A Customer Case: 236 cm² of Projected Area and a Potential Force of 118,000 kgf
When selecting a hydraulic cylinder for an injection mold, it is essential to distinguish between moving a mold component and resisting the force generated by injection pressure.
A cylinder may be perfectly suitable for moving a slide, core or punch, while being completely unsuitable for directly resisting the force generated by the plastic during injection.
A Customer case analyzed by the Vega Team provides a clear example of this situation.
The Customer asked the Vega Team to review a mold drawing and help select the correct cylinder. The initial analysis immediately showed that the forces generated by the plastic pressure were extremely high.
Based on the drawing supplied by the Customer, the Vega Team calculated a total projected frontal area of approximately 236 cm².
Assuming a cavity plastic pressure of 500 bar, the resulting thrust force would be approximately:
118,000 kgf
Even at a lower cavity pressure of 350 bar, the resulting force would still be approximately:
82,600 kgf.
The critical point was then identified: the locking-cylinder range considered by the Vega Team did not include a version capable of resisting 118,000 kgf. The stated maximum locking force was 70,000 kgf without preload.
The technical conclusion was therefore clear:
The hydraulic cylinder should not be relied upon as the sole element for resisting the injection force. The mechanical locking system of the mold should perform this function.
1. The Starting Point: The Mold Drawing
The Customer asked the Vega Team to check the mold drawing and help select the appropriate cylinder.
This is the correct engineering approach.
A hydraulic cylinder for an injection mold should not be selected simply according to:
- bore diameter;
- stroke;
- available installation space;
- previous applications.
The first question should always be:
What force does the cylinder actually have to resist?
In this case, the drawing showed that the potential injection forces were exceptionally high.
2. The Projected Frontal Area: 236 cm²
The Vega Team calculated a total projected frontal area of approximately:
236 cm².
This value is fundamental because the force generated by the cavity pressure depends directly on the area exposed to that pressure.
The basic relationship is:
F = P × A
where:
- F = force;
- P = pressure;
- A = projected area.
The equation itself is simple.
The engineering challenge is correctly identifying the effective projected area.
3. Why Projected Area Matters
The total geometric surface of a molded component is not necessarily the surface that should be used for calculating the opening force.
The relevant area is the surface on which the cavity pressure produces a force in the direction that tends to open or move the mold mechanism.
In this Customer case, the calculated projected frontal area was approximately:
236 cm².
That value became the basis for the force calculation.
4. First Scenario: 500 bar Cavity Pressure
For the first calculation, the Vega Team considered a plastic pressure inside the cavity of:
500 bar.
Applying this pressure to the 236 cm² projected area resulted in a total thrust force of approximately:
118,000 kgf.
This is an extremely large force.
In SI units, 118,000 kgf corresponds to approximately 1.16 MN.
At this level, the application can no longer be treated as a simple cylinder-sizing exercise.
The entire mechanical locking concept must be considered.
5. Second Scenario: 350 bar Cavity Pressure
The Vega Team also evaluated a lower plastic pressure:
350 bar.
Even with this lower pressure, the resulting force remained very high:
82,600 kgf.
The comparison is therefore:
| Cavity Pressure | Calculated Force |
|---|---|
| 500 bar | approximately 118,000 kgf |
| 350 bar | approximately 82,600 kgf |
Reducing the assumed cavity pressure significantly still did not bring the required force below the available locking-cylinder capacity.
6. Comparing the Required Force With Cylinder Capacity
The next step was to compare the calculated force with the available locking force.
The technical communication states a maximum locking force of:
70,000 kgf without preload.
The comparison is straightforward.
At 500 bar
118,000 kgf required
versus
70,000 kgf available
At 350 bar
82,600 kgf required
versus
70,000 kgf available
In both scenarios, the calculated load exceeds the stated locking capacity.
7. Why a Larger Cylinder Was Not the Answer
When a cylinder is not powerful enough, the obvious response might be:
“Use a larger cylinder.”
However, that approach was not sufficient in this case.
The Vega Team explicitly stated that the available locking-cylinder range did not include a version capable of resisting the calculated force.
This leads to an important engineering principle:
Not every force problem can be solved by increasing cylinder size.
At a certain point, the correct solution is to change the way the force is carried through the mold structure.
