A Customer Case: Eight Hydraulic Cylinders, Two Cylinders Lagging Behind the Others
When several hydraulic cylinders operate together on the same mold mechanism, synchronization is essential.
If the cylinders are expected to move simultaneously but one or more begin to lag behind, the problem can originate from the hydraulic circuit, from differences in the mechanical behavior of apparently identical cylinders, or from damage to an internal sealing component.
A technical case analyzed by the Vega Team involved a Customer who had received eight hydraulic cylinders, of which two were no longer operating correctly. The Customer sent a video showing the problem and requested an urgent technical assessment.
After reviewing the video, the Vega Team identified the unbalanced oil circuit as the principal cause that could generate the problem. At the same time, Vega pointed out that synchronization problems can sometimes occur even when the hydraulic circuit is balanced, because manufacturing tolerances in the seals and guide-ring seats can result in slightly different interference between otherwise identical cylinders.
The analysis also did not exclude the possibility that the piston seal of the cylinder that was lagging behind could have been damaged. Vega therefore recommended disassembling the cylinder and inspecting both the piston seals and the internal surface of the cylinder body.
This case is an excellent example of why synchronization problems should be investigated systematically rather than immediately attributed to a defective cylinder.
1. The Customer’s Problem
The Customer had received:
8 hydraulic cylinders
and reported that:
2 cylinders were not working correctly.
Because the problem was affecting multiple cylinders within the same application, the Customer sent a video to Vega and requested technical comments and suggestions. The request was marked as urgent.
The key issue was therefore not simply whether one cylinder could generate sufficient force.
The problem was the different behavior of cylinders that were expected to operate together.
2. Why Synchronization Matters
When multiple hydraulic cylinders move the same mechanical component, their movements need to remain sufficiently synchronized.
Imagine several cylinders moving a common plate:
Cylinder 1 → movement
Cylinder 2 → movement
Cylinder 3 → movement
Cylinder 4 → movement
If one cylinder moves more slowly than the others, the plate can experience:
- uneven movement;
- mechanical stress;
- tilting;
- increased friction;
- incorrect positioning;
- abnormal loads on the cylinders.
The more rigidly the cylinders are mechanically connected, the more important synchronization becomes.
3. The First Suspect: An Unbalanced Oil Circuit
After reviewing the Customer’s video, the Vega Team identified the unbalanced oil circuit as the principal cause capable of generating the problem.
This is a fundamental hydraulic principle.
If several cylinders are connected to the same hydraulic system but do not receive exactly the same hydraulic flow, they may not move at the same speed.
A cylinder receiving more flow can move faster.
A cylinder receiving less flow can move more slowly.
The result can be:
Cylinder A → normal movement
Cylinder B → normal movement
Cylinder C → delayed movement
even though the cylinders themselves may be mechanically identical.
4. What Does an Unbalanced Hydraulic Circuit Mean?
In a multi-cylinder system, the hydraulic circuit must distribute oil appropriately between the different actuators.
If the flow distribution is not properly balanced, the cylinders may receive different quantities of oil.
This can occur because of differences in:
- hydraulic line length;
- internal diameter of the pipes;
- fittings;
- restrictions;
- valves;
- pressure losses;
- flow-control devices;
- circuit layout.
The result is that one cylinder may receive a different flow from another.
Since cylinder speed is related to flow, the movements can become unsynchronized.
5. Cylinder Speed Depends on Flow
The fundamental relationship is:
Q = A × v
where:
- Q = hydraulic flow;
- A = effective piston area;
- v = cylinder velocity.
Rearranging:
v = Q / A
Therefore, if two cylinders have approximately the same piston area but receive different flows, their speeds will differ.
For example:
Cylinder A → higher flow → higher speed
Cylinder B → lower flow → lower speed
The cylinders can therefore appear to be “different” even though they are nominally identical.
6. Why the Cylinders May Not Actually Be Defective
This is one of the most important lessons from the case.
The Customer reported that two cylinders were not working correctly.
It would therefore be natural to assume that the two cylinders were defective.
But the Vega Team did not immediately reach that conclusion.
Instead, it identified the hydraulic circuit as the principal potential cause.
This is the correct approach to troubleshooting.
A cylinder is part of a system.
Its behavior depends not only on the cylinder itself but also on:
- the hydraulic circuit;
- the pressure;
- the flow;
- the valves;
- the mechanical load.
7. The Interesting Point: Even a Balanced Circuit May Not Guarantee Perfect Synchronization
The Vega Team made an important additional observation.
Even if the hydraulic circuit is balanced, synchronization problems can sometimes still occur.
