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and Controlsves Hydraulics Assembly Technologies Pneumatics Service Lean Manufacturing: Principles, Tools and Methods Versio2 5 Improve productivity and increase profits through lean manufacturing 2 Bosch Rexroth Corporation Lean Manufacturing: Principles, Tools, and Methods Introduction: The 9 Principles of Lean Manufacturing 1 The 9 Principles In today’s manufacturing environment, ent parts and to make maximum use of 1. Continuous assembly work is routinely character- personnel, equipment and floor space. ized by short production cycles and The flexibility inherent in manual assembly Flow constantly diminishing batch sizes, cells is therefore preferable to automated while the variety of product types and assembly. This requirement for maximum models continues to increase. Constant flexibility creates unique demands on the pressure to shorten lead times adds to lean workcell and the components that 2. Lean Machines/ these demands and makes the mix truly make up the lean workcell. Simplicity challenging, even for the most innovative manufacturers. Granted, the lean approach is not the solution for all manufacturing problems. The ability to respond quickly to rapidly But it does offer a uniquely flexible 3. Workplace changing customer demands requires solution for assembling more complex Organization the use of manufacturing systems that products. This guide describes 9 basic can be re-configured and expanded on lean manufacturing principles that should the fly, and which can accommodate help you evaluate lean manufacturing advances in assembly techniques solutions for your own applications. 4. Parts without making any initial manufacturing investments obsolete. Presentation The 9 principles discussed are: Continuous Flow, Lean Machines/Sim- Lean manufacturing, an approach plicity, Workplace Organization, Parts that depends greatly on flexibility and Presentation, Reconfigurability, Product workplace organization, is an excellent Quality, Maintainability, Ease of Access, 5. Reconfigurability starting point for companies wanting and Ergonomics. to take a fresh look at their current manufacturing methods. Lean tech- niques are also worthy of investigation because they eliminate large capital 6. Product Quality outlays for dedicated machinery until automation becomes absolutely necessary. Indeed, the concept of lean manufactur- 7. Maintainability ing represents a significant departure from the automated factory so popular in recent years. The “less is better” approach to manufacturing leads to a vastly simplified, remarkably uncluttered environment that is carefully tuned to the 8. Ease of Access manufacturer’s demands. Products are manufactured one at a time in response to the customer’s requirements rather than batch manufactured for stock. The goal is to produce only the quantity required and no more. And since limited 9. Ergonomics numbers of parts are produced, it may be necessary to change processes during the day--to accommodate differ- Bosch Rexroth Corporation Lean Manufacturing: Principles, Tools, and Methods A Typical U-Shaped Cell for Lean Manufacturing 4 7 1 9 2 3 8 6 5 4 Bosch Rexroth Corporation Lean Manufacturing: Principles, Tools, and Methods 1. Continuous Flow 1 The preferred shape of the lean workcell is 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 move the workpiece or assembly from one workstation to the next. Ultimately, one of the goals of the lean workcell is to eliminate all non-value-add- ed movement; hence its U-shape. When the worker has finished the process, he simply turns around and is back at step one. The workpiece may be carried from one value-added operation to the next. How- ever, there are times when the workpiece or the fixture holding the workpiece is too heavy and must be transferred me- Continuous Flow: chanically between workstations. • U-shaped cell Although very heavy parts may be trans- • Connect sub-processes ported on belt conveyors, manual push or gravity conveyors are ideal for moving • Value-add-to-value-add operation parts between workstations. Their • Machines in order of process • Parts arrive as needed minimum complexity makes them easy to service and minimizes down time. • Counterclockwise flow In addition, they are easy to connect • One-piece flow (small lot flow) end-to-end, which makes it easy to move workstations within a workcell. • Non-cyclical work done outside cell by support people Fig. 1a: Simple roller conveyor for The curved “corners” of the U-shaped movement of heavy parts. workcell can pose a problem. As Benefits: potential dead space, they may act as a Elimination of non-value added move- mini storage area, thereby encouraging a ments, work in process, and inventory. return to batch processing. Instead, the use of a ball roller transfer should facili- tate part movement through the corners of the U-shape. Fig. 1b: Ball roller transfer Bosch Rexroth Corporation 5 Lean Manufacturing: Principles, Tools, and Methods 2. Lean Machines/Simplicity Since continuous-flow, one-at-a-time manufacturing is another goal of lean manufacturing, it is important that each workstation or machine be designed to fit within a minimal envelope. The minimal envelope