In the machine tool industry, the word "precision" I hear a lot is "precision". For a machine tool, precision often represents the * high precision level of the workpiece that can be processed by the machine tool. Generally, there are two concepts of accuracy, one is machining accuracy, the other is measurement accuracy. How to reflect the size required by the designer is the machining accuracy, and how to know the size completed by machining is the measurement accuracy. These two accuracies are directly dependent on the accuracy of the working machine of the processing machine or the measuring machine. Today, we mainly discuss the problem of "absolute plane" involved in machining accuracy.

As we all know, the machining accuracy of mechanical equipment will only be lost and will not increase. For example, machines with a precision of 0.01mm can only process workpieces with an error greater than 0.01mm. Therefore, even without considering the assembly error, machines assembled with parts machined with medium machining accuracy can only achieve an accuracy greater than 0.01mm. If you want to produce and assemble mechanical parts with an error of less than 0.01 mm, you can only use processing machinery with an error of less than 0.01 mm. According to this principle, to manufacture high-precision processing machinery, only processing machinery with higher precision can be used. How to produce a higher level of machining accuracy?

In fact, this problem is the same as manufacturing production tools from nothing in the development of human society. Primitive humans * began to use stones as tools and then processed them into more exquisite stones. Then, with the development of society, human beings began to process bronze, iron and other products, from rough to precision, through continuous matching, finding standards and refining standards, and then manually polished by workers into more precise tools, which is a long process. From this law, it can be concluded that all high-precision machine tools are processed by machine tools with lower precision, and then processed by workers manually.

The overall accuracy of mechanical system is composed of the accuracy of each link in the system, but the accuracy of different links has different influence on the overall accuracy of the system. Among them, the guide rail has a great impact on the machining accuracy. The moving part of the machine is limited by the guide rail, and the accuracy of the guide rail directly determines the accuracy of the mechanical movement. The sliding surface of ultra precision mechanical guide rail is called "absolute plane", which requires an accuracy of more than 1 / 10000 mm. No machine can process this absolute plane, which can only be processed by hand. I believe everyone who has seen the sliding surface of high-precision machine tool guide rail knows that the so-called "absolute plane" is not a smooth mirror, but a plane covered with regular patterns. Those patterns are the traces left by the blade of the craftsman who made this plane.

To create an absolute plane is more difficult than the "difficult thing" in the public sense. It requires experienced craftsmen to shovel the rough machined plane one by one with a shovel. While shoveling out the required plane, they also need to make a control plane, then paint color on the control plane and slide the processing plane on the control plane. At this time, the part stained with color on the processing plane and the part losing color on the control plane are the higher part on the two planes, which needs to be removed again. This process often needs to be repeated many times until the color of the two planes is completely uniform. Often at this time, the knife marks left on the plane are just used as lubricating oil grooves, which can be said to kill two birds with one stone.

However, it is far from enough to make an absolute plane through the above steps, because if the same radian is formed between two faces, the same effect will be produced. Therefore, this can only mean that the two faces are exactly the same, and it cannot be guaranteed to be a plane. So you need to add another reference plane. Generally speaking, when processing an absolute plane, three planes need to be processed at the same time. Only when any two of the three planes are consistent can the absolute plane be calculated. This process is inseparable from rigorous measuring instruments and craftsman's hands.

In a sense, companies that can make absolute plane represent the level of high-end manufacturing industry, and now the companies that use this process to process the absolute plane required by machinery are mainly in Germany, Switzerland and Japan, which is also the reason why these countries can produce high-precision mechanical equipment.

Yu Tianren, a freelance writer who has lived in Japan for many years, wrote in "is the sun going to set in the east?" The book points out that Japan's precision processing companies are mainly concentrated around the 43 ° north latitude line in Niigata Prefecture. There are meteorological reasons for this. The precision technology of the Japanese was learned from the Germans. At that time, when selecting the address of the precision processing industry, Japan selected the 43 ° north latitude area with a climate similar to that of Germany. The humidity in this area is small and the temperature is around 20 ° C, which is very in line with the environmental requirements for precision processing. Since there was no constant temperature equipment such as air conditioner at that time, we must pay attention to the problem of temperature difference when selecting the processing site. The material expansion and contraction caused by temperature difference has a great impact on the manufacturing and assembly of precision products. The temperature difference not only affects the processing of workpieces, but also reduces the impact of temperature difference by using granite instead of ordinary cast iron for the bed of many ultra precision grinding machines.

These precision processing companies in Japan are basically small companies composed of several to dozens of people. It is not too much to call them small workshops, but it is precisely because of these small workshops that world-famous machinery brands such as Yasuda, Mori and Makino can become famous in the world. Japan's economy has been sluggish for more than a decade, but these companies engaged in hand-made sliding planes have never been affected, because this industry is the foundation of the manufacturing industry and requires superb technology and rich experience. Their products have never been enough and there is no surplus. Especially with the continuous expansion of the application scope of electronic technology, the requirements for high-precision machining machinery and equipment will only increase rather than decrease.

Although human hands can not be said to improve the accuracy infinitely, they can indeed create many miracles. In the future precision upgrading of the machine tool industry, I believe these hands will play more roles. This article mainly involves the problem of "absolute plane" in machining accuracy. The author will update more knowledge about machine tool accuracy in subsequent articles. Please correct the deficiencies in the comment area.