The feed control of the drilling pressure at the bottom of the hole by the weighing module during the drilling process is proportional to the pressure, ensuring that the unit pressure on the diamond contact surface is greater than the compressive strength of the rock, and the unit pressure value is less than the compressive strength of the diamond. According to the hardness of different rock strata, it should be controlled within a reasonable range. The feed system supplies oil to the feed cylinder through a quantitative pump. The relief valve regulates the pressure of the weighing module on the cylinder and serves an overflow function. The feed speed can be controlled through a throttling speed control valve. The method of controlling the cylinder speed by adjusting the opening area of the valve is essentially to change the magnitude of the back pressure force in the circuit through throttling, thereby achieving the purpose of regulating the feed speed.

When the weighing module is subjected to force and pressure reduction drilling is carried out, the weighing instrument displays the mass value of the upper chamber pressure. During the feed process, the pressure in the upper chamber of the cylinder can be controlled by adjusting the relief valve, thereby controlling the drilling pressure at the bottom of the hole. At this point, it is considered that the pressure value in the lower chamber of the oil cylinder is zero. However, in the actual drilling process, due to the existence of back pressure, the pressure value in the lower chamber also exists. With the change of rock layer hardness, the pressure in the large and small chambers of the oil cylinder is also constantly changing.