Polar 76 EM - Knife is slow to engage after running for a while

Discussion in 'Cutters and Trimmers' started by Devo9er, Jun 15, 2022.

  1. Devo9er

    Devo9er New Member

    Joined:
    Mar 2015
    Messages:
    4
    Location:
    Michigan, United States
    After 30min or so of cutting the knife starts delaying to cut. The clamp bar comes down normally but then it hangs for a few seconds before it cuts. From here it continually just gets worse and worse until it won't trigger the blade at all. Turning it off and letting it "cool" does the trick but can take an hour or so before you're back to good and proceed cutting at a normal rate. If you let it cool for 10-15 minutes you might get another 20-30 cuts or so before its unbearably slow again. This has been an issue for several years of us owning it but just recently it has gotten much worse.

    I've cleaned all the control boards, checked the hydraulic solenoids, topped up the gear box fluid...While the behavior seems like it might be heat related, I cannot find anything that seems warm. When pressing both buttons you can hear the clamp hydraulic pressure squeeze with full pressure. It sometimes takes 5-10 seconds for the knife clutch to then in engage. once it does it finishes the cut normally. The clamp delay knob is set to zero but perhaps this circuit is malfunctioning? causing it to indefinitely delay?

    Out of ideas here!
     
    Nouman Javed Hakim Kh likes this.
  2. CHOCK

    CHOCK Senior Member

    Joined:
    Dec 2016
    Messages:
    2,387
    Location:
    Managua,Nicaragua
    Hi sir:

    I believe the you must forget something:

    1) Replace the Hydraulic oil, by the recommended by Polar operator manual, and then here is the secrete: a( BLEEDING THE HYDRAULIC SYSTEM FROM AIR...!. Since this model POLAR 76 EM, only the Clamp work with hydraulic system.

    2) His machine must be Safety bolt, and you must LUBE it, with Graphite, and adjust the limit switch in the S. Bolt or test the sensor, is out of distance, or loose cables, or defective.

    3) The electronic board 7sb, for control Safety bolt, must be test with the small relais, for dirty, or Cold+dry solder joint colder...Reheating ...!

    4) Test the cut button, s28a+s28b, FOR loose wires, or out of ajustment, or defective !

    Good luck.
     
  3. oabrahim

    oabrahim Member

    Joined:
    Apr 2016
    Messages:
    33
    Location:
    Venezuela
    Hello

    ...Since this model POLAR 76 EM, only the Clamp work with hydraulic system....

    so the trouble must be caused in addition for the malfunction of the clutch system.

    Carbon brushes worn or misaligned, dirty or worn cooper slider rings, exhausted clutch coil, bad voltage for this coil... the clutch gap.

    try some of these tips

    good luck...!
     
  4. CHOCK

    CHOCK Senior Member

    Joined:
    Dec 2016
    Messages:
    2,387
    Location:
    Managua,Nicaragua
    Please test the Electromagnetic Clutch for +42Vdc, and test the brush as like say my colleague.

    See if the winding for clutch can be Reheating, ( NOT burning) but the Varnish inside can be defective, to due the cicle operation of the machine, review ball bearing, and Gap of clutch.
     
  5. Mehanka Abortmaher

    Mehanka Abortmaher Senior Member

    Joined:
    Apr 2022
    Messages:
    106
    Location:
    Russia
    Replace the gearbox drive belts, check the gap between the brake disc and the friction linings, a large gap can be eliminated with sheet metal pads. We also encountered the problem of knife drive belts, they are worn out on the side surfaces and slip when heated (20-30 cuts), pulling them does not work. Yes, these were genuine ContiTech belts with no cracks or other visible defects.
     

  6. CHOCK

    CHOCK Senior Member

    Joined:
    Dec 2016
    Messages:
    2,387
    Location:
    Managua,Nicaragua
    Did you fix it Sir?

    Let me know, sincerely
     
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