8. The Mechanical Locking System Becomes Essential
The solution indicated by the Vega Team was to:
use the mechanical locking system on the mold.
This is the key point of the Customer case.
The hydraulic cylinder can be responsible for:
- moving the mechanism;
- positioning the mechanism;
- opening the mechanism;
- closing the mechanism.
Once the mechanism reaches its working position, however, the mechanical locking system can take over the structural load.
This separates the movement function from the load-bearing function.
9. Movement and Locking Are Different Functions
This distinction is extremely important in mold engineering.
Movement
The hydraulic cylinder provides force to move a component from one position to another.
Locking
The mechanical system keeps the component in position and resists the process load.
These functions can sometimes be integrated into one hydraulic cylinder.
However, when the process forces become very high, separating them can be a much more effective engineering solution.
10. A Hydraulic Cylinder Is an Actuator, Not Automatically a Structural Lock
A hydraulic cylinder converts hydraulic pressure into mechanical force and movement.
If it is also expected to resist a very large injection force, the engineer must verify much more than the cylinder’s nominal thrust.
The complete system must be evaluated in terms of:
- hydraulic force;
- locking force;
- pressure;
- preload;
- mechanical strength;
- alignment;
- side loads;
- structural deformation;
- operating conditions.
The Customer case demonstrates that there is a point where the mold’s mechanical locking system should carry the process load instead of the hydraulic cylinder.
11. The Importance of Preload
The stated maximum locking force of 70,000 kgf is explicitly specified as being without preload.
This is an important technical detail.
Preload can influence the behavior of a mechanical locking system, but the available documentation does not provide a higher validated capacity that would make the 118,000 kgf condition acceptable.
Therefore, it would be incorrect to assume that preload automatically solves the difference between:
70,000 kgf
and
118,000 kgf.
The documented recommendation remains to use the mechanical locking system of the mold and carry out the necessary structural verification.
12. Cavity Pressure Is Not the Same as Hydraulic Pressure
Another essential concept is the distinction between:
plastic pressure inside the cavity
and:
hydraulic pressure acting on the cylinder piston.
The 500 bar and 350 bar values used in this case refer to the plastic pressure in the cavity used to calculate the force acting on the mold.
They should therefore not automatically be interpreted as the hydraulic operating pressure of the cylinder.
The purpose of the calculation is first to determine:
How much force can the molding process generate?
Only after that should the engineer determine how this force is resisted.
13. Following the Force Through the Mold
The correct engineering sequence is:
Plastic pressure
↓
Projected area
↓
Resulting force
↓
Mold geometry
↓
Mechanical mechanism
↓
Locking system
↓
Hydraulic cylinder
This is a much more reliable approach than starting with the cylinder catalog.
The cylinder should be selected according to the function it actually performs in this force chain.
14. The Customer Case in Numbers
The technical analysis can be summarized as follows:
| Parameter | Value |
|---|---|
| Projected frontal area | approximately 236 cm² |
| Cavity pressure — Scenario 1 | 500 bar |
| Resulting force — Scenario 1 | approximately 118,000 kgf |
| Cavity pressure — Scenario 2 | 350 bar |
| Resulting force — Scenario 2 | approximately 82,600 kgf |
| Maximum locking force indicated | 70,000 kgf |
| Preload | Not included |
| Recommended solution | Mold mechanical locking system |
These values are taken directly from the technical Customer documentation.
15. The First Question for the Mold Designer
When the Vega Team analyzes an application of this type, one of the most important questions is:
Does the hydraulic cylinder have to directly resist the injection force, or does the mold have a mechanical locking system?
This question was explicitly raised during the technical analysis of the Customer application.
The answer fundamentally changes the cylinder-sizing calculation.
If the cylinder must resist the injection force directly:
the cylinder must be sized for that load.
If the mold has a suitable mechanical locking system:
the cylinder can primarily perform the movement and positioning function.
16. Why the Molded-Part Drawing Is Important
The Vega Team also requested the drawing of the molded plastic component.
This is useful because the component geometry helps determine:
- pressure-exposed surfaces;
- projected area;
- force direction;
- slides;
- cores;
- undercuts;
- extraction mechanisms.
The cylinder should therefore be selected from the actual mold geometry, not simply from a nominal cylinder size.
