Automation in Lean Manufacturing
With the right automation, lean systems can improve manufacturing processes and boost productivity
By Patrick Waurzyniak
Common misperceptions about lean manufacturing and automation systems lead many manufacturing managers to dismiss the use of automation in a lean setting.
Confusion over lean manufacturing principles often results in a knee-jerk dismissal of automation, notes Bashar Abdo, Cartesian robotics product manager, Bosch Rexroth Linear Motion and Assembly Technologies, Bosch Rexroth Corp. (Hoffman Estates, IL), a unit of Bosch Rexroth AG (Lohr, Germany). But when manufacturers apply automation equipment effectively in a lean manufacturing system design, Abdo contends that manufacturing companies can reap rewards from automating lean operations.
"Early on, in the first stages of implementing lean, everybody started jumping on the bandwagon," notes Abdo. "Right now, you've got almost 40% of the companies today claiming that they're already running some sort of a lean operation, in one fashion or another. But there are a lot of misinterpretation and misconceptions about what is lean, and it stems from the misinterpretation of what is waste and what is value-add.
"When you ask the question, 'why do people think lean and automation didn't mix very well,' people think transportation is a waste and associate transportation with conveyance," states Abdo. "They look at conveyance technology as an evil technology, but you can't get automation done without conveyors."
By definition, a lean manufacturing production system is a management philosophy that embraces all aspects of industrial operations by focusing on the reduction of waste from the value stream to remain competitive, notes Abdo. Automation is critical to lean manufacturing, he says, due to miniaturization, increased quality demands, sophisticated product designs, increased use of clean-room manufacturing, and the competitive global economy.
Much of the confusion over using automation in a lean environment stems from several factors, including the glut of references to lean on the Internet, profitable commercialization of the lean enterprise, outsourcing of lean implementations, and the knee-jerk dismissal of automation without a proper total cost of ownership (TCO) evaluation, according to Abdo.
In addition, manufacturers are dealing with highly complex and diversified manufacturing processes due to competitive pressures. Companies today are also trying to do too much with too little, possess inadequate understanding of the concept of lean, and are trying to conform to the letter rather than the spirit of the philosophy.
Designing an automated solution in a lean system design can be a challenge when many customers resist the automated approach in favor of manual part-handling methods. "I've personally run into absolutely ridiculous situations," Abdo recalls. "I'll give you an example. Somebody asked us to design an automated assembly system, and they wanted it in a lean format. They interpreted lean as the fact that there are operators around the line, they can convert the line from different speeds or different production cycles by adjusting the number of operators running around the machines, which is effective if you're working in a very low-volume environment. But for high-volume manufacturing, trying to incorporate the two becomes really inefficient.
"So they've asked, rather than have a conveyor move the pallets around, maybe an operator can carry a pallet from one side to the other, place it, and let it go around one side and put it in a format of a U-shaped workcell. And you just start thinking, 'Where is all this misinterpretation coming?' There are a lot of things like that happening in industry where you start defining lean by the form rather than by the substance. If you look at a true definition of lean, it is basically a manufacturing concept that's designed to provide an optimum framework for efficient and competitive production. What is better than automation to provide that? There isn't anything really.
"A lot of companies are embarking on lean manufacturing and they believe in this semiautomated workcell, where there's an operator loading the piece of equipment that does the actual operation, and then they take a part out. So they're reducing people to simply load-and-unload mechanisms, without utilizing their expertise and their potential. In lean you maximize your expertise and your potential, including your people. The biggest waste in lean is basically the underutilization of people. Everybody claims a lot of waste out there, but this is one of the biggest."
For higher-volume operations, automation is the best form of achieving quality at the source, achieving high production speed, efficiency, Abdo adds. "It is the most effective form of production today, especially in the days when everything is getting smaller, cheaper, and faster. That's what industries are living by—smaller, faster, cheaper—so you cannot avoid automation. The issue is how you efficiently incorporate automation to maximize lean production in a lean environment. And that goes back to your Overall Equipment Effectiveness [OEE] return on investment, and how to calculate your efficiencies, and everything related to the maximization of automation." The use of OEE benchmarks is becoming much more popular, notes Abdo, as companies attempt to maximize manufacturing processes to become more efficient. "It is not prevalent yet, but it's becoming more popular, and there are companies that ask us to incorporate the OEE value calculation in our process."
Trimming waste from manufacturing processes means not fixating on a particular approach, such as only using a U-shaped work cells versus a modular or transfer-type system, to accomplishing automation in a lean system design. "Every process dictates its format," Abdo states, "and to make a process based on format, rather than a format based on a process, is a big mistake, and that's the problem."
Robotic automation options for lean systems design often combine robots with conveyance systems for flexibility in part handling. Manufacturers can incorporate Bosch Rexroth's Cartesian robotics, units that Abdo says transcend size and weight, as well as format. "Basically you can run the Cartesian unit across 10 m, the length of a manufacturing space," Abdo notes. "They're more customizable, and are applicable to all industries and a wide range of applications. They are more designed to fit the application, rather than have the application fit the robot. It is a big piece of our future development focus. We've just recently launched a new product, called the camoLINE. We have it in Germany, and it's in the process of being launched in the US." The company plans to introduce the camoLINE at the ATExpo in Rosemont, IL, in September.
