Lean Manufacturing Principles Rexroth Bosch Group

8/11/2019 Lean Manufacturing Principles Rexroth Bosch Group

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Electric Drivesand Controls

Linear Motion andAssembly Technologies Pneumatics ServiceHydraulics

Lean Manufacturing:Principles, Tools and Methods

Improve productivity and increase profits through lean manufacturing

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Lean Manufacturing: Principles, Tools, and Methods

Bosch Rexroth Corporation2

In todays manufacturing environment,assembly work is routinely character-ized by short production cycles andconstantly diminishing batch sizes,while the variety of product types andmodels continues 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-congured and expanded onthe y, and which can accommodateadvances in assembly techniqueswithout making any initial manufacturinginvestments obsolete.

Lean manufacturing, an approachthat depends greatly on exibility andworkplace organization, is an excellent

starting point for companies wantingto take 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 signicant departurefrom the automated factory so popularin recent years. The less is betterapproach to manufacturing leads to avastly simplied, remarkably unclutteredenvironment that is carefully tuned to themanufacturers demands. Products aremanufactured one at a time in responseto the customers 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 accommodate differ-

1. ContinuousFlow

2. Lean Machines/ Simplicity

3. WorkplaceOrganization

4. Parts Presentation

5. Recongurability

6. Product Quality

9. Ergonomics

8. Ease of Access

7. Maintainability

ent parts and to make maximum use ofpersonnel, equipment and oor space.The exibility inherent in manual assemblycells is therefore preferable to automatedassembly. This requirement for maximumexibility creates unique demands on thelean workcell and the components thatmake up the lean workcell.

Granted, the lean approach is not thesolution for all manufacturing problems.But it does offer a uniquely exiblesolution 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:Continuous Flow, Lean Machines/Sim-plicity, Workplace Organization, PartsPresentation, Recongurability, ProductQuality, Maintainability, Ease of Access,

and Ergonomics.

The 9 Principles

Introduction: The 9 Principles of Lean Manufacturing


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Bosch Rexroth Corporation


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A Typical U-Shaped Cell for Lean Manufacturing

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The preferred shape of the lean workcellis U-shaped. Each subprocess is con-nected to the next in order of process.With the worker in the interior of the U,minimum movement is required to movethe workpiece or assembly from oneworkstation to the next.

Ultimately, one of the goals of the leanworkcell is to eliminate all non-value-add-ed movement; hence its U-shape. When

the worker has nished the process, hesimply turns around and is back at stepone.

The workpiece may be carried from onevalue-added operation to the next. How-ever, there are times when the workpieceor the xture holding the workpiece istoo heavy and must be transferred me-chanically between workstations.

Although very heavy parts may be trans-ported on belt conveyors, manual push

or gravity conveyors are ideal for movingparts between workstations. Theirminimum complexity makes them easyto service and minimizes down time.In addition, they are easy to connectend-to-end, which makes it easy to moveworkstations 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 should facili-tate part movement through the cornersof 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 ow One-piece ow (small lot ow) Non-cyclical work done outside

cell by support people

Benets:

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


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Since continuous-ow, one-at-a-timemanufacturing is another goal of leanmanufacturing, it is important that eachworkstation or machine be designed to twithin a minimal envelope. The minimalenvelope ensures the elimination ofexcess at space at the workstation ormachine. This is done to avoid the pos-sibility of storing parts or subassembliesat the machine. Storing parts increaseswork in process and results in batchprocessing, which subsequently defeatsthe purpose of lean manufacturing. Inaddition, smaller, minimal size worksta-tions and machines eliminate unneces-sary steps taken by the worker betweensubprocesses.

Finally, signicant oor 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 workstation

to workstation. This customization canbe achieved with virtually any structuralmaterial. To save on cost, however, aswell as to minimize the environmentalconsiderations related to disposing ofinexible welded steel structures, prefer-ence should be given to material that isrecongurable and reusable. The modu-lar characteristics of extruded aluminum,bolt-together systems make them perfectfor the implementation of lean manufac-turing concepts.

Moreover, in a continuous improvement

environment, all workstations and work-cells must be easy to modify as processimprovements are identied. In additionto their superior exibility in layout anddesign, lightweight aluminum structuresare easier to move when re-congurationis necessary. Casters may be quicklymounted to the T-slotted proles to allowmovement without the use of fork trucksor other lifting equipment.