ensures the elimination of excess flat space at the workstation or machine. This is done to avoid the pos- sibility of storing parts or subassemblies at the machine. Storing parts increases work in process and results in “batch” processing, which subsequently defeats the purpose of lean manufacturing. In addition, smaller, minimal size worksta- tions and machines eliminate unneces- sary steps taken by the worker between subprocesses. Finally, significant floor space may be saved by properly sizing workstations and machines. Although tempting for the sake of conformity and standardization, the deployment of standardized machine Lean Machine Basics: bases or workstations for all processes should be avoided. Each machine base or workstation should be designed to • Continuous flow optimize assembly subprocesses, which • Save factory floor space in most cases will vary from workstation • No excess production to workstation. This customization can be achieved with virtually any structural • No extra shelf/drawer space material. To save on cost, however, as well as to minimize the environmental considerations related to disposing of Benefits: Fig. 2a: Bolt-together structural framing inflexible welded steel structures, prefer- system One-at-a-time manufacture, quick ence should be given to material that is production changeover, reduced reconfigurable and reusable. The modu- WIP, easily modified, customizable lar characteristics of extruded aluminum, bolt-together systems make them perfect production for the implementation of lean manufac- turing concepts. Moreover, in a continuous improvement environment, all workstations and work- cells must be easy to modify as process improvements are identified. In addition to their superior flexibility in layout and design, lightweight aluminum structures are easier to move when re-configuration is necessary. Casters may be quickly mounted to the T-slotted profiles to allow movement without the use of fork trucks or other lifting equipment. Fig. 2b: Any processes should take place in a minimal work envelope 6 Bosch Rexroth Corporation Lean Manufacturing: Principles, Tools, and Methods 3. Workplace Organization 1 Tool holders A smooth, uninterrupted flow of complet- ed workpieces is the desired result of a properly designed lean workcell. Nothing can slow or stop this flow faster than the loss or misplacement of tools. Thus, all tools used at a workstation should have their own holder. There should be exactly as many holders as there are tools so that the absence of a tool is quickly noticed. Using a modular tool holder sys- tem with a specific holder for each tool is ideal. If holders can easily be added to or taken away from a workstation, this simply adds to the flexibility of the work- station and increases its usefulness in a lean manufacturing process. To minimize downtime, backup tools should also be available at any auto- Workplace Organization mated workstations. These tools should Basics: be out of the worker’s way until a failure occurs at the automated workstation. Of • Organize tools with appropriate maximum benefit are tool holding struc- tures that allow tools to be swung or slid tool holders into the work space and easily returned • Provide back-up tools at automatic to the storage position when no longer stations needed. • Insist on flexible tool mounting structures Information Boards • Put the right information where it’s needed Naturally, the ready availability of work- Fig. 3a: Mount for backup tool Benefits: critical information also adds to effi- ciency in a workcell. Supplying the right Minimize downtime, reduce wasted information at the workplace, such as motion, uninterrupted workpiece flow, assembly processes, work instructions, improve quality repair procedures, or even production targets, allows workers to make the right decisions and act on them on the spot, limiting downtime often spent chasing down a busy supervisor. As with everything in a lean workcell, the information board should be simple, easy to reposition, and reusable. Fig. 3b: Modular tool holders Fig. 3c: Information Board Bosch Rexroth Corporation 7 Lean Manufacturing: Principles, Tools, and Methods 4. Parts Presentation Naturally, during the average work shift, additional parts will be required for the workcell. Traditional methods of resup- plying workstations are not useful in a lean workcell. Each worker should go about his work with the minimum number of interruptions. Therefore, all parts should be supplied to each workstation from outside the workcell. The use of gravity feed conveyors or bins fits the simplified design of the lean workcell. Parts bins should load from behind (out- side the working area of the workcell) so that the worker may continue production without interruption. Gravity carries the Parts Presentation Basics: parts to the worker’s reach area. Bins should also be reconfigurable. The bins • Supply parts as needed in the photo use a key stud to lock them • Parts loaded from outside the cell in position. Bins are easily stackable and provide the ultimate in flexibility when • Use gravity feed as the preferred reconfiguring the workplace. method • FIFO parts presentation Although bins are ideal for small parts, many