One-sentence answer: A pneumatic cylinder body consists of an extruded profile barrel and two end covers, with sealing maintained by the end cover O-rings and the piston dynamic seal. Internal leakage causes insufficient output force and sluggish action, while external leakage wastes air supply and generates noise. Using the CTS Sentinel A28 differential pressure leak detector to compare a master part against the part under test enables stable judgment on cylinder parts with high volume and low unit price, making it suitable for 100% inspection on the production line at pneumatic component manufacturers.
Cylinders are general-purpose pneumatic components with low unit value, so the testing solution must minimize fixture investment and cycle time per part while ensuring reliable judgment; otherwise the production line cost becomes unsustainable.
The aluminum profile drawing process may produce inner wall scratches, porosity and slag inclusions. After the barrel is cut, these defects are located at different positions, and whether the mating face with the end cover O-ring falls in a defect zone determines whether sealing is achieved.
The cylinder end cover is pressed tight by four tie rods. Uneven torque leaves the O-ring locally under-compressed. This assembly variation cannot be found by part inspection and can only be covered by testing the complete assembly.
The seal between the piston and barrel is a dynamic seal. Testing in the static state reflects the static sealing condition and is not equivalent to sealing performance during motion. The positioning of the test solution must be clearly defined.
Sealing locations:
Consequences of leakage: Internal leakage causes insufficient cylinder thrust, sluggish action and inaccurate positioning, affecting the repeat positioning accuracy of automated equipment. External leakage causes compressed air waste and increased workshop noise. Long-term leakage also causes grease loss and accelerated aging of seals.
Cylinder parts are a typical workpiece with small volume, high cycle rate and high volume. The solution must balance cost and judgment capability:
Both need to be tested, but the criteria differ. External leakage refers to gas leaking from the end cover or fittings to the atmosphere, affecting energy consumption and noise. Internal leakage refers to gas passing from one chamber to another, affecting output force and positioning. Use the A28 to create separate test programs and compile the two types of results separately, so that problems can be accurately fed back to the end cover assembly or piston sealing process.
Not entirely. Static testing reflects sealing performance in the stationary state. The performance of the dynamic seal during reciprocating motion is also affected by lubrication, speed and wear. A reasonable approach is to use the air tightness test as a factory interception method, and then cover dynamic conditions through durability and action tests, judging with both combined.
The cylinder chamber volume is small and the leakage amount is also small. In the low flow range, the flow method generally has lower reading resolution and repeatability than differential pressure comparison. The differential pressure method uses a master part as the reference and mainly measures the relative change between two workpieces, making it easier to obtain stable and comparable readings at low leakage levels.
For sealing tests on pneumatic cylinder bodies, the sealing condition of the end cover and piston must be quantified under the constraints of low cost and high cycle rate. The differential pressure comparison structure of the CTS Sentinel A28, combined with plugging fixtures changed according to bore diameter and 32 test programs, is suited to high-volume 100% inspection on mixed multi-specification lines at pneumatic component manufacturers.
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