Lean Machine Basics:

Continuous ow Save factory oor space No excess production No extra shelf/drawer space

Benets:

One-at-a-time manufacture, quickproduction changeover, reduced

WIP, easily modied, customizableproduction

Fig. 2a: Bolt-together structural framingsystem

Fig. 2b: Any processes should take place in a minimal work envelope

2. Lean Machines/Simplicity


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A smooth, uninterrupted ow of complet-ed workpieces is the desired result of aproperly designed lean workcell. Nothingcan slow or stop this ow faster than theloss or misplacement of tools. Thus, alltools used at a workstation should havetheir own holder. There should be exactlyas many holders as there are tools sothat the absence of a tool is quicklynoticed. Using a modular tool holder sys-tem with a specic holder for each tool

is ideal. If holders can easily be addedto or taken away from a workstation, thissimply adds to the exibility of the work-station and increases its usefulness in alean manufacturing process.

To minimize downtime, backup toolsshould also be available at any auto-mated workstations. These tools shouldbe out of the workers way until a failureoccurs at the automated workstation. Ofmaximum benet are tool holding struc-tures that allow tools to be swung or slidinto the work space and easily returnedto the storage position when no longerneeded.

Information Boards

Naturally, the ready availability of work-critical information also adds to ef-ciency in 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 appropriatetool holders

Provide back-up tools at automaticstations

Insist on exible tool mountingstructures

Put the right information where itsneeded

Benets:

Minimize downtime, reduce wastedmotion, uninterrupted workpiece ow,improve quality

Fig. 3b: Modular tool holders

3. Workplace Organization

Fig. 3c: Information Board

Tool holders

Fig. 3a: Mount for backup tool


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Naturally, during the average work shift,additional parts will be required for theworkcell. Traditional methods of resup-plying workstations are not useful in alean 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 ts thesimplied design of the lean workcell.

Parts bins should load from behind (out -side the working area of the workcell) sothat the worker may continue productionwithout interruption. Gravity carries theparts to the workers reach area. Binsshould also be recongurable. The binsin the photo use a key stud to lock themin position. Bins are easily stackable andprovide the ultimate in exibility whenreconguring the workplace.

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: Flow Rack

Fig. 4b: VarioGrab 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

Benets:Easy reconguration, reduce wastedmotion, uninterrupted production, quickchangeover


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A properly designed lean workcell mustbe easy to recongure. 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 xtures are one way thiscan be accomplished. With a goodquick-change xture, changeover can beaccomplished in a matter of seconds.A number of different xtures may bestored at the workstation and swappedas the situation requires.

In Fig. 5a, for example, an assembly x-ture is locked to the T-slot at the front ofa workbench with a star knob and quarterturn connector. Once the assembly ofa specic product is complete, a newxture can be easily positioned.

At times, due to process changes orother factors, a lean cell must be quickly

recongured 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 efcient changeover.

Recongurability Basics:

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

as possible

Benets:

Minimize downtime, quick changeover,uninterrupted workpiece ow

Fig. 5b: Casters on a machine stand

Fig. 5a: Quick change xture

5. Recongurability


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One of the results of one-at-a-time manu-facturing is a decrease in quality prob-lems. As each part is produced, visualinspection by the worker can verify that itis correctly assembled. If verication isrequired through gages, they should bemounted to the machine or workstationand be easily replaced. Quick release ofxtures using star knobs or locking leversis a necessity.

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

In the case of a awed process, thestructural framing system allows chang-es, no matter how great, in a minimumamount of time. Once again, bolt-togeth-er construction solves a major problem inminimum time.

A malfunctioning machine may also

be easily 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 reconguration and changeovereliminate any reluctance on the partof the worker or management to try tomake 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 xtures & gages must be easy to replace or change out Easy recon guration encourages changes for qualitys sake

Benets:

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 veries parts are correctly assembled and function properly.


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7. Maintainability

Maintainability Basics:

Ease of service

Manual back-up Put the operator manual on the

machine Standardize as many components

as possible Use common tools and xtures No nish work required on system

components. Minimum spare parts necessary

Benets:

Minimum down time, easy-to-source

replacement 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 or recon-gured in a matter of minutes. Bolt-together construction ensures machinestands, guards, workstations, or partspresentation equipment can be servicedin a matter of minutes. Even entire ma-chine bases can be rebuilt in a minimumamount of time.

The structural framing system alsoprovides a source for common com-ponents for all machine bases, guards,and workstations. With standardizedcomponents, a minimum number of toolsis required to maintain a structure. Witha structural framing system, three or four

simple hand tools are sufcient to buildor repair any structure.

Another benet is that common com-ponents eliminate the need for a largeinventory of spare parts. It is possibleto standardize on one size of aluminumprole, one or two connectors, and afew accessories to create virtually anystructure.

