A double-acting cylinder has a full piston area on one side and a smaller annular area on the rod side. That difference affects speed, force and the flow that must pass through the return circuit.
Calculate both effective areas
The cap-end area is based on the bore diameter. The rod-end area subtracts the rod's cross-sectional area. Keep units consistent and use drawing dimensions rather than an approximate external measurement of the cylinder barrel.
Trace flow during retraction
When pump flow enters the smaller rod-end area, the piston can move faster than it would with that flow entering the cap end. The larger cap end then discharges more flow than the pump supplies. Return valves and filters must accommodate the resulting flow.
Include backpressure in the force balance
Pressure acting on the opposite chamber reduces available net force and can create unexpectedly high chamber pressures in some circuit arrangements. Review load-holding valves, meter-out controls and pressure intensification with the machine designer, particularly when the rod is large relative to the bore.
Practical checklist
- Calculate cap-end and rod-end flow for each speed.
- Check peak return capacity across the full stroke.
- Include both chamber pressures in force calculations.
Discuss your application
Explore related hydraulic products, or send JIUDING your model code and application details. Include the circuit drawing and the operating conditions relevant to the checks above so the required configuration can be reviewed.
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