TL;DR
Clamping faults are usually a hydraulic pressure shortfall, worn toggle pin, or position sensor misalignment. Verify hydraulic pressure at the clamp cylinder before adjusting the mechanical system.
What you might see
- clamp fault alarm on the machine controller
- mold does not fully close or seal
- flash leaks from parting line under pressure
- clamp force reading below setpoint
Likely causes
Hydraulic clamp cylinder pressure below the minimum clamping force setpoint
Worn toggle pin or bushing allowing mechanical play in the clamping system
Clamp position sensor misaligned or failed
Contaminated hydraulic fluid causing sluggish clamp valve response
Required tools
- Hydraulic pressure gauge
- Grease gun with toggle-pin-rated grease
- Proximity sensor alignment tools
- Hydraulic oil sample kit
- LOTO kit
Safety first
- Mold clamping forces can exceed several tons. Never place hands between platens without a full lockout.
- Do not override clamp pressure safeties to diagnose a clamping fault. Find the root cause mechanically or hydraulically.
Procedure
- 1
Initiate a manual clamp cycle and monitor the hydraulic pressure gauge at the clamp circuit during the closing stroke.
Warning: Do not place hands near the mold or platen during a clamp cycle. Clamping force is sufficient to cause crush injuries. - 2
Verify the clamp circuit pressure matches the setpoint value in the hydraulic circuit diagram.[1]
- 3
Lock out the machine before inspecting the toggle or platen mechanical system.
- 4
Inspect the toggle pins and bushings for wear, scoring, or seized lubrication points. Grease all toggle pins per the maintenance schedule.[1]
- 5
Inspect the clamp position sensor (typically a proximity switch or linear transducer) for correct alignment to the target.
- 6
Check the hydraulic oil sample for contamination or moisture. If the sample is milky or heavily contaminated, perform an oil change.
- 7
After repairs, perform 10 manual clamp cycles and verify the clamp force reading is consistent and above the minimum specification.
Sources
Bekum Bekum H-Series Blow Molding Machine general technical documentation, Bekum
Bekum H-Series blow molding machine hydraulic and mechanical maintenance documentation (general)
More guides for Bekum Bekum H-Series
How to fix blow pin seal leakage on a Bekum H-Series blow molding machine
Blow pin air leakage causes parts to blow poorly and increases cycle time. Inspect the blow pin O-ring seals and blow needle seal faces before adjusting blow air pressure.
How to fix parison thickness variation on a Bekum H-Series blow molding machine
Parison wall variation is usually an uneven die gap, worn die pin, or incorrect parison programming. Check die concentricity before adjusting parison programming.
Stop fixing the same fault twice.
Dovient turns guides like this into your team's shared playbook, with AI that catches recurring issues before they break the line.