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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 compensation.
This new knowledge has led to significant innovations in the tooling
for Flexformed parts. Until now, tool design has been a rather inexact
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 economics
of fluid cell parts production. In the example above, a reconfigured
tool (Figure 3) has reduced the total processing time for this
part (Figure 4) by more than 80 percent. These tool design innovations
result in far more precision in the control of materials, producing
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
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Figure 1. Typical example of tooling
used with lower pressure rubber
pad presses
Figure 2. Inappropriate tooling will
only produce defective parts.
Figure 3. Redesigned Flexform tool
with blank holder
Figure 4. Finished part using
redesigned Flexform tool
The body of knowledge accumulated through intense research
and testing has enabled Agon Consultancy to develop a portfolio
of tooling solutions that can be easily transferred across a
variety of part configurations. This enables rapid and costefficient
design and construction of tooling for both development
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 illustrates
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 handwork,
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 highpressure
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 completion.
The latest test part formed by the fluid cell press over
the new tool is pictured in Figure 10. The part exhibits consistent
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.
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Continuing research with complex
component geometries
Figure 5. Initial pressing on a rubber pad press
Figure 6. Hours of handwork later
Figure 7. Elongation trial during development
of new Flexform tool
Figure 9. Precise, uniform control of
material movement
Figure 10. Near final pressing after
trimming
Figure 8. Final
design of Flexform tool
　
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