Why?
Because two cylinders that have the same nominal dimensions are still manufactured within specified tolerances.
The sealing system and guide components may not have exactly identical characteristics.
8. Manufacturing Tolerances Matter
The Vega Team specifically identified possible differences in the tolerances of the seals and guide-ring seats.
This is a subtle but important point.
Two cylinders can be:
- the same model;
- the same bore;
- the same stroke;
- manufactured according to the same drawing;
and still have slightly different mechanical resistance.
Small differences in interference between components can affect how easily the piston begins and maintains its movement.
9. Different Seal Interference Can Affect Movement
The Vega Team explained that differences in interference can result in one cylinder lagging behind the others.
In simplified terms, if one cylinder has slightly greater resistance to movement, it may require a different pressure condition before it begins moving.
This can become particularly visible when several cylinders are expected to move together.
The cylinder with greater internal resistance may begin moving later.
10. Why This Can Be Difficult to Diagnose
From the outside, the symptoms of these two problems can look similar.
Hydraulic imbalance
The cylinder receives insufficient or different flow.
Internal mechanical resistance
The cylinder itself has greater resistance to movement.
Both situations can produce:
one cylinder moves later than the others.
Therefore, simply observing the movement is not enough to identify the root cause.
A systematic diagnosis is required.
11. The Second Possible Cause: A Damaged Piston Seal
The Vega Team also stated that it could not exclude damage to the piston seal of the cylinder that was lagging behind.
This introduces another possible failure mechanism.
A damaged piston seal can alter the internal behavior of the cylinder.
Depending on the nature of the damage, it can affect:
- sealing;
- internal friction;
- hydraulic efficiency;
- movement consistency.
For this reason, Vega recommended an internal inspection rather than simply replacing the cylinder without investigation.
12. Why the Piston Seal Is Important
The piston seal separates the hydraulic chambers inside a double-acting cylinder.
Its function is to maintain the required pressure difference between the two sides of the piston.
If the seal is damaged, the hydraulic behavior of the cylinder can change.
Possible consequences can include:
- internal leakage;
- reduced efficiency;
- abnormal movement;
- slower response;
- inconsistent operation.
The Customer case did not establish that the piston seal was damaged. Vega explicitly described it as a possibility that needed to be checked.
This distinction is important.
13. Vega’s Recommended Diagnostic Procedure
Rather than immediately concluding that the cylinder was defective, the Vega Team recommended:
disassembling the cylinder
and checking:
- the condition of the piston seals;
- the internal surface of the cylinder body.
Vega also requested photographs of the components if possible.
This creates a logical diagnostic sequence:
Observe the problem
↓
Check the hydraulic circuit
↓
Compare cylinder behavior
↓
Inspect the suspect cylinder
↓
Check seals
↓
Check internal cylinder surface
↓
Identify the actual cause
14. Why the Cylinder Body Must Also Be Inspected
The inspection was not limited to the piston seal.
The Vega Team specifically recommended checking the internal surface of the cylinder body.
This is important because the interaction between the piston sealing system and the internal cylinder surface directly affects the movement of the piston.
If the internal surface shows abnormal conditions, the piston may experience increased resistance or other irregular behavior.
The case document does not specify what was eventually found during the inspection, so no specific internal damage should be attributed to this case.
15. A Systematic Troubleshooting Approach
When multiple hydraulic cylinders do not move synchronously, a useful troubleshooting procedure is to divide the problem into two main categories.
Hydraulic causes
Check:
- circuit balancing;
- flow distribution;
- valves;
- restrictions;
- connections;
- hoses;
- pressure conditions.
Cylinder-related causes
Check:
- piston seals;
- guide rings;
- internal cylinder surface;
- mechanical friction;
- possible internal damage.
This approach prevents the technician from replacing components unnecessarily.
16. Why Replacing the Cylinder Immediately May Be the Wrong Approach
If one cylinder is moving slower than the others, replacing it immediately may appear to be the easiest solution.
But if the real cause is an unbalanced hydraulic circuit, the replacement cylinder may behave in exactly the same way.
The new cylinder could simply become the next cylinder to receive insufficient flow.
The Vega Team’s diagnosis therefore began with the hydraulic circuit rather than assuming that the cylinder itself was defective.
17. Hydraulic Circuit Balance Comes First
For systems using several cylinders in parallel, the circuit design should ensure an appropriate distribution of hydraulic flow.
Depending on the application, this may involve:
- balanced pipe lengths;
- appropriate valve selection;
- flow regulators;
- synchronized hydraulic circuits;
- appropriate manifold design.
