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July/August Feature

Thermoforming Jobs Fly at UAL’s Maintenance Operations Facility

United Airlines’ San Francisco-based Maintenance Operations facility manufactures plastic replacement parts for its fleet of airplanes.

By Karen Koenig

Job orders and expedites for replacement parts fly through United Airlines’ San Francisco Maintenance Operations facility on a daily basis. It is in this facility that the 3,200-square-foot thermoforming shop manufactures plastic components for the more than 600 planes in UAL’s commercial fleet.

Plastic replacement seat components, inlcuding chair sides, armrests and trays are thermoformed and machined at UAL's San Francisco-based Maintenance Operations facility.
United Airlines has been thermoforming its replacement plastic components since the 1960s, says Jerry Severance, lead mechanic-Component Maintenance at the San Francisco facility. “We’ve found it to be more cost-effective (than outsourcing). On average, we found we can manufacture a part in-house for approximately 40 percent of what it would have cost us to buy the same part from an outside vendor,” Severance adds.

“Also, we can be more sympathetic to the airline’s needs with (regards to) turnaround time,” he continues. While most job orders are to replace items taken from stock and therefore have a longer lead time, expedites require a fast turnaround time, oftentimes the same day.

Scheduling of “standard” jobs is done on a daily basis, with expedites fit into the mix. As orders come in, part numbers and control numbers are assigned to each item on the sheet. Information on mold location, blank size, trim fixture, type of aircraft, haircell and material to be used is also made available to the machine operator. The majority of parts are made from Kleerdex’s Kydex 100, which the company says meets the Federal Aviation Administration’s flame retardant requirements for commercial aircraft. The shop also manufactures replacement 727 T-Tail clear lenses which it forms from GE’s Lexan material.

Every fleet of aircraft has different styles and requirements,” says Dean Bosso, supervisor. “For example, in a typical 747 you might need 28 galley pans (which are located in the bottom of an aircraft and used to contain moisture), 300 seats, 300 trays, 400 armrests, 15 lavatory pans (which are used as the flooring in aircraft lavatories) and 15 lavatory shrouds.” In addition to the 747s, the shop also manufactures parts for United Airlines’ fleet of 777s, 767s, 757s, 737s, 727s, as well as the A319 and A320 Airbuses.

Although 90 percent of the shop’s work involves forming and fabricating of replacement aircraft parts, approximately two years ago the company contracted with Boeing to also manufacture galley pans for installation in new United Airlines 777 planes. Opportunities within United Airlines for manufacturing non-aircraft components have also arisen.

“For example, for our maintenance facility in Indiana we manufactured tote tubs for parts distribution,” Severance explains. “We looked at the samples, worked with some different materials and developed the product. We produced 900 totes, 32 inches wide by 32 inches long by 18 inches deep, which will run on conveyor belts.” Other non-aircraft parts developed and manufactured by the thermoforming shop include protective covers for transporting of parts.

Thermoforming the Parts

With its lower tool costs and ability to inexpensively produce short runs, the
Joe Krepelka adheres a non-skid vinyl sheet with a photo-sensitive cap onto the lavatory pan. The pan was thermoformed from Kydex 100 material on the Maac single-station vacuum former.
rmoforming is a more cost-efficient method of manufacturing for UAL’s shop than other means of molding, Severance says. “Thermoforming is more cost effective, especially if we’re doing only six large pieces at a time, such as the galley pans. If we were manufacturing 10,000 pieces in a single order, then injection molding would be a consideration. But for now, we don’t want to keep too much in inventory,” Severance explains.

In-house thermoforming has also brought tangible cost savings to the company. For example, galley pans which could have cost more than $1,000 each to purchase from an outside vendor can be manufactured by United Airlines employees for approximately $200.

Galley pans and other components are formed on one of three vacuum machines: a Maac Machinery 5-foot by 8-foot single-stage former purchased two years ago to handle large parts, an older Brown 32-inch by 32-inch single-stage former and a Parker 40-inch by 48-inch rotary former.

Prior to purchasing the Maac, large parts were manually formed. “On a large part such as the handicapped lavatory pan for a 777, it would have taken four people to clamp the sheet into place and carry it into a 400F walk-in oven. After it heated, they would have to carry it out, place it over a tool, manually apply vacuum to form the piece, then wait for it to cool,” says Neil Lundy, supervisor. “With this machine, not only has our quality improved, but the cycle time also has improved tenfold.”

