Aerospace manufacturing continues to soar. For example, through March 31, Boeing’s commercial aircraft division had a backlog of 5,835 orders, while rival Airbus had a backlog of 7,189 jets.

Better yet, those numbers are expected to grow significantly. Boeing predicts the global market for air travel will be 2.5 times larger in 20 years than it is today. As a result, the aerospace giant expects the global fleet of commercial jets to double in size by 2036. In addition to the need for new airplanes to meet growth demand, three quarters of today’s 23,500 commercial jets will likely need to be replaced over the next 20 years, contributing to overall demand for 41,030 new airplane deliveries by 2036. That’s a $2.8 trillion pie for Boeing, Airbus and other OEMs to compete for.

Those figures are music to the ears of Doug Rose, founder and president of Aero Gear Inc. in Windsor, CT. Founded in 1982, Aero Gear designs and manufactures gears and gearboxes for fixed and rotary wing aircraft. The aerospace supplier counts Boeing, General Electric, Sikorsky, Rolls Royce, Pratt & Whitney, and UTC Aerospace Systems among its customers.

If Boeing’s predictions are correct, Aero Gear will be ready. On June 14, the company officially opened a 24,000-square-foot addition to its manufacturing facility. The expansion provides the company with some 93,000 total square feet to accommodate 175 employees, a new lobby, conference room, offices and manufacturing space for several new programs.

“We’re starting to move equipment in. It’s exciting,” says Rose.

Recently, we spoke with Rose about gearbox assembly, lean manufacturing and manufacturing technology.

ASSEMBLY: Congratulations on your expansion!

Rose: The aerospace industry is busy these days. Our industry, by nature, is cyclical, due to the long lead times to get product built. But, it’s a little unusual to have both commercial and defense aviation up at the same time. Usually, they cycle differently.

We expect at least three to five years of strong growth, and we’re trying to stay ahead of the curve. We won’t need all of the 24,000 square feet immediately, but we’ll fill up a third of it right away. Over the next few years, we will continue to add equipment.

ASSEMBLY: Tell us about gearboxes.

Rose: We make accessory gearboxes for jet engines. These gearboxes tap off of the rotary motion of the engine to drive the aircraft’s fuel pump, oil pump and electrical generator. The gearbox also drives the starter for the engine.

The gearbox housing is typically made of aluminum, but some are made of magnesium. The gears are made from carburized and hardened steel.

Our core competency is producing aerospace gears. The teeth need to have a really hard surface so they last long. And, of course, they must be very precise for high-speed operation. We case-harden the gears and then grind the teeth. The gear teeth are typically hardened to 60 Rockwell C. Underneath that, the parent material typically has a hardness of 38 to 40 Rockwell C. That way, the gears won’t wear out, but they can still bend and flex under load.

We also case-harden the bearing journals and grind them very precisely.

ASSEMBLY: What’s the trickiest part about making a gearbox?

Rose: Mostly, it’s controlling the case depth. We do heat treating in house.

The gearbox housings must be very precise, too. The bores must be precisely located, so all the gears line up right.

ASSEMBLY: How do you assemble a gearbox?

Rose: An accessory gearbox might have 250 to 300 parts: everything from simple studs to complex components such as bearings and oil nozzles.

Each gearbox we make is produced on a dedicated U-shaped lean cell. It’s a lot of manual labor. All the components are placed in shadow boxes, and the process just flows. Good work instructions are essential.

Quality control people verify that standards are being met. If a fastener must be tightened to a certain torque, they document that.

It’s low-volume, high-mix assembly. We’re not making thousands of pieces per day. With a good gearbox program, we might make a couple hundred per year. So it’s a different takt time than an automotive plant.

ASSEMBLY: Aero Gear was an early adopter of lean manufacturing. Talk about your flow line concept.

Rose: Our whole factory is set up to flow, especially for making gears. The raw material comes in one end of the building, and continuous-flow lines convert it from slugs of steel into gears.

Before we converted to lean, our company, like most companies, was set up in departments. We had a grinding department, a turning department, a milling department and a gear grinding department. And of course, we were always scheduling the next operation in the next department.

With lean, we lined up our equipment in the sequence of the processes, and we do relatively small batches of parts that flow through one after the other, ideally to takt time. A particular flow line might have 100 or so part numbers assigned to it. And you’ll see small batches of maybe 20 pieces moving down the line, depending on which machines they need.

Because we’re a job shop, we must be able to adapt to whatever product we’re asked to make.

ASSEMBLY: What technologies have made a big impact on your manufacturing operation?

Rose: We have been investing more in high-tech equipment, such as integrated mill turn centers that can turn both sides of a gear, do any milling operation, and create the gear teeth all in one machine.

There have also been breakthroughs in heat-treating technology. We recently installed new vacuum carburizing furnaces that precisely control case depth and hardness.

We’ve added high-tech inspection equipment, too. In the aerospace industry, everything must be carefully inspected and documented. Sometimes, that takes as much time as the machining! We have coordinate measuring machines, like every aerospace manufacturer, but we do a lot of white-light inspection, too. It’s incredibly precise. It can measure to within 0.0001 inch.

We don’t necessarily want to be the first ones to use a new technology, but we do try to adopt new technologies to stay competitive. Which is what we need to do in the U.S., right? Our overall cost structure might be higher here in Connecticut, but we work very hard to be more productive and therefore, we can be globally competitive. We compete all the time with places like Poland and Singapore, because we’ve invested in technology and, of course, our skilled people. We have smart, capable, talented people, and when you combine that with technology, we can compete with anyone in the world.

ASSEMBLY: What does the future hold for Aero Gear?

Rose: We always invest $2 million to $3 million per year in new equipment.

One reason we built the addition is to create production cells with a tighter product definition. Our flow lines can make a variety of parts. We would like to set up more specialized cells to produce some higher volume parts.

Our latest addition is the fifth time we’ve expanded our building. We keep growing and moving the company forward. We’re at about 175 employees, and we’ll probably hire another 20 to 25 people in the next year.