Hydraulic Troubleshooting

Outer squeeze feet operating slow

SYMPTOMS:

The Slow outer squeeze feet left a high ring of sand around the outside of mold. The high sand was knocked off by the upset at index back on to the pattern for the next mold. We struggled with blow off pressures to blow off the extra sand. @20 psi we had more control of the sand and helped remove it for the east west rails on pattern. We did not change the center blow off pressure of 7psi as to not wear on the pattern. Fin on drums increased by thickness at parting line. Bolt holes were thick on drums and filled all holes at times. Line cycle was effected with the longer squeeze. Biggest problem was the amount of stickers we were getting from the sand on pattern getting between pattern and the flask.

PROBLEM:

Oil flow to the head for the outer feet was the core issue. The inner and outer squeeze valves were triggered on at the same time but outer feet were slower with four less cylinders than the inner .There were many places this could be effected from. Here is a list of Items We Checked not in the order we checked them.

SOLUTION:

We found the adjuster for the valve F had been removed (could have been early on, installing it on other valves to adjust and work on the problem) We installed the adjuster and adjusted the valve to a shorter stroke as it was at full stroke. This allowed the timing to close the valve we needed. Although we restricted the flow by doing this to the squeeze feet it was far less than the amount going to tank before.

Look For Leak By In Squeeze Manifolds.

Inner outer feet squeeze manifolds , removed all valves checked replaced orings along with all the cartridge valves. No Change

Change Multiple Plugs On Pilot Valves For Inner Outer

Idea was have low voltage or signal causing slow valve shift. No change

Check The Squeeze Head For Cross Pressure.

The idea was we have the outer feet oil passages and inner feet passages connected through a failure in the head construction (plugs missing ,cracks ect.) The test was done by squeezing the outside feet only and looking for pressure rise in the inner feet using gauges on manifolds. Then we did the opposite test with the inner only. Both of the test were good with no leakage from one to the other.

Check The Cylinders For Blow By.

The idea was we are bypassing too much oil from leaking seals in cylinders we have to overcome the bypass before the feet will go down. We ran test on both the inner and outer separately. This was done By squeezing and holding the squeeze for the inner or outer feet, then after full stroke of the cylinders we close the tank valve on B side of cylinder. Next watch the pressure on B side and time the pressure increase up to full system pressure. We did this for extend of both inner and outer and retract of both at the inner outer manifolds using the test box with the plugs . The results were the same for all test. Time was 15 seconds to see pressure start to rise and 45 seconds to full pressure. These were determined to be good test and cylinders were in good condition. A sharp or quick pressure rise would indicate a considerable leak by (with in a few seconds).

Regen Valves Timing Changes

The idea was were not using the oil from B side of the cylinder adding it to the a side and wasting it to tank. After multiple changes to the timing of the valve in the program we ended up back at the .052 area where we had started with out any significant changes.

Change The Proportional Strip Valve

The idea was we were pushing down the table or not getting the resistance we needed. No change

Sand Fall

The idea was the sand was low in the center of mold letting the inner feet go down first, outer feet were held up by sand . Ran squeeze feet with no sand by hand still had delay outer feet. Ran with out sand diverter, had to much sand all over no control of sand fall no change outer feet. Changed sand fall timing, table height. Change the timing of the sand fall with the speed of the scale doors. By adding more sand weight to the mold. Remove the rubber from the head plow, (created more sand falling on pattern) All no change. We ruled out sand fall as part of the problem.

Hydraulic Hoses

The iIdea was one of the hoses for the squeeze or feet return had a loose inner cover restricting flow. Replaced and inspected two outer hoses from outer manifold to hard piping. Replaced and inspected two outer squeeze hoses to the head from hard piping. Replaced and inspected two outer (inner) return hoses to the head. All of these items had no findings and no change.

Transducers And Hoses

The idea was transducers reading slow or inner covers on hoses loose, pipe manifold plugged with foreign materials. We changed the manifold, new transducers and hoses. No change

Y Blocks Inpection

The Idea was the two Y blocks for the outer squeeze lines where the hoses go to hard plumb may be wearing and creating a flow restriction. No findings, no change

Quarter Turn Valves.

Idea was the quarter turn valves in the two squeeze lines from the outer manifold block were coming apart inside creating a flow restriction. Inspected them with no findings, no change.

Return Filters For Manifolds Inner And Outer

The idea was we were restricted at the time of the squeeze when we had the highest oil flow. Checked and changed the filters, no findings, no change.

Check All Accumulators High Pressure And Low Pressure

The idea was we were lacking oil volume. We checked the pressures for pre-charge, for residual oil on top of pistons. There were some findings here of low pressure and some oil. There were no changes after repairs.

Pump Amps And Pressure Settings

The idea here was we had some lazy pumps and not achieving our max oil volume. All pumps were checked a few were changed and reset. No changes after repairs.

Listen To Manifold With The Ultra Sound Tool For Oil Leaks

The idea here was is there a leak or slow logic cartridge we cant feel or see on pressure gauges. Use this tool to listen inside the manifold. Checked the inner and outer manifold and found a valve closing very slow, valve F on outer manifold. Valve F is for the A side of squeeze cylinder to tank when squeeze feet are retracted it is open at this time. When we would go to squeeze this valve should close quickly it would not close quickly allowing oil to bypass to tank instead of going to the outer squeeze feet. This was causing our lack of oil to the squeeze feet and slow feet. Comparing the inner manifold with the outer and watching the coils for the pilot valves lights compared to the flow of oil in each valve we determined this as the problem.

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