Vega’s official accessories range includes check valves, one-way flow regulators, hydraulic connections and reducers, specifically to support cylinder connection and hydraulic-circuit management.
However, these accessories should be selected according to the actual hydraulic circuit and application requirements.
18. Flow Regulators Can Help Control Movement
Vega offers one-way flow regulators among its hydraulic-cylinder accessories. The official accessories page explains that these components can help ensure that the cylinder receives the required quantity of oil.
In a multi-cylinder application, flow control can therefore be part of the overall strategy for managing movement.
However, simply adding flow regulators does not automatically solve every synchronization problem.
The complete circuit must be correctly designed and adjusted.
19. Why Identical Cylinders Can Behave Differently
One of the most technically interesting aspects of the case is the statement that even identical cylinders can sometimes behave differently.
The Vega Team specifically explained that differences in:
- seal tolerances;
- guide-ring seat tolerances;
- interference;
can cause one cylinder to lag behind another.
This does not necessarily mean that the cylinder is outside specification.
It means that, in a highly synchronized application, very small differences in mechanical resistance can become visible.
20. Synchronization Is More Difficult Than Simple Parallel Operation
Suppose eight cylinders are connected to the same hydraulic circuit.
It is tempting to assume:
same cylinder + same pressure = same movement.
In practice, the situation is more complex.
Movement depends on:
pressure + flow + mechanical resistance + friction + load.
Even small differences in these variables can influence the timing of movement.
This is why multi-cylinder systems require careful hydraulic and mechanical design.
21. The Customer Case: Eight Cylinders, Two Problems
The documented situation involved eight cylinders supplied to the Customer, with two reported as not working correctly.
This distribution is itself useful diagnostically.
The fact that some cylinders worked while others did not does not automatically prove that the two cylinders were defective.
It could also indicate differences in:
- hydraulic flow distribution;
- line resistance;
- mechanical loading;
- internal cylinder friction.
The Vega Team therefore considered several possible causes rather than focusing immediately on one component.
22. The Video Was an Important Diagnostic Tool
The Customer sent a video showing the problem.
The Vega Team reviewed the video before providing its technical assessment.
Video can be particularly useful for synchronization problems because it allows the technician to observe:
- which cylinder moves first;
- which cylinder lags;
- whether the delay is constant;
- whether the movement becomes synchronized later;
- whether the problem occurs during extension, retraction or both.
Although the file does not provide those detailed observations, the video was sufficient for Vega to identify the hydraulic circuit as the principal potential cause.
23. What the Vega Team Did Not Assume
The technical response is notable for what it did not claim.
Vega did not say:
“The cylinder is definitely defective.”
Instead, it stated that:
- an unbalanced oil circuit was the principal possible cause;
- differences in tolerances could also produce the symptom;
- a damaged piston seal could not be excluded.
This is an excellent example of responsible technical troubleshooting.
The diagnosis remains open until the relevant components are inspected.
24. From Symptom to Root Cause
The observed symptom was essentially:
one or more cylinders lag behind the others.
Possible causes identified by Vega were:
Cause 1
Unbalanced oil circuit
Cause 2
Different interference caused by component tolerances
Cause 3
Damaged piston seal
The recommended next step was therefore inspection rather than immediate replacement.
25. A Practical Diagnostic Flowchart
The case can be translated into a practical troubleshooting sequence:
Several cylinders move together
↓
One cylinder lags
↓
Check hydraulic circuit balance
↓
If circuit is balanced → investigate cylinder behavior
↓
Disassemble suspect cylinder
↓
Inspect piston seals
↓
Inspect internal cylinder surface
↓
Take photographs
↓
Compare findings with normal cylinder
This approach helps distinguish between a system problem and a component problem.
26. Comparing a Suspect Cylinder With a Correct Cylinder
In a multi-cylinder system, an extremely useful diagnostic method is to compare the suspect cylinder with one that is functioning correctly.
Possible comparison points include:
- seal condition;
- guide-ring condition;
- internal surface;
- friction;
- mechanical resistance;
- hydraulic behavior.
The original Vega response specifically recommended inspecting the suspect cylinder and sending photographs.
A comparison can help determine whether the problem is isolated to one cylinder or related to the overall hydraulic system.
27. Why Internal Inspection Should Be Performed Carefully
Disassembling a hydraulic cylinder is not simply a matter of opening the body.
The cylinder should be handled according to appropriate maintenance procedures, with attention to:
- cleanliness;
- seal protection;
- component orientation;
- inspection of sealing surfaces;
- correct reassembly.
