Lean Manufacturing: Principles, Tools and Methods...Lean Manufacturing: Principles, Tools, and Methods Linear Motion and Assembly Technologies Aluminum Framing 8981 500 246 9/04 1

IndustrialHydraulics

Electric Drivesand Controls

Linear Motion andAssembly Technologies

ServiceAutomation

MobileHydraulicsPneumatics

Lean Manufacturing:Principles, Tools and Methods

Improve productivity and increase profits through lean manufacturing

Version 2.0

Lean Manufacturing: Principles, Tools, and Methods

Aluminum FramingLinear Motion and Assembly Technologies 8981 500 246 9/04

1

Bosch Rexroth Corp.2

In today’s manufacturing environment,assembly work is routinely characterizedby short production cycles and con-stantly diminishing batch sizes, while thevariety of product types and modelscontinues to increase. Constantpressure to shorten lead times adds tothese demands and makes the mix trulychallenging, even for the most innovativemanufacturers.

The ability to respond quickly to rapidlychanging customer demands requiresthe use of manufacturing systems thatcan be re-configured and expanded onthe fly, and which can accommodateadvances in assembly techniqueswithout making any initial manufacturinginvestments obsolete.

Lean manufacturing, an approach thatdepends greatly on flexibility andworkplace organization, is an excellentstarting point for companies wanting totake a fresh look at their currentmanufacturing methods. Lean tech-niques are also worthy of investigationbecause they eliminate large capitaloutlays for dedicated machinery untilautomation becomes absolutelynecessary.

Indeed, the concept of lean manufactur-ing represents a significant departurefrom the automated factory so popular inrecent years. The “less is better”approach to manufacturing leads to avastly simplified, remarkably unclutteredenvironment that is carefully tuned to themanufacturer’s demands. Products aremanufactured one at a time in responseto the customer’s requirements ratherthan batch manufactured for stock. Thegoal is to produce only the quantityrequired and no more. And since limitednumbers of parts are produced, it maybe necessary to change processesduring the day--to accommodatedifferent parts and to make maximum

1.Continuous Flow

2.Lean MachinesSimplicity

3.WorkplaceOrganization

4.PartsPresentation

5.Reconfigurability

6.Product Quality

9.Ergonomics

8.Ease of Access

7.Maintainability

use of personnel, equipment and floorspace. The flexibility inherent in manualassembly cells is therefore preferable toautomated assembly. This requirementfor maximum flexibility creates uniquedemands on the lean workcell and thecomponents that make up the leanworkcell.

Granted, the lean approach is not thesolution for all manufacturing problems.But it does offer a uniquely flexiblesolution for assembling more complexproducts. This guide describes 9 basiclean manufacturing principles that shouldhelp you evaluate lean manufacturingsolutions for your own applications.

The 9 principles discussed are: Continu-ous Flow, Lean Machines/Simplicity,Workplace Organization, Parts Presenta-tion, Reconfigurability, Product Quality,Maintainability, Ease of Access, andErgonomics.

The 9 Principles

Introduction: The 9 Principles of Lean Manufacturing

Bosch Rexroth Corp.Linear Motion and Assembly Technologies8981 500 246 9/04 Aluminum Framing


3

A Typical U-Shaped Cell for Lean Manufacturing

1

2

3

4

5

6

7

8

9



1


The preferred shape of the lean workcellis U-shaped. Each subprocess isconnected to the next in order ofprocess. With the worker in the interiorof the U, minimum movement is requiredto move the workpiece or assembly fromone workstation to the next.

Ultimately, one of the goals of the leanworkcell is to eliminate all non-value-added movement; hence its U-shape.When the worker has finished theprocess, he simply turns around and isback at step one.

The workpiece may be carried from onevalue-added operation to the next.However, there are times when theworkpiece or the fixture holding theworkpiece is too heavy and must betransferred mechanically betweenworkstations.

Although very heavy parts may betransported on belt conveyors, manualpush or gravity conveyors are ideal formoving parts between workstations.Their minimum complexity makes themeasy to service and minimizes downtime. In addition, they are easy toconnect end-to-end, which makes it easyto move workstations within a workcell.

