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Aerospace parts manufacturer upgrades bending capability

Electric bender helps fabricator thrive on complex shapes, expensive materials, fast turnarounds

Thin-wall material. Tight bend radii. Several radii per part. Low-volume runs. Fast turnarounds. A limited number of skilled equipment operators. It sounds like one difficulty after another, but this is business as usual at SL Engineering (SLE), Sleaford, U.K. Founded in 1959, the company’s core capabilities include CNC tube forming; multiaxis CNC machining; welding; brazing; assembly; and support activities such as pressure testing, dimensional verification, and nondestructive testing.

As a Tier 1 supplier of rigid tube assemblies and precision machined parts for aerospace applications, the company supplies major engine and airframe components for commercial programs for manufacturers such as Airbus and Boeing and for military programs such as the Joint Strike Fighter (JSF). The company also does quite a bit of business in fabricating components for industrial gas turbines and marine propulsion systems.

These are solid markets, but they have substantial fabricating challenges.

“Engine and aircraft manufacturers are taking advantage of the advanced shape forming capability of state-of-the-art tube bending machines by specifying more complex shapes and highly challenging tighter-radius bends to save weight and space and eliminate welded joints,” said Director and General Manager Shaun Stevenson. “The sophisticated bending capability of [today’s] machines, which allow greater control over tube clamp and carriage push forces, helps us to achieve these new levels of precision.”

SLE's business today is characterized by a need for manufacturing flexibility. The average batch is from five to 25 parts, and occasionally the company receives an order for a single part. A single-part order often is an emergency repair for an aircraft, an order that must be filled as quickly as possible. Airlines and their suppliers do everything they can to minimize the aircraft on ground (AOG) time, which refers to the time needed to complete any unscheduled repair that prevents an aircraft from flying. Every hour of AOG is an hour of lost revenue, which is substantial in the airline industry.

Another factor in SLE’s work concerns the demand for greater precision and shape complexity. Until recently, few tubular parts required bend radii less than 2D (twice the tube diameter). Today, however, SLE regularly receives requests for bends of 1D and for shapes with minimal straight sections between bends. The use of thinner-walled tubing and expensive, specialized materials such as titanium and INCONEL® alloy drives the company to look for ways to increase precision and minimize waste.

Fast and Flexible

To this end, the company recently invested in a second all-electric CNC tube bender from Unison. The new machine enhances the company’s ability to produce increasingly complex tubular shapes and extends the diameter range it can handle with all-electric, servomotor-controlled motions to 3 1⁄8 in. (80 mm).

The first all-electric machine proved critical for SLE, allowing it to handle small-batch setups much more efficiently and quickly and often make a good part on the first attempt, eliminating scrap.

“If we did the same jobs on our old hydraulic machines we would be much more reliant on highly skilled operators to both set up the machines and make the parts with additional weld joints, and hence additional cost,” Stevenson said.

SLE installed its first such machine in 2010, a Breeze 30, also manufactured by Unison. Capable of bending diameters up to 1-1⁄8 in. (30 mm), it handles a significant portion of the company’s bending work. SLE channels most new work for small parts to this machine and transfers many older parts to the machine by creating new bending programs as orders come in.

The company’s newest machine, a Breeze 80, extends the advantages of an all-electric machine to diameters up to 3 1⁄8 in. (80 mm). The machine also incorporates stacked tooling, reducing the number of tooling changeovers, which is necessary for bending multiradius parts efficiently.

“We continue to see many challenging opportunities in the sector, but it does require significant capital investment,” Stevenson said. “The new bender, along with further investments in 5-axis machining, has helped SLE take its manufacturing capability to a new level. We can meet the most complex tube assembly specifications that aerospace companies require today, and the combination of advanced machinery and our know-how gives us a platform to raise the bar even higher and differentiates SLE from our competitors.”

The company doesn’t keep its manufacturing expertise to itself, but shares it with its customers when such opportunities arise.

“Another service we offer to clients who are able to provide us with pre-release drawings is evaluating manufacturability and advising on the potential for manufacturing and cost-saving improvements before final drawing release.”

As an example of the exacting specifications that SLE faces, one current part for a military fighter program calls for a shape with multiple 2D bends but minimal straight sections between bends in thin-wall titanium tubing. Tube ovality also has to be less than 5 percent after bending, which is half the industry norm, and the part shape has a positional and length tolerance of just ± 0.005 in. after bending and welding.

Because the part is made from titanium, bending must be right the first time—adjustments after forming are almost impossible. The consistency and repeatability of the bender is a critical enabler for fabricating this part, as well as other titanium tube parts that SLE currently makes.

Another aspect of the advantages of the bending machine for a contractor such as SLE is the ease of programming. Tubes are often the last parts

to be defined and designed, whether they are for an engine or airframe. Using its own macro-driven CATIA® V5 closed-loop CAD/CAM facility and Unison's 3-D simulator, SLE can create new CNC bending programs for the machine rapidly, supporting clients who are unable to supply tube and pipe details until late stages of project development.

Qualifications

To support its work in aerospace, SLE has attained qualifications for many key industry standards, including AS9100 (Revision C) aerospace quality management systems; BS EN ISO9001; and Nadcap special process approvals for welding, brazing, and NDT. The company’s continued investment in forming equipment is another qualification—one that readies the company for more growth in the years ahead.

About the Author
FMA Communications Inc.

Eric Lundin

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Elgin, IL 60123

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Eric Lundin worked on The Tube & Pipe Journal from 2000 to 2022.