17. Why the Existing Cylinder Must Also Be Identified
The technical analysis also asked whether the cylinder shown in the drawing was produced by another supplier and requested its bore size.
This information becomes particularly important when evaluating a replacement or retrofit.
The existing cylinder can be checked for:
- bore;
- stroke;
- hydraulic force;
- installation dimensions;
- pressure rating;
- rod configuration;
- locking capability.
Knowing the existing cylinder also helps determine whether the problem is one of sizing, function or mechanical integration.
18. The Risk of Undersizing the System
If a hydraulic cylinder is selected without properly calculating the force generated by injection pressure, the system may appear to work correctly during a dry cycle.
The problem may only appear when injection begins.
Possible consequences include:
- slide movement;
- punch retraction;
- flash;
- dimensional defects;
- damage to shut-off surfaces;
- premature wear;
- mechanical collision.
A cylinder that moves a mechanism correctly without load is not necessarily a cylinder that can hold that mechanism during injection.
19. The Opposite Problem: Oversizing
Oversizing is also undesirable.
An unnecessarily large hydraulic cylinder can result in:
- larger installation dimensions;
- greater oil consumption;
- higher hydraulic flow requirements;
- slower movement at a given flow rate;
- higher component costs;
- unnecessary loads on the mold structure.
The goal is therefore not to select the largest possible cylinder.
The goal is to select the correct cylinder for the actual function it performs.
20. When Mechanical Locking Is the Better Solution
When process forces become very high, mechanical locking can provide an efficient way to transfer the load directly through the mold structure.
The hydraulic cylinder can bring the mechanism into position.
Then:
the mechanical locking system carries the process force.
This principle can be particularly useful when the hydraulic cylinder would otherwise need to be extremely large.
Vega’s current product range also includes self-locking hydraulic cylinders. The official Vega website identifies the V270CG as a self-locking hydraulic cylinder with integrated end-stroke switches.
The important distinction is that a self-locking cylinder and a separate mechanical locking mechanism in the mold are not necessarily the same engineering solution.
21. Self-Locking Cylinder vs. Mold Mechanical Locking
These concepts should not be confused.
Self-locking hydraulic cylinder
The locking function is integrated into the cylinder design.
Mold mechanical locking system
The mold itself incorporates mechanical geometry or components designed to resist the process load.
In the Customer case, the Vega Team specifically recommended using the locking system on the mold because the calculated force exceeded the available locking-cylinder capacity.
22. Why Cylinder Selection Should Start With Force
The Customer case demonstrates why cylinder selection should not begin with the catalog.
The correct sequence is:
1. Analyze the mold geometry
Determine the effective projected area.
2. Determine cavity pressure
Use the expected process pressure.
3. Calculate the resulting force
F = P × A
4. Determine the force direction
Understand how the force acts on the moving mechanism.
5. Analyze the mold mechanism
Identify slides, wedges, locks and other mechanical elements.
6. Determine the cylinder’s actual function
Movement only, or movement plus locking?
7. Select the cylinder
Only now choose the appropriate bore, stroke and configuration.
8. Verify the locking system
Ensure that the mold structure can safely carry the process load.
23. Why Technical Review Before Ordering Matters
In this case, the Customer requested a technical review before selecting the cylinder.
That review identified an issue that could easily have been missed:
the process force was greater than the available locking-cylinder capacity.
A technical review before ordering can prevent:
- purchasing the wrong cylinder;
- redesigning the mold later;
- unnecessary machining;
- production delays;
- unsuccessful mold trials;
- premature cylinder replacement.
24. The Real Objective Is Not to Find a “Powerful Cylinder”
The real objective is to design a system capable of managing the process force.
In this case:
236 cm²
×
500 bar
↓
118,000 kgf
while the available locking-cylinder capacity was:
70,000 kgf without preload
↓
Insufficient
↓
Use the mold’s mechanical locking system
This simple sequence captures the central engineering lesson of the case.
25. A Practical Checklist for Mold Designers
For applications involving hydraulic locking cylinders, the following checklist can be useful.
Mold geometry
- What is the actual projected area?
- In which direction does the force act?
- Are there wedges or inclined surfaces?
- Are there mechanical locking elements?
Process
- What is the expected cavity pressure?
- What is the maximum possible pressure?
- Are transient peak loads relevant?
Hydraulic cylinder
- What force can it generate?
