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resistance. But, at ambient temperature, it is difficult to form titanium to the complex curved geometries of aircraft
components. The achievable strain at room temperature is rather limited, springback is unpredictable and
after trimming parts often change shape.
There are few titanium parts designed and built from sheet metal for current structures due to the described difficulties
and high cost per kg. Scrap reduction and careful handling of materials´ resources has sense and will
get a much bigger item with the increasing number of composite fuselages. Further, unlike aluminum titanium
inherently resists corrosion . This paper describes an option for reducing the cost of titanium parts and therein
increasing its use on future aircraft. Forming titanium is simpler at elevated temperatures than at room temperature.
Complex shapes can be formed if the material is raised to temperatures approaching 900°C .
At such temperatures some titanium alloys will strain up to some hundred percent without degrading structural
properties. In this condition, the titanium is pliable, shows high ductility and forms with such a low flow stress
that it is possible to form with gas pressure. After de-moulding and cooling, parts don´t exhibit residual stresses
and trimming doesn´t change part contour. Tooling for such applications can be relatively simple. For the gas
pressure forming process, the tools just need a shaped cavity bottom die half and a flat closure top die half.
Gas pressure forming of titanium sheets is competitive when compared to machining components from thicker
15
plate material. Formed parts can be designed thinner and weigh less than comparable machined parts due to
the practical limitation of not being able to machine down to thickness less than 2,5mm. Another advantage of
forming is minimal scrap.
Whereas machining scrap ratios of more than 90% are typical, formed parts seldom have scrap ratios exceeding
30%. Gas pressure forming can typically be cost justified as production quantities increase and there are
more parts over which to amortize tooling costs. Weight and cost balance compared against the accumulated
parts quantity count show an early break-even point. FormTech is a leader in titanium forming with gas pressure
at elevated temperature. In this paper an overview of the process is presented from a production point of
view and many different shapes are discussed as a way of illustrating a wide range of possible future applications.
Title: On site machining (on an airport) of wings and fuselage of a twin jet with
HEXAPODE CMW 380
Authors: F. Wildenberg
CMW
Time: November 3, 2009 3:00 pm
Room: Candela
• CMW has developed (with research centers and university) a new technology to make 5 axes High Speed
Machining on very large parts:
HEXAPODE CMW 380.
• It is very similar to the human machine:
o The support is the arm and wrist: a serial machine without rigidity like any milling machine
o The hand is a parallel kinematic machine with high rigidity
o The hand correct the positioning errors of the wrist
o It works on a sequential way: successive mesh machining
o They are no measuring system into the machine
o They are 2 external measuring technology: eyes (laser tracker), internal ear ( electronic level)
• One application which was not initially anticipated is the on-site machining
• The first use was made for aircraft industry.
• Now CMW is discovering that they are a lot of other uses of this new technology
• How it started:
o The problem:
The customer is a company specialized in maintenance of twin jet aircraft
A twin jet had a leakage problem of fuel at the junction between the wings and the fuselage.
So they disassemble the wings and fuselage and discover a lot of corrosion. During the manual grinding of the
corrosion they created a lot of hollow small surfaces. This was going to induce more leakage. So it was necessary
to make a full machining of the surfaces. The wings were on a trolley and the fuselage was on fixed jack.
So it was impossible to move the fuselage.
o The answer:
CMW came and made the on-site machining of the wings and fuselage with HEXAPODE CMW 380
It was necessary to make High Speed Machining (HSM)
-First to induce very low forces on the wings and fuselage since their support had no rigidity
-Second to achieve very low residual stresses. So the aircraft will have a longer life expectancy
-Third to get a very good surface finishing
-Forth to be able to machine very thin extra thickness in some places
It was necessary to make automatic correction in 6 directions (3 positions and 3 angles) due to the initial
positioning errors of the machine. This is automatically done with the use of external measuring systems. 2 different
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