The curved “corners” of the U-shapedworkcell can pose a problem. Aspotential dead space, they may act as amini storage area, thereby encouraging areturn to batch processing. Instead, theuse of a ball roller transfer shouldfacilitate part movement through thecorners of the U-shape.

Continuous Flow:

• U-shaped cell• Connect sub-processes• Value-add-to-value-add operation• Machines in order of process• Parts arrive as needed• Counterclockwise flow• One-piece flow (small lot flow)• Non-cyclical work done outside cell by support people

Benefits:Elimination of non-value added move-ments, work in process, and inventory.

Fig. 1b: Ball roller transfer

Fig. 1a: Simple roller conveyor formovement of heavy parts.

1. Continuous Flow



5

Since continuous-flow, one-at-a-timemanufacturing is another goal of leanmanufacturing, it is important that eachworkstation or machine be designed tofit within a minimal envelope. Theminimal envelope ensures the eliminationof excess flat space at the workstation ormachine. This is done to avoid thepossibility of storing parts or subassem-blies at the machine. Storing partsincreases work in process and results in“batch” processing, which subsequentlydefeats the purpose of lean manufactur-ing. In addition, smaller, minimal sizeworkstations and machines eliminateunnecessary steps taken by the workerbetween subprocesses.

Finally, significant floor space may besaved by properly sizing workstationsand machines. Although tempting for thesake of conformity and standardization,the deployment of standardized machinebases or workstations for all processesshould be avoided. Each machine baseor workstation should be designed tooptimize assembly subprocesses, whichin most cases will vary from workstationto workstation. This customization canbe achieved with virtually any structuralmaterial. To save on cost, however, aswell as to minimize the environmentalconsiderations related to disposing ofinflexible welded steel structures,preference should be given to materialthat is reconfigurable and reusable. Themodular characteristics of extrudedaluminum, bolt-together systems makethem perfect for the implementation oflean manufacturing concepts.

Moreover, in a continuous improvementenvironment, all workstations andworkcells must be easy to modify asprocess improvements are identified. Inaddition to their superior flexibility inlayout and design, lightweight aluminumstructures are easier to move when re-configuration is necessary. Casters maybe quickly mounted to the T-slottedprofiles to allow movement without theuse of fork trucks or other liftingequipment.

Lean Machine Basics:

• Continuous flow• Save factory floor space• No excess production• No extra shelf/drawer space

Benefits:One-at-a-time manufacture, quickproduction changeover, reduced WIP,easily modified, customizable produc-tion

Fig. 2a: Bolt-together structural framingsystem

Fig. 2b: Belt welding station in minimalenvelope

2. Lean Machines/Simplicity



1


A smooth, uninterrupted flow of com-pleted workpieces is the desired result ofa properly designed lean workcell.Nothing can slow or stop this flow fasterthan the loss or misplacement of tools.Thus, all tools used at a workstationshould have their own holder. Thereshould be exactly as many holders asthere are tools so that the absence of atool is quickly noticed. Using a modulartool holder system with a specific holderfor each tool is ideal. If holders caneasily be added to or taken away from aworkstation, this simply adds to theflexibility of the workstation and increasesits usefulness in a lean manufacturingprocess.

To minimize downtime, backup toolsshould also be available at any auto-mated workstations. These tools shouldbe out of the worker’s way until a failureoccurs at the automated workstation. Ofmaximum benefit are tool holdingstructures that allow tools to be swung orslid into the work space and easilyreturned to the storage position when nolonger needed.

Information Boards

Naturally, the ready availability of work-critical information also adds to efficiencyin a workcell. Supplying the rightinformation at the workplace, such asassembly processes, work instructions,repair procedures, or even productiontargets, allows workers to make the rightdecisions and act on them on the spot,limiting downtime often spent chasingdown a busy supervisor.

As with everything in a lean workcell, theinformation board should be simple, easyto reposition, and reusable.

