Flexible Manufacturing System
for Agile Production

MITSUYUKI KONISHI*1
TAMAYA SUGANO*1

The diversification of customer needs in recent years has brought about a shift in manufacturing systems in theautomotive industry from "mass production" based systems to "Various kinds and medium volume production" andstill further to "agile production (flexible kinds & volume)". Accordingly, there is a growing need in the industry for
flexible production lines that are capable of easily coping with design changes and equipment conversions. Further,
there is also increasing demand for the placement of high speed, highly reliable, and low cost metal cutting machineson production lines. To meet these needs, Mitsubishi Heavy Industries, Ltd. (MHI) has developed a commercializedmachining center for mass production. An overview of this system and its recent application in a flexible manufacturing system are introduced here.

After it was first released at JIMTOF2002 (the 21st
Japan International Machine Tool Fair), the machining
center has since earned a good reputation from automobile manufacturers and related manufacturers. In thelast two years, a cumulative total of 250 units of the system have been adopted in more than 10 projects (basedon orders received as of 31 May 2005).
The main specifications of the M-CM4A are shown in
Table 1
1.
The major features of the system are outlined below.
(1) High productivity due to a reduction in production
time
The feed speed for all travel axes X, Y, and Z
has been set to a rapid rate of 50 m/min with arapid feed acceleration of 1 G in order to shorten
non-machining time. A rapid feed speed of 60 m/
min with a rapid feed acceleration of 1 G can also
be selected optionally.

1. Introduction
Since the adoption of the "mass production of limited
goods" approach in the field of mass production as represented by the production of automobile parts,
production has mainly consisted of using manufacturing systems with an emphasis on productivity based ontransfer machines in which multi-spindle type specialpurpose machine are arranged in series to produce thedesired item.
The diversification of customer needs these days has
resulted in a successive shift from mass production and"Various kinds and medium volume production" of approaches to what is known as agile production.
Accordingly, there is an ever greater need for flexible
production lines equipped with high-speed, compact
machining centers capable of easily dealing with designchanges and equipment diversions.
This report first introduces the M-CM4A machining
center for mass production, which has been commercialized by MHI as a metal cutting machine that can bereadily installed on a flexible production line. Recent
examples are then presented of flexible manufacturingsystems that utilize the machining center.

2. M-CM4A machining center for mass production
A view of the external appearance of the standard MCM4A machining center for mass production is shownin Fig. 1
1. Machining processes in this machine tool are
limited to the machining of aluminum or cast steel parts
such as engines, transmission cases, suspensions, andother automotive parts to increase productivity, flexibility, and maintainability, particularly in rough finishingand semi-finishing.

Fig. 1 View of M-CM4A machining center formass production.

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 42 No. 2 (Apr. 2005)*1 Machine Tool DIvision1

Table 1 Specifications of M-CM4A Machine Body
Specifications of Machine Body
M-CA4 A

Item

Travel strokeof axisRapid feed rate
(acceleration)

X-axis(mm)

700 (standard) /600 (op.)

Y-axis(mm)

610 (standard) /600 (op.)

Z-axis(mm)

650 (standard) /600 (op.)

B-axis(deg)

360

Rapid feed rate (X,Y,Z)(m/min)50(1.0 G) (Standard)60(1.0 G) (op.)

Rapid feed rate (B)(min-1)Taper of spindle
Spindle(min-1)

12 000

Output power of motor(kW)

15/11/7.5(10 min/30 min/ continuous)

Stored capacity of tools(piece)24 (standard) /32 (op.)

Maximum speed

Automatic toolchanger (ATC)discharging capability of the system. This also helps
to suppress any machine problems that could occur
due to the accumulation of chips during mass production operations.
Increased reliability of major devices
The reliability of the major components of the
manufacturing system (machining center) such as thespindle, turn table (B-axis), ATC (Automatic Tool
Changer), and other devices has been further enhanced to increase the time period during which thesystem can operate without any trouble (Target MTBF
[Mean Time Between Failures]: 5000 hours).
Fig. 3
Improved maintainability (Fig.
3)
The following measures have been taken to improvethe maintainability of the system in order to reduce
the time required for maintenance (Target MTTR
[Mean Time To Repair]: 0.5 hours].

(2) Construction of manufacturing system in a small
space
In the standard system model, the strokes of thefeed axes are set to 700 mm for the X-axis, 610 mm
for the Y-axis, and 650 mm for the Z-axis. This rangeof strokes thus makes it possible to accommodate themachining of most major automotive parts. On theother hand, a compact model with strokes of 600 mm
for all axes can be optionally prepared for those users
who place importance on the need to save space.
(3) Stable sustainment of high productivity based on highreliability and maintainability
Center trough structure
A central trough structure has been adopted forFig. 2the bed of the machine (Fig.
2) in which an opening
for recovering chips is formed at the center of the bed
just below the spindle in order to increase the chip.
.