The purpose of the inspection in this case was specifically to assess the piston seals and internal cylinder surface, as recommended by the Vega Team.
28. The Importance of the Guide Ring
The Vega Team specifically referred to the tolerances of the guide-ring seat as one possible reason why identical cylinders could behave differently.
The guide system has an important role in maintaining the piston and rod assembly correctly aligned inside the cylinder.
Differences in interference can influence mechanical resistance.
In highly synchronized applications, these differences may become visible as a timing difference between cylinders.
29. Hydraulic Balance Versus Mechanical Resistance
The case illustrates an important distinction.
Hydraulic imbalance
Different cylinders receive different effective flows.
Result:
different movement speeds.
Mechanical resistance
The hydraulic flow may be available, but one cylinder requires more force to overcome its internal resistance.
Result:
delayed or slower movement.
The two effects can produce similar symptoms.
This is why both the hydraulic circuit and the cylinder itself must be considered.
30. What a Maintenance Team Should Check First
When a synchronized-cylinder system develops a problem, a logical first-level inspection can include:
Hydraulic system
- Is the circuit balanced?
- Are the flow regulators correctly adjusted?
- Are there restrictions?
- Are the hydraulic connections correct?
- Is the pressure stable?
Mechanical system
- Is the common load correctly aligned?
- Is one cylinder mechanically loaded differently?
- Is there unusual friction?
Cylinder
- Are the piston seals intact?
- Are the guide components in good condition?
- Is the internal body surface undamaged?
The exact troubleshooting procedure should always be adapted to the specific machine.
31. Why the Problem May Appear Only After Some Operating Time
The file does not specify when the problem began or how it evolved, so no conclusion can be drawn about operating time.
However, from a general engineering perspective, synchronization problems may become visible when operating conditions change, for example because of:
- seal wear;
- temperature;
- hydraulic viscosity;
- contamination;
- changes in flow;
- changes in load.
These are general considerations and are not documented causes in this specific Customer case.
The documented causes considered by Vega remain the unbalanced circuit, tolerance-related differences and possible piston-seal damage.
32. Why the Case Is Relevant to Injection-Mold Design
Multiple hydraulic cylinders are often used when a mold mechanism requires several actuation points.
In such systems, synchronization can be critical because the cylinders may be connected to a common mechanical element.
A small movement difference can become a mechanical problem if the components are rigidly connected.
For this reason, hydraulic circuit design should be considered part of the mold design itself.
33. The V450CM Platform
The cylinder supplied in this Customer case is identified in the original correspondence by the product code CM 040 … 050, which corresponds to the V450CM family with Ø40 mm bore and 50 mm stroke.
Vega’s official Italian product pages confirm that the V450CM range includes:
- Ø40 mm bore;
- Ø50 mm bore;
- 50 mm stroke;
- compact heavy-duty construction. (vegacylinders.com
This provides the product context for the Customer application.
34. Hydraulic Circuit Accessories
Vega’s official accessories range includes components intended to support hydraulic-cylinder installation, including:
- check valves;
- one-way flow regulators;
- hydraulic connections;
- reducers. (vegacylinders.com
These components can be useful when designing and tuning hydraulic circuits, particularly where several cylinders need controlled and repeatable movement.
35. Why Flow Regulation Can Be Important
If several cylinders are connected to a common circuit, controlling the quantity of oil delivered to each actuator can be important.
A flow regulator can be used to manage the hydraulic flow in the circuit, but its correct application depends on the hydraulic architecture.
The goal should be:
stable and repeatable cylinder movement
rather than simply reducing flow.
In a synchronized system, flow-control components should be selected and adjusted as part of the complete hydraulic design.
36. The Customer Case as a Maintenance Lesson
The case demonstrates a valuable maintenance principle:
When one cylinder in a multi-cylinder system behaves differently, do not immediately assume that the cylinder itself is defective.
First investigate the system.
Then investigate the component.
In this case, the Vega Team’s first assessment identified the unbalanced oil circuit as the principal possible cause. Only after that did the response address potential differences in cylinder tolerances and possible piston-seal damage.
37. A Recommended Troubleshooting Sequence
For a similar situation, the investigation can be organized as follows:
1. Record the symptom
Identify exactly which cylinder is lagging.
2. Observe the movement
Use video where appropriate.
3. Check the hydraulic circuit
Verify flow distribution and circuit balance.
4. Check the mechanical system
Make sure the cylinders are not experiencing different external loads.
5. Compare cylinders
Compare the suspect cylinder with a correctly functioning unit.
6. Inspect the cylinder
If necessary, disassemble and inspect the piston seals and internal body surface.
