The nitrogen spring in the stamping die is an elastic component that uses high-pressure nitrogen as the working medium. Its working process can be roughly regarded as isothermal expansion and compression process. The structure of nitrogen gas springs can generally be divided into two types: piston type and plunger type. The gas chamber structure of single chamber or multiple chamber is adopted, and the gas chamber design is mostly back pressure structure. The main working medium is high-pressure nitrogen, which is sealed in the pipeline. It must not only be well sealed for a long time, but also work under high pressure. This is a comprehensive technology. How to choose nitrogen gas spring for stamping die? The following points:
1. The choice of elastic force:
According to the calculated pressing force, select the number and model of nitrogen springs and the spring pressure of each nitrogen spring. Generally speaking, the pressure of the nitrogen gas spring should be selected based on the calculated punching pressure plus an increase of 15%-20%, which is more in line with the actual situation. The reasons are as follows:
<1> When the mold wears out, there will be gap changes. Changes in process parameters such as cutting edge bluntness, inconsistency of mold thickness and mold plate deformation resistance will cause changes in the deformation resistance of the workpiece, so the deformation resistance should be left in the design.
<2> When the nitrogen gas spring is inflated, the high-pressure gas will inevitably have a throttling loss, which will make the elasticity float down.
<3> The life of the nitrogen gas spring is very long. After a period of use, the high-pressure nitrogen gas may leak to a certain extent, resulting in a slight drop in the spring pressure.
2. Selection of the number of nitrogen gas springs:
The mold structure and the position of the focus point should be combined according to the molding requirements, so that the mold will not be unbalanced when it is working, and it must be convenient to adjust the mold. In this way, the service life of the nitrogen gas spring can be longer.
3. Selection of the boost ratio of the nitrogen gas spring:
It can be selected according to the characteristic curve of the nitrogen gas spring and the requirements of the stamping process to determine the type of the gas spring to be used. Especially when the working force is required to change steadily, or the working force is basically constant and the initial force is relatively large, it is more important to determine the boost ratio.
4. Selection of nitrogen spring stroke:
Regardless of the process, when choosing a nitrogen gas spring, we always hope that the total height of the gas spring should not be too high, so as to avoid instability and too complicated structure when installing on the mold. The larger the stroke, the higher the price of the gas spring. High, this is particularly important for independent nitrogen gas springs. If the stroke is really large due to process requirements, it is recommended to use the nitrogen spring seat plate system, which can reduce the height of the mold and improve the stability and reliability of the nitrogen spring. Sometimes in order to be safe and avoid accidents, when choosing a nitrogen gas spring, it is necessary to increase the safety stroke of 3-5mm.
