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Hydraulic Shapes and Reciprocating Machines

12/12/2009 8:04 AM

Hi

I am presently teaching students about reciprocating machines like shaper, slotter etc.

One of the aspects that need elucidation is the quick return motion effected in a shaper driven by hydraulic mechanism. I consulted various textbooks available with me, but it is not very clear as to how exactly the quick return mechanism is achieved - rather the principle behind it, both when the working fluid is supplied under constant pressure and constant volume.

I'll be grateful if someone could lead me to a detailed explanation with sketches.

Thanks and regards

S.k

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Guru

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#1

Re: Need insight into hydraulic shaper operation

12/12/2009 8:33 AM

This might help:

Shaper Mechanism Types

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Guru
Technical Fields - Technical Writing - New Member Engineering Fields - Piping Design Engineering - New Member

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#2

Re: Need insight into hydraulic shaper operation

12/12/2009 1:30 PM

Great article!

The key to the hydraulic cylinder operation is the difference between the larger volume below/behind the piston versus that of cylinder-minus-rod above/in front of the piston. At same flow, filling the smaller volume takes less time. With a relatively large rod, the retraction speed can be several times the extension speed.

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#4
In reply to #2

Re: Need insight into hydraulic shaper operation

12/13/2009 12:59 AM

Thanks for your elucidation.

S.K

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#3

Re: Hydraulic Shapes and Reciprocating Machines

12/12/2009 11:29 PM

Hi Kichu

Any motion that you describe, such as the shaping machine (or a compactor) operates with 'full bore' of the cylinder to provide the necessary force required to to the job. This means that very little force is required to return the cylinder to its home position with the 'rod end of the cylinder.

As little return force is required, a REGENERATIVE direction control valve is used. This valve directs the returning oil from the full bore side of the cylinder into the rod end of the cylinder giving VERY rapid return motion.

Just google Regenerative valve for it's actual mode of operation.

Good luck with it!

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#6
In reply to #3

Re: Hydraulic Shapes and Reciprocating Machines

12/13/2009 1:07 AM

Thanks, Beej50 for a very useful additional info about the regenerative valve mechanism. Yes. I am digging into the resources about it.

I'll be grateful if you or someone can tell me about the working of constant pressure flow, if any, in this kind of machines.

S.K

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#7
In reply to #3

Re: Hydraulic Shapes and Reciprocating Machines

12/13/2009 11:32 PM

Sorry BEEJ50 regeneration circuits only work on cylinder extention not retraction.

Both ends of the cylinder are pressurized at the same time, because the rod side has less area then the cap side the cap side pushes the cylinder out. The effective force is the area of the rod.

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#8
In reply to #7

Re: Hydraulic Shapes and Reciprocating Machines

12/14/2009 12:03 AM

Hi Mike.......must have lost the plot for a minute! Of course you are correct.......otherwise it couldn't work!

It would be rather ironic to get a GA for a BA!

I hope the OP sees this!

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#5

Re: Hydraulic Shapes and Reciprocating Machines

12/13/2009 1:01 AM

Please correct the word "Shapes" as "Shaper" in the title of this thread.

The typo regrets! :)

S.K

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