Modular gets popular

Howard Jenkins can't think of a single application for which a modular enclosure would not be the appropriate choice.

He should talk to Dan Sullivan.

Vice president of the Advanced Technologies Group at Electromotive Systems, Sullivan is convinced that at some point there will be an application for modular enclosures within his company's standard panel line. Electromotive builds custom and standard control panels for suppliers of overhead cranes and monorails.

But in every comparison thus far, the scales have tilted--however slightly--in favor of traditional solid-wall enclosures.

Like a growing number of engineers, Sullivan is fully aware of the many benefits of modular enclosures: flexibility, aesthetics, metric sizing for the European market, to name a few. But again, like many of his counterparts, he continues to wrestle with the design trade-offs associated with any technology substitution.

"Right now our perception is that we will require more time to assemble all of the individual pieces of a modular enclosure," says Sullivan. "With a solid wall enclosure, all we have to worry about is the subpanels, and we can wire those up in advance."

Not all engineers would agree with Sullivan on that particular point. Most, however, are quick to acknowledge that there is no such thing as a free lunch. Enclosure selection is a delicate balancing act that requires engineers to make the appropriate trade-offs between flexibility, ease-of-use, durability, and aesthetics.

Many options. One of the strongest selling points of a modular enclosure is its flexibility. Typically, an engineer starts with a frame, then configures a custom solution by choosing from a wide range of interchangeable and removable bases, tops, sides, and doors (see box next page). The engineer also has many options for mounting components, having the choice of subpanels, swing-out frames, a grid strap system, and electronic racks. Furthermore, engineers can position these mounting systems forward and rearward in the enclosure or interconnect individual cabinets.

Howard Jenkins, who is an executive VP at Youngstown Systems (North Lima, OH), couldn't be more enthusiastic about the number of options he has with modular enclosures. For the past 15 years, he's been using them for the custom control systems and machines his company builds for the steel industry.

On occasion, Jenkins still uses solid- wall enclosures, but only when customers insist. And he usually attempts to talk them out of it first. "I try to find out what their objections are, and sometimes the answer is that they just aren't aware of the benefits of modular enclosures," says Jenkins.

If those customers knew more about them, Jenkins says, it would be an easy recruit. Flexibility is the operative word here. "We can mount components to the back, sides, front of a modular enclosure, or whatever. And you never know when you need to make a change, so the fact that the cabinets can be interconnected is terrific. Even years later we can go in and add another section simply by taking the panels off and bolting another frame on," says Jenkins.

Of course, engineers can also design flexibility into a solid-wall enclosure. But this typically requires some type of design enhancements or modifications that come at a premium price.

That was the case for Michael Tokar, an electrical designer at Elizabeth-Hata. Historically, engineers used solid-wall enclosures for the controls of the rotary tableting presses the company builds for the pharmaceutical industry. "One of the problems we were getting into was that nothing was standard anymore. Whenever someone wanted a different bottom or top, or we needed to mount components in an unusual way, we either had to compromise or we had to order a custom-built enclosure," explains Toker.

After making the switch to modular enclosures two years ago, he has been able to meet most customer needs--even special requests--with off-the-shelf components. "With the variety of components available, I can still offer a 'customized' solution at a lower cost," says Tokar.

Easy does it. Ironically, it is precisely this degree of flexibility that is viewed by some engineers as a shortcoming of modular enclosures.

"I remember when the suppliers' catalogs were only a few pages thick, and you ordered one part number," says Sullivan. "Now, they're saying build your own enclosure, and we are suddenly confronted with all of these choices. I can order different sides, different doors, and so on, yet our customers' requirements are often so unique that I still can't order standard part numbers."

The supposed ease-of-use of modular enclosures--ranging from specifying to component-mounting to assembling them--can actually represent a source of trepidation for some engineers.

One reason is their basic comfort level with solid-wall enclosures, which essentially come in one piece with a door. Engineers mount components to a subpanel, which they then typically mount to the back wall of the enclosure.

With a modular enclosure, a designer is confronted with more mounting options and a separate frame, sides, top, and bottom that must all be assembled together.

Yet, Youngstown Systems' Jenkins is always surprised when the reason a customer insists on solid-wall enclosures is "they're easier to work with." In his mind, the differences between modular and solid-wall enclosures are not all that great. "If someone has never used a modular enclosure before, I guess I can see how they might be taken aback," Jenkins acknowledges, "but once you've assembled a few, well you get the hang of it."

Several years ago, Paul Davis, electrical engineering manager at HK Systems and a guy who knows a lot about enclosures, cautiously joined the ranks of modular enclosure users. "We were happy with the solid-wall enclosures we were using, but at the time we were searching for ways to give our equipment a more high-tech appearance," says Davis.

