Die-making and stamping
Pressing · deep drawing · ejection
Pressing, deep drawing, sheet-metal holding and ejection in dies and moulds — high forces in the scarce space of the die. It is the sector standard.
Nitrogen
gas springs
Sealed cylinders charged with high-pressure nitrogen that deliver force through a piston rod. They don't store energy through elastic deformation: the force comes from gas pressure — F = P × A.
Principle
F = P × A
Pressure
≈ 150 bar
Standard
ISO · interchangeable
01
What a gas spring is and how it works
Nitrogen gas springs —known internationally as nitrogen gas springs, gas cylinders or die springs— are a robust alternative to mechanical springs. They consist of a sealed cylinder charged with high-pressure nitrogen and a piston rod.
Unlike a helical spring, they don't work through elastic deformation of the material, but through the pressure of a confined gas. They are a self-contained unit: once charged with (inert) nitrogen during assembly, they need no further input. As the rod is pushed inward, the gas is compressed and reacts by exerting an opposing force.
The force is given by the relationship F = P × A, where P is the internal nitrogen pressure (typically around 150 bar / ~2,000–3,000 psi) and A is the cross-section of the rod. They are used as standardized spring elements where high forces are needed in tight spaces.
Schematic section: the piston rod compresses the nitrogen; the force is the product of the pressure and the rod's cross-section (F = P × A).
— Two key traits
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01
Immediate force from first contactA mechanical spring needs travel to build up load; the gas spring already exerts its force from the very first instant.
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02
Very flat force curveThe force barely increases throughout the stroke: the rod's cross-section is small relative to the gas volume, so the pressure stays almost uniform.
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03
Adjustable forceIncreasing or reducing the nitrogen charge adjusts the element's force — something impossible with a mechanical spring.
— General specifications
- Type
- Sealed cylinder charged with high-pressure nitrogen.
- Principle
- F = P × A (not through elastic deformation).
- Internal pressure
- Around 150 bar (~2,000–3,000 psi).
- Force at contact
- Immediate from the very first instant of travel.
- Force curve
- Very flat throughout the stroke (low increase).
- Adjustment
- Adjustable by varying the nitrogen charge.
- Standardization
- ISO standards · interchangeable mounting.
- Sealing
- Rod-sealed (rod) · bore-sealed (cylinder).
02
Advantages over the mechanical spring
The big advantage is force density: a gas spring delivers far higher tonnage than a mechanical spring of the same size. That's why it is the standard in stamping die-making, where space in the die is scarce and forces are enormous.
| Feature | Gas spring | Mechanical |
|---|---|---|
| Force per unit volume | Very high | Limited |
| Force at the start of travel | Immediate, high | Builds from zero |
| Force curve | Very flat | Linearly increasing |
| Force adjustment | Yes — gas charge | No |
| Installation space | Compact | Larger |
| Synchronization of several elements | Yes — linked systems | No |
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- Force density Much more tonnage in the same size.
- Immediate force Available from first contact.
- Flat curve Barely grows throughout the stroke.
- Adjustable Regulated with the nitrogen charge.
The gas spring starts from a high immediate force and stays almost flat; the mechanical one starts at zero and grows linearly with travel.
03
Construction and components
The gas spring is a simple self-contained unit but demanding to manufacture: the quality of the sealing determines service life, especially in die-making environments contaminated with oil and grinding dust.
Longitudinal section: steel cylinder, pressurized nitrogen (≈ 150 bar), piston rod, elastomer seals and G 1/8 charge port on an ISO mounting plate.
- 01 Cylindercylinder bodySteel body that contains the pressurized nitrogen.
- 02 Piston rodpiston rodTransmits the force; its cross-section, together with the pressure, determines the force.
- 03 Seals and scrapersseals & scraperRubber or advanced elastomers; they withstand pressure cycling and prevent leaks and the ingress of contaminants (oil, dust).
- 04 Charge port (G 1/8)charge portAllows charging, adjusting the pressure or connecting the element to a linked system.
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Rod-sealed · sealing on the rod
Standard construction; the sealing acts on the rod. A good balance of force, stroke and service life for most applications.
