Reconstruction of hydraulic circuit of balancing hydraulic cylinder for milling head of gantry machine

I have been engaged in the design and manufacture of CNC machine tools for nearly 10 years. I have gained some experience in the design and calculation of the balance weight of the vertical milling head or grinding head of this type of machine tool.

Metal processing online prompt: the vertical milling head or the grinding head of the vertical machine tool does not move in the X direction, so the balance weight hammer can be placed in the column cavity to move only up and down. The X-axis moving head is synchronized with the weight, while the gantry-type vertical milling head or grinding head is to be X-moving. The balance weight has no installation space on the beam, and the vertical milling head or When the grinding head is walking, it will cause swaying instability, and it is impossible to configure the counterweight. Therefore, such machine tools at home and abroad generally have two balance hydraulic cylinders on both sides of the vertical milling head instead of the counterweight to achieve balance.

In the process of trial production, we refer to the hydraulic schematic diagram or the physical object of the same type of machine tool, and the reversing valve is arranged in the hydraulic circuit of the two balance hydraulic cylinders, but the trial and error effect is not good. To this end, we have visited relevant companies and some manufacturers with such machine tools, and some have stopped using the hydraulic system, because the balance of hydraulic cylinders is still feasible in the machine principle, but due to the vertical milling head or grinding head The overall size is generally above 1 000 kg, plus the cutting force, when the vertical milling head is up, there will be greater resistance, resulting in the guide rail and the ball screw - the nut pair produces a large friction and damages the accuracy and life of the machine. .

After a period of exploration and practice, we analyzed the function and problems of the circuit. The crux of the problem lies in the up-and-down motion and speed (ie hydraulic system) of the vertical milling head during machining, especially when machining complex molds. The commutation frequency is irregular, which is quite different from the regular commutation loop of the general hydraulic drive machine table. From the performance analysis of the reversing valve, the reversing valve can not be switched too fast to avoid the impact, so the pilot valve is usually assembled on the reversing valve. However, once the pilot valve is installed, the commutation has a buffer period that delays the commutation time. This is completely contradictory to the requirements of the vertical milling head machining action.

In view of the above understanding and practice, we take measures such as removing the reversing valve and accumulating the accumulator, so that the hydraulic system circuit only acts on the uplifting force of the vertical milling head, and the downward direction of the opposite milling head is caused by the self-weight. The hydraulic pressure is at "0" pressure. The test and the results of the use are satisfactory. Some of the factory hydraulic systems run smoothly and safely and reliably for several years.

Improved hydraulic circuit

Of course, at the upper end of the hydraulic cylinder, there will be a small amount of leakage oil due to the release of air and the wear of the piston seal after operation. As long as a small pipe joint is installed on the upper cylinder head, the oil will leak. Return to the fuel tank.