It was an unexpectedly easy transition. "The first modular enclosure we wired up turned out to be a rather time-consuming chore," he recalls. "Instead of mounting everything to a single panel, you have all of these separate pieces assembled together like a 3-D puzzle. But our designers eventually got to a point where they could assemble them in their sleep."

Change is not always so easy. "Maybe it's just the way we crane guys do things," says Sullivan. "But we're talking about some major cultural changes that we and our customers will need to make in order to adopt modular enclosures. For example, we'll have to revise all of our present drawings, because we still use English units. That will be a huge undertaking."

Companies already using metric sizing are finding advantages by going modular, which has long been the standard in Europe. "We do business all over the world--Europe, South America, Japan, you name it," Jenkins explains. "International customers, particularly in Europe, want metric sizing and are already familiar with using modular enclosures."

Pretty boxes. One aspect of modular enclosures that nearly all engineers seem to agree on is the aesthetics. In other words, they're pretty.

"Some customers don't care if the equipment runs, just so it looks good," jokes Tokar. Seriously, though, their sleek appearance was a major reason his company made the switch to modular enclosures. "Maybe if the equipment is going into a grimy factory somewhere appearances don't matter that much, but we're in the pharmaceutical business where everyone wants everything to look high-tech," says Tokar.

Another company, HK Systems, made a big splash a few years ago when it unveiled a palletizer featuring modular enclosures at a major trade show. They had never been used in the industry before. "We got all kinds of praise and positive comments about the high-tech look of the cabinets. Our competitors were green with envy," recalls Davis.

The engineers admired the clean lines of that machine so much they were reluctant to drill any additional access points for conduit. Instead, they hid the rat's nest of wires dangling out of the machine under a swatch of carpet.

There are better ways to hide wires, for example by using a cableway or drilling a hole in the base and running it under the floor. But HK ultimately went back to solid-wall enclosures.

"The problem is that people expect a modular enclosure to look good," says Davis. "We just felt any modifications we had to make detracted from that appearance, which was the whole reason why we were using them to begin with."

Rough or tough? Prettiness comes at the cost of ruggedness, though. Generally speaking, traditional solid-sided enclosures are heavier in construction than modular enclosures. One vendor that makes both types calls it "a robust design versus a graceful design."

It's not to say that modular enclosures are not durable. Engineers have designed the frames to withstand many times their own weight in a vertical direction. To resist lateral forces, they have also sought to stiffen the rails and strengthen the welded connections--which are typically the weakest part of the design (see box).

Nonetheless, several suppliers acknowledge that modular enclosures are probably not going to hold up in especially abusive environments. Hitting them with an angle iron or ramming them with a lift truck, for example, are not terribly good ideas.

Interestingly enough though, engineers at Harley Davidson (see following article), do not share that particular concern.

And Jenkins, who ships modular enclosures all over the world, has never had a problem with durability. Once, an enclosure in transit to Australia tipped over and was slightly damaged. But that was an isolated case. He even mounts them on overhead handling equipment.

Sullivan, on the other hand, has concerns about the ruggedness of modular enclosures when they become part of the equipment. Engineers at Electromotive mount the enclosures directly onto the crane, where they are subjected to the same environment and duty cycle.

"Our equipment is exposed to forces on the order of about 4 Gs, so all of the components need to be fairly durable," says Sullivan. "I tend to feel that the more clips and bolts and individual joints you have on anything, the more opportunities you have for things to shear or break off."

Hoping to convince more engineers to make the switch to modular enclosures, suppliers have taken steps to address some of the concerns described above. At least two companies have developed software to aid in component selection. Simply by plugging in as little information as a frame size, an engineer can automatically generate a list of the required part numbers.

Also, engineers can order partially assembled modular enclosures from some suppliers. Other improvements include greater parts standardization across multiple markets. And anyone who has searched for anything in a Hoffman catalog will be glad to hear it will soon be available online.

Clearly, these measures are having some effect on the market. Industry leader Hoffman--practically a household name among engineers--reports that sales of its modular enclosures are growing at the explosive rate of 45% annually. Last year, they accounted for approximately 15% of the company's total enclosure sales. And Rittal Corp. and Saginaw Control & Engineering, other top suppliers, report that sales of their modular enclosures are also on the rise.

Is a modular enclosure in your future?

The following questions will help you determine what type of enclosures you need.

- What environment are your enclosures going in to?

- What is the weight and density of your components?

- Do you use a wide variety of enclosure sizes and types?

- Do you have a need to remove or interchange sides, top, bottom, doors, .?

- Are you planning to expand an existing system at a later date?

- Will you need to make design changes in the field?

- How important are aesthetics?

- Can you protect your enclosures against extreme abuse (lift truck ramming, etc.)?

- What standards do your enclosures need to meet?

- Do (or will) you ship product overseas?

- Does your company use metric sizing?