A Customer Case on cushioning adjustment, oil leakage and the correct procedure for setting the adjustment screw
Hydraulic-cylinder cushioning is designed to control the piston as it approaches the end of its stroke, reducing impact and protecting the cylinder from repeated high-energy shocks.
However, an incorrectly adjusted cushioning system can create serious problems.
A Customer reported oil leakage caused by a broken cushioning seal. The problem had been found on three out of four cushioning units.
The Vega Team investigated the situation and identified a recurring cause found in other similar cases: incorrect adjustment of the cushioning screw.
This Customer Case provides an important lesson for anyone working with hydraulic cylinders equipped with adjustable end-of-stroke cushioning:
The adjustment procedure is part of the correct operation of the cylinder.
Incorrectly loosening the wrong nut can damage the adjustment system and lead to oil leakage.
1. What Is Hydraulic Cylinder Cushioning?
When a hydraulic cylinder moves at high speed, the piston has considerable kinetic energy when it approaches the end of its stroke.
Without suitable cushioning, the piston can reach the cylinder head or end cover with a significant impact.
The result can be:
- mechanical shock;
- vibration;
- increased stress on the cylinder;
- premature wear;
- reduced service life;
- damage to internal components.
Vega developed an adjustable hydraulic cushioning system specifically for applications where high cylinder speeds are required.
The official Vega cushioning technology is designed to absorb kinetic energy by trapping oil in a virtually closed volume near the end of the stroke and forcing it through a restricted passage. (vegacylinders.com)
2. Why Cushioning Becomes Important at High Speed
High-speed mold applications can impose particularly severe loads on hydraulic cylinders.
Vega explains that speeds above approximately 0.1 m/s can become damaging to a piston if the cylinder does not have an appropriate cushioning system. (vegacylinders.com)
The problem is not simply the speed itself.
The critical factor is the kinetic energy that must be dissipated when the piston approaches the end of its stroke.
The cushioning system therefore acts as a controlled braking mechanism.
3. How the Cushioning System Absorbs Energy
Vega’s cushioning system uses a hydraulic principle.
As the piston approaches the end of the stroke, oil becomes trapped in a nearly closed volume.
The oil is then forced through a very narrow orifice.
This creates a pressure drop that absorbs the kinetic energy of the moving piston. (vegacylinders.com)
The principle can be summarized as:
High piston speed
↓
Oil flow through restricted passage
↓
Pressure drop
↓
Energy absorption
↓
Controlled deceleration
This allows the cylinder to reach the end of its stroke with a much lower impact.
4. Why the Adjustment Screw Is Important
The cushioning effect needs to be adjusted according to the actual application.
A cylinder operating at relatively low speed does not require the same cushioning adjustment as one operating at very high speed.
Vega therefore uses custom-made cushioning screws with a specifically designed cone angle, allowing the cushioning effect to be adjusted precisely. (vegacylinders.com)
The adjustment screw therefore controls the hydraulic restriction and consequently the braking effect.
It is not simply a mechanical stop.
5. The Customer Reported Broken Cushioning Seals
In the Customer Case, the Customer sent a photograph showing a cushioning component with a broken seal causing oil leakage.
The same problem had been discovered on three of four cushioning units.
The Customer consequently asked whether Vega could provide replacement seals or complete replacement sets and whether the problem could have been caused by a manufacturing error or by incorrect operation.
The Customer also questioned whether there was a pressure limit that could explain the failure.
The subsequent technical analysis pointed in a different direction.
6. The Cause Was Related to Incorrect Adjustment
The Vega Team explained that it had already encountered two or three similar cases in which customers had incorrectly adjusted the cushioning screws.
The specific mistake was:
loosening the large nut instead of the smaller adjustment nut.
This is a very important distinction.
A cushioning adjustment system can contain more than one locking or adjustment element.
The operator must therefore understand exactly which component is intended to be loosened before making an adjustment.
7. The Correct Adjustment Procedure
The Vega Team gave a very specific procedure.
For correct operation:
Step 1
Loosen the small nut.
Step 2
Adjust the cushioning screw using a screwdriver.
Step 3
Lock the small nut again.
This procedure is simple, but following the correct sequence is essential.
The important point is that the small nut is the adjustment-locking element.
The large nut should not be loosened as part of the normal adjustment procedure described in this Customer Case.
8. Why Loosening the Wrong Nut Can Cause Problems
The technical documentation contained in the Customer Case does not provide a detailed failure-analysis calculation showing the exact mechanical sequence that caused each broken seal.
Therefore, it would be incorrect to claim more than the source supports.
What the Vega Team does establish is that similar cases had occurred and that the customers had made the same incorrect adjustment: loosening the large nut rather than the small one.
This makes correct adjustment procedure a key preventive measure.
9. Cushioning Must Be Adjusted, Not Simply Fully Opened or Closed
The purpose of an adjustable cushioning system is to find the correct balance between:
sufficient braking
and
acceptable cycle performance.
If the cushioning effect is too weak, the piston can approach the end of the stroke too aggressively.
If the restriction is too strong, the cylinder may decelerate too early or too severely, potentially affecting the required cycle time.
