Principle of CNC machine tool hydraulic system

　The hydraulic system of the CNC machine tool uses a pressure-limiting variable vane pump to supply oil. The working pressure is adjusted to 4MPa, and the pressure is displayed by a pressure gauge. The pressure oil output by the pump enters the branches of each subsystem through the one-way valve. Its working principle is as follows:

　　1. Clamping and releasing of chuck.

　　When the chuck is required to be in positive clamping (the claws clamp the outer circumference of the workpiece inward) and under high pressure and large clamping force, 3YA loses power, the valve works in the left position, and the pressure reducing valve is selected to work. The clamping force is adjusted by the pressure reducing valve, and the clamping pressure is displayed by the pressure gauge.

　　When 1YA is powered on, the valve works in the left position, and the flow direction of the system pressure oil is: oil pump → one-way valve → pressure reducing valve → left position of the reversing valve → left position of the reversing valve → right chamber of the hydraulic cylinder. The oil in the left chamber of the hydraulic cylinder returns directly to the tank through the left position of the valve. At this time, the piston rod moves to the left and the operating chuck is clamped.

　　When 2YA is powered on, the valve works in the right position, system pressure oil enters the left chamber of the hydraulic cylinder, and the oil in the right chamber of the hydraulic cylinder returns directly to the tank through the valve. At this time, the piston rod moves to the right and the control chuck is released.

　　When the chuck is required to be in a positive position and under low pressure and small clamping force, 3YA is powered on, the valve works in the right position, and the pressure reducing valve is selected to work. The size of the clamping force is adjusted by the pressure reducing valve, and the clamping pressure is also displayed by the pressure gauge. The adjustment pressure value of valve 9 is smaller than that of the valve. The working condition of the reversing valve is the same as that under high pressure and large clamping force.

　　When the chuck is in reverse clamping (the claws clamp outwards to clamp the inner hole of the workpiece), the action is opposite to that in forward clamping. That is, the clamping of the reverse jam is the loosening of the positive jam; the loosening of the reverse jam is the clamping of the positive jam.

　　2． Tool change of rotary tool holder.

　　When changing tools with the rotary tool holder, the tool holder is first raised and released, then the tool holder is indexed to the designated position, and finally the tool holder is pulled down and reset and clamped.

　　When 4YA is powered on, the reversing valve 6 works in the right position, and the tool holder is lifted and released. When 8YA is powered on, the hydraulic motor rotates forward, driving the tool holder to change tools. The rotation speed is controlled by the one-way speed regulating valve (if 7YA is powered on, the hydraulic motor drives the tool holder to reverse, and the rotation speed is controlled by the one-way speed regulating valve). After the tool holder is in place, 4YA is powered off, the valve works in the left position, and the hydraulic cylinder clamps the tool holder. Whether the forward conversion tool or the reverse conversion tool is determined by the CNC system is based on the shortest path principle.

　　3． Telescopic movement of the tailstock sleeve.

　　When 6YA is powered on, the reversing valve 7 works in the left position, and the pressure oil flows in the following direction: pressure reducing valve → reversing valve left position → left chamber of the tailstock sleeve hydraulic cylinder. The flow direction of oil in the right chamber of the hydraulic cylinder is: one-way speed regulating valve → valve → oil tank. The hydraulic cylinder drives the tailstock sleeve to extend and tighten the workpiece. The size of the tightening force is adjusted through the pressure reducing valve, and the adjusted pressure value is displayed by the pressure gauge.

　　When 5YA is powered on, the reversing valve works in the right position, and the pressure oil flows in the following direction: pressure reducing valve → reversing valve right position → check valve of the combination valve → right chamber of the hydraulic cylinder. The oil in the left chamber of the hydraulic cylinder flows to the oil tank through the valve, and the sleeve retracts quickly.