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  1. #1
    adbuch is offline Plastic
    Join Date
    Nov 2007
    Location
    Arizona
    Posts
    21

    Default Power Assist for Pexto 16ga x 52" sheet metal shear?

    Hi,

    I purchased a new Pexto 16 ga. x 52" foot shear a about 5 years ago. Although this shear is rated at 16 ga. capacity, I have been told by a local machine tool dealer that it would require approximately 800 lbs of force on the foot lever to shear a piece of 16 ga. steel that is a full 48" wide. I am considering adding some sort of power assist to reduce the required operator effort. One possibility would be to use air cylinders for power assist. By this I mean the type of air cylinders that operate in the same manner as a porto-power ram. Another approach would be to convert the shear to full hydraulic operation.

    Do any of you have any ideas or experience with this type of conversion, or have you seen a power upgrade kit that is commercially available?

    Thanks,
    David
    Attached Thumbnails Attached Thumbnails pexto-shear.jpg  

  2. #2
    Tom1 is offline Stainless
    Join Date
    Jan 2003
    Location
    Stamford, CT
    Posts
    1,603

    Default

    I don't know about 800lb of force. With the blades set properly a average man should be able to stand on the pedal give a bit of a jump and start the cut. The length of cut really makes no difference as to cutting force. The machine cuts like scissors only one point.

    As far as adding air cylinders or hydraulic. I have never seen a kit. I have seen air cylinders added, but with air, the pressure builds then shoots through the cut with a big bang, not good. Air over hydraulic is better or fully hydraulic. The down side is that there really isn't a great spot to mount the cylinders. You wind up adding stress someplace that really can take it long term. The machine will wind up with cracks, twists etc. If you need hydraulic, save up and buy a good used one, you will be much happier in the long run.

    Many years ago we had a job to convert one of these things. Some engineering company designed a air over hydraulic set up. It had all kinds of flow controls, dampers. It worked OK, I don't know long term. I don't know where the cylinders were mounted anymore. I do know that it cost a bundle. From all the parts to our labor...

  3. #3
    agrip is offline Cast Iron
    Join Date
    Aug 2005
    Location
    Atlanta Georgia USA
    Posts
    256

    Default

    Air over Oil works quite well.
    Only one side of the cylinder needs it.

    Use the oil as media for a forward travel (cutting) speed limit.
    If the sheet metal is not there the pressure on the oil absorbs any runaway.
    If the sheet metal is there the pressure on the oil goes down.

    Working a cylinder extending up, this is easy to get rid of air bubbles, and easy to restrict the flow to control the blade advance speed.

    Only things I had to modify was a rig to diffuse both air and oil going into oil reservoir which was a piece of 3" pipe.
    I just mounted the diffusers in the end caps, by screwing onto the end of the entry fitting "tapped" in deeper than usual.

    Diffuser was/ is a side ported eight hole cross.

    Hope that made sense. Ag

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