Tips on industrial enclosure design options

ControlDesign.com

As machines today become more and more modular, the job of today's industrial enclosure has become more complex. Control system designer Jason Christopher has a few tips to give you more design options.

By Jason Christopher, Field Editor

INDUSTRIAL ENCLOSURES often are viewed as necessary evils that present more of a challenge than they should. There rarely is anything glamorous about them, and if they do everything they should for your customer, you’ll never hear about them again. If your enclosure fails to do something it’s supposed to, you’ll never hear the end of it.

The task of the industrial enclosure seems simple, yet when presented with all of the constraints that it needs to work within, it can get very complex.

The job of the industrial enclosure is to protect control components from the rigors of the environment, including exposure to dirt, chemicals, moisture, heat and physical harm. Further, it should provide protection for all personnel working in the vicinity of equipment under control (EUC) from electric shock.
This sounds simple enough, except when you add constraints such as footprint, thermal loading, and other dimensional aspects. After you have figured all this out, which may take a bit of doing, you then need to ensure that it fits within the ever-shrinking budget that you’ve been allotted.

Advances in the area of industrial enclosures over the past several years have been impressive and make the job of specifying them easier, but many of the tried-and-true principles still apply (See Figure 1 below).

Modular Rules
Machines today are more and more modular. The base machine is designed, then options are added to and subtracted from this base design as directed by the customer. With modular machine design, a modular enclosure design makes sense as well. “Enclosure systems that can be scaled to meet specific needs save me a lot of time,” states Keith Beadle, controls engineer for Valeo Electrical Systems (www.valeo.com), Rochester, N.Y., a systems supplier to the automotive industry. “By using a flexible enclosure, it allows me to maximize the amount of engineering that I get to re-use from one project to the next.”

Figure 1: Get the Most From the Box

The components in this enclosure might be densely populated, but application of proper design principles makes it a workable and visually agreeable panel.

Modular enclosures hold other advantages over more traditional enclosure systems as well. Enclosures described as modular typically acquire their strength not from the structure of the sidewalls and back of the box, but rather from a frame construction within the enclosure (See Figure 2 below). “By using the frame construction, we can typically save three inches of mounting panel space on all sides compared to traditional enclosures” states Mike Herzog of Rittal Corp. (www.rittal-corp.com). This frame construction provides tremendous strength and stiffness in a relatively small area, and, as a result, a bigger opening for a larger mounting panel is possible.

Because of the frame, modular enclosures can grow quite large by “baying” the enclosures together. Just bolt a couple of frames together for one contiguous mounting panel. Further, the hole patterns in the enclosure frame lend themselves to mounting devices just about anywhere.

Beadle recalls equipping modular enclosures with mounting bars that allowed him to affix devices on sidewalls, doors and floors. He says he’s even seen them mounted to ceilings. Accessories are also available that allow the user to make use of nearly every piece of real estate available inside of the box.

Won’t Fit? Customize It
Despite the enhancements added to the modular enclosures, sometimes all your devices still won’t fit into the space allotted. The mechanical design of the EUC, footprint constraints, or custom control hardware requirements might still dictate something different, including varying degrees of depth within the enclosure’s rectangular geometry (See Figure 3 below). “When we create a control system, some of our enclosures are standard catalog items, and some are heavily customized from the factory,” says Robert Spencer, applications engineer from Electric Service and Sales Inc. (www.esscoinc.com), a system integrator out of Greensboro, N.C., with its own UL508A panel shop.

“Product costs and labor costs are a balancing act for us. We have found that the deciding factor [whether to customize enclosures ourselves or have them made] is volume and quantity discounts. For our OEM accounts that use a high volume of identical enclosures, the manufacturer modifications are the way to go. But for smaller quantities, we can do it cheaper and faster in our shop.”

In addition to custom modifications from his enclosure vendors, adds Spencer, he gets detailed CAD drawings of the enclosures. Saginaw Controls (SCE, www.saginawcontrol.com), says it understands the need machine designers have for CAD drawings and the convenient customization of enclosures. “Our customers can download a standard drawing from our web site, add modifications to the drawing and send it back to SCE,” explains Dave Pankow, national sales manager for SCE. “Our Customized Standard Enclosures Program provides the cost effectiveness of using standard enclosures, while providing the cost savings of having these modifications done before the enclosure arrives at your facility.”