Cubic millimeter per minute (mm³/min)

The cubic millimetre per minute is a unit of volumetric flow rate equal to one cubic millimetre passing a point every minute. Its symbol is mm³/min. It measures flows so slight that a whole minute yields a volume the size of a coarse grain of salt, and it exists because a great deal of precision engineering happens at exactly that pace.

Electrical-discharge machining is the classic user. A wire eroder cutting hardened tool steel removes 20 to 100 cubic millimetres per minute, and a sinker eroder finishing a mould cavity may remove less than one. The rate is the whole economics of the process: a die that takes eight hours to cut cannot be quoted like one that takes eight minutes, and the removal rate is what separates them.

Grinding and honing are described the same way when the tolerance is tight. A creep-feed grinder roughing a turbine blade root runs at hundreds of cubic millimetres per minute per millimetre of wheel width, but a final spark-out pass approaches zero by design, because the last few micrometres must come off without heating the workpiece.

Adhesive and solder-paste dispensing lives here too. A dot of adhesive on a circuit board is a fraction of a cubic millimetre, and a dispensing valve laying a bead is programmed by rate so the bead stays the same width as the head speeds up and slows down around corners. Underfill, conformal coating and potting are all specified in this unit or its microlitre twin.

Biology and medicine borrow it for slow perfusion. Organ-on-a-chip devices, microdialysis probes and slow-release implants move fluid at single-digit cubic millimetres per minute, and cerebrospinal-fluid production in an adult is about 350 to 500 millilitres a day, which is roughly 250 to 350 cubic millimetres per minute — a useful reminder that the body itself works at this scale.

Sixty cubic millimetres per minute is one cubic millimetre per second, and a million is one litre. Put together, that means a flow of one cubic millimetre per minute would need almost two years to fill a one-litre bottle.

One cubic millimetre per minute equals 0.001 millilitres per minute, about 0.01667 cubic millimetres per second, or one microlitre per minute.

Cubic millimeter per minute conversion table