Hydrajacks Pressure

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Hydrajacks Pressure

Postby Javier Quevedo » Thu Sep 21, 2017 6:01 pm

Does somebody have the formula to calculate the pressure to apply to a rotary die?
I had it but I lost my notes

Thanks!
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Re: Hydrajacks Pressure

Postby TexMaintMan » Thu Sep 21, 2017 7:23 pm

When the knob is completely bottomed out in the clock wise direction the Jack can be reset by the following steps...

Unscrew the knob three to four full turns.
Place the tip of the jack on a hard smooth surface.
Apply downward pressure with the palm of your hand to the top of the know until the piston is reset.
The procedure is complete.
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Re: Hydrajacks Pressure

Postby RollerGuy » Fri Sep 22, 2017 9:48 am

We typically go by 100lbs per lateral inch of of die cut. This does not factor in any curvature of the cutting blade, only straight lateral cuts. So, if we are cutting with an RCR die that has 2 5" wide cavities, we would shoot for 1000lbs of pressure.
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Re: Hydrajacks Pressure

Postby Injinnius » Thu Sep 28, 2017 1:10 pm

I've never heard of a pressure formula. I would think it would vary a lot by the type of die, type of material, etc.
I was taught to adjust the die pressure by ear. As you apply pressure, the "thunk" sound gets louder. (My understanding is this is the bearer "slap"; as the die doesn't cut completely through, it lifts up a little ... the "thunk" is the bearer slapping back down onto the anvil roll.) As you apply more pressure, at some point the noise will suddenly drop dramatically. That is the point when the bearer is no longer lifting off the anvil roll. Since the bearer is now in contact with the anvil roll continuously, that is how the die was engineered to be run, and should cut perfectly.
Recording the pressure at this point is a good thing. As the die wears, the pressure needed will increase. At some point, when you start having problems with the die cutting properly, record the pressure. Now you have numbers for a new die, and one that's too worn to be reliable. That lets you plan for sharpening or replacing the die before getting into the middle of a big job.
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