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  1. #1

    Hydraulic Linear Actuator

    I'vebeen tasked with retrofitting a horizontal bending machine. It currently runsoff 17 year old DC servo system. The bending jaws are actuated by 30 tonhydraulic ram that is given a variable stopping point provided by a mechanicalswitch that rides on a DC servo driven ball screw. This is a jumble of parts,it's truly amazing it ever worked. Would I be able to use something along thelines of a servo valve driven by a PLC to set various stopping points for thecylinder? Would it be repeatable and accurate? Thank you for your time.

  2. #2
    Join Date
    Dec 2003
    Posts
    24216

    Re: Hydraulic Linear Actuator

    Machines such as Pines benders use both servo motor/ball screw combo and Hydraulic servo valves.
    But both methods use a servo loop with encoders.
    Using an arbitrary stop point using a PLC would not be very precise.
    At the very least you may have to use a analogue module and encoder input module in the PLC, but it is open as to whether this will be accurate enough.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  3. #3
    Join Date
    Jul 2007
    Posts
    1602

    Re: Hydraulic Linear Actuator

    Does it really need to be re-engineered or just retrofitted? The current concept of operations as you describe it appears sound (as evidenced by the 17 years they got out of it so far). Perhaps the wisest approach would be to modernize what is there. You might be able to reduce the parts count some but what they have there is pretty hard to beat. If I understand it correctly there is no coupling between the servo part and the actual operation of the machine once the switch is positioned. If that is the case, then even if the servo blows up, they could still do a run of parts by manually positioning the switch. If you do something that ties the positioning with the operation of the press, then you potentially take that away from them.

    bob

  4. #4

    Re: Hydraulic Linear Actuator

    You make an excellent point Bob, thank you.

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