a widerange of production requirements.Modular construction permitscomplete freedom in system con-figurations, including rectangular,carousel, serpentine, over/under,parallel, and in-line (see Figure 7,below). The ability to run multipleproduct models on a single lineprovides another significantopportunity to conserve space.

10. Reusability – Like the abilityto reconfigure lines, reusabilityis an important consideration in

an assembly system investment.Not only do assembly operationschange, but entire manufacturingfacilities might be moved fromone site to another. The fact thatassembly conveyor modules canbe “packed up and moved” is asignificant factor in reducingtheir life-cycle costs.

For more information aboutoptimizing assembly operations,write or call:

Bosch Automation Products816 E. Third StreetBuchanan, MI 49107Phone: 1-800-32-BOSCHFax: (616) 695-5363

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Rectangular In-line

Carousel Serpentine

• Ideal layout for surrounding awork cell or robotic stations.

• Best layout for limitedfloor space.

• Most self-contained system layout.

• Ideal for joining twoproduction areas, orgetting around obstruc-tions on a plant floor

Figure 7: Modular construction allows complete freedomin system configurations

Bosch - The World Brand Leader inFlexible Assembly Conveyor Systems

Bosch Automation Products provides the modules that make up theseflexible conveyor systems. They are pre-engineered and have establishedan extensive track record in the field with well-documented performancecapabilities by thousands of companies worldwide. This proven performanceleads to a high probability of successful system performance. Bosch includesextensive product documentation to simplify both start-up and maintenanceoperations.

System design and support is yet another benefit that Bosch provides.Because of their modular, standardized design, components can be shippedquickly for replacement, resulting in minimum downtime.

Why wait? Put the Bosch advantages of improved productivity, better prod-uct quality and cost reductions to work in your manufacturing operationnow. For systems integration assistance call us at 1-800-32-BOSCH. We’lltake it from there.

Visit us on the Web: www.boschautomation.com

NORTH AMERICABosch Automation Products816 E. Third St.Buchanan, MI 49107Hot Line (800) 32 BOSCHTelephone (616) 695-0151FAX (616) 695-5363

EUROPERobert Bosch GmbHGeschäftsbereichAutomationstechnikMontagetechnik

Wernerstraße 51D-70469 Stuttgart (Feuerbach)Telefax (0711) 811-7712

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