Innovations in Fluid Cell Tooling andProcess Efficiency Dramatically Lower the

Costs of Aerospace Sheet Metal Parts

by Graham Beaumont

Agon Consultancy

June 2009

Graham Beaumont is

Managing Director of U.K.-

based Agon Consultancy, an

aerospace supply chain and

manufacturing process

improvement consultancy

serving all areas and levels of

aerospace manufacturing.

Mr. Beaumont has provided

design, engineering and

project management services

for programs including the

Airbus A320, A380, and

A400M and the Boeing 737.

Since the 1960s, aerospace manufacturers, including Boeing, Airbus,

Bombardier, Cessna, TAI, Embraer and others, have successfully used fluid

cell (or “bladder”) presses to precisely form a wide range of aluminium and

other sheet metal components. Today, however, strategic shifts among the

major airframe OEMs mean that a growing number of these parts are being

outsourced to tier 2 and 3 suppliers. With the advent of new intermediate-

size presses, these subcontractors are beginning to invest in fluid cell tech-

nology to cut production costs and improve their competitive position.

In this paper, we examine recent advancements in tooling and the resulting

process efficiencies that are enabling tier 2 and 3 suppliers to profitably

incorporate this flexible forming (“Flexforming”)

process into their operations. Cost reductions

(compared to conventional mechanical pressing)

can be achieved through the pressing of multiple

parts per cycle with little or no rework, precise

forming to tighter tolerances, much lower tool

costs, shorter part lead times, improved levels of

quality, and the ability to design and produce com-

plex shapes that would be prohibitively expensive

with conventional presses. Compared to rubber

pad presses, Flexforming generates two to four

times more forming pressure more uniformly over

the tool, creating deeper, more intricate shapes

with higher accuracy and part definition.

There is little question that, despite the recent economic downturn, the projected

growth for commercial, private, and military aircraft will continue well into the

future. Sales of new commercial aircraft have slowed, but a large backlog of prior

orders remains. The global air cargo business has already stabilized and is set to

resume expanding activity as global economic conditions improve. Aging fleets

need replacing, emerging nations have growing needs for modern aviation, and

there is increasing demand for affordable light jets for corporate and private

travel.

With these opportunities come new challenges for airframe manufacturers: new

and intensifying global competition, extreme pressure to control costs at all levels,

the need for advanced technology to expand capacity and productivity, reduction

of labor-intensive processes, and the ever-growing demand for lighter, more fuel

efficient, and environmentally compliant aircraft.

Abstract:

Changing dynamics in the aerospace industry

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As with most major manufacturers in industrialized nations, many aerospace compa-

nies are concentrating on core competencies. They are becoming aircraft integrators

and outsourcing an increasing share of their production, most notably the fabrication

of sheet metal components. In some cases, strategic “manufacturing offset” agreements

are negotiated with vendors in countries with the potential to purchase aircraft.

Similarly, many of the original tier 1 suppliers have shifted to more value-added

assembly and integration activities, and are contracting parts production to

smaller tier 2 and 3 sources. While some of these sources are still using older, lower

pressure rubber pad presses, others have made the switch to fluid cell technology to

meet the stepped-up quality and delivery demands of the airframe producers.

To be successful, aerospace OEMs and their first tier subcontractors must be assured

of low-cost, high-quality, on-time components. By the same token, tier 2 and 3 suppli-

ers must ensure their reliability in these areas to be competitive. The answer to both

concerns may well be the recent availability of mid-size, supplier-focused fluid cell

presses and advancements in Flexforming processes and tooling technology.

Flexforming is basically a simple process. Unlike mechanical and hydraulic presses

which use upper and lower forming dies, (often in three pieces), Flexforming uses a

single, rigid, shape-defining tool half (also known as a hydroblock or die). A sheet

metal blank is placed over this tool and is pressed into shape by a flexible rubber

diaphragm under uniform hydrostatic pressures as high as 20,000 psi (140 MPa, an

equivalent pressing force of up to 150,000 tons). Multiple tools and blanks are placed

freely in large forming trays at each end of the press which shuttle in and out of the

central frame containing the pressurized diaphragm. Multiple part sizes, shapes and

gauges can be formed in a single one- to three-minute cycle.

