Mitsubishi Heavy Industries Technical Review Vol. 53 No. 4 (December 2016)
10High-Precision Double-Column Machining Center“MVR-Fx” for Die Molds-Achieves High-Definition, High-Precision Surface Machining-

M i ts u b i s h i H e a v y I n d u s t r i e s
M a c h i n e To o l C o . , L td .

The tendency to accumulate machining data as expertise has been increasing in the field oflarge die molds used for the pressing and injection molding of automotive parts. With such abackground and in conjunction with the improvement of three-dimensional high-precision
measurement technologies, the realization of even higher-quality and higher-precision cutting
surfaces is in demand. However, large die mold processing takes a long time and has the issue ofthe deterioration of machining accuracy caused by thermal displacement during processing, toolwear, the deviation of the blade tip position after tool changes, etc. Therefore, it is difficult to attainhigh-precision cutting surfaces. We have developed a large, high-precision machine tool thatincorporates the precision improvement technologies and high-precision measurement technologies
of our micro milling machine, and realized high-quality and high-precision cutting surfaces tocontribute to the reduction of lead time through the elimination of the need for polishing.

|1. Advantages and technologies(1)

Precision improvement technologies
For the prevention of accuracy deterioration in die mold machining caused by the thermal
deformation of the machine body, a high-rigidity symmetrical machine body structure and athermally stabilized column (Figure 1) that are less subject to changes in temperature wereadopted. For the prevention of thermal displacement and the deterioration of the rotational
accuracy of the spindle caused by heat generated from the high-speed rotation of the spindle,
internal spindle cooling (Figure 2) that uses temperature-controlled oil to directly cool thespindle was adopted to eliminate the need for the correction of thermal displacement. A
high-rigidity spindle with no rotational deflection was attained by reducing the temperature
difference between the inner ring and the outer ring of the spindle bearing. In addition, for theprevention of the deterioration of motion accuracy due to the backlash of the feed drive system,
each ball screw of the X, Y, and Z axes was connected directly to the motor, and the X and Y
axes, which have a larger range of travel and a long ball screw, had motors on both edges of theball screw in order to suppress lost motion and enhance high-speed performance.
(2) High-precision measurement technologies
For the prevention of effects of changes in tool length caused by the high-speed rotationof the spindle, an imaging-type tool measurement system (Figure 3) was adopted tocontinuously measure the tool blade tip and automatically determine the stabilization of thethermal displacement of the machine, holder and tool. In addition, the use of a noncontact,
three-dimensional workpiece measurement device to check machining accuracy of athree-dimensional shape was made possible. Furthermore, a machine condition measurement
and sign diagnostic system utilizing IoT was mounted for the early detection of machineabnormalities.

Mitsubishi Heavy Industries Technical Review Vol. 53 No. 4 (December 2016)
11

Figure 1 Thermally stabilized column

Figure 2 Internal spindle cooling

Figure 3 Imaging-type tool measurement system|2. Specifications
Table 1 shows the main specifications. The machine sizes that can handle the machining ofvarious large die mold used for the pressing and injection molding of automotive parts areavailable. These machines have a full enclosure as standard equipment in consideration ofenvironmental improvement and the safety of the factory, while taking energy saving such as thereduction of air consumption and the adoption of LED lighting into consideration.
Table 1 MVR-Fx main specifications

Table work area

Widthmm

Lengthmm

Load weight (table)
Distance between columns
Distance between spindle end andworkpiece mounting surface(EXT spindle end to table surface)
Axis travel

Rapid traverse

tons
mmXYZWX，YZ
W

Cutting feed
Spindle head

Ram size
Rotation speed
Output(30 min / continuous)

MVR30Fx
2000
3000(OP 4000, 5000)
20
2550

MVR35Fx
2500
4000(OP 5000)25 (30)
3050

mm

1650
(OP 2000)

mmmm
mm
mm
m/min
m/min
m/minm/minmm
mm-1

Table length + 200
3000
3500
800
1100 (OP1300)
2015515 (OP 20)
□420
20000

kW

22/18.5

Mitsubishi Heavy Industries Technical Review Vol. 53 No. 4 (December 2016)12|3. Benefit of introduction(1)

Improvement of die mold machining surface quality
The enhancement of productivity due to the elimination of the need for polishing isenabled by the realization of high-quality cutting surfaces without a difference in surface step.
(2) Shortening of die mold manufacturing time
A product that accurately reflects the designer's intention can be produced by the accurate
reproduction of the machining data onto the die mold. In addition, the creation of a database ofexpertise and the accumulation of technologies (advanced reverse engineering) in conjunction
with three-dimensional workpiece measurement contribute to a reduction in the number ofprototypes, resulting in shortened delivery times and fewer man-hours.
(3) Automation and manpower saving at manufacturing site
The biggest obstacles for the automation of processing facilities, the deterioration of theaccuracy caused by changes in the outdoor air temperature and the heat generated from theinside of the machine are suppressed to the utmost, and therefore next-generation automationand manpower saving, which were impossible in the past, can be realized.