"Social Device" Special Interview

The contents were published from July 2015 to February 2016 on"Nikkei Technology Online", the engineering information website run by Nikkei Business Publications, Inc., and reprinted with the author's permission.

Industrial Machinery Evolving Apace with Society:Electronic Devices Offer Significant Savings in Energy Us

Energy-saving technology includes utilizing energy efficiently and eliminating wasteful energy consumption. Today, the need to conserve energy is recognized as one of the most pressing issues facing humanity. What initiatives are under way in industrial machinery, which accounts for a major part of energy consumption? And what technologies are needed? Tetsuya Miyake, Director of the Mitsubishi Heavy Industries Machine Tool Co., Ltd., involved in large-scale construction equipment such as double-column, 5-face milling machine, discussed the issues with General Manager Takashi Nakamura, involved in high-efficiency semiconductor devices as the head of the ROHM Research & Development Division.


 We face a variety of problems today, including global warming and natural resource depletion. Resolving the energy problem on the global scale is an especially pressing issue. Rohm has been supplying customers with a wide range of products, from consumer electronics to the automotive and industrial machinery fields, and accumulated considerable expertise in making products smaller and more energy efficient. Our work in the field has made us very aware of the rising urgency of the energy problem.

Tetsuya Miyake
Mitsubishi Heavy Industries Machine Tool Co., Ltd.

 I think most manufacturers recognize that saving energy is a key point in developing products in the machine tool field. It's not a new idea, though: I think reducing energy consumption has been a priority for at least a decade. A comparison of modern designs with similar machines from a decade ago will show how much lower energy consumption has become.

 Machine tool manufacturers were among the first to recognize the need to slash energy consumption because they wanted to provide their customers with lower running cost. In other words, building in energy-saving technology increased product value. By selecting a machine tool that uses less energy, the customer can use a lower-power electricity supply contract, which reduces the utility bill. I think this cost savings would be especially important for small-scale companies.


 In consumer electronics, too, energy efficiency has been an important issue for quite some time. The original reasons were primarily the need to make equipment smaller, prolong battery-drive life, and enhance product function and performance.

 As a semiconductor manufacturer, Rohm is expanding its efforts to find new solutions to the energy problem, such as innovating low-power large-scale integrated (LSI) chips and high-performance discretes, and developing highly efficient power semiconductors made with silicon carbide (SiC), a next-gen material that promises dramatic reductions in energy usage (Fig. 1). Recognizing the impact of energy use on society, we propose total solutions that slash cumulative energy consumption in the automotive and industrial machinery fields including sensors, devices, and control systems.

Fig. 1 SiC power semiconductors

Slashing power consumption through adaptive control


 What sort of measures are you implementing to reduce energy consumption in your machine tools?


 Well, let me introduce one of our most important products, the double-column, 5-face milling machine. It is a machine to cut square & large metal components by various cutting tools.The MVR-Ex Series, announced in 2014 and our newest product, has a large number of energy-saving measures built into it (Fig. 2). We were able to significantly reduce energy consumption, and our estimates using in-house data indicate that equivalent CO2 emissions are reduced by about five tons/year as a result.

Fig. 2 MVR-Ex Series of double-column, 5-face milling machine, from Mitsubishi Heavy Industries Machine Tool

 The power-hungry parts of this machining center are the hydraulic unit and the mechanism that rotates the tools, consisting of the spindle motor and 3-phase motor. Energy saving measures were concentrated there. One important technique was to turn the hydraulic unit off instead of letting it idle when not in use. In prior designs the hydraulic unit was always running, whether the machine was in use or not, but in the MVR-Ex series it is activated only when needed. That alone provides about one ton/year of CO2 emission reductions.

 A cooling system is provided to prevent main spindle overheating when machining, and we turn off the oil cooler drive when it's not in use, too. It was constantly on whenever the main spindle was in operation on previous models, but it's more efficient to monitor main spindle temperature and turn on the oil cooler as needed. We calculate the CO2 emissions saved by that change at about 2.4 tons/year.

Power semiconductors: fundamental improvements in social issues

Takashi Nakamura
ROHM Co., Ltd.
General Manager Research & Development Division

 We provide a range of devices to help people use electricity efficiently, to reduce energy waste. One product line is power semiconductors, which make an enormous contribution to cutting energy use. By improving energy utilization efficiency, we believe they can make a big difference in cutting power use throughout society.

