Mitsui hydraulic surface grinder

jim may · Feb 18, 2017

We have 3 Hydraulic Mitsui surface grinders 8 x 18 we bought them at different times thru 2 years all 3 of them blew there hydraulic hoses
We put stronger hoses on them. All seem to be ok but seems like their reversal is much harder. 2 of them we got adjusted better
but 1 we are only getting 20 strokes per minute and a hard reversal on the right to left. I have adjusted the cushioning solenoid
several times trying to soften up to no avail. Hydraulic pressure is in spec. With the stock hoses we noticed quite a bit of movement
of the hoses on the reversals of the table. Seems like they are taking in account for the flex in the hoses. Our new hoses are rated
for a much higher pressure. Cant seem to get a hold of Mitsui service to talk to them about this.
Any ideas to get my speed up and soften the reversals?
Other then that very accurate grinders.

Lost in LA · Feb 18, 2017

Sounds like you need something to absorb the hydraulic shock. You may be seeing the equivalent of a water hammerer effect. Sounds like Mitsui is using their hoses as a way to soften the reversal.

Talk to a pump expert.

A quick fix may be to increase the length of the hydraulic hoses--Maybe double them or more to give more expansion room and soften the shock.

You could drop the hydraulic pressure a bit and see what you get.

Lost

dkmc · Feb 18, 2017

Talk with a knowledgeable hydraulics expert.
If things can't be adjusted properly to compensate,
you may be able to fix the problem by installing
an accumulator.

EdCWC · Feb 21, 2017

jim may said:
We have 3 Hydraulic Mitsui surface grinders 8 x 18 we bought them at different times thru 2 years all 3 of them blew there hydraulic hoses
We put stronger hoses on them. All seem to be ok but seems like their reversal is much harder. 2 of them we got adjusted better
but 1 we are only getting 20 strokes per minute and a hard reversal on the right to left. I have adjusted the cushioning solenoid
several times trying to soften up to no avail. Hydraulic pressure is in spec. With the stock hoses we noticed quite a bit of movement
of the hoses on the reversals of the table. Seems like they are taking in account for the flex in the hoses. Our new hoses are rated
for a much higher pressure. Cant seem to get a hold of Mitsui service to talk to them about this.
Any ideas to get my speed up and soften the reversals?
Other then that very accurate grinders.

I upgraded my Mattison from mechanical valves to servo valves with the same problem. The old mechanical valves had a "two step" system to slow the table at the end before reversing. After about a year of hydraulic experts, I went back to a similar system to old valves. I am using 2 servo valves with a variable flow restricter on one valve. When the end of stroke switch is triggered, the signal is sent to the PLC it closes the main valve, then 1/4 second later the secondary valve reverses. a 1/4 second later the main valve reverses. This gives be the ability to slow the table before reversing in both flow rate, and time. So far so good, hoses and fitting are holding up better, low temp gains, good grinding results.

jim may · Feb 21, 2017

Going to take the hoses off one of the other Mitsui's and get some new hoses made. Thinking that the other hoses
we put on were smaller diameter. Worth a try

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Mitsui hydraulic surface grinder

jim may

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Lost in LA

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EdCWC

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jim may

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