Core Summary
A hydraulic press with a stroke of 2200 mm originally equipped with a rod-type hydraulic cylinder experienced end vibration and creeping during the pressure maintaining phase, affecting the consistency of the pressed parts. During the modification, a Conforti HD/HK wafer-type hydraulic cylinder was adopted, and the installation interface and connection dimensions were verified against the original equipment. The vibration disappeared, and the production cycle returned to normal. This case illustrates the importance of considering structural rigidity when selecting a hydraulic cylinder for long-stroke applications.
I. On-site Issues
End Vibration during Pressure Maintaining Phase
The press was used for medium and thick plate forming with a stroke of approximately 2200 mm. After operating for a period of time, it was discovered that visible vibration occurred at the end of the cylinder during the pressure maintaining phase, leading to increased thickness fluctuations in the pressed parts and an increase in scrap rates. Maintenance personnel first replaced the hydraulic oil and seals, but the vibration did not significantly improve.
Creeping and Position Drift
Creeping was also observed during the low-speed return phase, and the position repeatability decreased. The preliminary on-site diagnosis suggested that the problem lay with the cylinder itself, rather than the control system, as the same control program performed normally on short-stroke equipment.
II. Cause Analysis
Rod Stretching under Long Stroke Conditions
The original cylinder was of a rod-type structure, with four rods subjected to stretching during high-pressure pressure maintaining. After the stroke exceeded two meters, the cumulative elastic elongation of the rods reached a perceptible level, reducing the rigidity between the cylinder barrel and the end cap, causing micro-motions at the pressure maintaining instant, manifested as vibration and creeping.
Standard and Pressure Margin
The original cylinder was designed according to ISO 6020/2, with a working pressure of 160 bar, and the body strength was sufficient. However, the structural form did not match the long stroke conditions. The problem was not "insufficient pressure", but rather "incorrect structural selection for long stroke conditions".
III. Renovation Plan
Switch to Wafer Flanged Cylinders
Select the Conforti HD/HK series wafer flange hydraulic cylinders, remove the tie rods, and use the flange on the outside of the cylinder barrel for direct clamping. This provides better rigidity for long strokes, with a working pressure of 210 bar, leaving a wider pressure margin than the original 160 bar.
Prioritize Interface Verification
Before the renovation, send the original cylinder's installation flange drawings and connecting threads to the supplier for verification, ensuring that the installation dimensions of HD/HK can be reused, thus avoiding additional downtime for machining and hole modification. This step is more critical than model selection, determining whether direct replacement is possible.
IV. Renovation Effect
Elimination of Jitter and Creeping
After replacing the cylinder, jitter at the end of the pressure maintaining section no longer occurs, and creeping during return stroke is eliminated. The thickness fluctuation of the pressed parts returns to an acceptable range, and the scrap rate decreases. The equipment resumes stable production under the original control program without modifying the electronic control part.
Easier Maintenance
The wafer flange structure is also convenient for disassembly and assembly. If seals need to be replaced in the future, it can be done with on-site tools, without increasing maintenance burden.
V. Reusable Experience
For long strokes (over 2000 mm), prioritize evaluating wafer flange types rather than tie rod types
If jitter and creeping increase with longer strokes, it is mostly due to structural rigidity rather than control system issues
Before renovation, be sure to verify the original installation interface. Only if direct replacement is possible can we talk about "minimizing downtime"
Leave the pressure margin based on peak values rather than common values, ensuring a more stable pressure maintaining section
> This case is based on the practice of Conforti HD/HK flange hydraulic cylinders. Specific renovations should be based on on-site working conditions and original factory data. QN TECHNOLOGY can assist in verifying installation interfaces and model selection.
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