The Oil Cup on Your Unclamping Booster: A Window Into the Health of the Whole System

The transparent oil cup on a BPF/BPFQ unclamping booster is more than a place to top up oil. Because it connects directly to the oil chamber, it reflects the condition of the entire unclamping circuit. Learn to read it, and you can catch small issues early and keep tool changes consistent.

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1. What the oil cup does

The booster's oil chamber and the spindle's hydraulic unclamping cylinder form a closed circuit: the same oil moves back and forth between them and does not need a continuous supply. The oil cup only makes up for the very small losses at the seals over long operation, and for volume changes caused by temperature.

The bottom of the cup connects straight to the oil chamber, with no check valve in between. Any air in the circuit rises into the cup, and the oil level is always visible. That is what makes the cup a health window. On models with a level sensor (M type), a signal goes to the machine controller when the level reaches the low mark.

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2. What is normal

• Bubbles during first filling or bleeding: air is leaving the cylinder and hoses. Keep cycling manually until the bubbles stop, then top up to the upper red line.
• Oil gradually turning dark: this is pigment from friction between the aluminium body and graphite-filled O-rings. It does not affect function; change the oil if you prefer. If oil darkens very quickly on a new installation, check the high-pressure hose for cutting debris (blow it out with air before assembly).

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3. If you see these, check here first

• Oil spraying from the cup at the moment of unclamping: usually the spindle air blow is starting at the same time as unclamping. Delay the air blow until about 0.1 s after unclamping is complete.
• Continuous bubbling when idle, or the float pushed to the top: air is entering the oil circuit. First check and tighten the high-pressure hose fittings, since a loose fitting can draw in air. If a synchronised return air line runs from the booster to the unclamping cylinder, disconnect it temporarily, fold and secure it, and cycle the booster on its own a few times. If the bubbling stops, check the hydraulic unclamping cylinder at the spindle; if it continues, contact HINAKA technical support for help.
• Oil level dropping faster than usual: look for oil traces at fittings and along the hoses.

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4. Just two routine checks

1. Check the level once a week: top up to the upper red line before it reaches the low mark, using ISO VG32 (CPC-R32) or equivalent hydraulic oil. Do not overfill.
2. Refill within 7 days after a low-level alarm: 7 days is the factory setting; check whether the machine builder has changed it.

If you are unsure what you are seeing, contact HINAKA technical support through Contact Us.

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