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Custom Molding Firm Converts Metal Telecommunications Box to Plastic

Weatherproof Plastic Housing is Designed to Safeguard Sensitive Internal Electronics

ASHTABULA, Ohio--Protecting sensitive electronic circuitry from the elements is an essential function of the box-like housings that enclose outdoor telecommunications equipment. For telecom OEMs, the issue of whether to manufacture the housings from metal or plastic has ramifications for not just which manufacturing process will be used, but also for production time, cost, and product performance. It's also a question that MODRoto (formerly Meese Orbitron Dunne Company) (www.rotomolding.com) tackles regularly. The custom rotational molding and design firm, headquartered in Ashtabula, Ohio, offers a conversion analysis service through which it helps OEMs assess whether a part, product, or design may be more effectively manufactured in plastic by rotational molding, or as a wholly integrated design involving multiple processes.

MODRoto recently converted a fabricated metal telecommunications box to rotationally molded plastic, providing a tangible example of the cost and time savings that can be achieved through such a conversion. Designed and developed for a global telecommunications company, the new design replaced multiple metal parts and fasteners with a two-piece plastic housing that eliminated assembly steps and secondary coating operations, according to the company. In addition to accelerating production, reducing lead times, and lowering manufacturing costs, the design is said to have strengthened the unit to thrive in permanent, outdoor installations without risk of water infiltration, rust, or deterioration due to weather.
 
The polyethylene plastic housing was designed using advanced 3D solid modeling to test several different design concepts before producing a prototype. To verify and document that the outer plastic housing effectively safeguards the sensitive electronics inside, MODRoto tested it inside its own hurricane simulation chamber, which simulates the conditions of a hurricane that has spawned a tornado. As a service to the telecommunications customer, MODRoto also pre-assembles the units with their internal electronics and ships them ready for installation.

Design-2-Part Magazine recently spoke with MODRoto President Robert Dunne about the metal-to-plastic conversion. Following is an edited transcript of the interview.

Design-2-Part (D2P): How did this project come about?

Robert Dunne (RD): The [OEM] company first used a metal box for this enclosure, but then decided to convert it to a plastic box, mostly for environmental issues and customer acceptance. Some customers want to use metal and others like plastic better for its performance, so it's a personal preference based on the end user.

D2P:  What were some of the important requirements that the OEM was looking for?

RD: A weatherproof seal was number one, and then corrosion and UV light resistance, and lighter weight. Shipping costs will be less and they won't have to pour a stronger concrete pedestal to hold it.

D2P:  What are the weatherproof features of the box?

RD: It has a special gasket and door system. We worked with several gaskets with different profiles to make sure that we got the right seal--we wanted to make sure that there wasn't too much dragging when the door was opened. And we wanted the end user of the box, since it's probably a different person each time, to feel that it's easy enough to pull open and that it would latch securely. We also put spin-weld fittings (it's a plastic fitting that has threads on it) in the openings, so that any pass-throughs of electrical cables can go through spin-welds and be sealed. We tested the gaskets and spin welds in our hurricane chamber.

D2P:  What is the approximate size and weight of the plastic box?

RD: Thirty-five inches wide, 37 inches deep, and 52 inches high. The plastic box was probably half the weight of the metal box. Its shipping weight, assembled on a pallet, is 336 pounds.

D2P:  How does its cost compare with that of the previous metal box?

RD: We were told that our plastic enclosure was about half of the cost of the metal enclosure. So this was a considerable savings for them. And our plastic box is just as strong as the metal box. Longevity is an issue, so we've made sure our box will last a long time and it won't rust.

D2P:  Can you explain the rotomolding process and why it was used?

RD: Molds are placed in a rotational molding machine that has loading, heating, staging, and cooling areas. Plastic resin is loaded into each mold and then moved into the oven, where it's slowly rotated. The melting resin sticks to the hot molds and coats every surface evenly. The mold continues to rotate during the cooling cycle, so the parts retain a uniform wall thickness, if that is desired. 

Rotomolding differs from injection molding because there's no pressure used in the process. It allows gathering of the corners, so we can get really strong, stress-free corners; injection molding has a tendency to thin out the corners. The materials used with rotomolding tend to be better for the environment, and it makes a stronger part without any pressure. The molds are also less expensive, since they don't need to withstand the clamping pressure, and tend to last longer.

D2P:  Can you tell us about the hurricane simulation chamber that was designed to test the housing?

RD: The enclosure's main job is to protect the electronic components inside, so the integrity of the enclosure is very critical. We designed and manufactured this test chamber at our Madison, Ind., metal fabrication plant. We made the chamber so that we could simulate the wind velocity and moisture during a hurricane. Each and every box is tested in the chamber, so we know it won't fail during hurricane force winds.

We have another project where we make gas tanks for a generator trailer that's used for cell phone towers during storms. If the main power goes down, they bring the trailer to the tower to get it up and running. So we're very familiar with the effects of hurricanes. We make several products that can handle the effects of hurricanes. The generators will run for 24 hours without refueling, because during a hurricane, you may not be able to get diesel fuel.

D2P:  Has MODRoto produced other parts for the telecom industry? For what other telecom applications can MODRoto provide parts?

RD: For the telecom industry, we make a lot of enclosures, covers, and cable TV boxes that connect to houses. We also produce a cell tower communications cabinet, and we make various telecom protective devices for cell tower switching equipment.  

In one case, we made a telecommunications part at our plant in Ashtabula, Ohio. Afterwards, by some weird coincidence, I was approached by a cell phone company to put up a cell phone antenna on our property at the La Mirada, Calif. plant. After the antenna was put up, I found out that one of the parts was made at our plant in Ashtabula. I about fell over; I knew I'd seen this part before.

D2P:  How are MODRoto's capabilities suited to providing unique advantages to OEMs in the telecom industry?

RD: Design and engineering are two of our strengths, and we particularly like to work with complex designs. Flexible manufacturing within our plants allows us to adapt easily to secondary and quality control (QC) requirements, so a product not only gets designed correctly, it also gets manufactured correctly.

A large amount of quality control and testing goes into manufacturing precision telecom parts and components. We're not a “one size fits all” shop: We always develop a program for each customer, since some industries require more QC and testing than others. The telecom industry's parts and components require a great deal of extra care because of the longevity of the products and the fact that most of them are used in an outdoor environment. So there are stringent requirements in terms of strength and durability for the telecom parts.

Our four plant locations help our customers in many ways. We have plants in La Mirada, California; Anderson, Indiana; Ashtabula, Ohio; and Saddle Brook, New Jersey. First, we centralize our designs, and we do our manufacturing at each plant tailored to each customer. If they need nationwide distribution in large products, we can help them. For example, we may design products for the telecom industry in Indiana, but we are able to run the parts in our plants in Ohio or California and then send them to Mexico for assembly, or to wherever the customer needs them at a lower shipping cost. We offer nationwide service that a lot of other molders can't offer.

D2P:  Why do customers in this industry choose MODRoto's parts and services?

RD: Most of our customers come from referrals from other customers, who tend to cite consistent quality, on-time delivery, and our customer service. Customer service is very important with the telecom parts. We stress communications at all of our locations, and we have the computer systems, web access, and software that are needed to tie everything together.

We spend a lot of time working on our website (www.rotomolding.com), which even helps us in our proprietary business. A customer might ask us what our 16 standard colors look like. We can be talking with them on the phone while they are looking at the colors on our website. In the old days, we would have to overnight them a sample color, and it would take another day for them to get back with us. So our website really shortens product development time. A lot of rotomolders don't put the information out there for competitive reasons, but we don't worry about that. We put the information out there on our website that we feel will help our customers.