What kind of hydraulic valve is appropriate for double acting test devices

[smmoosavian]

Hi professionals

We are working on a bending test machine that applies reciprocating force on a product. It goes to right and when the force reaches to a specific value it stops and returns to the left and when it reaches to that value again it stops and this cycle continues for 1000 cycles. We get feedback from a force sensor and the graph should be semi sinusoidal. We have made a hydraulic unit with a 3 phase simple 2 directional valve and we control the pump speed by a simple driver. But it doesn't work, because in low speeds the pump doesn't work properly and we have some air traps inside the system. I think we should use proportional valve so that the pump can work in nominal speed. And here is the question: Can we solve the problem by using the proportional valve and a control circuit?
Thanks for response

 

[PNachtwey]

A small servo quality valve with a zero or underlapped spool will work. You should use a small accumulator so the supply pressure can be kept relatively constant. Also, keep the cylinder as short as possible. The smaller the volume of oil being compressed the smaller the volume required to compress it.

The frequency, amplitude and offset were not mentioned.

If you go to the applications area on the website we have a small app note on a project just like the one you describe.
In this application they were testing joints by pushing and pulling just as you have shown in your diagram.

I can supply more information upon request.


Peter Nachtwey
Delta Computer Systems

http://www.deltamotion.com

http://forum.deltamotion.com/