Maximum Cylinder Acceleration

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Re: Maximum Cylinder Acceleration

Postby Peter Nachtwey » Fri Jun 03, 2016 2:07 pm

You application should be easy if the frequency of the valve is high enough and that shouldn't be too hard too find.
Are you going to try a 4WRPEH? Or does Bosch have something faster. What flow?
I calculate Qdumb to be 63.845 L/min using Mathcad.
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That is just over the 60 L/min flow of many valves and forces you to the next bigger and slower size.
The size 6 is much faster than the size 10. I don't think the size 6 is big enough. I don't think the size 10 will be fast enough.
Yuken has some nice valves too.
Peter Nachtwey
 
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Re: Maximum Cylinder Acceleration

Postby ndzied1 » Fri Jun 03, 2016 5:28 pm

The customer would love to use the size 6 4WRPEH because they have standardized on it in their other machines. It is supposed to have a flow limit about 75 LPM. That's cutting it close and taking all the pressure drop across the valve. I'm probably really going for a consistent kinetic energy in the tooling since I'm doing a staking operation so maybe that doesn't matter.

The valve I'd like to try is the Rexroth 4WRREH which is almost twice as fast as the 4WRPEH but again only size 6. Flow limit of 80 LPM at 250bar drop.

If I have to go size 10 then I would use the 2 stage 4WRVE with the 55L (nominal at 10 bar) spool. It uses the 4WRREH for a pilot valve and with a consistent 175 bar pilot supply it rivals the speed of the size 6 4WRPEH... even a little faster if I max out the pilot to 250 bar.

Yuken does make some great valves but commercially I'd never be allowed to do that. I could probably get away with using a Moog servo valve but in this plant that is asking for trouble as oil maintenance is something we are constantly harping on them for.

The parts are indexed on a dial and if they can shave some time off that, perhaps the size 6 will work. It would probably be best if I have the RMC control the indexer as well now that I'm counting milliseconds. Right now the PLC is doing coordination through digital I/O with is really fast in the RMC and servo drive but maybe not as much in the PLC. Same with the scan time. I could be losing 20-30 milliseconds in PLC scans to do interlocks in the PLC.
ndzied1
 
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Re: Maximum Cylinder Acceleration

Postby Peter Nachtwey » Sat Jun 04, 2016 3:55 pm

Good, I learned about two faster Bosch valves. I saved the pdfs in my valve library.
I agree those valves are faster but not that much faster.
The largest 4WRR valve is 40 lpm which is not enough.
We both know the flow can be higher than this but I don't think the valve flow can be increased by over 50%
You need to look at the 100% frequency curves on the Bode plots.
Peter Nachtwey
 
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Re: Maximum Cylinder Acceleration

Postby ndzied1 » Tue Jun 07, 2016 6:06 am

They don't call it Systems Design for nothing.

Just got a change from the customer. Previous system was set for 20ton max force but they are now changing this one to 12tons.

It takes down the Natural Frequency a little bit but still, it's around 600Hz which is awesome.

With a 4" bore and 2" rod, the Qdumb is now about 36.5 L/min which gets me to the size range of the 4WRREH valve.

And, just to make it interesting, they have told us we can't change the indexer drive right now. Actually, it makes my job a little easier because now I get to say, "the cylinder will move in xx msec and when I prove it with a plot from RMCTools I'm done.
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