Single Acting Cylinder
Why choose single-acting instead of double-acting?
When the machine only needs powered motion in one direction and wants simpler control, lower cost, and a default return position during air loss or power loss.
What determines clamp force?
Bore size and operating pressure primarily determine force; return springs reduce net output on the working stroke.
What is the main shop-floor failure mode?
Incomplete return or insufficient clamp force, usually caused by spring weakness, low pressure, contamination, or poor sizing.
A single-acting cylinder is a linear actuator that uses fluid pressure or compressed air in one direction only; return stroke is produced by a spring, gravity, or an external load rather than by pressure on the opposite side of the piston. In CNC machining and millwork automation, this design offers simple one-way force with a default return, making it ideal for clamps, ejectors, and stops. It features one active port for the working stroke and vents the opposite side, reducing complexity and cost.
On the shop floor, single-acting cylinders are valued for their simplicity. With only one active port for the working stroke, the return relies on a spring, gravity, or external load. This makes them ideal for CNC workholding clamps, part ejectors, tool-change assists, door latches, and positioning stops. In a typical CNC cell, a clamp cylinder is sized by bore (Ø25–50 mm), stroke (5–40 mm), and supply pressure (1–35 MPa), reflecting the compact, short-stroke nature of clamping. Proper venting is critical—blocked exhaust or contamination around the rod can cause slow return or incomplete reset, especially in repetitive CNC cycles. The cylinder components—body, piston, rod, grooves, seal boxes, threads—are CNC-machined to tight tolerances to ensure sealing integrity and straightness, directly impacting leakage, stiction, and repeatability. Similarly, in millwork automation, single-acting cylinders power simple pressing, stop gates, hold-downs, and ejectors where one-way force and a mechanical reset are sufficient. The design is favored for being simpler and cheaper than double-acting alternatives, and it provides a default return position during power loss, enhancing safety.
Slow or Stalling Return: An undersized spring or gravity return cannot overcome seal drag, hose friction, or misalignment, causing the rod to stall or return slowly, risking incomplete clamp release.
Wrong Force Calculation: Effective clamp force is limited by bore area, supply pressure, and spring load. If undersized, the clamp cannot hold the workpiece against cutting forces, leading to part shift or vibration.
Poor Venting or Contamination: Blocked exhaust ports or dirty seals prevent the return side from venting freely in pneumatic cylinders, causing slow return, stick-slip motion, or incomplete reset during repetitive cycles.