Nitrogen gas spring for molds (referred to as die gas spring or nitrogen gas spring or nitrogen cylinder or nitrogen cylinder) is a new type of elastic component that uses high-pressure nitrogen as the working medium. It has advantages of small size, large elasticity, long stroke, stable work, precise manufacturing, long service life (1 million times), flat elasticity curve, and no need to tighten up in advance, etc. It has properties that are not available in conventional elastic components such as metal springs, rubber and air cushions, which can make up for its shortcomings and replace conventional components to complete tasks that are difficult to complete with conventional components, simplify mold design and manufacturing, facilitate mold installation and adjustment, extend mold use Life, to ensure stability of product quality. It can be used as an independent part and installed in mold, or it can be designed as a nitrogen gas spring system. As a part of mold, it can easily achieve constant elastic pressure and delayed action in system. It is a new generation of the most ideal elastic component with many properties.

 

 

 

1. Nominal spring pressure F: refers to initial pressure of this series of nitrogen gas springs at 20℃ with an inflation pressure of 15Mpa: if user has no special requirements, initial spring pressure value is manufactured according to nominal spring pressure. Nominal spring pressure of same series of nitrogen gas springs is same.
2.Stroke S: refers to working stroke of nitrogen gas spring of this model. These strokes can be fully utilized. However, in order to prevent sudden event of nitrogen gas spring exceeding stroke and overload during mold replacement or debugging, it is recommended to reserve a free stroke of ≤5mm or 10%S in design.

 

3.Total length L: refers to manufacturing length of this type of nitrogen gas spring, that is, maximum length in natural state. It must meet: total length L≥ base length J+2X stroke S
4. Working life: Under correct installation and correct use, working life of nitrogen gas spring (stroke≤50mm) is more than one million times. If stroke is greater than or equal to 50mm, actual cumulative stroke of nitrogen gas spring is about 100,000 to calculate its life. That is: working life=100000 meters ÷ (actual stroke X2)

A compact nitrogen gas spring BKH50.0-025-135 (bore diameter of 75mm, stroke of 25mm)] is equivalent to 14 SSWH50-300 super-heavy load coil springs (diameter of 50mm, 20mm preload K=16.7, preload=20mmX16.7=334kgf, 4700/334=14 coil springs)
advantage:
Reduce installation area: nitrogen gas spring needs 44.16 square centimeters, while coil spring needs 247.75 square centimeters, which is close to 6 times lower installation height: gas spring cylinder only needs 135 cm, while coil spring needs 280 cm to reduce installation space: gas spring only needs 596.16 square centimeters, while coil spring needs 7963 square centimeters. Compared with installation of 14 coil springs, one gas spring does not require preloading, guiding and positioning operations.

A short nitrogen gas spring BK J5.0-080-210 (diameter 45mm, stroke 80mm, total height 210mm, final pressure 636kgf) is equivalent to a medium-load coil spring with a diameter of 63mm, a working stroke of 80mm, a total height of 305mm, and a final elastic force of 518kgf.
Advantage:
Same working stroke and elasticity, height is obviously reduced, structure of mold becomes compact, and cost is reduced.

Nitrogen gas spring can provide a large known initial force when it wants to contact mold, ranging from 45daN (BKB0.45 cylinder diameter is 12mm) to 18300daN (BKB180.0 cylinder diameter is 150mm), while coil spring requires a pre-compression and load to achieve this initial force
Advantage:
Nitrogen gas spring does not need to be preloaded. Nitrogen gas spring installation is easier and faster, cost is reduced.

After nitrogen gas springs are connected into a pipeline system through hose, pressure of gas inside each gas spring is same, so that entire system is balanced. These cannot be achieved by using coil springs, because force provided by each coil cannot be exactly same.
Advantage:
Each contact point has equal force-balance mold
Ejection force of nitrogen gas spring can be set according to needs-convenient for production
Gas pressure inside system can be monitored at any time-to produce high-quality parts
No need to repair mold, will not cause production stop, extend life of punch and other parts, reduce costs

Initial force of nitrogen gas spring can be adjusted by changing internal gas pressure. For pipe connection, pressure can be adjusted by control gauge (maximum pressure is 150bar), and coil spring force cannot be adjusted.