assemblies require larger parts. Benefits: These may be delivered in bins or boxes. Easy reconfiguration, reduce wasted Again the parts should be delivered to motion, uninterrupted production, quick the workcell without entering the work changeover space. Gravity feed conveyors serve this purpose well. In the event that scrap or containers must be removed from the cell, an additional gravity feed conveyor may be mounted in the reverse direction. Fig. 4a: Flow Rack In instances where parts are very heavy, lift assist devices are recommended. Heavy parts or boxes of parts can be loaded onto a case lifter and raised to the proper work height with electric, pneumatic, or hydraulic power. Fig. 4b: VarioGrab bins Fig. 4c: Case Lifter 8 Bosch Rexroth Corporation Lean Manufacturing: Principles, Tools, and Methods 5. Reconfigurability 1 A properly designed lean workcell must be easy to reconfigure. In fact, the ability to change the process and go from good part to good part as quickly as possible is a must. The faster the changeover, the less production time is lost. Quick-change fixtures are one way this can be accomplished. With a good quick-change fixture, changeover can be accomplished in a matter of seconds. A number of different fixtures may be stored at the workstation and swapped as the situation requires. In Fig. 5a, for example, an assembly fix- ture is locked to the T-slot at the front of a workbench with a star knob and quarter turn connector. Once the assembly of Reconfigurability Basics: a specific product is complete, a new fixture can be easily positioned. • Fixtures must be easy to change • Mobility is critical At times, due to process changes or • Good part to good part as quickly other factors, a lean cell must be quickly as possible reconfigured or even moved to accom- modate assembly of a new product. In the event that a machine or workstation Benefits: must be changed, the ability to move Minimize downtime, quick changeover, each component of the workcell quickly Fig. 5a: Quick change fixture uninterrupted workpiece flow becomes extremely important. Lockable casters on machines or workstations provide the mobility necessary for rapid and efficient changeover. Fig. 5b: Casters on a machine stand Bosch Rexroth Corporation 9 Lean Manufacturing: Principles, Tools, and Methods 6. Quality One of the results of one-at-a-time manu- facturing is a decrease in quality prob- lems. As each part is produced, visual inspection by the worker can verify that it is correctly assembled. If verification is required through gages, they should be mounted to the machine or workstation and be easily replaced. Quick release of fixtures using star knobs or locking levers is a necessity. There may be time when a quality problem cannot be easily fixed. A flawed process or malfunctioning machine may be the source of the quality problems. In the case of a flawed process, the structural framing system allows chang- Quality Basics: es, no matter how great, in a minimum amount of time. Once again, bolt-togeth- er construction solves a major problem in • Visual inspection is the primary means of quality assurance • Test fixtures & gages must be easy to replace or change out minimum time. • Easy reconfiguration encourages changes for quality’s sake A malfunctioning machine may also be easily replaced, particularly if quick Benefits: disconnects for all pneumatic or electric lines are provided for when the lean cell Immediate feedback on quality as workers inspect parts; platform for continuous is designed. In addition, no pneumatic or improvement; eliminate rework areas; encourage changeover to solve “minor” quality electrical connections should be present problems; greater quality assurance by giving the responsibility to the assemble▯r; between machines in the lean cell. These rapid change of quality gages as assembled product or process changes. would slow the changing of the machines within the cell. Once the machine has been discon- nected from all power sources, it can be easily transported if mounted on lockable casters. Ease of reconfiguration and changeover eliminate any reluctance on the part of the worker or management to try to “make do” with machines or processes that are “almost” right. This change in attitude can contribute greatly to true quality production. Fig. 6: Visual Inspection verifies parts are correctly assembled and function properly. 10 Bosch Rexroth Corporation Lean Manufacturing: Principles, Tools, and Methods 7. Maintainability 1 Ease of service is another requirement of a lean cell. Long down times cannot be tolerated in a pull-through system. When customer demand exists, the product must be produced. A modular structural framing system provides the ultimate in maintainability. Components can be replaced or recon- figured in a matter of minutes. Bolt- together construction ensures machine stands, guards, workstations, or parts presentation equipment can be serviced in a matter of minutes. Even entire ma- chine bases can be rebuilt in a minimum amount of time. The structural framing system also provides a source for common com- ponents for all machine bases, guards, and workstations. With standardized Maintainability Basics: components, a minimum number