.

Sure and careful treatmentof cutting chips. Center trough + Stainless steel chute. Direct transfer of cutting chips tothe rear section of the machine

Center trough water-jet conveyor
enabling the sure and proper
discharge of cutting chips

33.3
BBT 40 (Standard)
HSK-A 63/KM 6350
(op.)

500

TPM (Total Productive Maintenance)
Cartridge type spindle

Large capacity
center troughand stainlesssteel chuteOIL
AIR
SPINDLE
THROUGH
COOLANT
Cartridge type
spindle600

Machining chamber
without flat section
where cutting chips
accumulate lessCoupling

DRAIN

Accessible B-axis table motor
Top view ofmachineAC SPINDLE MOTOR
Spindle motor
Concentrated arrangementof auxiliary equipment

Direct transferof cutting chips

Side view of machine
Fig. 3 Stable sustainment of high productivity through highmaintainability and high reliability

Fig. 2 Bed of center trough structure

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 42 No. 2 (Apr. 2005)2.

(a) Cartridge type spindle
A cartridge type spindle structure has been
adopted to facilitate the replacement of the spindle
in the event of failure.
(b) Accessible B-axis table motor
The B-axis drive motor has been arranged on
the outer circumference of the machine to improveaccessibility and maintainability. This has also
been done with the X-axis motor and Z-axis motor.
(c) Collective arrangement of auxiliary equipment
Equipment for controlling hydraulic pressure,pneumatic pressure, lubrication, and coolant has
been collectively arranged in the maintenance zone
at the rear of the machine center to improve maintainability, such as routine inspections and ease ofservicing and repairs.
Fig. 4(d) Spare tool change device (optional) (Fig.
4)
A spare tool change device has also been prepared as an option. It can be used to replace a wornout tool in the tool magazine with a spare tool or
new tool on the outside of the machine during machining.

(4) Convert ability and flexibility for agile production
Accommodation of various part transfer systems
Part transfer systems that match all types of specifications and line configurations such as (a) manual
loading, (b) manual loading + APC, (c) gantry loader,Fig. 5and (d) gantry loader + APC can be selected (Fig.
5).
Matching of table type with various part fixture jig
patterns
Although the turn table (B-axis) is generally
adopted as the standard table, other types of tables
such as the tilt table (A-axis), turn table (B-axis) +tilt table (A-axis), tilt table (A-axis) + turn table (Baxis), and other arrangements can also be optionallyFig. 6).
6 These tables can be selected arbiadopted (Fig.
trarily according to the type of work process being
done and type of part fixture jigs being used.

.

Accommodation of various typesof part transfer systems
Selection of part transfer systems matching
all specifications and line arrangements

APC

Manual loading

Spare toolchange device

Toolmagazine

Manual loading+APC

Gantry loader

Gantry loader

APC
Gantry loader

APC+Gantry loader

Fig. 5 The system can accommodate various types ofpart transfer systems

Fig. 4 Spare tool change device

Standard table

Tilt table

Easy change of table type
Accommodation of various
types of part fixture jig patterns
by setting optional table

Turn table (B-axis)

Tilt table

Turn table (B-axis)+Tilt table (A-axis)

Turn table

Fixed saddle
Tilt table (A-axis)

Tilt table (A-axis)+Turn table (B-axis)

Fig. 6 A diverse range of table types allows ready accommodation of various types of part fixture jig patterns

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 42 No. 2 (Apr. 2005)

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1st operation
Fig. 7 Layout of machining line forleading U.S. automobile manufacturer(Rough machining line using
several machining centers).

4th operation(a) Upper surface, cylinder bore, rough boring,rough milling of front and rear surfaces(b) Boring of front and rear surfaces,rough milling of lower surface

Fig. 8 Vertical type part fixture jig for rough machining line for leading U.S.
automobile manufacturer
Installed on the B-axis turn table; Part to be machined: engine cylinder block

3. Example applications of flexible manufacturing systems

parallel process type arrangement using the sametypes of machining centers in series on each respective operation row.
Fig. 8Since the jigs (Fig.
8), tooling, and a portion of theoptional devices must be changed for each operation,
five types of machine variations are used in the overall rough machining line.
In the sequential process line (process distributed
type line) which has been the mainstream approach
used for conventional mass-production lines, all machining processes are completed after a part has
passed through all of the machine tools. However,there is a risk that the entire line could be stopped if
any of the machine tools fail.
Adoption of a parallel process type approach in thisproduction line can eliminate the risk of stoppage ofthe entire line, even if a machine tool fails, since production can be continued by the same type of machine
in a parallel operation row, though the volume of overall production will be reduced. Another advantage ofthis type of line is that machine tools can be suitably
adjusted, added or converted to accommodate increases or decreases in the volume of production
required.
Parts are conveyed on the line by high-speed gantry loaders that are installed for each conveyor
operation, in which the high-speed gantry loader feeds
Fig. 9the part to each machine tool (Fig.
9).