Special nitrogen gas spring for mold is a high-pressure sealing product. It has undergone strict inspection and testing before leaving factory, and no gas leakage is allowed. Therefore, correct installation and use of customer are required to ensure its safety, reliability and best service life.
1. When special nitrogen gas spring for mold is used as an independent part, after being installed in mold, there is generally no need for disassembly and maintenance within service life.
2. If nitrogen gas spring is connected as a system, it generally needs to be instructed by specially trained personnel or professionals. Special attention should be paid to disassembly or maintenance before nitrogen in cylinder is completely released to prevent accidents.
3. Screw at the lower end of special nitrogen gas spring for mold mainly plays a role of protection and strengthening of seal, shall not be disassembled or knocked at will.
4. Recommended working stroke ≤ 0.9XS (manufacturing stroke)
5. Working base pressed by upper end of piston rod is not perpendicular to axis of piston rod and should be ≤1° (that is, it should be kept vertical, and partial load is strictly prohibited)
6. Direction of movement of upper end of piston rod must be parallel to direction of movement of piston rod.
7. After nitrogen gas spring is compressed, do not allow piston rod to return freely, so as not to cause internal damage to nitrogen gas spring.
8. Pay attention to keep cylindrical surface of piston rod clean, be careful of scratches, and strictly forbid magnetic impact.
9. It is strictly forbidden to expose nitrogen gas spring in scorching sun and high temperature environment, maximum allowable temperature is +80℃ (except for special high temperature resistant nitrogen gas spring)
10. Nitrogen gas springs for molds should be stored in a dry, ventilated, non-corrosive gas environment. After unpacking and installation, if they are not used for a long time, grease can be applied to surface to protect against corrosion.

 

1. It is forbidden to disassemble and modify joints of nitrogen gas springs and hoses. Careless disassembly will cause parts to pop out under high pressure, which is very dangerous.
2. It is forbidden to follow-up processing of nitrogen gas springs.
3. It is forbidden to weld nitrogen gas spring or throw it into fire.
4. It is forbidden to use it in a high temperature environment, the highest temperature of use environment is 70 ℃. When temperature of working environment exceeds temperature (20℃), please refer to instructions for use and adjust pressure to same pressure as maximum inflation pressure at 20℃ before use.
5. Please use it within specified stroke S (actual use stroke Sa≤S). If it is used beyond stroke range, piston rod will contact bottom of cylinder, deforming piston rod and cylinder, causing air leakage. In addition, when selecting a nitrogen gas spring with a stroke of 32mm or more, in order to maintain lubrication effect in cylinder normally, use stroke Sa should be selected within range of S-25≤Sa≤S.
6. Please do not use piston rod to be subjected to eccentric load (allowable eccentric angle is below 0.5℃). Eccentric load will seriously affect service life of nitrogen gas spring. Especially when it is used horizontally, piston rod is easy to tilt due to its own gravity, so please pay attention to it when installing.
7. To make piston rod receive a full and even load, please adjust position of buffer and baffle.
8. Be sure to pre-press: Never use piston rod to return sharply when in use, otherwise it may damage nitrogen gas spring, which is very dangerous. In particular, you must never use percussive power devices.
9. Please do not use threaded hole at the top of piston rod to fix nitrogen gas spring.
10. Never use screw hole at the top of piston rod to lift mold as a whole. Screw hole at the top of piston rod is used to lift single nitrogen gas spring when installing or removing gas spring from mold.
11. When installing nitrogen gas spring, please use screw holes on the bottom surface or flange bolts to fix it firmly.

 

The total output force of nitrogen gas spring is 3 to 5 times weight of all ejector systems (experience value). When mold is oversized, multiple is appropriately reduced, and vice versa. See figure below for precautions for assembly of nitrogen return spring.

 

 

Arrangement and selection criteria of nitrogen gas springs require large resetting force of ejector system, higher ejection stroke for medium and large automobile molds. Balance of ejection and resetting of mold is required to be high, mold with a relatively long molding cycle needs to use nitrogen gas spring in series, pipe connection can be removed if there is no special requirement for other molds.