 When electricity is used, it must be converted to match the specific equipment or system it is used with. That can mean converting between AC and DC, or changing the voltage or frequency, for example. Conversion technology today has reached an efficiency of about 90%, which makes it look as if there isn't much energy loss in a conversion. The electricity generated at the power plant, however, is converted many times before it reaches the consumer, and there is a loss every time. In fact, only about half of the generated power actually reaches the destination.

 Power semiconductors are extremely effective in reducing the losses accompanying power conversion. Rohm was the first in the world to launch volume production of next-generation SiC-MOSFET power semiconductors. Efficiency is significantly higher than conventional Si power semiconductors, and the energy saving effects of replacing, for example, all of the Si power semiconductors in Japan with SiC chips would represent the output of several nuclear reactors. Rohm was also the first in the world to adopt a trench architecture in SiC-MOSFET chips, which further boosts performance. We have recently switched to 6-inch wafers, and ramped up our system to provide quality chips in quantity.

 We believe that in the future, power semiconductors will find increased use in the machine tools Mitsubishi manufactures.

Proposals must cover design considerations, too


 I agree; the role of electronics in machine tools will continue to grow in the future. I used to be in electronics engineering, developing control circuits and other electronics for machine tools. When I entered Mitsubishi Heavy Industries most of the machine tool was mechanical systems, with just a little electronics, but these days they are packed with electronics technology. There's a much higher ratio of electronics in modern machine tools, and the role of software has grown apace.

 I think this trend will continue. Machine tools use hydraulic mechanisms throughout, and already inverters are being used on the drive circuit for the motor running the hydraulic unit. The goal is to improve efficiency, and I think eventually the hydraulic mechanism itself will be replaced by motor drives. When that happens there will be a big surge in the number of power semiconductors in every machine tool.


 As power semiconductors are used in a growing variety of applications, it is more important than ever to accurately grasp customer requirements. In the past device manufacturers have tended to pursue specific specifications for individual devices. It is certainly important to offer superior functionality and performance, but that isn't always what the customer wants. Rohm prioritizes joint development with customers, so that they can get the products they want, with the specific functions and performance they need for their application, promptly. In SiC power devices we have begun to propose entirely new applications that Si power semiconductors simply cannot handle, instead of targeting replacement demand.

 One example is pulse generators, which demand the high voltage used in accelerators, plasma generations, and laser machining systems. These applications have traditionally replied on vacuum tubes and Si power semiconductors as switching devices, but Rohm SiC power semiconductors have made it possible to create very small pulse generators with performance that conventional designs cannot match.

 I think it is vital for device manufacturers to study up on user applications and to make proposals that address their real requirements. We have to work on resolving issues that affect all of society, like saving energy.


 It is very difficult for machine tool designers to collect all the latest information on devices, and very common for them to keep on using existing devices and technologies unless there is some compelling reason to adopt a new technology. I think it is an excellent idea for device manufacturers to get involved in applications, and help innovate technology through new proposals.

Suppliers, manufacturers, and users working together


 Industrial machinery, including machine tools, plays a critical role in supporting the manufacturing industry. I think you must encounter a variety of social problems in your work, not just energy consumption.


 Yes, we do. We're quite aware of the "ageing population" problem developing in primarily industrialized nations, for example. The Japanese manufacturing industry is experiencing a labor shortage, while the number of elderly citizens is rising. There are many companies now where shop floors are supported by older, veteran engineers partnered with young, inexperienced ones. We strive to make products that are easy to use, but when you have experienced and inexperienced operators working together, things get more difficult. They have different definitions of what "easy to use" means, and the basic conceptual approach is different. It is not easy to find the perfect balance.

 Another point is the change in the perception of safety in the manufacturing workplace, and we feel the need for a new approach to equipment safety measures. The most common approach in the past was to just surround dangerous machines with barriers to prevent people from approaching, but these days there is increased need for people and machinery to share space. And that might mean a dramatic change in the way that machine tools and other manufacturing systems are designed.


 The barriers to finding the perfect solution seem to grow taller as the problems become more sophisticated. Finding the solution will demand an even closer, more cooperative relationship between parts and material suppliers, machine manufacturers, and users.

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