Machine tools, known as "machines that manufacture machines," are the core competitiveness of the new industrialization. China's machine tool industry started late, and in the beginning, high-precision computer numerical control (CNC) machine tools mainly relied on imports.

"In order to be self-independent, we decided to develop high-end CNC machine tools that belong to the Chinese people," Li Li, deputy general manager of Jiangxi Just CNC Technology Co., Ltd， told Science and Technology Daily. The company started from scratch and eventually developed a tool with a repeat positioning accuracy of 0.4 microns. This was an epic journey that took more than 20 years.

From repairing to producing

In 2003, Liu Hua, exceptionally skilled in repairing imported machine tools, became the youngest technical expert at the AVIC Jiangxi Hongdu Aviation Industry Group Co., Ltd. At that time, high-precision CNC machine tools were almost exclusively the domain of foreign brands. The imported machine tools were not only expensive and difficult to maintain, but also subject to usage restrictions.

In 2004, Liu founded Just to manufacture independently developed high-precision CNC machine tools. In the first three years, the enterprise derived its profit mainly from repairing machine tools and processing precision parts, and invested the majority of its revenue in technological research and development.

In 2007, Just successfully transformed its business from repairing machine tools to manufacturing them, independently developing its first machine tool with a precision of 10 microns. This achievement strengthened its determination to delve deeply into the field of machine tool manufacturing. After another six years of efforts, Just developed its first automated production line in 2013, raising the precision of its machine tools to eight microns.

Technical breakthroughs

But problems followed after that. Foreign companies mainly adopt the technical route of lead screw transmission in manufacturing machine tools, which has decades of technological experience behind it and significant advantages in high-precision lead screws, high-precision bearings and other aspects. However, the notorious Wassenaar Agreement to control exports restricted the export of machine tools with a repeat positioning accuracy of 1 micron to the Chinese mainland.

It was unfeasible to conduct R&D along foreign technological routes, said Zhang Jun, the chief R&D engineer of Just. Mechanical engineering experts from Huazhong University of Science and Technology (HUST) proposed another option: replacing the traditional lead screw nuts with linear motors.

Based on a theory similar to "magnetic levitation," the original mechanical transmission structure was greatly simplified, and the dynamics and accuracy of the machine tool improved accordingly.

In 2015, Just formed a R&D team of over 40 experts to test the application of linear motors in CNC machine tools. However, they found that the body of traditional machine tools is prone to deformation due to temperature changes. Then they had a brainwave: "Why not replace the cast iron body with marble?" Marble is widely used in manufacturing due to its physical properties and stability.

In January 2017, a high-speed and high-precision CNC machine tool using linear motor direct drive technology was successfully developed. Its full-range positioning accuracy was 2 microns, and the repeat positioning accuracy as high as 1 micron.

Industrial collaboration

To improve the precision from 2 microns to 1 micron was a challenge. This leap not only required comprehensive innovation in manufacturing technology, but also vast improvement in R&D, production and manufacturing, and quality control.

Just built a scientific research system integrating an academician workstation, a postdoctoral innovation practice base and a provincial expert workstation. It also established cooperation with universities such as HUST and Nanchang University, and reached a comprehensive strategic cooperation with Wuhan Huazhong Numerical Control Co. (HNC).

With the application of 5G+, a manufacturing execution system, and automated production lines, machine tools began moving towards the precision of 1 micron and 0.6 micron. Finally, in March 2024, Just developed a high-speed and high-precision CNC machine tool with a positioning accuracy of 0.6 micrometer and a repeat positioning accuracy of 0.4 micrometer, reaching the top of the CNC metal cutting machine tool niche market.

Just machine tools can meet the demands of manufacturing automobiles, semiconductors, and aerospace, said Chen Jihong, a professor at HUST and the chairman of HNC. The company joined hands with HNC to release the newly developed intelligent vertical five-axis machining center, which is equipped with the world's first intelligent numerical control system integrating AI chips and large models.