Mitsubishi Heavy Industries Technical Review Vol. 52 No. 3 (September 2015)
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Large-sized Special-purpose Machines
for Turbine 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

Large special-purpose machines are tools optimized in terms of their processing functions incompliance with the material, shape and machining details of large workpieces. Mitsubishi Heavy
Industries, Ltd. (MHI) is one of the world’s few machine tool manufacturers handling large
special-purpose machines, and its Machine Tool Division provides products to those industrial
sectors manufacturing large-sized parts such as for power system equipment (power plants), aircraft
and construction machinery, thereby gaining a high reputation. In addition, MHI is well-known as aleading global manufacturer of power system equipment and aircraft, and this division has
supported its in-house manufacturing sectors for more than 20 years, thereby accumulating
abundant experience, technologies and expertise concerning machining of large workpieces.
This paper introduces a large special-purpose machine to process turbine rotors and gas
turbine rotor disks as key components of power system equipment, i.e., side-entry processingmachine, chain broaching machine and disk coupling grinder.

|1. Side-entry processing machine
The side-entry processing machine cuts grooves on the vane of an integrated turbine rotor by
milling (Figure 1). The lower right of Figure 1 is the shape of the milling tool that is manufactured
and sold by this division. The workpiece placed in the center is supported by a hydrostatic journal
support and indexed in the rotational direction by a face plate chuck on one side to cut grooves one
by one. We have so far manufactured a variety of side-entry processing machines, and the largest
corresponds to a workpiece of 3 600 mm in diameter, 13600 mm in length and 300 tons in weight.

Figure 1(1)Side-entry processing machine and shape of milling tool (lower right)

The following are the advantages of our side-entry processing machine.
High-efficiency machining
Simultaneous machining with opposite four spindles promises high-efficiency tasks.
Nevertheless, 2- or 1-head machines are also delivered to users with many workpiece models
unsuitable for simultaneous machining with multiple heads.

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Stable cuttingThis machine has high damping properties owing to its casting structure and thus permits
stable cutting.
(3) Design concept of ‘protecting expensive workpieces!’
The price of large workpiece material is extremely high. A number of highly reliable
monitoring/detecting devices are therefore equipped to minimize the damage incurred by aworkpiece due to unexpected abnormalities.
- A tool locus monitoring device- A scale-duplicated face plate index monitoring device- A chuck slip detecting device- An AE sensor-system tool breakage detecting device(4) User friendliness measures
Specifications were added for the analysis of customer work procedures to alleviate theburden on workers. This has realized easier preparatory and centering operations for a 300-tonworkpiece.

|2. Chain broaching machine
The chain broaching machine cuts grooves by broaching the vane of a gas turbine rotor disk
(Figure 2). The workpiece is mounted on a tilting table – known as a cradle – that is equipped witha horizontal slide table and index table. A broaching tool attached to each of the pallets connected
together by a chain is precisely guided to the cutting position for broaching, and then returns to theoriginal position after making a circuit. The largest machine we have ever manufactured
corresponds to a workpiece of Φ2500 mm in diameter and 12 tons in weight, and a final-stage
workpiece with a shaft can also be machined. The broach’s maximum pull-out force is 35 tons andthe maximum broach edge length is 15.47 m with 17 pallets (0.91 m per pallet).

Figure 2 Chain broaching machine for gas turbine rotor disk processing,and state of broaching (lower right)

The following are the advantages of our chain broaching machine.
(1) High-efficiency machining
The machining efficiency is higher than that of a normal ram-sliding broaching machine
due to the fact that return motion of the broach is unnecessary.
(2) Space saving
As the machine only requires half or less the typical longitudinal floor space, a great dealof space can be saved.
(3) Multi-model compatibility
The machine was structured so that the index table for three different diameters (Φ380,Φ744, and Φ1180) is interchangeable, making it compatible with multiple workpiece models
with diameters ranging from Φ400 to Φ2500.

|3. Disk coupling grinder
The disk coupling grinder shapes by grinding curvic couplings to connect one gas turbine
rotor disk to another (Figure 3). The cup-type grindstone is trued by the NC dressers installed onboth sides, and grooves are plunge-ground two at a time in parallel with the indexing of theMitsubishi Heavy Industries Technical Review Vol. 52 No. 3 (September 2015)
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workpiece on the index table. The lower right of Figure 3 shows how an actual workpiece isground. The maximum diameter of the workpiece is 2500 mm and the maximum weight is 18 tons.
The following are the advantages of our disk coupling grinder.
(1) Compatibility with a workpiece with a shaft
A 1000 mm-diameter through-hole is bored on the index table so even the turbine’sfinal-stage workpiece with a shaft can be machined. The indexing accuracy of this index table
is as high as ±2 seconds.
(2) Interactive automatic programming system
NC programs that include truing can be automatically developed from nothing more thansimple entries such as grindstone and coupling specifications, and compensation entries are alsoeasy for the detection of contact with the master coupling.

Figure 3

Disk coupling grinder and state of grinding (lower right)|4. Future development
In the future, MHI will continue to share the issues and efforts to consider solutions withcustomers toward the realization of machining accuracy and efficiency exceeding what is possible
with general-purpose equipment. In addition, we will propose and provide completely new-concept
machine tools that have never existed, meeting market needs as they arise.