Flexforming’s key advantage over mechanical and rubber pad forming methods is the

uniform application of very high pressure, forcing the metal evenly into intricate

shapes, including undercuts. In some cases, forming, trimming and hole punching can

be performed in the same cycle.

-2-

Supply chain opportunities

The fluid cell concept

A “rebirth” of fluid cell processing has taken place over the past three years. A

great deal has been learned through testing and research about predicting and

controlling the behaviour of aerospace aluminium alloys and other metals under

very high forming pressures. Much of this recent work has been done in Europe,

funded and carried out by Agon Consultancy.

Studies centered on several materials and a variety of processing characteristics:

stretching and elongation under varying pressures, draw ratios, bending radius,

strain hardening, elasticity modulus, etc. The result has been a much

greater practical understanding of the elastic/plastic thresholds and

the tensile and yield strengths of aerospace metals. Among the many

findings is the value of introducing tensile stress during the forming

process to better control stretching uniformity and springback com-

pensation.

This new knowledge has led to significant innovations in the tooling

for Flexformed parts. Until now, tool design has been a rather inex-

act science, often involving the modification of existing rubber pad

tooling. Owners of fluid cell presses have either built their own

hydroblocks or sought the aid of toolmakers who were experts in

mechanical pressing but had little experience with the Flexform

process. Through trial and error, a degree of acceptability was

achieved, although manual rework of formed parts was nearly always

required.

On this and the following pages are examples of the significant cost

savings made possible by the new tooling and processing innovations.

Figure 1 is an example of the tool design which had been a typical

configuration in the rubber pad pressing industry, but not suited to

fluid cell technology. The part being formed presented numerous

manufacturing difficulties: very deep flanges relative to part size,

joggles to the flanges, and a tight bend radius. Figure 2 shows the

result when this part was formed on the modified rubber pad tool in

a fluid cell press.

Better understanding of material behaviour has led to more effective

tools and forming processes that are dramatically changing the eco-

nomics of fluid cell parts production. In the example above, a recon-

figured tool (Figure 3) has reduced the total processing time for this

part (Figure 4) by more than 80 percent. These tool design innova-

tions result in far more precision in the control of materials, produc-

ing final net size components often in one operation with closer

assembly tolerances and little or no manual correction.

Major advances in production efficiency with next generation tooling

-3-

Figure 1. Typical example of toolingused with lower pressure rubberpad presses

Figure 2. Inappropriate tooling willonly produce defective parts.

Figure 3. Redesigned Flexform toolwith blank holder

Figure 4. Finished part usingredesigned Flexform tool

The body of knowledge accumulated through intense research

and testing has enabled Agon Consultancy to develop a port-

folio of tooling solutions that can be easily transferred across a

variety of part configurations. This enables rapid and cost-

efficient design and construction of tooling for both develop-

ment prototypes and finished part production.

Complex, high-profile parts are common in the aerospace

industry, and are difficault to manufacture economically. A

representative example is an aluminium air intake lip skin that

was being manufactured on a rubber pad press. Figure 5 illus-

trates the problems encountered with this lower-pressure

process. There is little part definition after the initial press

cycle, minimal elongation of the metal, and numerous defects

to be corrected.

In Figure 6, the part has undergone nearly 20 hours of hand-

work, yet defects remain. This time-consuming process resulted

in costly parts with high levels of scrap after testing.

Agon recommended changing the forming process to a high-

pressure fluid cell press, and began a development program

using prototype tooling for trial pressings to explore the limits

of material elongation required for this specific part (Figure 7).

The tool (Figure 8) and the process was designed to yield the

optimum balance of elongation and uniformity of material

thickness. Flexforming’s ability to apply even forming pressure

to all areas of the workpiece is shown in Figure 9.

At the time of this writing, the project was nearing comple-

tion. The latest test part formed by the fluid cell press over

the new tool is pictured in Figure 10. The part exhibits consis-

tent elongation with no draw markings, excellent thinning

properties around the outer radius, and retention of the close

tolerance undercut side flange. The lip skin will support all of

the geometric requirements, eliminating most of the hand

forming operations and reducing total production time from

20+ hours to a about 3 hours, with virtually zero scrap loss.