- What is its maximum locking force?
- What is its pressure rating?
- What bore and stroke are required?
- Is it intended for movement or locking?
Mechanical locking
- Is the cylinder expected to carry the process load?
- Does the mold have a mechanical locking system?
- Is preload involved?
- Has the mold structure been verified for the calculated force?
Final verification
- Is the maximum process force below the validated system capacity?
- Is there an adequate engineering margin?
- Can the cylinder move and release the mechanism correctly?
26. The Main Lesson From the Customer Case
The most important lesson is simple:
Calculate the force before selecting the cylinder.
In this case, a projected area of approximately 236 cm² generated a theoretical force of approximately 118,000 kgf at 500 bar.
Even at 350 bar, the force remained approximately 82,600 kgf.
Both values exceeded the stated maximum locking force of:
70,000 kgf without preload.
The correct response was therefore not simply to search for a larger cylinder.
The Vega Team recommended using the mechanical locking system of the mold and carrying out the necessary checks.
Conclusion
This Customer case is a clear example of why hydraulic-cylinder sizing for injection molds must begin with the actual forces generated by the molding process, rather than simply with cylinder dimensions.
The Vega Team analyzed the mold drawing and calculated a projected frontal area of approximately:
236 cm².
With a plastic cavity pressure of:
500 bar
the resulting thrust force was approximately:
118,000 kgf.
Even when a lower pressure of:
350 bar
was considered, the resulting force remained approximately:
82,600 kgf.
The maximum locking force available in the considered cylinder range was:
70,000 kgf without preload.
The technical solution was therefore not to rely on the hydraulic cylinder to resist the entire injection force, but to use the mechanical locking system incorporated into the mold.
The broader engineering principle is:
A hydraulic cylinder capable of moving a mold component is not automatically capable of resisting the force generated by injection pressure. Movement and locking must be analyzed separately whenever process forces become significant.
The correct design path is therefore:
projected area → cavity pressure → injection force → mold geometry → mechanical locking → cylinder function → cylinder selection.
This approach helps prevent both undersizing and unnecessary oversizing and leads to a more reliable hydraulic system for demanding injection-mold applications.
Useful and Verified URLs
1. Hydraulic Cylinders for Injection Molds
Official Vega website presenting the current range of hydraulic cylinders specifically designed for plastic injection molding and die-casting applications. The range includes compact, heavy-duty and self-locking cylinders.
Hydraulic Cylinders for Injection Molds – Vega Cylinders
2. Vega Hydraulic Cylinder Shop and 3D Configurator
The official Vega shop groups the hydraulic cylinders by application and provides access to the 3D configurator. It includes block cylinders, self-locking cylinders, accessories and end-stroke switches.
Hydraulic Cylinder Shop & 3D Configurator – Vega Cylinders
3. V450CM Heavy-Duty Block Cylinder
Official product page for the V450CM heavy-duty block cylinder. The page provides available bores, strokes and technical documentation.
V450CM Heavy-Duty Block Cylinder – Vega Cylinders
4. V450CM-YES Heavy-Duty Block Cylinder
Official product page for the V450CM-YES, designed for short and long strokes and equipped with key-way clamping and bottom manifold oil delivery.
V450CM-YES Heavy-Duty Block Cylinder – Vega Cylinders
5. V220CC Block Cylinder
Official V220CC product page, useful when evaluating compact long-stroke block-cylinder solutions for injection-mold applications.
V220CC Long-Stroke Block Cylinder – Vega Cylinders
6. How to Size a Locking Cylinder for an Injection Mold
Official Vega technical article explaining why projected area and cavity pressure must be calculated before selecting a locking cylinder. It provides a useful technical reference closely related to the Customer case.
How to Size a Locking Cylinder for an Injection Mold – Vega Cylinders
7. Calculating Pulling Force With Mechanical Locks
Official Vega technical article explaining how mechanical locking systems change the force calculation for hydraulic cylinders in injection molds.
How to Calculate Pulling Force With Mechanical Locks – Vega Cylinders
8. Vega Cylinders – Company and Technical Support
Official company page describing Vega’s experience in designing and manufacturing hydraulic cylinders for plastic injection and aluminum die-casting molds, including design, R&D and technical support.
Vega Cylinders – Hydraulic Cylinder Manufacturer