Any robotic automation system can dramatically help manufacturers boost their efficiency in parts-loading applications, he adds. "In terms of utilization of personnel, there are machinists and toolmakers that spend 60% of their time loading and unloading the equipment, and very little time programming the equipment to do the job. When you do that, you're totally underutilizing these highly skilled operators, and reducing them to machine load and unload duties. This is where robotics and automation can make a great difference by maximizing efficiencies and utilization on the shop floor, and making the process more lean."
In applications with top-loading capability, the camoLINE can function for such CNC machine loading, he adds. "In most cases, a six-axis articulated arm would be best-suited for machine loading, side loading, of CNC equipment," Abdo says, "so even though we're not into that business, that's probably a requirement when you're talking about lean. But all CNC machines use our ballscrew drives, rails, guide rails, and we sell a lot into the machining industry. We also provide support and automation expertise to help them solve their issues."
Many industries can best use automation in a lean environment, ranging from the automotive, medical, food and packaging, and semiconductor industries, Abdo says. "If you look at all of these, they all rely on fast cycle time, and effective rates of assembly, as well as perfection in assembly. So you need inspection, you need monitoring of your processes, you need poke yoke—the Japanese word for mistake-proofing. You need full systems that are designed to manufacture the product without fault. You cannot afford to re-work products in this day and age."
Production flexibility for lean systems also is a key requirement for remaining competitive in today's marketplaces. "If you look at robotic automation, the flexibility that you can have with robotics to react to constant shifts in demand for production capacity requirements is happening on a daily basis," Abdo notes. "People are using JIT methods of operation, and if you look at it from the automotive point of view, in many cases, they want to build cars on demand by getting an order at the dealership and in three days, a car comes off the end of the line. That means you can't really just tool your line to build only one kind of car and run production, you have to be able to switch.
"That's what robotic automation gives you—the ability to shift that production immediately—and it's just through programming, without any sort of interaction by operators who can make mistakes, to produce a totally different product."
The global automotive industry has embraced lean manufacturing as a way to stay competitive and become more cost-efficient at the OEMs as well as in Tier-level automotive parts-supplier companies. Companies running three shifts daily must automate their operations in order to be as lean as possible, Abdo says. "No matter where you are in the world, if you're running three shifts with people, that's a big mistake," he says. "You should be automating if you're running 24 hours a day because a single machine is now replacing three operators. No matter what the cost, most threeshift production should be automated almost immediately."
Modular automation systems at Bosch Rexroth customer Sitech Sitztechnik GmbH (Polkowice, Poland, and Wolfsburg, Germany), a subsidiary of Volkswagen Group, have enabled the automotive seat manufacturer to design a high-volume, automated assembly line that saved factory floor space, lowered cycle times, and improved quality.
Using the Rexroth TS 2plus transfer system at Sitech's Polkowice manufacturing plant, the company produces car seats for use in VW automobiles. With coordinated modules, the transfer system provides not only the short cycle times required, but also the ruggedness needed for the production of steel structures for car seats to protect passengers. The Polkowice plant employs 1500 workers who assemble metal and steel structures for car seats.
With Volkswagen's high demand for car seats and seat backrests, the plant required a new production line designed to build roughly 53,000 seats and 77,000 seat backrests per week. The factory's requirements for the transfer system specified "short cycle times, and simple to convert," notes Clemens Haller, project manager responsible for planning at the Sitech facility. "We needed to maintain our head start and competitive edge with the ability to respond quickly to market changes," he says. High reliability, quality, functionality, and flexibility were why Haller recommended Rexroth's modular transfer system for the seat factory.
With loads of up to 100 kg and workpiece pallets measuring 160 x 160 mm to 1040 x 800 mm, the TS 2plus system covers the entire spectrum of automation required for assembling car-seat substructures. The plant makes full use of the modular system: in addition to the conveyor sections and workpiece pallets, the factory also uses electrical transverse conveyors, modular units for positioning the workpiece pallets, and the transportation control. The facility is subdivided into four production sections: backrest preassembly, and final assembly, seat preassembly and final assembly. It has all the equipment for modern steel-structure production: automatic riveting, tightening and joining stations, 32 robotic welding workcells, and several dozen manual workstations.
The connecting link between all the stations is the TS 2plus transfer system, which uses over 500 workpiece pallets measuring 640 x 640 mm that are conveyed on a flat top chain. Steel structures are first placed manually on the workpiece pallets, then taken to the individual processing stations by three parallel, production-cycle-independent sections. The twin-tier system setup—the workpiece pallets are conducted back underneath the flat top chain on a double belt—saved around 30% of the space originally planned. "Due to the technical requirements, our solution for feeding the workpiece carriers to the welding robots had to be special," says Andreas Hahn, project manager at integrator BWM (Bremen, Germany). "That's why we used the 90 and 180° curves composed by arcuate profiles from the Rexroth modular transfer system."
The automation components also were easy to integrate, notes Haller. "In view of some 60 models and the linkage between different operational steps, we needed a system solution," he says. "Interplay between transfer systems, manual workplaces, and the necessary special solutions, composed of standard components, is a must to ensure short cycle times and maintain quality."
Optimal ergonomic conditions also played a role. To not only offer optimal quality of the steel structures for assembly but also good conditions for the employees assembling the seats, BWM equipped the workpiece pallets with fixtures that present seats at the manual workstation in an inclined position, allowing an upright posture for better ergonomic work conditions. The system will pay off even after the current application, which has a life cycle of around six years. Even with three-shift work at the Sitech plant, the system has a far longer service life.
This article was first published in the July 2007 edition of Manufacturing Engineering magazine.