of tools is required to maintain a structure. With a structural framing system, three or four • Ease of service simple hand tools are sufficient to build or repair any structure. • Manual back-up • Put the operator manual on the machine Another benefit is that common com- ponents eliminate the need for a large • Standardize as many components inventory of spare parts. It is possible as possible • Use common tools and fixtures to standardize on one size of aluminum profile, one or two connectors, and a • No finish work required on system few accessories to create virtually any components. structure. • Minimum spare parts necessary Finally, no finish work is required with an Benefits: aluminum structure. No welding or paint- ing is required. Repairs can be accom- Minimum down time, easy-to-source plished in the minimum amount of time. replacement parts, quick service Fig. 7: A lean cell constructed from modular aluminum framing provides for easy maintenance and repair Bosch Rexroth Corporation 11 Lean Manufacturing: Principles, Tools, and Methods 8. Ease of Access Using an aluminum framing system as the foundation of a lean cell, all necessary work components can be mounted in easily accessible locations because each surface is a potential mounting surface. Parts bins, tools, shelves, and fixtures can all be positioned in the optimum location for efficient work. The T-slot on the framing system’s surface also allows quick repositioning of pneumatic or hydraulic components if clearance space is critical (Fig. 8a). Components may be added quickly to any workstation and easily repositioned Accessibility Basics: to insure accessibility for each worker. In addition, entire guards or individual panels (Fig. 8c) can be removed quickly • All controls or fixtures positioned with simple hand tools, enabling service with ergonomics in mind technicians to perform maintenance in a • All serviceable components at rear matter of minutes. of machine/workstation to elimi- nate interference of maintenance personnel with production • Clearance for all tools for ease of use • All guards easy to remove with simple hand tools Benefits: Minimum down time, easy serviceabil- Fig. 8b: Accessibility in workstation ity, optimum ergonomic design. design Fig. 8a: Valves mounted to T-slot Fig. 8c: Machine guard with sliding access doors and easy to remove panels 12 Bosch Rexroth Corporation Lean Manufacturing: Principles, Tools, and Methods 9. Ergonomics 1 Height Finally, the worker must be protected from ergonomic problems. Any prop- erly designed lean workcell must, by definition, be ergonomically designed. Maintaining the work at the ergonomically correct height throughout the workcell is always important. Although it is frequent- ly not taken into consideration, designing for the average worker height is also a necessity. Since average heights vary from country to country, the height of a machine or workstation must be easily changed if there is any chance that a workstation may be shipped from country to country. Ergonomics Basics: workcell is constructed can be a power- • Position workpiece at optimum ful tool. Use of such a software package height for worker lets you settle ergonomic issues in the • Use NIOSH standards to de- design stage rather than on the factory termine maximum lifting loads floor, providing significant potential • Position all tools within the savings in both time and money. worker’s field of reach • Provide lighting sufficient to accomplish the task Fig. 9a: Proper height is critical in any Benefits: lean workcell Fewer work-related injuries, lower employee turnover, better work- ing environment, fewer cumulative Lifting trauma problems Lift assist devices must be considered where the weight of parts or boxes of parts exceeds lifting standards. In this case, pneumatic, hydraulic, or electric devices may be used, but it is important to keep in mind that simpler is better in lean manufacturing cells. In order to prevent delays in manufactur- ing caused by faulty design, a software package that allows you to test the ergonomics of a workcell before the Fig. 9c: Software for Ergonomic Workstation Layout Fig. 9b: Case Lifter Bosch Rexroth Corporation 13 Lean Manufacturing: Principles, Tools, and Methods Final Considerations: Hybrid Systems With all of its promise, the lean cell may system. The result is a system in which In this case, the automated portions of not be the answer to all assembly needs. some assembly is done manually while the process supply sub-assemblies or At times the U-shaped configuration more dangerous or ergonomically difficult parts to the lean cell. Here, although the simply does not fit the existing facility or tasks are accomplished by machine. technologies are separated, both are still process, and a change from automation required to accomplish the task at hand. or semi-automation to lean cell manufac- In a hybrid system, workstations or cells turing could be counterproductive. may be combined with non-synchronous The key to hybrid implementation is assembly conveyor systems to achieve construction with components which In keeping with the flexibility requirement desired production goals. The synergy are easily reconfigured. Bolt together for