Model packaging lines.

How do you judge the performance of your packaging lines? Most people rely on a combination of efficiency, downtime and waste.

Paul Zepf, director of engineering and a packaging analyst with Zarpac Inc., Oakville, Ontario, isn't most people. He argues that the above measures are misleading.

Here's an example: Suppose a packaging supplier makes a dramatic breakthrough in quality, reducing the number of defects per delivery from 10% to 1.56%. If a line runs 96,000 containers per eight-hour shift (design run speed of 250 bpm at 80% system utilization), the cost to produce an item is 41 cents and the cost of production time is $342/hour, how much are the savings from improved quality? One more thing: The line must run for 92% of each shift to meet the production schedule.

Actually, it's a trick question. For conventional formulas to work, you would need to know what the containers cost. Most people stop calculating as soon as they realize this information is missing.

Which is Zepf's point. Even without knowing container costs, he calculates that under these conditions, a company would save $1,036,318.40 per year, the kind of savings plant managers dream about.

Performance index

Zepf calculated these savings with a technique he calls the Performance Index or Pl. Instead of evaluating fines based on "containers in" vs. "product out," Zepf created four variables that affect total performance. In the process, he applied "real world" sense to simulate what happens on a packaging floor.

Consider how Zepf s performance index applies to the above example. In the real world, defective containers would be fed into the packaging line as inputs, then rejected as waste. Zepf factors this into his performance index, calculating that once the supplier improves the containers, the line will save 41.5 minutes per shift. Over the course of one year, the line will gain 179.5 hours. What's more, the line will need 2,377,960 fewer containers to hit its schedule. Putting time and container savings together equals $1.04 million.

PI is simple to use. Mathematically, PI = n x Us x Cp x Sf, where n is the effeciency of all inputs, Us is the system utilization, Cp is the capability and Sf is a speed factor. The result is somewhere between 0 and 1, with 1 being ideal.

In the food industry, Zepf has found PIs on the low end of the scale. An ideal PI, in his opinion, would be greater than 0.60. He has found PIs of 0.10 to 0.45 for food companies, 0.45 to 0.80 for beverage companies.

To create the performance index, Zepf redefined the terms most companies use to measure performance. "When I talked with clients, I was always confused by what they meant when they quoted specifications," he says. "What customers were telling us was different from what they meant!

The E-U-C equation

Take efficiency, a universal term for performance. Zepf says it doesn't truly clock a packaging line. "The proper engineering definition of efficiency is not merely inputs divided by outputs. Over time, efficiency has been so badly beaten up, it's misused," he explains. As a result, companies often hold up efficiency like a gold standard, forgetting where it came from. A classic case is the plant manager who sets an efficiency target for a packaging line because "it's always been that way."

"By setting false numbers, companies miss opportunities for better performance," says Zepf.

It's no coincidence that the first variable in Zepf s model is efficiency, but not the usual "input divided by output." The actual calculation is beyond the scope of this article. Suffice it to say that Zepf s efficiency factor encompasses quality, human intervention, damaged packages and components, and test samples removed from the line. Seen through these filters, packaging lines running below 99% are unacceptable, Zepf believes.

His second variable is utilization, or the effectiveness of the line. It comprises the effects of changeover, cleanup, stoppages and meal breaks.

The third variable in Zepf's equation is capability. Capability is the ratio of the total time it takes to complete a package run cycle over the scheduled run cycle. Capability and utilization are Zepf s way of leveling the playing field.

"Plant people play games with their scheduling," he says. "A lot of the reality isn't factored in, and they fool themselves. Basically, I'm taking a simplistic approach. If you need six shifts to complete a product run and you take eight, you're penalized."

The last variable in the performance index is speed. As with efficiency, Zepf defines it differently than the number of containers moving down the line. He factors in losses due to rework, how quickly the line recovers (or ramps up) after a stoppage, the design speed and the actual run rate.

"Speed is an area of contention. People say they want 400 per minute because they want X units in the warehouse, but they don't get X. It's because they don't buy the proper equipment," says Zepf. "If the end goals aren't met, nothing else matters."

Aside from the math, Zepf's equation deserves attention because it makes issues of the forces driving packaging fines. It measures the quality of incoming materials as well as the quantity. it challenges the notion that faster is always better. It accounts for just-in-time parts inventory and allows not only for downtime but planned "disturbances" or stoppages.

"You don't need tons of data, he says. "Just the right data. "

In the end, Zepf says his equation is nothing more than a down-to-earth model of what he's seen on packaging floors. His one word of advice: Go in objectively. "Build honesty in your analysis system first," he says.

The computer as professor

Have you looked at the price of computers lately? For less than $2,000, you can own a 486 microprocessor with 210 MB of memory. And at the rate computers are advancing, the powerful 486 is old news.

While IBM and Apple may find little to cheer about in this market, other companies are taking advantage of the power and low price to simulate packaging fines for training purposes. Pacific Animated Imaging, Annapolis, Md., supplied Mead Packaging with a three-dimensional "training manual" for a beverage filler that teaches fine operators how to service the machine. The software isn't located in an office, however. It's on the line, ready to use.

The simulation shows machine parts, product flows, package movement, and the components of different stations. It's animated in full color, so operators can call up exactly what they need.

"It's a perfect means of training," says Tony Whittlesay, vice president of sales. "Operators look at the animation and see what happens when they make a change."

PAI calls the process of converting a written operator's manual to animated images "Manual-mation." Artists render sketches which are scanned into a computer. PAI can develop cut-away views or detailed sections, whatever is necessary to bring the machine to life.

"We've found that a computer image fills the gap between the engineer and the operator," says Whittlesay. "Instantly they show operators what to do and what could happen when they change something."

Mead reportedly wanted an imaging system to animate changeover procedures. The end product turned out to be a touchscreen that not only shows changeovers, but preventative maintenance, systems needs and process information in real time.

The graphics are dear and easy to follow. The parts are in three dimensions and appear as pictures come to life. Operators can zoom in on views or blow them up when necessary.

PAI developed the manual for Mead in 60 to 70 days, although 70 to 90 days is typical. The video requires less than 7 MB of hard drive and appears in 16 colors on EGA, VGA or SVGA monitors. A CD-ROM based manual is available for high-resolution graphics.

Stereolithography & 3-D CADs

Cutting-edge 3-D computer-aided design software allows package designers defined, three-dimensional computer models and make experimental changes at will. No expensive, time-consuming prototypes required.

The computer file then can be fed into a stereolithography system (SLA) that can manufacture a package component such as a plastic closure then can be sent to the food company for examination and evaluation Also, the solid model design can be fed directly to the machining operation that generates the mold ping the usual blueprint

Sunbeam Plastics, an Evansville, Ind., manufacturer of plastic dispensing closures, uses 3-D CAD and stereolithography technologies. The company reports that closure development, now takes a week or less. The old time frame - which involved mold changes - averaged 10 to 12 weeks.