EpicWill (Customer) asked a question.

August 16, 2023 at 4:08 PM
Help selecting components for a CMV assembly.

I'm planning a system that will run 4 actuators but at different pressures for each direction. The retract side will be line pressure but the extend side will be regulated for user control (regulator and pressure sensor under touch panel in below image). I'll also need to be able to shut these off completely in sets of two (2 actuators per unit) - see image below.

 

rolls 

I watched the CMV component selection video (https://www.automationdirect.com/videos/video?videoToPlay=BlLk_pCkeQs&cat1=59) but they go through everything kinda quickly. I know I want the CMV-CX-4X left end plate (line pressure inlet) and I know I'm going to need a CMV-D2X-3X intermediate plate for the second pressure bank (user-regulated pressure inlet).

 

I'm kinda lost after this as to exactly what I'll need to finish this setup. Both sides will need an exhaust so do I need a right end plate with an exhaust or do I use a CMV-D3X-3X in the second bank for an exhaust? I'll also need a 2-way basic on/off for each bank in case the main machine only uses a left or right assembly.

 

Control will be PLC via touch panel, left and right units will be able to be selected (on or off, units can be installed/removed from main machine) . So I need to be able to turn off the left or right unit if it's not installed on the machine (shutoff for both feeds to air cylinders). The line pressure will be to lift the pressure roll and the regulated extend pressure will be for roll down force.

  • 9 answers
  • 353 views

  • EpicWill (Customer)

    Upon thinking this through some more I don't know if the CMV system will be right for this given the flow pattern and the common-pressure inlet of the CMV system. It seems I might be better off using two standard 3-port valves and 4 standard 2-port valves.

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  • EpicWill (Customer)

    I've added an MS Paint diagram of the layout. Green line is line pressure. Blue line is regulated pressure. The 2-way valves will be wired in parallel so one will open and the other will close (one NO and one NC I would think). Same with the 4 shut off valves (all NC), wired in parallel 2 per side to shut off both line and regulated air so the sub assembly can be removed from the machine.

     

    rolls2

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  • EpicWill (Customer)

    Upon thinking this through some more I don't know if the CMV system will be right for this given the flow pattern and the common-pressure inlet of the CMV system. It seems I might be better off using two standard 3-port valves and 4 standard 2-port valves.

    Selected as Best

    • Todd Dice (Customer)

      Yup! Reading the first paragraph my immediate thought was separate valves. Good luck!

      • EpicWill (Customer)

        Talking with a coworker we decided to replace the double-acting cylinders with single-acting with spring returns. The springs are stiff enough to pull the roller back up so it's got a double benefit of less wiring and tubing as wella s it defaulting to the roll being in the up position on startup/shutdown of the machine.

      • PouchesInc (Customer)

        AutomationDirect doesnt sell them, but various other places that sell air cylinders you can get ones with an option of a piston lock on either the extend or retract side of the cylinder. These are nice for applications that have the cylinder facing downwards because when you turn off the air when the cylinder is retracted it will lock and stay in the retracted position.

         

        I prefer double acting with a rear lock in these applications because spring returns you cannot adjust how fast the cylinder retracts, only how fast it extends. A double acting cylinder you can use speed control valves to make it work more slowly or faster for both directions, depending on what you are trying to do.

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      • Todd Dice (Customer)

        You can place a flow control on a spring return cylinder and manage how fast it retracts. You just can't control "pneumatically" how fast it extends.

      • PouchesInc (Customer)

        "You can use a flow control valve on the exhaust side of a 3-port valve to control the retraction speed"

         

        Hmm. Never thought to try a speed control on an exhaust port. That doesnt cause issues with the valve itself and its switching?

      • EpicWill (Customer)

        I suppose if it's something that's rapidly switched back and forth it might cause problems. For our use case though the roll is either up or down and it stays there rather than being moved back and forth over and over.

 

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