Vega’s system is specifically designed to allow fine adjustment of the cushioning effect. (vegacylinders.com)
10. The Cushioning Screw Is a Precision Adjustment Component
The Vega system uses a specifically shaped cone on the cushioning screw.
This allows the hydraulic restriction to change progressively as the screw is adjusted. (vegacylinders.com)
This is why the adjustment should be performed carefully.
A small change in screw position can influence the available flow passage and therefore the cushioning behaviour.
The adjustment should therefore be made progressively rather than through uncontrolled movement of the locking components.
11. The Safety Nut Has an Important Function
Vega’s official documentation also explains that its cushioning screw cannot simply be loosened indefinitely.
A safety nut prevents excessive opening beyond the permitted safety limit. (vegacylinders.com)
This is an important design feature.
It means that the cushioning adjustment system incorporates a mechanical safeguard against excessive opening of the screw.
Nevertheless, the correct adjustment procedure must still be followed.
A safety feature should not be considered a substitute for correct operation.
12. Why the Cushioning System Also Needs to Allow Fast Reverse Movement
A hydraulic cylinder normally has to operate in both directions.
The cushioning system therefore cannot simply create a permanent restriction.
Vega explains that its bushing closes the oil passage when cushioning is required, while allowing oil to flow in the opposite direction when the cylinder starts its return movement. (vegacylinders.com)
This allows the system to combine:
controlled deceleration
with:
rapid restart in the opposite direction.
This is particularly valuable in high-cycle mold applications.
13. Cushioning Is Not Only About Comfort
It might be tempting to think of cushioning as a feature that simply makes the cylinder movement smoother.
In high-speed industrial applications, it is much more important than that.
Cushioning protects the cylinder from repeated high-energy impacts.
Without effective cushioning, the piston can repeatedly strike the end of the cylinder.
Over thousands or millions of cycles, these impacts can contribute to premature wear and failure.
Vega developed its cushioning technology specifically to address high-speed applications. (vegacylinders.com)
14. The Problem Was Found on Multiple Cylinders
One particularly significant detail in the Customer Case is that the problem was not found on just one unit.
The Customer reported the broken cushioning seal on three out of four cushioning units.
When the same type of problem occurs on several cylinders within the same application, it is reasonable to investigate common operating or adjustment conditions rather than immediately assuming that every component has experienced an independent manufacturing defect.
In this case, the Vega Team’s experience with similar cases led it to focus on incorrect adjustment.
15. Why Repeated Failure Is an Important Diagnostic Signal
Suppose one cushioning seal fails.
Possible causes might include:
- component damage;
- contamination;
- installation issue;
- excessive load;
- incorrect adjustment;
- another local problem.
But if several identical units show a similar failure, the investigation should also consider common operating conditions.
For this Customer Case, the common factor identified by the Vega Team was incorrect adjustment of the cushioning screws.
16. Is There a Pressure Limit?
The Customer specifically asked whether there was a pressure limit that could explain the failure.
The available correspondence does not provide a numerical pressure limit for the specific cushioning component.
Therefore, the correct conclusion from this case is not that pressure played no role.
Rather:
The available technical correspondence identifies incorrect adjustment as the suspected recurring cause, but it does not provide a specific numerical pressure limit or a complete failure-analysis report.
This distinction is important when converting a Customer Case into technical content.
17. Correct Adjustment Is a Preventive-Maintenance Activity
The adjustment procedure should be treated as part of normal cylinder maintenance.
A suitable maintenance procedure should ensure that operators know:
- which nut must be loosened;
- which component must be adjusted;
- which tool should be used;
- which component must be locked again;
- how to recognize abnormal cushioning behaviour.
In the Customer Case, the Vega Team explicitly instructed the Customer to loosen the small nut, adjust the screw with a screwdriver, and then lock the small nut again.
18. Training Operators Can Prevent Repeated Failures
The technical solution is not necessarily a more expensive component.
Sometimes the most effective improvement is simply ensuring that the adjustment procedure is understood.
This is particularly important when cylinders are installed on molds that may be serviced by different technicians over their lifetime.
A short maintenance instruction can prevent:
- incorrect adjustment;
- unnecessary seal replacement;
- production downtime;
- repeated troubleshooting.
19. Vega Also Offered Replacement Adjustment Screws
Although the technical investigation identified incorrect adjustment as the likely recurring cause, Vega still offered practical support.
The Vega Team offered to ship three complete adjustment screws free of charge, with the Customer paying only the transportation cost. These were intended for the affected cylinder configuration.
This is a useful example of how technical support can combine:
root-cause identification
with:
practical spare-parts support.
20. The Correct Response to a Cushioning Failure
When oil leakage is observed around a cushioning system, the first step should not automatically be replacing every seal.
A structured investigation should include:
1. Inspect the leakage
Determine where the oil is escaping.
2. Inspect the cushioning components
Look for visible damage.
3. Check the adjustment
Verify whether the adjustment procedure was followed correctly.
4. Check operating conditions
Review pressure, speed and cycle conditions.