7. Document the findings
Photographs can be useful for technical analysis.
This follows the logic of the diagnostic recommendations provided by the Vega Team.
38. What This Case Teaches About Hydraulic Cylinder Reliability
Reliability is not determined only by the quality of the cylinder.
It depends on the interaction between:
cylinder + hydraulic circuit + mechanical system + maintenance.
Even a high-quality cylinder can behave incorrectly if:
- the hydraulic circuit is unbalanced;
- the cylinder receives insufficient flow;
- the mechanical system imposes uneven loads.
Conversely, a cylinder that behaves differently from the others may need internal inspection if the hydraulic circuit has already been confirmed as balanced.
39. Final Lessons From the Customer Case
The most important lessons are:
Hydraulic balance matters
Several cylinders operating together need an appropriate flow distribution.
Identical cylinders are not mathematically identical
Manufacturing tolerances can produce small differences in mechanical resistance.
Seals must be inspected when abnormal movement occurs
Vega specifically recommended checking the piston seals.
The cylinder body must also be inspected
The internal surface was explicitly included in Vega’s recommended inspection.
Do not replace components before identifying the root cause
A system-level problem can easily be mistaken for a cylinder defect.
Conclusion
A Customer reported a problem involving a set of eight hydraulic cylinders, with two cylinders not working correctly. A video was sent to the Vega Team for an urgent technical evaluation.
After reviewing the video, Vega identified the unbalanced oil circuit as the principal possible cause of the problem.
However, the analysis did not stop there.
The Vega Team explained that even with a balanced circuit, cylinders that are nominally identical can sometimes behave differently because of tolerances in the seals and guide-ring seats. Different interference can cause one cylinder to lag behind the others.
Vega also could not exclude the possibility of a damaged piston seal in the cylinder that was lagging. For this reason, the recommended action was to disassemble the cylinder and inspect the piston seals and the internal surface of the cylinder body, with photographs to be provided if possible.
The broader engineering lesson is particularly useful for applications using multiple hydraulic cylinders:
When cylinders do not move synchronously, the root cause may be in the hydraulic circuit, in the mechanical behavior of the cylinders, or in an internal component. A systematic diagnosis should therefore begin with the circuit and then move to the individual cylinder.
This approach helps avoid unnecessary replacement of components and makes it possible to identify whether the real problem lies in flow distribution, component tolerances or cylinder condition.
Useful and Verified URLs
- V450CM Hydraulic Cylinders — Official Vega product page for the V450CM family, including the available bore and stroke configurations and the main technical characteristics of these heavy-duty short-stroke cylinders.
V450CM Hydraulic Cylinders – Vega Cylinders - V450CM Block Cylinder – Clamping EOE — Official product page for a V450CM configuration with Ø16–100 mm bores and 10, 30 and 50 mm strokes. It also provides the V450CM technical datasheet.
V450CM Block Cylinder – Clamping EOE - V450CM Block Cylinder – Clamping CGH — Official V450CM configuration with longitudinal through holes and BSP oil connections. Useful when discussing hydraulic connections and circuit configuration.
V450CM Block Cylinder – Clamping CGH - Mechanical Switches for V450CM — Official Vega page explaining the mechanical end-stroke switch solutions available for V450CM cylinders, including the MS5, MS6 and MS7 versions.
V450CM Mechanical End-Stroke Switches - MS5 Mechanical Switch for V450CM — Official product page for the MS5 mechanical switch, compatible with V450CM bores Ø40, Ø50, Ø63, Ø80 and Ø100 mm.
MS5 Mechanical Switch for V450CM - Hydraulic Cylinders for Injection Molds — Official Vega catalog covering the complete range of hydraulic cylinders for plastic injection molding and die-casting applications.
Hydraulic Cylinders for Injection Molds – Vega Cylinders
- How to Calculate the Correct Hydraulic Cylinder Size for Injection Molds — Technical article explaining hydraulic-cylinder sizing, force calculation and the relationship between mold forces and cylinder selection.
How to Calculate the Correct Hydraulic Cylinder Size for Injection Molds - How to Calculate the Pulling Force of Hydraulic Cylinders in Injection Molds with Mechanical Locks — Technical article focused on calculating pulling force and correctly sizing hydraulic cylinders.
How to Calculate the Pulling Force of Hydraulic Cylinders in Injection Molds with Mechanical Locks - Hydraulic Cushioning in Injection Mold Cylinders — Useful complementary article about cylinder movement, speed and controlled deceleration in injection molds.
Hydraulic Cushioning in Injection Mold Cylinders