Finally, no nish work is required with analuminum structure. No welding or paint -ing is required. Repairs can be accom-plished in the minimum amount of time.

Fig. 7: A lean cell constructed frommodular aluminum framing provides foreasy maintenance and repair


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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 xturescan all be positioned in the optimumlocation for efcient work. The T-slot onthe framing systems surface also allowsquick repositioning of pneumatic orhydraulic components if clearance space

is critical (Fig. 8a).

Components may be added quickly toany workstation and easily repositionedto insure accessibility for each worker.In addition, 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 xtures positionedwith ergonomics in mind

All serviceable components at rearof machine/workstation to elimi-nate interference of maintenancepersonnel with production

Clearance for all tools for ease of

use All guards easy to remove with

simple hand tools

Benets:

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


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Ergonomics Basics:

Position workpiece at optimumheight for worker

Use NIOSH standards to de -termine maximum lifting loads

Position all tools within theworkers eld of reach

Provide lighting suf cient toaccomplish the task

Benets:

Fewer work-related injuries, loweremployee turnover, better work-ing environment, fewer cumulativetrauma problems

9. Ergonomics

Fig. 9b: Case Lifter

Finally, the worker must be protectedfrom ergonomic problems. Any prop-erly designed lean workcell must, bydenition, be ergonomically designed.Maintaining the work at the ergonomicallycorrect height throughout the workcell isalways important. Although it is frequent-ly not taken into consideration, designingfor the average worker height is also anecessity. Since average heights varyfrom country to country, the height of amachine or workstation must be easilychanged if there is any chance that aworkstation may be shipped from countryto 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.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

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

Height

workcell is constructed can be a power-ful tool. Use of such a software packagelets you settle ergonomic issues in thedesign stage rather than on the factoryoor, providing signicant potentialsavings in both time and money.

Fig. 9c: Software for ErgonomicWorkstation Layout


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

In keeping with the exibility requirementfor lean manufacturing, there may betimes when a hybrid system rather than a

pure lean system is best for the manufac-turing process.

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

Final Considerations: Hybrid Systems

system. The result is a system in whichsome assembly is done manually whilemore dangerous or ergonomically difculttasks 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.

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

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 whichare easily recongured. Bolt togethertechnology ts the description per-fectly. Flexible assembly systems using

aluminum 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.


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Bosch Rexroth - Your Partner in Lean Manufacturing

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The Bosch Rexroth Structural Framing Network

BOSCH REXROTHBuchanan, MI

A switch to lean or hybrid manufacturing may entail radical changes in plant layout and equipment design. To ensure that youimplement these changes smoothly and efciently, you need a partner - Rexroth. Bosch Rexroth Corporation has a network ofstocking distributors nationwide. In addition to local inventory, each distributor has Rexroth design experts on staff to assist youwith your lean manufacturing projects.

Once your equipment is designed, your Rexroth distributor will provide machining, assembly, and other value-added services tomove your project to a successful conclusion. Each Rexroth distributor is backed by more than 100 years of experience andquality. And worldwide availability of all Rexroth products ensures successful implementation even when lines are moved abroad.For lean manufacturing solutions, count on Bosch Rexroth Corporation as your expert partner.


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Bosch Rexroth Corporation supplies the U.S. market with exible manufacturing equipment for every manufacturing need.All Rexroth components are modular to provide maximum exibility for easy reconguration 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 of work-station accessories. Combined with the Rexroth Aluminum Structural Framing System, these components let manufactur-ers build exactly the work environment required to match the parts, workers and workcells to their manufacturing processes.

If youve never used our aluminum structural framing before, youll 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.Its a fully functional online catalog, now with an easy-to-use workstation congurator.

Bosch Rexroth Corporation is also the worlds 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 systems

are available from a single source, with completely interchangeable structural components.

When youre ready to order, you have several options. Call us toll-free at 1-800-REXROTH (739-7684) for the name of yourlocal distributor, or follow the step-by-step ordering instructions at our website. A nearby Rexroth distributor will ship yourorder promptly. The Rexroth customer support system gives you tremendous exibility to meet tight schedules and budgets.

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

NEW! Visit our lean resource center on the web: www.boschrexroth-us.com/lean

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


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

Bosch Rexroth CorporationHydraulics2315 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


Hydraulics8 Southchase CourtFountain Inn, SC 29644-9018Telephone (864) 967-2777Facsimile (864) 967-8900

Printed in the United States8981 500 246 (11.2009)

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

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Lean Manufacturing Principles Rexroth Bosch Group