5. Check all similar cylinders
If multiple units have the same problem, look for a common cause.
6. Replace damaged components
Use the correct spare parts and follow the correct assembly procedure.
21. Why the Adjustment Procedure Should Be Documented
A cylinder with adjustable cushioning should ideally be accompanied by clear instructions explaining:
- the adjustment point;
- the locking nut;
- the adjustment direction;
- the safe adjustment range;
- the correct tool.
This reduces the possibility of an operator confusing the adjustment nut with another mechanical component.
The Customer Case demonstrates exactly why this matters.
22. Cushioning Technology for High-Speed Mold Applications
Vega’s cushioning technology is designed specifically for demanding applications where high piston speeds are required.
The company states that the cushioning system is available not only on ISO 6020/2 tie-rod cylinders, but also on selected compact cylinders such as the V500CZ, allowing speeds of up to approximately 1 m/s. (vegacylinders.com)
The V500CZ product page also describes the cylinder as a high-speed hydraulic cylinder and states a maximum piston speed of approximately 1 m/s. (vegacylinders.com)
This makes correct cushioning adjustment particularly important in high-speed applications.
23. Cushioning and Cylinder Life
The relationship can be summarized as:
Higher speed
→ higher kinetic energy
→ greater impact risk
→ greater importance of cushioning
→ greater importance of correct adjustment
The cushioning system is therefore part of the cylinder’s overall reliability strategy.
It is not simply an accessory added for smoother movement.
24. A Practical Checklist for Technicians
Before adjusting a hydraulic cylinder with adjustable cushioning, verify:
Mechanical adjustment
- Identify the correct adjustment nut.
- Do not loosen the wrong locking component.
- Use the appropriate screwdriver or adjustment tool.
- Make small adjustments.
- Lock the adjustment nut again.
Hydraulic operation
- Verify operating pressure.
- Verify piston speed.
- Check for abnormal impact.
- Check for oil leakage.
Maintenance
- Inspect the cushioning seal.
- Inspect the adjustment screw.
- Check for visible damage.
- Replace damaged components where necessary.
25. What This Customer Case Teaches
The most important lesson is not simply that a seal can fail.
It is that a hydraulic cushioning system is a precision adjustment mechanism and must be operated correctly.
In this case, the Customer discovered broken cushioning seals and oil leakage on three of four units.
The Vega Team recognized that similar cases had previously been caused by customers loosening the large nut instead of the smaller adjustment nut.
The correct procedure was clearly defined:
Loosen the small nut → adjust the screw with a screwdriver → lock the small nut again.
This simple procedure can make the difference between correct cushioning operation and damage to the adjustment/sealing system.
Conclusion
Hydraulic-cylinder cushioning plays a critical role in high-speed applications, particularly in injection molds where cylinders can perform thousands of cycles under demanding conditions.
The Customer Case examined here involved oil leakage caused by a broken cushioning seal, discovered on three out of four cushioning units.
The Vega Team’s experience with similar cases identified a recurring issue: incorrect adjustment of the cushioning screw caused by loosening the large nut instead of the smaller adjustment nut.
The correct adjustment procedure is straightforward:
- Loosen the small nut.
- Adjust the cushioning screw with a screwdriver.
- Lock the small nut again.
Vega’s cushioning system is designed to absorb piston kinetic energy by restricting oil flow near the end of the stroke. Its adjustable screw allows precise control of the cushioning effect, while a safety nut limits excessive opening. (vegacylinders.com)
The broader engineering lesson is clear:
Correct cushioning adjustment is an essential part of hydraulic-cylinder maintenance and should be treated as a technical procedure, not as a simple mechanical adjustment.
When oil leakage or cushioning failure occurs, the correct approach is to inspect the adjustment, operating conditions and affected components before assuming that the cylinder itself has a manufacturing defect.
Useful and Verified URLs
I verified these links on the official vegacylinders.com domain. The descriptions are in English, matching the article.
- Hydraulic Cylinders with Cushioning — Official Vega technology page explaining how the cushioning system absorbs piston kinetic energy, how the adjustment screw works, the safety mechanism and the reverse-flow principle.
Hydraulic Cylinders with Cushioning - V500CZ Long-Stroke Compact Hydraulic Cylinders — Official Vega product page for the V500CZ high-speed compact cylinder, including its cushioning technology, maximum piston speed and applications in injection molds.
V500CZ Long-Stroke Compact Hydraulic Cylinders - V215CR Tie-Rod Hydraulic Cylinders ISO 6020/2 — Official Vega product page for the V215CR tie-rod cylinder series, including its applications and the availability of cushioning technology.
V215CR Tie-Rod Hydraulic Cylinders ISO 6020/2 - Hydraulic Cylinder Technologies — Official Vega technology overview listing Cushioning together with SpeedPorts, Self-Locking, Integrated Cooling and Materials & Components.
Hydraulic Cylinder Technologies - Cart and Plug Movement — Official Vega application page covering hydraulic cylinders used to move carts, pins and plugs that create undercuts in plastic injection molds, including cylinder families available with cushioning.
Cart and Plug Movement
