BIZOMAT MAKEOS · Pneumatics
Pneumatic Cylinder Swept Volume
What volume does a double-acting cylinder sweep in one complete cycle?
Calculate the geometric volume a double-acting cylinder sweeps on its extend and retract strokes.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Bore diameter | mm | Cylinder bore diameter. |
| Rod diameter | mm | Piston rod diameter; must be smaller than the bore. Enter 0 to see the full-bore volume on both strokes. |
| Stroke | mm | Working stroke length. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Bore diameter
- What it is
- The inside diameter of the cylinder barrel, which equals the piston diameter. It sets the full-bore area that air acts on during the extend stroke.
- Units and format
- Enter a number in mm: millimetres. The form accepts 1 mm to 1000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 50 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Volume rises with the square of bore, so a small change in bore has a large effect.
- Get it right
- Use the catalogue bore size, not the outside diameter of the barrel or profile.
What this means: Rod diameter
- What it is
- The diameter of the piston rod. On the retract stroke the rod takes up part of the cylinder, so air only fills the ring-shaped annulus around it.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0 mm to 1000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 20 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A larger rod reduces only the retract-stroke volume.
- Get it right
- The rod must be smaller than the bore. Enter 0 for a full-bore volume on both strokes.
What this means: Stroke
- What it is
- The distance the piston travels from fully retracted to fully extended in normal operation.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.1 mm to 10000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 200 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- All three volumes are directly proportional to stroke.
- Get it right
- Use the stroke actually used; if end stops or sensors limit travel, it can be shorter than the catalogue stroke.
Method and formulas
- Extend volume = π × bore² / 4 × stroke; retract volume = π × (bore² − rod²) / 4 × stroke.
- Complete cycle = extend + retract, converted from mm³ to litres by dividing by 10⁶.
- Example: 50 mm bore, 20 mm rod and 200 mm stroke give 0.392699 L + 0.329867 L = 0.722566 L per cycle.
Limitations
- Geometric volume at cylinder conditions only. It is not free-air consumption: use the Pneumatic Cylinder Air Demand tool for pressure and temperature conversion.
- Dead volume at the stroke ends, tubing and valve volume, and leakage are excluded.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Find the volume to fill per cycle
- Compare bore and rod sizes
- Prepare an air or oil consumption estimate
Who it is for
- Design engineers
- Maintenance engineers
What you get
- Swept volume per complete cycle (L)
- Extend and retract stroke volumes (L)
Interpreting the result
- Multiply by cycles per minute to get a volume flow at cylinder pressure, then convert to free air for compressor sizing.
References
- Festo: Air consumption of cylinders — https://www.festo.com/ca/en/s/air-consumption
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed CD pp. 3027–3036. Topic reference; no source tables or recommended settings are reproduced.
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