Workplace OrganizationBasics:

• Organize tools with appropriate toolholders

• Provide back-up tools at automaticstations

• Insist on flexible tool mountingstructures

• Put the right information where it’sneeded

Benefits:Minimize downtime, reduce wastedmotion, uninterrupted workpiece flow,improve quality

Fig. 3b: Modular tool holders

3. Workplace Organization

Fig. 3c: Information Board

Tool holders

Fig. 3a: Mount for backup tool



7

Naturally, during the average work shift,additional parts will be required for theworkcell. Traditional methods ofresupplying workstations are not useful ina lean workcell. Each worker should goabout his work with the minimum numberof interruptions. Therefore, all partsshould be supplied to each workstationfrom outside the workcell. The use ofgravity feed conveyors or bins fits thesimplified design of the lean workcell.

Parts bins should load from behind(outside the working area of the workcell)so that the worker may continue produc-tion without interruption. Gravity carriesthe parts to the worker’s reach area.Bins should also be reconfigurable. Thebins in the photo use a key stud to lockthem in position. Bins are easilystackable and provide the ultimate inflexibility when reconfiguring the work-place.

Although bins are ideal for small parts,many assemblies require larger parts.These may be delivered in bins or boxes.Again the parts should be delivered tothe workcell without entering the workspace. Gravity feed conveyors serve thispurpose well. In the event that scrap orcontainers must be removed from thecell, an additional gravity feed conveyormay be mounted in the reverse direction.

In instances where parts are very heavy,lift assist devices are recommended.Heavy parts or boxes of parts can beloaded onto a case lifter and raised tothe proper work height with electric,pneumatic, or hydraulic power.

Fig. 4a: Gravity feed conveyor

Fig. 4b: Gravity feed parts bins Fig. 4c: Case Lifter

4. Parts Presentation

Parts Presentation Basics:

• Supply parts as needed• Parts loaded from outside the cell• Use gravity feed as the preferred

method• FIFO parts presentation

Benefits:Easy reconfiguration, reduce wastedmotion, uninterrupted production, quickchangeover



1


A properly designed lean workcell mustbe easy to reconfigure. In fact, the abilityto change the process and go from goodpart to good part as quickly as possibleis a must. The faster the changeover, theless production time is lost.

Quick-change fixtures are one way thiscan be accomplished. With a goodquick-change fixture, changeover can beaccomplished in a matter of seconds. Anumber of different fixtures may bestored at the workstation and swappedas the situation requires.

In Fig. 5a, for example, an assemblyfixture is locked to the T-slot at the frontof a workbench with a star knob andquarter turn connector. Once theassembly of a specific product iscomplete, a new fixture can be easilypositioned.

At times, due to process changes orother factors, a lean cell must be quicklyreconfigured or even moved to accom-modate assembly of a new product. Inthe event that a machine or workstationmust be changed, the ability to moveeach component of the workcell quicklybecomes extremely important. Lockablecasters on machines or workstationsprovide the mobility necessary for rapidand efficient changeover.

Reconfigurability Basics:

• Fixtures must be easy to change• Mobility is critical• Good part to good part as quickly

as possible

Benefits:Minimize downtime, quick changeover,uninterrupted workpiece flow

Fig. 5b: Casters on a machine stand

Fig. 5a: Quick change fixture

5. Reconfigurability



9

One of the results of one-at-a-timemanufacturing is a decrease in qualityproblems. As each part is produced,visual inspection by the worker can verifythat it is correctly assembled. If verifica-tion is required through gages, theyshould be mounted to the machine orworkstation and be easily replaced.Quick release of fixtures using star knobsor locking levers is a necessity.

There may be time when a qualityproblem cannot be easily fixed. A flawedprocess or malfunctioning machine maybe the source of the quality problems.

In the case of a flawed process, thestructural framing system allowschanges, no matter how great, in aminimum amount of time. Once again,bolt-together construction solves a majorproblem in minimum time.

A malfunctioning machine may also beeasily replaced, particularly if quickdisconnects for all pneumatic or electriclines are provided for when the lean cellis designed. In addition, no pneumatic orelectrical connections should be presentbetween machines in the lean cell. Thesewould slow the changing of the machineswithin the cell.