Lundy also notes that there is increased design flexibility and quicker mold change capability now available with the newer thermoformer. For example, the increased vacuum pressure available on the machine has enabled the division to produce parts with a variety of styles, textures and mold patterns, he adds

The molds themselves are built in-house and maintained by UAL employees. More than 1,100 molds are in stock to supply the company’s existing fleet of planes. The tooling is kept in inventory until approximately one year after the airline retires the fleet, Severance says.

Molds are constructed from wood, typically kiln-dried poplar, and made using standard woodworking tools such as shapers, hand-h
Ben Wood uses a Maac 5-foot by 8-foot single-station machine to form a handicapped lavatory pan for use in a 777 airplane. Cycle time for this piece is apporximately seven minutes, compared to more than 30 minutes with the old method.
eld routers and planers. “This material works well for us. We’re not making a large quantity of parts, where you would need to go to aluminum or steel,” Bosso says. He adds that the small amount of moisture released by the plastic sheet does not affect the wooden mold nor cause swelling.

Possible swelling is an important consideration for the shop. The thermoforming department must adhere to specified tolerance levels of ±0.030 inch on the formed parts. ”The moldmakers typically have to figure in any shrinkage factor. That’s why having a consistency in the plastics blend is very important,” Severance says.

Trimming and Assembly

Parts are typically formed as a single piece, so mechanical bonding is not required. After forming, excess material is first removed on a bandsaw. Parts are then taken to a Powermatic shaper for final trimming. Portable routers are also used for small trimming jobs.

“We’re looking at getting a five-axis CNC router into the shop area, especially for trimming armrests and trays, when you might do 500 at a time,” Severance says.

On average, nine people work in the trimming and assembly areas; in addition to trimming the parts, the shop is also responsible for such things as adhering the non-skid vinyl onto the formed Kydex floor components. Employees are also responsible for assembling chair components into complete units. The only component excluded from the mix are the cellular phones mounted in the seat backs.

Maintaining Quality Control

With the diversity of jobs performed by employees, monitoring and maintaining quality control is essential. In the thermoforming and trimming areas, for example, employees sign off on the job card after each operation is performed. Severance’s signature is required before the job ships out.

“We have very little turnover here. Everyone is experienced and does a great job,” Severance adds.

United Airlines: A History of Flying the Friendly Skies

It was on April 6, 1926 that entrepreneur Walter T. Varney launched his “air mail” operation, marking the birth of commercial aviation in the United States. Because Varney was a predecessor of United, it also marked the birth of the airline.

As the aviation industry grew, airlines, aircraft manufacturers and airport operators merged into giant cor
Jerry Severance removes a formed Kydex 100 lavatory shroud from the thermoformer. He estimates that the plastic component costs the company approximately $130 to manufacture, compared to $1,100 for the original fiberglass model.
porations. But in the 1930s, following the claims by media of a monopoly, the conglomerates were dismantled by the government. It was during that time, William A. Patterson took over as president of United.

United had resumed its mail service in the United States. But during World War II, the company instead turned its attention to modifying war planes for the armed forces. It also helped train more than 7,000 ground crew members and flew thousands of missions to Alaska and across the Pacific to transport soldiers and supplies.

Following the war, the economic boom included a demand for air travel. Patterson expanded United’s routes and purchased its first jet aircraft. Patterson continued as president until 1963, when he became chairman and CEO. United’s new president, George Keck, added to the company’s momentum by acquiring second-generation jetliners and seeking United’s first trans-Pacific route beyond Hawaii. In late 1968, Keck also formed UAL Inc., a holding company that would allow United to diversify.

But in 1970, United’s fortunes changed; the company posted a loss of $46 million just two years after making record profits. After going through six presidents and two name changes, United was forced to divest and return to its core airline business in 1987.

Now employee owned, the company has since redefined itself through its expanded services to worldwide destinations. Last year, it transported an average of 231,000 passengers per day to destinations throughout 28 countries. Today, it continues to be the largest commercial airline in the world.

Information gleaned from United Airlines’ Web site,

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