In figure below hydraulic circuit for Milling Machine is shown. In Milling Machine cutter is situated at a fixed position and rotates with high speed. And the workpiece is clamped on table, which move linearly in to & fro motion. Table movement in milling machine is comparatively slower. It has a main pump which is a low pressure and high discharge pump and one booster pump ,which boost the hydraulic pressure to higher level. By using a booster pump expensive high flow and high discharge pump is avoided. There are two set of flow control valve and check valves, fitted in both supply and return line of the cylinder to achieve speed control in both direction. A manually operated spool valve decides the direction of flow to the cylinder. The stroke length of the cylinder is adjustable through limit switches. The limit switch disconnect supply of oil to cylinder when table reaches the set position.
Hydraulic liquid is pumped by a constant discharge pump into the direction control valve. It has four ports and three stages. If the pressure goes beyond desired limits, the same is released by the pressure relief valve. The liquid reaches the right side of the cylinder through the inlet E and outlet A of the valve. Due to the pressure of the liquid, the piston moves towards left. The tool head moves forward to perform the forward cutting stroke. The liquid on the left side of the piston is sent back to the reservoir through B and P. Due to the change of position of plunger inside the valve, the liquid reaches the left side of the cylinder through the inlet E and outlet B. Piston moves towards right. The tool head moves in the opposite direction and this movement is known as the return stroke. The liquid on the right side of the piston is sent back to the reservoir through A and P. Quick Return of the Ram Due to the change of stroke volume of the cylinder during forw