by Doug Hanson » Mon Nov 01, 2010 9:41 pm
I think the difference here is your current system is meter out, which means there is back pressure through the entire system. That combined with the open transition valve cause the surging, as well as shifting of the feed control valve. You can try using counterbalance valves, but I think they will be piloted open because of the back pressure from the feed control valve. There are a few variables here, so the easiest thing to do would be to try it out.
The load sensing systems I proposed allow you to have a pressure comepnsated flow control as a meter in function, which eliminates the whole meter out back pressure issue. This will also allow you to use counterbalance valves without worying about backpressure piloting them open. It will also generate a lot less heat.
The only way to get even more precise throttle and position control would be to go with a closed loop motion control system, which is quite an expensive way to go.
If you have a system there that is ready to go, I would try out the counterbalnce valve arrangement. If that doesn't work out, you would need them for the load sensing system anyway. You could try using a 4 port, vented counterbalnce valve and plumb the vent port into the T port of your control valve so the back pressure in the meter out portion is additive to the counterbalance setting, but I don't think this is a good design idea.
Doug Hanson
Predsident
Hanson Hydraulics Ltd.