Multitasking Forms Hub of Shop’s Propeller Production Efficiency

Whirlwind Propellers in El Cajon, California, wanted to grow and expand its product offerings, but farming out the machining of its propeller hub assembly components was hindering the shop’s progress. Not only was the shop unable to fully control its processes and production lead times, but outsourcing reduced cost effectiveness, which in turn stifled new product design.

According to company President Jim Rust, the shop’s product line had become stagnant. It was neither developing new designs nor making design improvements to existing products. This changed when the shop incorporated multitasking machine technology from Mazak into its part production. 

Bringing Production In House

Whirlwind Propellers produces two types of propellers: constant-speed propellers for aerobatic aircraft and ground-adjustable propellers for simpler, light aircraft. One propeller hub assembly can involve as many as 23 different parts. The low-volume/high-mix production strategy required to keep up with customer demand for propeller hubs eventually rendered outsourcing no longer viable.

“Hub assemblies are comprised entirely of close-tolerance, high-precision parts,” Mr. Rust says. “Most are aluminum, but there are some made from 440C stainless steel. Most are round, but they require a lot of milling from solid billets.” The largest assembly components, he says by way of example, begin as 10-inch-round stock weighing 85 pounds. The finished part is only 7 pounds. 

When Whirlwind Propellers outsourced its hub assembly parts, turnaround times would stretch out for months. Now, the shop machines all the parts for a hub assembly in about 10 hours total on a Mazak Integrex i-200S multitasking machine. The shortest machining cycle time is around one minute, while the longest is close to four hours.

“The Mazak multitasking machine has eliminated the need to work around the schedules of our machining suppliers,” Mr. Rust says. “We are no longer at the mercy of outside suppliers and can control our production schedule.” He says the machine has driven three main outcomes: 

1. The shop now has more time available for product development because it makes all parts in house;
2. Lead times for propeller production are reduced; and
3. The shop can now better control its part costs.

Multitasking Machine Features

Whirlwind Propellers’ Integrex i-200S features twin turning spindles and a milling spindle with power equal to that of a vertical machining center. The machine is designed to productively turn, drill, tap and mill while offering off-centerline and full simultaneous five-axis contouring. 

The vertically mounted milling spindle provides 30 horsepower (22 kW), speeds ranging to 12,000 rpm and a rotating B-axis range of -30 to +240 degrees. A 36-tool magazine speeds tool changes and accommodates enough tooling for continuous part processing. Because its tool magazine is located in the front, Whirlwind Propellers’ machine operators can perform programming and tool setup with minimal required movement.

With bore capacities measuring 3 inches (76 mm) in diameter, both turning spindles on the Integrex i-200S provide spindle speeds of 5,000 rpm and C-axis turning control. The machine’s main headstock features an integral spindle/motor design that can accommodate a range of applications, from heavy-duty cutting at low speeds to high-speed cutting of aluminum and other nonferrous materials. The second spindle also features an integral spindle/motor to ensure high-efficiency machining for secondary operations.

Wrangling Lead Times

Whirlwind Propellers initially acquired the Integrex machine for one product line in particular. For this project, it could not afford the time and cost involved with outsourcing the components. Doing so would’ve eaten away all the time needed for designing, prototyping and proving out the parts.

“To contend with the farmed-out part turnaround times, we would carry a lot of work in process and order parts two months in advance,” Mr. Rust says. “But that really hurt our product deliveries and our responsiveness to customer demands. The critical aspect of these parts is maintaining close tolerances for assembly/fitting purposes, and for some parts, tolerances must be held to within 0.0005 inch to avoid stacked tolerances. When we would farm these parts out to different shops, accurate fit and finish during assembly would be hit or miss.”

The shop now makes all its hub assembly parts on the Mazak. The new product line involves propellers for some of the most popular kit airplanes on the market. The production would ordinarily involve three to five setups on multiple different types of machines. “We just weren’t willing to make that investment in not only the multiple machines but also the amount of shopfloor space they would have required,” Mr. Rust says.

Once the line is in full swing, the Integrex i-200S will run five days a week, all day long, with single-setup operations.

Flexibility as Well as Productivity

In addition to capital equipment savings, the multitasking machine gives Whirlwind Propellers the flexibility to change its production flow.

“Instead of having the machine setup for a particular part and running thousands of them, we can efficiently and cost-effectively make five of one part, three of another, 30 of another, and so on as production needs dictate,” Mr. Rust says. He attributes this capability to the ease of both setup and programming, which is done on a Mazatrol SmoothX control. 

Mr. Rust didn’t start out as a machinist by trade, though he had some three-axis milling experience. Regardless, he now programs, sets up and runs the Integrex i-200S and attributes that short learning curve to new CAD/CAM software, the machine’s advanced control and the training and application support the shop receives from Mazak.

On average, Whirlwind Propellers produces 3,000 propeller blades per year and as well as carbon fiber plastic reinforced (CFPR) constant-speed propellers. The shop’s operations center around four major processes – composites molding, metal bonding, Class-A composite finishing, electro forming and machining. According to Mr. Rust, the easiest of these processes is machining.

Since its inception in 1995, the 14-person shop has expanded to producing a full line of constant-speed propellers for light airplanes, airboat propellers and wind tunnel fan propellers. Whirlwind also specializes in rapid propeller and fan prototyping for some of the world’s largest aerospace companies. Mr. Rust sees business continuing to increase, as will the need to add more Mazak multitasking machines.