lean manufacturing, there may be between these two technologies can technology fits the description per- times when a hybrid system rather than a produce results far beyond the capabili- fectly. Flexible assembly systems using pure lean system is best for the manufac- ties of either technology alone. aluminum framing as the main structural turing process. element allow companies to mix and It is also possible to accomplish assem- match manual and automatic operations at will, and to change them at any time in Hybrid manufacturing systems combine bly in a lean cell and to have operations the future. The result is a worker-friendly, the economies of the lean system with which are purely automated take place the safety and efficiency of an automated off line. economically-sound system designed for optimum production. 14 Bosch Rexroth Corporation Lean Manufacturing: Principles, Tools, and Methods Bosch Rexroth - Your Partner in Lean Manufacturing 1 A switch to lean or hybrid manufacturing may entail radical changes in plant layout and equipment design. To ensure that you implement these changes smoothly and efficiently, you need a partner - Rexroth. Bosch Rexroth Corporation has a network of stocking distributors nationwide. In addition to local inventory, each distributor has Rexroth design experts on staff to assist you with your lean manufacturing projects. Once your equipment is designed, your Rexroth distributor will provide machining, assembly, and other value-added services to move your project to a successful conclusion. Each Rexroth distributor is backed by more than 100 years of experience and quality. 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. The Bosch Rexroth Structural Framing Network Manitoba Alberta British Columbia CANADA Ft. Albany Vancouver Calgary Saskatchewan Quebec Ontario Regina New Seattle Brunswick Winnipeg Quebec Nova Scotia WA ME Portland Helena MT ND Montreal Augusta Bismarck VT Billings BOSCH REXROTH OR Buchanan, MI MontpelieNH Boise MN ID SD Minneapolis St. Paul Concord Pierre MI Toronto Albany WI MABoston Madison NY CT RI WY Lansing Buffalo Detroit New York City NE Chicago PA Philadelphia Reno Cheyenne Cleveland Trenton Sacramento Salt Lake City OH Harrisburg NJ NV IA IL IN Pittsburgh Lincoln MD Denver SpringfieldIndianapolis DE San Francisco UT Cincinnati Washington DC CO Frankfort VA CA KS St. Louis Louisville WV Norfolk Wichita MO KY Durham Raleigh Knoxville Asheville NC Nashville Charlotte Los Angeles Wilmington AZ OK TN Albuquerque Columbia San Diego Oklahoma City Atlanta SC Phoenix NM Little Rock MS Birmingham Charleston Mexicali Augusta AR AL Dallas GA El Paso Ft. Worth Savannah Shreveport Jackson Albany TX LA Mobile Jacksonville Baton Rouge Austin FL Houston New Orleans Orlando San Antonio Tampa W. Palm Nuevo Laredo Laredo Beach MEXICO Miami Brownsville Matamoros Key West Bosch Rexroth Corporation 15 Lean Manufacturing: Principles, Tools, and Methods Bosch Rexroth, the world brand leader in structural framing systems, ergonomic workstations and flexible assembly conveyors 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 manufacturing changeovers. For years, Rexroth has supplied manufacturers worldwide with a broad range of erg▯onomic components ideally suited for lean 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 you’ve never used our aluminum structural framing before, you’ll be surprised how easy it is. And our customer support system makes it even easier. For fastest service, order from your distributor on-line at www.boschrexroth-us.com/framing. It’s a fully functional online catalog, 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 a unique 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 you’re ready to order, you have several options. Call us toll-free at 1-800-REXROTH (739-7684) for the name of your local distributor, or follow the step-by-step ordering instructions at our website. A nearby Rexroth distributor will ship your order promptly. The Rexroth customer support system gives you tremendous flexibility to meet tight schedules and budgets. Bosch Rexroth invites you to specify the leader in lean manufacturing - Spec▯ify Rexroth! NEW! Visit our lean resource center on the web: www.boschrexroth-us.com/lean Bosch Rexroth Corporation Linear Motion and Assembly Technologies 816 E. Third Street Buchanan, MI 49107 Telephone (269) 695-0151 Facsimile (269) 695-5363 www.boschrexroth-us.com Bosch Rexroth Corporation Corporate Headquarters 5150 Prairie Stone Parkway Hoffman Estates, IL 60192-3707 Telephone (847) 645-3600 Facsimile (847) 645-6201 Bosch Rexroth Corporation Hydraulics 2315 City Line Road Bethlehem, PA 18017-2131 Telephone (610) 694-8300 Facsimile (610) 694-8467 Bosch Rexroth Corporation Electric Drives and Controls 5150 Prairie Stone Parkway Hoffman Estates, IL 60192-3707 Telephone (847) 645-3600 Facsimile (847) 645-6201 Bosch Rexroth Corporation Pneumatics 1953 Mercer Road Lexington, KY 40511-1021 Telephone (859) 254-8031 Facsimile (859) 281-3491 Bosch Rexroth Corporation Hydraulics 8 Southchase Court Fountain Inn, SC 29644-9018 Telephone (864) 967-2777 Facsimile (864) 967-8900 Printed in the United States 8981 500 246 (11.2009)
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