RA, RC, RS, RV: how Colombo cools its spindles and why it matters

A high-frequency spindle motor turns a few kilowatts of electricity into cutting, and a good share of it into heat. Giordano Colombo builds four series around four ways of getting that heat out, and the letters in the model name tell you which one you have.

RV: a fan on the shaft

The simplest arrangement. A fan mounted on the motor shaft draws air through the housing whenever the spindle turns.

• Needs: clean air around the spindle and an unblocked inlet.
• Fails when: dust packs the fan and the fins, or the spindle runs slowly for long periods (less airflow at low rpm).
• In the catalogue: RV series.

RS: a powered fan

A separate electric fan (230 V or 24 V) blows air through the motor regardless of spindle speed, so cooling does not fall away at low rpm.

• Needs: a fan supply that is actually connected and running.
• Fails when: the fan motor dies or its supply is lost and nobody notices until the spindle is hot.
• In the catalogue: RS series.

RC: compressed air

Dry compressed air is piped through a cooling circuit in the housing. Flow and pressure depend on the spindle's size and power.

• Needs: dry, clean, regulated air at the specified flow. Water in the line is the enemy.
• Fails when: the air is turned off, throttled, or wet. Wet air corrodes from the inside.
• In the catalogue: RC series.

RA: liquid through a chiller

A water-and-glycol mix circulates through the housing from a chiller that holds it at a set temperature. The most stable thermally, and the most demanding to install.

• Needs: a chiller sized for the spindle, the right mix, clean lines and the correct flow.
• Fails when: the chiller loses capacity, the mix is wrong, or a line is kinked. A liquid-cooled spindle that runs warm is telling you about the chiller before it tells you about the bearings.
• In the catalogue: RA series.

Why it matters on the bench

When an RC or RA spindle arrives with cooked bearings, the first question is whether the cooling was doing its job. Rebuilding the spindle and returning it to the same dry chiller or wet air line solves nothing. Tell us how the spindle is cooled and how the supply is looking when you request a quote; it changes the advice.