This section introduces two example applications inwhich the M-CM4A machining center for mass production described above has been adopted in recent flexible
manufacturing systems.
(1) Parallel process type serially arranged production line
A brief overview is presented here of the cylinder
block machining line for automotive engine that wasdelivered to a leading U.S. automobile manufacturer
last year (August 2004).
This machining line consists of two parts: a roughmachining line in which several of the machining centers for mass production described above are arranged
Fig. 7in series (Fig.
7, photo showing the line under construction), and a finishing line in which special
purpose machines (transfer machines) are arranged
in series. The rough machining line is mainly formedof the machining centers so as to cope flexibly withchanges in machining patterns. The finishing line consists of special purpose machines, since emphasis isplaced on accurate machining and production efficiency in critical processes (finishing of crank bores,
cylinder bores, front and rear faces, as well as finishing of top faces).
Both the rough machining line and finishing line
are comprised of two rows of lines with similar capacities. The main types of parts machined on thisline consist of aluminum cylinder blocks, with athroughput (production time for each part) in the tworows of lines of the manufacturing system of approximately 35 seconds.
The rough machining line consists of thirty-eight
M-CM4A machining centers. The rough machining
line is divided into five serially arranged operations(five operations for each row x 2 rows). The same part
fixture jigs and tooling arrangements are mounted on
the corresponding centers of the same type on each
operation row. Thus, this machining line adopts a

Fig. 9 Gantry loader

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 42 No. 2 (Apr. 2005)

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Machining line based on tandem arrangement ofmachining centers (dotted line section is to beconstructed in the future)

HSK-100A holder typerotary tool (drill)

Machining center forfinishing crank bores

Long tool (crank bore boring tool)

Broaching toolFig. 11 Spindle head (with broaching tool)

Machining line consisted of
special purpose machines
for finishing process

SpindleFig. 10 Layout of machining line for leading
automobile manufacturer in Malaysia

Fig. 12 Line bar for crank bore finish
boring being inserted into part

Further, the critical process of crank bore finishing can be accomplished using a special tool magazine(known as a blade hooking device) which is capable ofautomatically replacing a long tool (app. 1000 mm inlength) such as a boring bar that is added to the machining center in addition to the conventional
Fig. 12
magazine (Fig.
12). Since the machining center canbe partially modified with additional functions, bothaccurate machining and flexibility can be achievedthat are compatible with each other, while also facilitating ready servicing and maintenance.

(2) Parallel process type tandem-arranged production line
Figure 10 shows the engine cylinder block machining line for automobiles delivered to a leading
automobile manufacturer in Malaysia at the end of
2004.
This production line consists of a rough machining
line, in which twenty-one machining centers for mass
production are arranged in tandem, and a finishing
line, in which two special machining centers and a special purpose machine are arranged in series. Parts
machined on this line are cast iron cylinder blocks withthroughput of approximately 100 seconds per block.
Since the tandem arrangement has been adopted
in the rough machining line, additional machines canbe easily added or removed according to variations in
the volume of production desired.
By partially modifying mainly the machining centers on the line, machining operations that normally
could only be performed using special purpose machines can be accomplished with the machining
centers.
In finishing the sides of the seat face of a bearing
cap, for example, broaching can be done using a machining center by adding a broaching tool holder tothe spindle head of the machining center, even though
this operation can usually only be performed with a
Fig. 1
1 ).
specialized broaching machine (Fig.
11

Mitsuyuki Konishi

4. Conclusion
Some typical examples of application of the M-CM4A
machining center for mass production and the flexible
manufacturing systems using it were introduced above.
There are moves afoot among the world's leading automobile manufacturers having tie-ups with each otherto integrate production models as a part of efforts to globalize their operations. At the same time, however,
manufacturers are also accelerating the conversion to
production lines capable of accommodating agile production. Accordingly, it is thought that there will be anever-increasing need for production systems that makeit possible for often conflicting requirements such as highproductivity and flexibility to be compatible with eachother.
Based on its long and extensive experience in the production of both special purpose machines and universal
type machining centers, the Machine Tool Division of
Mitsubishi Heavy Industries, Ltd., firmly believes that
it is well placed to take on the mission of positively proposing and realizing optimal manufacturing systems thatbest meet the unique and specialized needs of each individual customer.

Tamaya Sugano

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 42 No. 2 (Apr. 2005)

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