Once the machine has been discon-nected from all power sources, it can beeasily transported if mounted on lockablecasters.

Ease of reconfiguration and changeovereliminate any reluctance on the part ofthe worker or management to try to“make do” with machines or processesthat are “almost” right. This change inattitude can contribute greatly to truequality production.

Quality Basics:

• Visual inspection is the primary means of quality assurance• Test fixtures & gages must be easy to replace or change out• Easy reconfiguration encourages changes for quality’s sake

Benefits:Immediate feedback on quality as workers inspect parts; platform for continuousimprovement; eliminate rework areas; encourage changeover to solve “minor” qualityproblems; greater quality assurance by giving the responsibility to the assembler;rapid change of quality gages as assembled product or process changes.

6. Quality

Fig. 6: Visual Inspection verifies parts are correctly assembled and function properly.



1


7. Maintainability

Maintainability Basics:

• Ease of service• Manual back-up• Put the operator manual on

machine• Standardize as many components

as possible• Use common tools and fixtures• No finish work required on system

components.• Minimum spare parts necessary

Benefits:Minimum down time, easy-to-sourcereplacement parts, quick service

Ease of service is another requirement ofa lean cell. Long down times cannot betolerated in a pull-through system. Whencustomer demand exists, the productmust be produced. A modular structuralframing system provides the ultimate inmaintainability.

Components can be replaced orreconfigured in a matter of minutes. Bolt-together construction ensures machinestands, guards, workstations, or partspresentation equipment can be servicedin a matter of minutes. Even entiremachine bases can be rebuilt in aminimum amount of time.

The structural framing system alsoprovides a source for common compo-nents for all machine bases, guards, andworkstations. With standardizedcomponents, a minimum number of toolsis required to maintain a structure. Witha structural framing system, three or foursimple hand tools are sufficient to buildor repair any structure.

Another benefit is that common compo-nents eliminate the need for a largeinventory of spare parts. It is possible tostandardize on one size of aluminumprofile, one or two connectors, and a fewaccessories to create virtually anystructure.

Finally, no finish work is required with analuminum structure. No welding orpainting is required. Repairs can beaccomplished in the minimum amount oftime. Fig. 7: A lean cell constructed from

modular aluminum framing provides foreasy maintenance and repair



11

Using an aluminum framing system as thefoundation of a lean cell, all necessarywork components can be mounted ineasily accessible locations because eachsurface is a potential mounting surface.Parts bins, tools, shelves, and fixturescan all be positioned in the optimumlocation for efficient work. The T-slot onthe framing system’s surface also allowsquick repositioning of pneumatic orhydraulic components if clearance spaceis critical (Fig. 8a).

Components may be added quickly toany workstation and easily repositionedto insure accessibility for each worker. Inaddition, entire guards or individualpanels (Fig. 8c) can be removed quicklywith simple hand tools, enabling servicetechnicians to perform maintenance in amatter of minutes.

8. Ease of Access

Fig. 8a: Valves mounted to T-slot

Fig. 8c: Machine guard with sliding access doors and easy to remove panels

Fig. 8b: Accessibility in workstationdesign

Accessibility Basics:

• All controls or fixtures positionedwith ergonomics in mind

• All serviceable components at rearof machine/workstation toeliminate interference of mainte-nance personnel with production

• Clearance for all tools for ease ofuse

• All guards easy to remove withsimple hand tools

Benefits:Minimum down time, easy serviceabil-ity, optimum ergonomic design.



1


Ergonomics Basics:

• Position workpiece at optimumheight for worker

• Use NIOSH standards todetermine maximum lifting loads

• Position all tools within theworker’s field of reach

• Provide lighting sufficient toaccomplish the task

Benefits:Fewer work-related injuries, loweremployee turnover, better workingenvironment, fewer cumulativetrauma problems

9. Ergonomics

Fig. 9b: Case Lifter

Finally, the worker must be protectedfrom ergonomic problems. Any properlydesigned lean workcell must, by defini-tion, be ergonomically designed.Maintaining the work at the ergonomi-cally correct height throughout theworkcell is always important. Although itis frequently not taken into consideration,designing for the average worker heightis also a necessity. Since averageheights vary from country to country, theheight of a machine or workstation mustbe easily changed if there is any chancethat a workstation may be shipped fromcountry to country.

