Analysis of the details of the unstable hydraulic press

In engineering practice, Hydraulic Press has a large number of unstable and asymmetric cycle loads. In each stress cycle, the average stress and stress amplitude often change. Therefore, in order to carry out the fatigue design of the part under the action of unstable asymmetric cyclic load, the load spectrum of the part under various typical working conditions must be determined first as the basis of analysis and calculation.

However, the actual working conditions of four-column hydraulic presses for various purposes are diverse. Some process conditions are more regular, while others are messy and changeable. Therefore, it is necessary to select some typical working conditions, perform statistical analysis on the basis of actual measurement of the load, and gather the results together according to a certain regularity, and cooperate with the frequency of various working conditions to obtain the load spectrum.

  • 1. The spool of the fixed differential pressure reducing valve of the hydraulic machine is stuck by dirt. We can remove the screw plug on the valve core, pull out the pressure reducing valve core from the valve sleeve, deburring and cleaning for inspection, pay attention to whether the size of the pressure reducing valve core is concentric.
  • 2. The small hole a of the spool of the hydraulic pressure reducing valve is blocked or the diameter of the small hole on the valve sleeve is blocked by dirt, which causes the inlet and outlet pressure difference of the joint flow valve spool to be unstable and the flow rate is unstable. At this time, the hydraulic press can use 1mm diameter steel wire to perforate the valve sleeve and the feedback hole on the valve core or blow through with compressed air.
  • 3. The inlet and outlet ports are easy to connect reversely.
  • 4. The one-way valve core of the hydraulic machine is not closed with the valve seat, and there is internal leakage.
  • 5. The spring of the pressure reducing valve is invalid, the spring is broken, and the installation is wrong.
  • 6. Leakage inside and outside the speed control valve causes unstable flow and the leakage should be dealt with.
  • 7. The inlet and outlet of the hydraulic press are reversed, so that the speed control valve is like a normal throttle valve, without pressure feedback compensation. There is no positioning pin on the installation surface of the speed control valve, so be careful not to connect the inlet and outlet of the hydraulic press reversely.

The load spectrum should be typical, systematic, concentrated and general. In the fatigue design of a typical part of a hydraulic press, the stress of the critical section of the part should be used as the die forging to formulate the load spectrum, and the stress of the dangerous part of the working cylinder should be measured during die forging of these types of typical forgings. Program to determine the frequency of its occurrence. This load spectrum is relatively simple and has strong regularity. However, it is very complicated to measure the load spectrum of the column of a free forging hydraulic press.

There are many types of forgings forged on a free forging hydraulic press. There are shafts, discs, rings, plates and squares of various sizes. The weights of the steel ingots used for forging are also different. In the forging process of forgings, there may be various processes such as chamfering, cutting risers, lengthening, upsetting, punching, reaming, shaping, finishing and cutting.

The stress caused by the dangerous section of the column in the various processes of each forging is different, and the randomness is very large. Therefore, for the measured data, more work of collation, induction and statistical analysis should be carried out in order to obtain the available The design load spectrum of the design calculation.

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