TL;DR
If the hold-down does not clamp, check for a faulty hold-down pressure solenoid, low hydraulic pressure, or worn pad contact surface. Verify solenoid valve function before adjusting pressure.
What you might see
- material moves during cut stroke
- hold-down alarm or warning on controller
- hold-down beam does not descend
- low or zero hold-down pressure reading
Likely causes
Hold-down pressure solenoid valve coil failed or valve spool stuck
Hydraulic pressure set below minimum hold-down threshold
Worn or hardened urethane hold-down pads losing contact area
Proximity sensor detecting missing hold-down beam descent not functioning
Required tools
- Multimeter for solenoid coil resistance and voltage check
- Hydraulic pressure gauge
- Replacement hold-down pads (urethane per OEM specification)
- LOTO kit
Safety first
- Lock out before reaching near the hold-down beam. The beam can drop suddenly on hydraulic restoration.
- Do not operate the shear with a defective hold-down. Material migration during a cut can cause blade damage and injury.
Procedure
- 1
Lock out and tag out the shear electrical and hydraulic power.
- 2
Locate the hold-down hydraulic solenoid valve and confirm it has power at the coil when the hold-down is commanded on.
- 3
With power restored and solenoid energized, listen for the valve click. A solenoid that energizes but produces no pressure change indicates a stuck spool.
- 4
Check the hold-down hydraulic circuit pressure at the gauge port. Compare to the minimum pressure specification in the service manual.[1]
- 5
Inspect the hold-down pads for compression set or tearing. Replace pads that are more than 30 percent compressed from their original height.
- 6
Check the hold-down descent proximity sensor for alignment. Re-align or replace if the target passes within 1 mm of the sensor face without triggering.[1]
- 7
After solenoid or pad replacement, run three test clamp cycles and verify the material is held securely against the back-stop.
Sources
Cincinnati Cincinnati CL Series Shear / Guillotine general technical documentation, Cincinnati
Cincinnati shear service documentation, hold-down hydraulic circuit and solenoid valve maintenance (general)
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