No matter how a product is assembled, continuous improvement, customer focus, one-piece flow, pull, value and waste elimination play a key role in lean manufacturing. The goal is to eliminate non-value-added activities that prevent a one-piece flow of product.

Lean thinking focuses on value-added flow and the efficiency of the overall system. Lean principles allow manufacturers to significantly boost throughput, reduce time to market and quickly increase capacity. Implementing a lean philosophy also has the potential to lower costs and improve product quality. Whether an assembly process is manual or fully automated, lean manufacturing shortens the time between customer order, product build and shipment by eliminating sources of waste. No matter where it's applied, lean is a concept that attacks waste within a plant or company.

"The underlying value of lean applies everywhere," says Drew Locher, managing director of Change Management Associates (Mt. Laurel, NJ). "Many people incorrectly think lean is only for labor-intensive assembly processes."

Same Rules, Different Tools

In an automated assembly process, lean manufacturing principles must be applied to support processes, such as maintenance. Common terms, such as standard work instructions and poka yoke or error proofing, apply to changeover and setup of equipment.

However, it can be more challenging to implement lean with high-speed automated equipment. "It's much easier to do lean in a manual assembly environment," notes Jamie Flinchbaugh, a partner in the Lean Learning Center (Novi, MI). "It's a cakewalk. It's easy to observe people working and then shift work or tools accordingly."

That simply isn't the case with automated assembly applications. While the rules of lean are the same, the applications are different. For instance, kaizen events [continuous, incremental improvement of an activity to create more value with less waste] may take longer to implement. Traditionally, a kaizen event lasts 1 week.

In an automated setting, it's harder to make constant, everyday improvements. "[In a kaizen], Thursday is often ‘go do it' day," says Flinchbaugh. "Anything that involves new tooling, programming or moving equipment may have to go on a 30-day action plan."

In a manual assembly process, however, actions are often implemented on the spot. Moving a rack of parts 2 feet to the left or 3 feet to the right isn't too difficult. However, reprogramming a robot or retooling a bowl feeder or parts fixture is much harder and takes more time.

Capital equipment expenditure in a lean environment should be justified based on two factors: the amount of manufacturing waste eliminated and the reduction in production lead times. Productivity improvements and labor cost reduction are internal measures that are less important.

"As a general rule, if takt time is 10 seconds or less, you should use automation," says Locher. Takt time forms the heartbeat of any lean system. It sets the pace of production to match the rate of customer demand. Takt time is determined by dividing the available production time by the rate of customer demand.

The pace of production should be a critical consideration when acquiring capital equipment. It's important to remember that takt time is customer demand-something that engineers can't change-divided into available production time-something that engineers can change.

Locher says scheduling and forecasting are important. "With automation, it's very easy to overproduce," he warns. In fact, Locher says misusing automation is a common problem. "A lot of people buy an automated line and run the heck out of it. They think, ‘We spent a lot of money on this, so we need to make it pay for itself.' When you do that, you run the risk of overproducing."

"A lot of companies with high automation rely heavily on forecasts," says Locher. "The challenge is to supply pull systems."

According to Locher, machine time should be closely calibrated to takt time. Changing feeds and speeds can help improve the capability of existing machines. Ideally, in a lean environment, equipment will operate at a rate determined by forecasted customer demand. Customer demand, including takt time, rapid response and quality improvement should play a major role in capital equipment justification.

Lean initiatives in an automated assembly environment should be measured by overall equipment effectiveness, which has three components: planned downtime, unplanned downtime and yield.

"Typically, in automated processes, a series of equipment or processes have been integrated together," says Locher. "When one goes down, it impacts the others. In manual, or even automated stand-alone equipment, the impact is limited to the piece of equipment that is down."

Maintenance Is Critical

Total productive maintenance (TPM) is critical for an automated process. It is the tool used to improve overall equipment effectiveness.

"It's easy to apply lean in an automated setting, but only if the machines are correctly maintained," says Erik Hager, a consultant at Lean Productivity Systems (Toronto). Hager defines TPM as an integrated set of activities aimed at maximizing equipment effectiveness by involving everyone in all departments at all levels, typically through small group activities.

Under TPM, basic maintenance work, such as inspection, cleaning, lubricating and tightening, is assigned to production team members. That frees up traditional maintenance staff for predictive maintenance, equipment improvement, overhauls and other high-value activities.

According to Hager, TPM represents a profound shift from the "I operate it, you fix it" mind-set to a "We are all responsible for our equipment" mind-set. The goal of TPM is zero breakdowns and quick changeovers. Variation of changeover times has to be eliminated to make an automated lean operation more stable and predictable.

Kevin Duggan, president of Duggan & Associates Inc. (West Warwick, RI), believes maintenance should be measured in takt time. "Everyone talks about quick changeovers, but no one thinks about quick maintenance," he says.

Duggan urges manufacturing engineers to implement "single-minute maintenance. That means maintenance should be viewed the same as changeovers or single-minute exchange of dies. Target maintenance to be done in a single minute. Of course, it may take many minutes or maybe even hours, but this statement sets the direction.

"Some companies target changeover time of 5 minutes or less, while the maintenance manager comes into a production meeting and states, ‘We have to take machine 10 off line on Friday.' We fight for saving minutes and seconds in changeover time, while maintenance can take hours or days.

"Maintenance should be viewed as a NASCAR pit crew, just like change-overs," Duggan points out. "They should have standard work-including standard times-and should always try to improve these times by videotaping the job and formally reviewing the tapes with a team." Maintenance task times should be charted to show continuous reduction of times.

"Single-minute maintenance is very important in a lean value stream," claims Duggan. "Every value stream should be measured in terms of EPEI (every part every interval), which means how long it will take to cycle through all of the part numbers in the value stream."

Duggan says EPEI is determined by the availability of the machine and run time for each part. If the machine has long maintenance times, this takes away from available time, which increases EPEI. "That's not a good thing, as this increases lead time and lot size-two things our customers don't want-and costs the company more money."

The Human Element

When implementing lean principles in an automated assembly setting, it's important not to forget the human element. "Any company that is fully automated still has people working there," notes Hager. "Any lean initiative should focus on that.

"Lean is about involving people and using their brain power," says Hager. "Toyota's strength is utilizing all of the brain power of its employees.

"No matter how you assemble products, the people part of lean is a key piece of it," warns Hager, who previously worked at Toyota's Cambridge, ON, assembly plant. "Even with processes that involve robots and other advanced automation, Toyota likes to keep manpower in place. They serve as the eyes of the previous process. People are the key to identifying when something has gone wrong."

With automation, it's easy to forget that assembly operations are only as successful as the people behind them. By contrast, the Toyota Production System seeks to maximize the utilization of people.

"In a manual assembly process, one of the keys is being able to support how the work is done. "It's easy to tap into worker knowledge," says Flinchbaugh. "In an automated environment, there's a tendency to focus on design. There's a ‘We're out to get it right the first time' mentality.

"But, the goal of lean is to accelerate the frequency and impact of experimentation," adds Flinchbaugh. "Most lean efforts miss this. You must be constantly experimenting in order for lean to work. Manufacturing engineers should be constantly challenging things." Flinchbaugh urges engineers to do as much experimentation as possible early in the process, during the automation design stage.