-4-

Continuing research with complexcomponent geometries

Figure 5. Initial pressing on a rubber pad press

Figure 6. Hours of handwork later

Figure 7. Elongation trial during developmentof new Flexform tool

Figure 9. Precise, uniform control ofmaterial movement

Figure 10. Near final pressing aftertrimming

Figure 8. Final design of Flexform tool

Advanced tooling designs can accomplish more than pro-

ducing good parts. They are frequently a key component in

a broader analysis of the entire manufacturing process for a

given part. These assessments are particularly beneficial for

complex formed parts that require a high number of dis-

creet production operations. The fundamental goal is to

enable the Flexform press and a redesigned tool to remove

as many of these operations as possible, especially the hand

forming bottlenecks often required to correct wrinkling,

deformation and springback.

The example on this page is typical of the time and cost

savings possible with process analysis. The part (Figure 11)

is made from aluminium alloy, and is nearly two metres in

length, with numerous manufacturing challenges: significant

hoop strain conditions due to its large circumference, jog-

gles in a number of planes, undercuts, and deep flanges.

The original manufacturing process included a total of 17

separate operations,

and yielded an aver-

age of 240 finished

parts per month.

A thorough assess-

ment was conducted

to identify those tasks

that could be eliminated by

redesigning the forming tool. The

new tool (Figure 12) was instru-

mental in reducing the number of

processing steps from 17 to six. As

shown in Figure 13, the steps

eliminated included four Flexform

press cycles plus the associated tool loading/unloading time, 2.5 hours in

hand forming time and five other out-of-press operations.

The new streamlined manufacturing process quadrupled the yield, producing

240 parts in a week rather than a month. Component recurring costs have

been cut by 50%. The new process also permitted a productive reallocation

of skilled labour hours and better utilisation of equipment.

-5-

CurrentManufacturing

Process

1st Flexform Pressing

2nd Flexform

Band Saw

Hand Rout

1st Hand Adjustment

3rd Flexform Pressing

De-grease

Anneal

2nd Hand Adjustment

4th Flexform Pressing

5th Flexform Pressing

Solution Treatment

3rd Hand Adjustment

5th Flexform Pressing

4th Hand Adjustment

5-Axis Rout

5th Hand Adjustment

ImprovedManufacturing

Process

1st Flexform Pressing

Solution Treatment

2nd FlexformPressing

1st Hand Adjustment

5-Axis Rout

2nd Hand Adjustment

Figure 13. Detailed process analysis and newtooling result in dramatic time and cost savingsfor this complex component for a major airliner.

Process assessment and restructuring

Figure 11

Figure 12

For decades, fluid cell pressing has been an established

but sub-optimized production process for suppliers to the

aerospace industry. The dramatic advances in tooling

and process design discussed above now make

Flexforming an even more cost effective technique for an

expanding variety of complex formed metal components.

Avure Technologies is the world’s largest producer of

Flexform presses. Agon Consultancy has accelerated the

tooling research work done by Avure over the past 40

years, focusing not only on tool design but also on

streamlining the forming process. Both companies share

a common interest in making Flexforming an economi-

cally viable technology at all levels of the supply chain.

-6-

Conclusion

Sales in the Americas:

Avure Technologies, Inc.

Columbus, Ohio USA

Phone: +1 614-891-2732

New knowledge of the behaviour of aerospace alloysunder high pressure results in new tooling conceptsand new opportunities for suppliers to take fulladvantage of the cost and quality benefits ofFlexforming.

This new precision, easily incorporated into Catia V5 CAD platforms, provides

critical support to the aerospace industry’s “part-to-part” manufacturing philoso-

phy. Until now, component assembly time has often been excessive due to mis-

alignment caused by failure of the component to meet key assembly tolerance

specifications. In addition, parts are generally made with pilot holes, requiring re-

drilling prior to attachment. Now, Flexforming can produce components that fit

the first time, with full-size holes, speeding assembly operations significantly by

eliminating time wasted on manual rework, multiple positioning and re-position-

ing, and redundant drilling.

These closer tolerance parts can also promote greater use of friction stir welding,

a joining process that is two to three times faster than traditional riveting, with a

subsequent reduction in the weight of the airframe.

Quality parts speed aircraft assembly

Sales and Manufacturing:

Avure Technologies AB

Vasteras, Sweden

Phone: +46 21 327000

www.avure.com

info@avure.com