Provost, Director of the Institute of Science and Technology Research, University Professor, Chubu University, Kasugai City, Japan, Honorary Professor at Keio University, Tokyo
Breaking the Wall of Manufacturing. How Symbiotic Technologies Can Reduce Environmental Impact
The title of my talk is “Breaking the wall of manufacturing”. I will talk about some challenges to attain sustainable manufacturing with less energy consumption, wastes, and emission.
Manufacturing is a lifeline for those countries, such as Germany and Japan, who do not have adequate amounts of natural resources.
In order to survive, we have achieved significant development in manufacturing in terms of the quality of products as well as the productivity. Let us quickly look back over the past progress off manufacturing.To start with, it is the progress of automation in the factory. As a result, human intervention has been considerably reduced.
If we look back over the past progress of manufacturing accuracy, it started from the order of mms and we are now going on to the order of nms through μms. The minimum thickness of material removal is on the order of angstroms, which means the handling of molecules. That is to say, we are approaching the limit of the material removal process in terms of the chip thickness.
Productivity can be quantitatively evaluated by the cutting speed. As we can see in this figure, the maximum cutting speed of steel exceeds 1000 m/min. Of course, these advances are continuing today and will continue in the future as well.
From the beginning of 1990, the environmental impact of manufacturing has become a big issue. The environmental impact of products is mostly assessed in their on-duty phase in terms of, for example, energy consumption and emission. However, energy is consumed in the production phase as well. Manufacturing engineers are now concerned with the environmental impact in the production phase and are making efforts to reduce energy consumption, waste, and emission.
There is, however, a difficult conflict to be solved between the productivity and the environmental protection. Increase of the productivity results in the increase of the load on the environment. Any environmental friendly technology which reduces the productivity cannot be accepted in the industry. Breaking the wall technology is needed. My talk today is the introduction of such technologies.
Such a paradigm shift in manufacturing started first in the automobile industry in Germany. In fact, I was appointed as one of the auditors with some German professors to assess the R and D activity of a German automobile company in 1994 and I knew that the company was making many efforts to reduce the environmental impact in manufacturing.
Manufacturing includes a broad range of activity in car production. As we can see in this figure, the machining process represented by cutting and grinding consumes a large amount of energy. My talk today will be focused on the breakthrough of this particular process.
The machining process is conducted in the factory and environmental issues exist on different scales.
Let us start from the factory. In order to attain high machining accuracy and precision, what is most important is to control the temperature in the factory and keep it constant., which consumes a large amount of energy. This is due to the fact that thermal deformation of the machine tool is the main reason for the machining error. The main part of the machine tool is made of cast iron or steel and its thermal expansion coefficient is 10-5. Therefore, a component 1 m in length expands by 10 μm due to a temperature rise of 1ºC, which is not acceptable for high-accuracy machining. This figure shows an underground factory developed for reducing the energy consumption for temperature control. The factory is built 17 m underground.
The effect of the underground factory is significant, as shown in this figure. The inside temperature is kept at 23ºC regardless of the variation of outside temperature between 10 and 26ºC
The energy saving with the underground factory is remarkable. Electrical power consumption is reduced by more than 80%.
We can find many application examples of solar energy generation today.
Let us move on to the next scale, which is the machine tool. Machine tools play a central part in the machining factory. They consume energy and generate waste as well as emissions. The energy consumption consists of a fixed part, such as the energy used by the cutting fluid supply pump and hydraulic pump, and the energy needed for the cutting operation. Surprisingly, the fixed part is a considerable part of the total machine tool energy consumption.
The total energy consumption is the integral of the power consumption against the operation time. Therefore, in order to reduce the energy consumption, there are two conceivable strategies: either decrease the cutting as well as non-cutting time through the development of high-speed machine tools or decrease the power consumption through improving the efficiency of machine tools and peripheral devices. Increasing the speed of machine tools could be attained through the application of high-speed spindles and linear motors. In this talk, I will concentrate on the reduction of electric power for machine tool operation.
Power reduction is possible by downsizing machine tools. In fact, the Japanese machine tool industry has been producing downsized machine tools for several years. This is one of those examples. Floor space is reduced to half of the original size and the motor power is reduced by about 20% while keeping its original functions. The reduction of floor space is attractive in Japan because land prices are very expensive.
