How to Measure Volume Non-Destructively

Volume is the amount of space an object or substance occupies. The SI unit for volume is the cubic meter (m³), though in the United States, cubic inches, cubic feet, and gallons remain common depending on the application. Mathematically, volume is calculated by integrating over a shape in 3D space, but in practice, dedicated instruments are used to measure it directly.

Common applications include measuring irregularly shaped raw materials, inspecting food product dimensions, and determining engine cylinder capacity. Capacity refers specifically to how much a container can hold, with units varying by industry — gallons for fluid systems, cubic inches or liters for engine displacement, and cubic feet for bulk storage.

Volume meters range from traditional measuring containers, such as flasks, graduated cylinders, pipettes, and burettes, to advanced non-contact methods. These include acoustic volume meters, which measure volume using sound pressure, and laser volume meters, which use lasers to capture geometry without touching the part.

Buoyancy = weight of the displaced fluid

Archimedes' principle states that an object immersed in fluid displaces a volume of fluid equal to its own volume. In practice, this is measured using a graduated cylinder: submerge the object in liquid, record the change in liquid level, and that difference equals the object's volume.

The seed displacement method works on the same principle as Archimedes' method but uses seeds instead of liquid, making it suitable for items that cannot be submerged, such as bread or confectionery. Similar approaches include the bead displacement method, which uses small beads as a pseudo-fluid, and the sand displacement method.

Archimedes-based measurement is precise but wets the object. Seed displacement avoids this but can compress soft materials, producing inaccurate results. When either method falls short, a laser volumeter offers an effective alternative. By scanning an object with lasers to capture its distances and geometry, a laser volumeter enables fast, contact-free volume measurement.

Archimedes' method can yield precise volume measurements with minimal equipment, but the requirement for liquid immersion introduces several limitations. Objects become wet during measurement, ruling out porous materials such as sponges and raising hygiene concerns for food products. Accurate results also depend on careful control of conditions, including stable liquid temperature and the removal of air bubbles.

Laser volumeters offer several advantages: no contact means nothing gets wet or damaged, and they deliver fast 3D readouts that make volume and shape quantification straightforward. The key limitation is line-of-sight dependency, as the laser can only capture surfaces it can directly see, making large objects or geometrically complex shapes difficult to measure completely.

While each of the methods described above has its limitations, the KEYENCE VL Series 3D Scanner CMM addresses them through fully non-contact volume measurement. The VL Series performs a full 360° scan in minutes, capturing an object's complete 3D geometry with high accuracy. Volume is calculated directly from the scanned data, and because no contact is required, even complex or irregular shapes can be measured reliably.

Contact-based methods can deform soft samples during measurement, introducing errors that make accurate volume measurement unreliable or impossible. The KEYENCE VL Series 3D Scanner CMM eliminates this risk through non-contact optical scanning, capturing precise geometry without applying any force to the part.

Accurate cylinder capacity measurement is critical in engine applications, yet conventional methods often struggle to deliver the required precision. Where the cylinder bore is open and accessible, the KEYENCE VL Series captures full 3D geometry in a single scan, calculating cylinder capacity directly from the scanned data with high accuracy and significantly reducing inspection time.