by Doug Hanson » Sat Jan 23, 2010 9:52 pm
The reason your clamping cylinder valve keeps shifting to reclamp over and over again, is that there is some leakge in the control valve, it only takes a few drops of leakage to get the pressure switch contacts to close, causing the control valve to shift to re-apply pressure to the clamping cylinder. There are a few ways to improve on this, One way is to replace the simple pressure switch with a double make, double break pressure switch which has seperate rising and falling pressure settings, so you can set a minimum and maximum clamping pressure. Bassically it gives you a larger dead band so the pressure switch is not constantly opening and closing. A better way is to also use an accumulator. However an even better arrangement is to use a sequence valve, and eliminate the pressure switch all together.
See the attached drawing for a rough idea. What I don't like about my drawing is that there is no seperate adjustment for feed rate or cutter speed. This would involve adding proportional flow controls, there are some 'auger/spreader' valves that are well equiped for this purpose.
Also when the cylinder strokes out, the motor will then stop because of back pressure so there should be a case drain on the motor, unless it is a Charlynn or equivelant operated at pressures that allow for there useage without case drain lines (less than 1500 psi I believe).
Notice the counter balance valve on the feed cylinder, to prevent lunging if the cut should become light, or a cutter breaks. The counter balance valve will keep the cylinder moving fairly smoothly regardless of load. It will generate a little extra heat though.
Another way to arrange motors and feed cylinders are to use the motor inlet line to back pressure the feed cylinder, so as the motor load increases, the feedrate automatically decreases.
A few questions on your drawing:
What are the blocks under the control valves to the far left and far right.
What is the valve at the far right for?
Is the 'boring' actuator a motor and the drilling actuator a cylinder?
- Attachments
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- drilling_clamping.pdf
- (185.62 KiB) Downloaded 513 times
Doug Hanson
Predsident
Hanson Hydraulics Ltd.