Let us move on to the process. A large part of energy is consumed by the cutting fluid supply pump in many machine tools, and a huge amount of cutting fluids is considered necessary to perform cutting processes with good lubrication and cooling. The fluid supply is also needed for chip elimination from the cutting area. In addition to such energy consumption issues, there is a strong demand to attain a clean working environment. Furthermore, cutting fluids may contain some harmful components.
In order to avoid these cutting-fluids related problems, dry cutting or near-dry cutting has been proposed and is being put into practice. The near-dry cutting is sometimes called MQL (minimal quantity lubrication) cutting. The ultimate goal is, of course, dry cutting without any cutting fluids. However, due to the excessive tool wear and the adhesion of material on the cutting edge, the application of dry cutting is limited. On the other hand, near-dry cutting has found wide applications, although there are still some technological problems to be solved.
One of these problems is chip removal from the cutting area, as shown in the right figure. Chip deposition on the machine tool table results in the thermal deformation of the machine tool, which leads to a machining error.
Through the application of near-dry cutting, the amount of the oil supply is reduced to one part per several 10,000 of the conventional flood cutting and consequently the energy consumption can be significantly reduced. Moreover, the synthetic oil for MQL cutting we developed is fully biodegradable.
The principle of this particular technology is to supply an extremely small amount of oil droplets with pressurized air to the cutting point through the main spindle of the machine tool and the cutting tool.
Today we can find some practical applications of MQL cutting. For example, in the production of car components, some parts of these components are machined with MQL cutting.
Thanks to the significant reduction of the supply amount, the cutting-fluid related cost is reduced to one-third of the conventional flood cutting cost.
In order to find further applications of MQL cutting, fundamental research regarding the tribology in cutting is necessary. Let me introduce you my contribution to the MQL cutting. We developed equipment that makes it possible to conduct the cutting under a controlled atmosphere, as shown in this figure.We can measure the adsorption of lubricant on the cut surface and the cutting force simultaneously to investigate the effect of lubrication. By using this equipment we could develop cutting fluids for MQL through the collaboration with the oil company. It is synthetic ester having very high biodegradability and commercially available on the market.
As I mentioned already, one of the core technologies to make the MQL cutting more practical is chip evacuation and removal. The right figure shows a chip evacuation device. The machine tool structure should be optimized to make chip removal smoother, as shown on the left.
The main wastes from the cutting process are the cutting tools, the cutting fluids, and the chips. Those wastes should be recycled. Most cutting tools become waste when they reach the end of their life. And, only a very small part of a tool is used for cutting and the main body remains as its original state. In order to extract tungsten carbide of 100 kg, raw material of 12,000 kg is necessary. On the contrary, if we can recycle wasted cutting tools, the necessary amount is only 120 kg. The advantage of recycling is obvious. Thanks to the development of recycling technology and a system of collecting used tools, this idea has already been put into practice.
Another typical example of recycling and reuse is the reconditioning of cutting fluids. This is a mobile reconditioning system. The idea is patented in the US and Japan and has become a business.
I talked about the breaking the walls of manufacturing by using examples of environmental issues. To meet the sustainable development of society, manufacturing should change to become more symbiotic by reducing the environmental impact. Difficulty in promoting this movement is that the productivity should not be decreased. Otherwise, it is not accepted in the industry.
An important concept to attain highly sustainable manufacturing is the inverse manufacturing. When we talk about the life cycle of products, we mostly pay attention to the flow of conventional manufacturing which starts from the material, components, products, and comes to wastes. However, in order to attain real sustainable manufacturing, we need to consider the flow of the other way round , which can be called inverse manufacturing. In this flow, design for ecology, recycling, disassembly and segregation of material will be the core technology to be developed. As a matter of fact, the inverse manufacturing is one of the national project in Japan launched 1996. Through the fusion of symbiotic manufacturing technology and inverse manufacturing technology the sustainable manufacturing will be further enhanced.What I would like to say as the conclusion of my talk is that there are still many issues to be solved in manufacturing.
I would like to close my talk by saying that “Manufacturing will remain one of the principal means by which wealth is created.