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Bore-sealed · sealing on the cylinder
The sealing acts on the internal diameter of the cylinder, which allows the maximum force per diameter in the same housing.
04
Standardization and formats
Gas springs are manufactured to ISO standards and standardized mounting patterns, which makes them interchangeable between manufacturers. The range of forces and strokes is very wide, from elements of a few newtons (ejector pins) to cylinders of several tens of tonnes for stamping presses.
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Full heightfull-height · ISO baseWidest variety of strokes; the standardized base family.
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Compact heightcompact-heightSaves installation height (typically 25–50 mm).
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Super-compactsuper-compactMaximum force per diameter in short strokes.
— Linked systems · linked / hosed
Several cylinders are connected by hose to a single gas charge, so they act in a synchronized way and share the same pressure. This is the solution for distributing a uniform force across several points of a large die.
- A single charge and a single pressure-adjustment point
- Force distributed and synchronized across all cylinders
- Ideal for large dies and extensive blank holders
Shall we talk about your project?
Tell us the required force, stroke, available space and format — our engineering team will help you choose the optimal gas spring and, if you need it, the right linked system. Specialist manufacturer since 1974.
05
Industrial applications
Gas springs are the standard wherever high force in little space with immediate force is needed. Their natural territory is die-making and stamping, but they appear in any high-tonnage tooling.
Pressure pads and blank holders
Clamping during forming
They hold the sheet metal firmly in place during forming, ensuring uniform holding with force available from first contact.
Panel ejection and lifting
Adjustable ejector pins
Ejection and lifting of parts and panels by means of ejector pins whose force can be adjusted with the gas charge.
Injection moulds
High-temp versions (~120 °C)
High-temperature versions that maintain the force inside the mould throughout prolonged cycles.
Tooling and automation
High, compact, adjustable force
Any tooling or automation assembly that requires a high, compact and adjustable force in minimal space.
Another application?
Custom · engineering
We select the model, force, stroke and mounting or linking system for your tooling. The Surisa engineering team, specialists since 1974, offers free engineering support.
06
Frequently asked questions
01 What is a nitrogen gas spring and how does it work?
It is a sealed cylinder charged with high-pressure nitrogen that delivers force through a piston rod. As the rod is pushed in, it compresses the gas, which reacts with an opposing force given by F = P × A (pressure times the rod's cross-section). Unlike a helical spring, it doesn't work through elastic deformation of the material, but through the pressure of the confined gas, and it is a self-contained unit that needs no further gas after its initial charge.
02 What advantages does it have over a mechanical spring?
Four main ones: it delivers far higher forces in the same space (high force density), the force is available immediately from first contact (a mechanical spring needs travel to generate it), the force curve is very flat throughout the stroke, and the force is adjustable by varying the nitrogen charge. In addition, several cylinders can be linked by hose to act in a synchronized way.
03 Why is a gas spring's force almost constant throughout the travel?
Because the force depends on the nitrogen pressure acting on the rod's cross-section, and that cross-section is small relative to the cylinder's gas volume. As the rod is pushed in, the gas volume is reduced only slightly in relative terms, so the pressure —and therefore the force— increases only marginally. The result is a very flat force curve, with a low increase between the start and end of the stroke.
04 Where are gas springs used?
Above all in die-making and stamping: pressing, deep drawing, sheet-metal holding and ejection in dies and moulds, where high forces are needed in the scarce space of a die. Also in pressure pads and blank holders, adjustable ejector pins, injection moulds (high-temperature versions) and automation tooling. They are the standard when a high, compact, immediate and adjustable force is required.
05 Can they be interchanged between manufacturers and can the force be adjusted?
Yes. They are manufactured to ISO standards and standardized mounting patterns, which makes them interchangeable between brands in many formats (full height, compact, super-compact). The force is adjusted by charging or discharging nitrogen through the cylinder's port, and several elements can be connected in a hose-linked system to share a single charge and act in a synchronized way.
Do you need a gas spring?
Tell us the required force, stroke, available space, format (full-height / compact) and whether you need a linked system — we select the ISO model, diameter, sealing type and gas charge, and respond with the optimal solution. Free engineering support, specialists since 1974.