Canadian Construction Equipment Shows Repeated End-of-Stroke Hydraulic Shock Despite Normal Cylinder Speed and System Pressure as Cushion-Valve Function Is Investigated

Case Background

Construction equipment operating in Canada developed a strong hydraulic impact each time one cylinder approached the end of its stroke.

Through the middle of the stroke, cylinder speed was normal and main hydraulic pressure behaved as expected.

The problem occurred only during the final part of extension or retraction.

Because overall cylinder performance remained acceptable, technicians investigated the internal cushioning system designed to slow the piston before it reaches the end cap.

Cylinder Cushioning Is a Separate Operating Phase

A hydraulic cylinder can be divided conceptually into two stages:

Main Stroke

Oil enters one chamber and exits the other with relatively unrestricted flow.

End-of-Stroke Cushion

As the piston approaches the end, a cushion spear, sleeve or other feature can restrict outgoing oil.

The sequence becomes:

Piston approaches end → Cushion feature engages → Outlet flow is metered → Piston decelerates → Mechanical impact is reduced

If cushioning fails, normal-speed movement continues too close to the physical stop.

Why System Pressure and Mid-Stroke Speed Were Normal

The main hydraulic circuit was able to supply and control the cylinder.

The fault existed only in the final deceleration mechanism.

This produced the pattern:

full-speed movement normal

but

end-of-stroke transition abnormal.

Possible causes include:

• damaged cushion spear;
• blocked or oversized metering passage;
• misadjusted cushion needle where adjustable;
• worn internal components;
• or incorrect cylinder assembly.

Canadian Repetitive Cycling Made the Impact Easy to Observe

Boom, attachment or industrial cylinder applications may cycle repeatedly throughout a shift.

If every stroke ends with a sharp impact, the effect becomes:

• mechanically noticeable;
• stressful to pins and mounts;
• and potentially damaging to cylinder end components.

This makes the timing of the shock more informative than general hydraulic pressure.

The Investigation Focused on the Final Stroke Section

Technicians reviewed:

• piston position near stroke end;
• cushion mechanism;
• metering passages;
• adjustment where applicable;
• cylinder assembly history;
• and oil condition.

Operator technique was also considered because deliberately driving the cylinder aggressively into its stop can create impact even with a functional cushion.

Difference From Cylinder Internal Leakage

Internal bypass causes loss of load-holding capability or slow drift.

Cushion failure allows the cylinder to work normally until it reaches the end of travel, where deceleration is inadequate.

The symptom timing is therefore fundamentally different.

Why Main Control-Valve Replacement Would Not Help

The control valve can provide correct flow throughout the stroke while the cylinder’s internal cushion fails to meter the final exhaust flow.

The fault lies inside the actuator.

Technical Lesson

Hydraulic-cylinder diagnosis should analyze not just whether the cylinder moves, but how its motion changes as it reaches the end of travel.

Normal mid-stroke operation does not prove that cushioning is functioning.

FAQ

Can a cylinder have normal speed but still have a failed cushion?

Yes. Cushioning operates mainly near the end of the stroke.

Does high end-of-stroke shock automatically mean the operator is moving too fast?

No. Operator input is one factor, but internal cushion faults should also be considered.