This project belongs to the field of electromechanical and hydraulic integrated systems. The product of this project is pile-working machinery among construction machinery. The application field of dual-wheel milling is mainly to make underground diaphragm walls. The biggest difference between dual-wheel milling and hydraulic diaphragm wall grab is that dual-wheel milling can be used for both soft and hard strata, but it is mainly used for hard to hard, even hard strata. Based on the current situation of continuous wall construction in China, the geological conditions are getting worse and worse, and ordinary drilling rigs are no longer able to meet the construction needs. In order to meet the construction needs of users, the company combines my country's geological conditions and integrates advanced machine-electricity-hydraulic integration technology at home and abroad, combined with the company's existing technology, developed and developed the SX40-A double wheel mill. The milling head developed by our company can be added to carry out continuous wall construction in hard formations (musty or sandy rocks from highly weathered to wind-weathered), and can be widely used in continuous wall construction in basic projects of industry, agriculture, and national defense construction. The core technologies designed in this project include: 1. The micro feed device of two-wheel milling and its use method and technology. 2. Two-wheel milling technology for mid-placed pipelines. 3. A central-mounted automatic balancing lifting point structure technology. The two-wheel mill adopting the central-mounted lifting point structure can easily utilize its gravity to achieve natural verticality. 4. The center soil cutting tool technology of double-wheel milling allows the teeth on the milling head to cut the soil and soil into grooves by rotating the milling head, reducing milling blind spots. Innovations of this project: 1. Air compressor is used for gas-lift slag removal. The slag removal pipe adopts telescopic, reasonable slag suction arrangement and large-diameter slag removal pipe have high construction efficiency and good slag removal effect in the tank. 2. The slag discharge pipe, double lifting point design and symmetrical layout of oil and gas pipes in the center of the frame body keep the milling wheel frame body in a balanced state of stress. 3. The milling head transmission shaft is a multi-section type. The transmission shaft is formed by connecting at least three ends of shafts with each other. Each section of shafts is connected through a ball-head universal shaft and a shaft seat structure. 4. Modular design, double winches and double lifting points lift the two-wheel milling frame body, which facilitates rapid switching between the functions of two-wheel milling and hydraulic grab, and can achieve dual use for one machine.  Main economic and technical indicators: Compared with foreign equipment, the price of SX40-A two-wheel mill is reduced by 50%. Compared with general underground diaphragm wall construction technology, the efficiency is improved by more than 50%, and it can be used for hard formation construction. Innovation achievements: 1 authorized invention patent and 9 utility model patents; 1 editor-in-chief standard and 1 book; the main achievements of the project have reached the domestic leading level. Application and Benefit: The results have been applied in more than 20 projects in more than ten regions across the country, and have been promoted and applied to major domestic and foreign projects such as the north bank of the Pingnan Third Bridge on Liyu Expressway in Guangxi and the anti-seepage wall of the Xe-pian Xe-namnoy Hydropower Station in Laos. In the past three years, the company has added more than 480 million yuan in output value and added more than 60 million yuan in profit for customers.