Mitsubishi Heavy Industries Technical Review Vol. 52 No. 3 (September 2015)
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Machine Tool for Machining Aircraft Parts

Equipment & Machinery Sales GroupS a l e s D e pa r t m e n t , M a c h i n e To o l D i v i s i o n
M a c h i n e r y, E q u i p m e n t & I n f r a s t r u c t u r e

Substantial growth in the aircraft parts machining industry will continue with planned
production increases by Boeing and Airbus, as well as the expected expansion of the regional jetmarket, including the MRJ of Mitsubishi Aircraft Corporation.
Aircraft parts are more difficult to machine than general parts. The reasons include theworkpieces being long with complex curved surfaces, as well as being susceptible to deformation
because of thin walls. There is also the issue of the materials used for the workpieces, namely
titanium, which generates large amounts of heat, and CFRP (carbon fiber reinforced plastic), whichtends to generate burrs and chips during machining.
To improve efficiency in parts machining to cope with the increase in the global productionof aircraft, there is demand for dedicated machine tools that combine a function specialized for theworkpieces to be machined, an automatic workpiece exchange function that enables long-term
continuous machining and manpower-saving and automation functions such as automatic
measurement using sensors.
Our machine tool division has delivered many machine tools to the aircraft parts machining
industry utilizing our advantage as a manufacturer of aircraft parts and the expertise and response
capability we have cultivated in automated machining lines in the automobile industry. This paper
introduces examples of the dedicated machines among machine tools for aircraft parts machiningthat our division has developed.

|1. Main wing panel perforating machine
The main wing box that is the target workpiece of this machine consists of composite
material (CFRP and metal), exceeds 20 meters in length and has a shape consisting of complicatedcurved surfaces. In addition, it is necessary to process many holes in a main wing box, andtherefore improvement in efficiency is an important issue.
This machine is a dedicated machine tool equipped with six separately-operating combined
heads (three on the upper side and three on the lower side of the workpiece) capable ofsimultaneous machining, auxiliary equipment such as a workpiece holding jig, and software
containing a machining scheduling function for the support of a high operation rate. As a result, alarge number of holes can be made at high efficiency (Figure 1).

Figure 1

Main wing panel perforating machineMitsubishi Heavy Industries Technical Review 52 No. 3 (September 2015)
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The features of a main wing panel perforating machine are as follows.
Combined head
Each of the six combined heads has a spindle for perforating and countersinking, apressure foot axis for improving the countersinking accuracy, and a spindle for automatic
measurement of the machined part. These spindles can be positioned to an arbitrary point
quickly by the NC five-axis function.
(2) Inline automatic measurement function
The measurement spindle mounted on the combined head measures the dimensions of themachined part automatically after machining by the machining spindle and can also
automatically report and make determinations on the acceptance of measurement results.
(3) Various compensation functions
Because the workpiece is long with a complicated shape, a large dimensional deviation
caused by a workpiece positional error, deformation by its own weight or thermal deformation
due to changes in the peripheral temperature may occur when the machining is performed withan NC program created based on drawing data.
For this reason, this machine was designed to automatically sense a reference part set on
the jig using a laser in order to compensate for the machining position through automatic
calculation. In addition, the above problem was resolved by combining advanced correction
functions including a surface orthogonal correction function that performs machining
perpendicularly to the curved surface of a workpiece and a function that compensates forthermal displacement errors by reading the spindle front end position based on the reference
position just before machining.
(4) Machining schedule management function
The machining area is shared by six heads and there are overlapping sections between thesix head machining areas. This machine has a machining schedule management function that
automatically assigns the overlapping machining section to heads with lower operational loadin order to level the operating time of the heads.
This function also determines the possibility of machining and automatically adjusts themachining order in order to avoid interference between heads on overlapping machining
sections. This results in a significant contribution to the improvement of the facility operating
rate and the enhancement of the cycle time.
(1)|2. Fuselage stringer processing machine
A fuselage stringer is a reinforcing member that is a component of the fuselage. This is aworkpiece characterized by its long size, various shapes, and thin wall. A fuselage stringer
processing machine is a dedicated machine tool that realizes space-saving and high-efficiency
operation even when processing a long workpiece due to the adoption of a gantry equipped with
two spindles (Figure 2). This machine has attained a fivefold increase in production capacity incomparison to existing equipment through the development of an automatic clamping jig, anautomatic workpiece conveying device, etc., that can handle various types of workpieces in
addition to the machine tool itself.

Figure 2 Fuselage stringer processing machine(1)

The features of a fuselage stringer processing machine are as follows.
High-speed, high-accuracy spindle
The spindle has an output of 22/18.5 kW and its maximum spindle speed is 20,000 min-1

Mitsubishi Heavy Industries Technical Review 52 No. 3 (September 2015)
55-1(or, as option, 79/95 kW, 17,000 min ). This enables cutting and reducing the wall thickness ofa workpiece (high-speed heavy cutting). This machine has two spindles and therefore cansimultaneously machine two workpieces. As a result, the production capability is twice as highas that of a general-purpose machine tool with only one spindle.
(2) Workpiece vacuum clamp
Conventionally, the clamping part needs to be changed according to the shape of theworkpiece because the clamping mechanism uses mechanical components. This machine
features a newly developed highly reliable vacuum clamping device to eliminate themechanical clamping components. This results in a significant reduction of tool changing time
during a change of workpiece type.
(3) Improvement in handling capacity of chip and coolant
In the past, a large number of chips were generated during machining and accumulatedon the workpiece and the fixing jig, and therefore lengthy cleaning work after machining wasnecessary. This machine reduces cleaning time to one-sixth of the norm by utilizing expertise
gained from automotive parts processing lines to optimize the cover shape and add a chip
washing function using a coolant shower.

|3. Fuselage skin processing machine
The fuselage skin is an aircraft fuselage outer panel component. This is a workpiececharacterized by its long size, large warpage, and complicated curved surface along the fuselage
shape. Conventionally, chemical milling that utilized chemical erosion to process the workpiece
was used, but environmental considerations have required the replacement of chemical milling withmachining.
Just like a fuselage stringer processing machine, a fuselage skin processing machine adopts agantry equipped with two spindles. In addition to the features of a fuselage stringer processingmachine, this machine combines a pallet changer that automatically exchanges the workpiece and aworkpiece positional error compensation function. As a result, it attains lengthy unattended
operation (Figure 3).

Figure 3

Fuselage skin processing machine

The features of a fuselage skin processing machine are as follows.
(1) NC two-axis head
The spindle has an output of 20 kW and its maximum rotating speed is 20,000 min-1, andis additionally equipped with an NC controlled two-axis indexing function on the head side.
This enables high-speed, complicated curved surface machining with NC five-axis control
including the two gantry moving axes.
(2) Workpiece positional error compensation function
On this machine, workpiece positional deviation and workpiece thermal deformation in
response to peripheral temperature changes can be automatically compensated for by automatic
measurement of the workpiece reference dimensions through the use of touch probe-type
measuring equipment mounted on the spindle. As a result, manual measurement andcompensation value calculation by the operator become unnecessary, and high-accuracy
processing can be carried out automatically.
We will continue to share client problems and offer dedicated machine tools as solutions, andthus contribute to the aircraft industry.