Lifting

Lift assist devices must be consideredwhere the weight of parts or boxes ofparts exceeds lifting standards. In thiscase, pneumatic, hydraulic, or electricdevices may be used, but it is importantto keep in mind that simpler is better inlean manufacturing cells.

Fig. 9a: Proper height is critical in anylean workcell

Fig. 9bc: Software for ErgonomicWorkstation Layout

Height

In order to prevent delays in manufactur-ing caused by faulty design, a softwarepackage that allows you to test theergonomics of a workcell before the

workcell is constructed can be apowerful tool. Use of such a softwarepackage lets you settle ergonomic issuesin the design stage rather than on thefactory floor, providing significantpotential savings in both time and money.



13

With all of its promise, the lean cell maynot be the answer to all assembly needs.At times the U-shaped configurationsimply does not fit the existing facility orprocess, and a change from automationor semi-automation to lean cell manufac-turing could be counterproductive.

In keeping with the flexibility requirementfor lean manufacturing, there may betimes when a hybrid system rather than apure lean system is best for the manufac-turing process.

Final Considerations: Hybrid Systems

system. The result is a system in whichsome assembly is done manually whilemore dangerous or ergonomically difficulttasks are accomplished by machine.

In a hybrid system, workstations or cellsmay be combined with non-synchronousassembly conveyor systems to achievedesired production goals. The synergybetween these two technologies canproduce results far beyond the capabili-ties of either technology alone.

In this case, the automated portions ofthe process supply sub-assemblies orparts to the lean cell. Here, although thetechnologies are separated, both are stillrequired to accomplish the task at hand.

The key to hybrid implementation isconstruction with components which areeasily reconfigured. Bolt togethertechnology fits the description perfectly.Flexible assembly systems usingaluminum framing as the main structuralelement allow companies to mix andmatch manual and automatic operationsat will, and to change them at any time inthe future. The result is a worker-friendly,economically-sound system designed foroptimum production.

Hybrid manufacturing systems combinethe economies of the lean system withthe safety and efficiency of an automated

It is also possible to accomplish assem-bly in a lean cell and to have operationswhich are purely automated take placeoff line.



1


Bosch Rexroth - Your Partner in Lean Manufacturing

A switch to lean or hybrid manufacturingmay entail radical changes in plantlayout and equipment design. To ensurethat you implement these changessmoothly and efficiently, you need apartner - Rexroth. Bosch RexrothCorporation has a network of stockingdistributors nationwide. In addition tolocal inventory, each distributor hasRexroth design experts on staff to assistyou with your lean manufacturingprojects.

