Why does the piston extend when the spool is at zero position in my valve circuit?

[Cris LaPierre]

We don't have enough information to say for certain, but this would happen when the force in A exceeds the force acting on R.

One thing to check - your forces must have opposited signs. Otherwise, they act in the same direction. So assuming a positive force in A is meant to extend the rod, then a negative force on R is needed to move it the opposite direction.

Therefore, one reason it may be extending is because your mass is positive.

[Taha]

Thanks for the reply, but the same thing happens even when there’s no mass in the system.

[Cris LaPierre]

Again, we don't have enough information to say for certain. Consider sharing your model, or provide more details on the setting you are using.

[Taha]

my model

Answer 1

[Cris LaPierre]

It looks like your 3-Way Directional Valve may be the issue. Spool travel between closed and open orifice is 0.005 while the open position is set to 0.0045 and the closed position is set to -0.0045. Change spool travel to 0.0045.

Rather than guess on parameter values here, I recommend using the Part selection option to open the parameterization manager and select a part that matches what you want to simulate.

[Taha]

thx