The pneumatic cylinder, rod seal and end cushion are part of the production sequence, and their condition can contribute to air leakage, slow travel, position drift or hard impact at the end of stroke.
Final limits, parts and adjustments remain configuration-specific; use the supplied pneumatic drawing, cylinder data and machine service procedure instead of applying a universal value.
Define the failure before touching the setup
Record cylinder tag, bore and stroke designation, valve output, mounting orientation and the mechanism moved by the rod. Mark when the concern appears during cold start, stable production, manual jog and stopped dwell. Include the operator observation, machine state, material or job identity and the last known acceptable production period. This prevents several different faults from being grouped under one general alarm or quality description.
Use an evidence table to narrow the cause
| Observed condition | Evidence to collect | Diagnostic direction |
|---|---|---|
| Hissing at the rod end | Sound location, soap-test result where approved, rod surface photo | Rod seal, rod damage or side loading |
| Cylinder creeps while commanded to hold | Valve state, load direction, port pressure and travel mark | Internal piston leakage or valve leakage |
| End impact becomes louder | Stroke time, cushion setting marks and exhaust condition | Cushion bypass, blocked restriction or excessive speed |
| Motion slows after warm-up | Repeated cycle times, pressure at the actuator and seal temperature | Friction, air supply loss or seal condition |
| One direction is slower | Extend and retract timing with the same machine state | Flow control, port restriction or unequal load |
The diagnostic directions are possibilities to investigate, not confirmed causes. Compare observations with the actual circuit, tooling and component documentation before replacing a part or changing a setting.
Control hazardous energy and preserve references
Apply the site lockout and isolation procedure for electrical, pneumatic, vacuum, thermal, gravity and stored mechanical energy that applies to this equipment. Verify the zero-energy state before guards, terminals, tubing, tooling or drive components are accessed. Hot surfaces and charged electrical parts may remain hazardous after the machine stops.
Photograph connectors, tube routing, witness marks, adjustment positions, wiring labels and component orientation before disassembly. Qualified personnel should perform live electrical or pressure measurements only when the approved diagnostic procedure specifically requires them and appropriate controls are in place.
Inspect the component in its complete load path
Compare cylinder behavior with valve spool response, flow-control orientation, tube condition, mechanical alignment and the moving load. A new seal will not correct a bent rod, misaligned clevis or contaminated valve.
Compare the affected component with the related solenoid valve response guide before deciding that one observation identifies the cause.
Verify the repair in stages
Before power or pressure is restored, confirm tools are removed, connections are secure, guards are reinstated and the work area is clear. Use the documented manual, jog or slow-cycle check first, then progress through small controlled production stages while watching the original symptom and any secondary effect.
Record extend and retract time, hold stability, end-stop sound, final position and leak observations across a small labeled production run. Do not release the machine based only on one acceptable cycle. Document the parts or settings changed, final observations, retained samples and the person authorized to return the equipment to production.
Does external silence prove that a cylinder is healthy?
No. Internal piston leakage can cause drift or weak force without an obvious external sound.
Should the cushion screw be fully closed to stop impact?
No. Use the delivered adjustment method; an excessive restriction can prevent full travel or create unstable timing.
Can a cylinder seal be selected only by bore size?
No. Seal profile, material, pressure, temperature, rod and cylinder design must match the supplied component.
What should be sent to the supplier?
Send the cylinder identity, videos of both directions, valve commands, pressure evidence, leak location, rod photos and recent service history.
Send the machine model, component identity, labeled samples, sequence video, measurements and service history through our inquiry page. HANNAI can review the evidence against the supplied machine configuration.