Raleigh

Shreveport

Buffalo

New York City

Cleveland

Albany

Montpelier

Augusta

Detroit

Concord

Chicago

Charlotte

Charleston

Savannah

Albany

Atlanta

Louisville

Columbia

Knoxville

Birmingham

Jacksonville

Orlando

Tampa

Key West

Augusta

W. PalmBeach

Miami

New Orleans

Baton Rouge

Brownsville

San Antonio

Ft. WorthDallas

Little Rock

El Paso

Albuquerque

Houston

St. Louis

Lincoln

Minneapolis

Wichita

Springfield Cincinnati

Lansing

Oklahoma City

Seattle

Portland

Boise

RenoSacramento

Phoenix

Los Angeles

San Diego

Salt Lake CityCheyenne

Denver

Helena

Durham

Norfolk

Indianapolis

Jackson

Madison

St. Paul

Bismarck

Pierre

Trenton

Wilmington

Asheville

Mobile

Austin

San Francisco

Frankfort

HarrisburgPittsburgh

Billings

Laredo

Nashville

Philadelphia

Boston

Nuevo Laredo

Mexicali

Matamoros

Toronto

Vancouver Calgary

Regina

Winnipeg Quebec

Montreal

Ft. Albany

MEXICO

CANADA

FL

NM

DEMD

TX

OK

KS

NE

SD

NDMT

WY

CO

UT

ID

AZ

NV

WA

CA

OR

KY

ME

NY

PA

MI

VT

NH

MARICT

VA

WV

OHINIL

NC

TN

SC

AL

MS

AR

LA

MO

IA

MN

WI

NJ

GA

Washington DC

Ontario

Quebec

Manitoba

Saskatchewan

AlbertaBritish Columbia

NewBrunswick

Nova Scotia

The Bosch Rexroth Structural Framing Network

BOSCH REXROTH Buchanan, MI

Once your equipment is designed, yourRexroth distributor will provide machin-ing, assembly, and other value-addedservices to move your project to asuccessful conclusion. Each Rexrothdistributor is backed by more than 100years of experience and quality. Andworldwide availability of all Rexrothproducts ensures successful implemen-tation even when lines are movedabroad. For lean manufacturing solu-tions, count on Bosch Rexroth Corpora-tion as your expert partner.



15

Bosch Rexroth Corporation supplies the U.S. market with flexible manufacturing equipment for every manufacturing need.All Rexroth components are modular to provide maximum flexibility for easy reconfiguration and rapid manufacturingchangeovers.

For years, Rexroth has supplied manufacturers worldwide with a broad range of ergonomic components ideally suited forlean manufacturing: easily customized workstations, tool holders, information boards, parts bins, and a broad range ofworkstation accessories. Combined with the Rexroth Aluminum Structural Framing System, these components let manu-facturers build exactly the work environment required to match the parts, workers and workcells to their manufacturingprocesses.

If you’ve never used our aluminum structural framing before, you’ll be surprised how easy it is. And our customer supportsystem makes it even easier. For fastest service, order from your distributor on-line at www.boschrexroth-us.com/framing_ec. It’s the world’s first fully-functional on-line framing shop, now with an easy-to-use workstation configurator.

Bosch Rexroth Corporation is also the world’s leading supplier of power and free non-synchronous assembly conveyors.These conveyors, in concert with the workplace equipment and structural framing system products, place Rexroth in aunique position as a supplier of overall factory automation. With this family of products, hybrid lean manufacturing systemsare available from a single source, with completely interchangeable structural components.

When you’re ready to order, you have several options. Call us toll-free at 1-800-REXROTH (739-7684) for the name ofyour local distributor, or follow the step-by-step ordering instructions at our website. A nearby Rexroth distributor will shipyour order promptly. The Rexroth customer support system gives you tremendous flexibility to meet tight schedules andbudgets.

Bosch Rexroth invites you to specify the leader in lean manufacturing - Specify Rexroth!

Bosch Rexroth, the world brand leader in structural framingsystems, ergonomic workstations and flexible assembly conveyors

Bosch Rexroth CorporationCorporate Headquarters5150 Prairie Stone ParkwayHoffman Estates, IL 60192-3707Telephone (847) 645-3600Facsimile (847) 645-6201

Bosch Rexroth CorporationIndustrial Hydraulics2315 City Line RoadBethlehem, PA 18017-2131Telephone (610) 694-8300Facsimile (610) 694-8467

Bosch Rexroth CorporationElectric Drives and Controls5150 Prairie Stone ParkwayHoffman Estates, IL 60192-3707Telephone (847) 645-3600Facsimile (847) 645-6201

Bosch Rexroth CorporationPneumatics1953 Mercer RoadLexington, KY 40511-1021Telephone (859) 254-8031Facsimile (859) 281-3491

Bosch Rexroth CorporationMobile Hydraulics1700 Old Mansfield RoadWooster, OH 44691-0394Telephone (330) 263-3300Facsimile (330) 263-3333

Printed in the United States8981 500 246 9/04

Bosch Rexroth CorporationLinear Motion andAssembly Technologies816 E. Third StreetBuchanan, MI 49107Telephone (269) 695-0151Facsimile (269) 695-5363www.boschrexroth-us.com

Lean Manufacturing: Principles, Tools and Methods...Lean Manufacturing: Principles, Tools, and Methods Linear Motion and Assembly Technologies Aluminum Framing 8981 500 246 9/04 1

Documents