No matter what kind of process, we always hope that the total height of nitrogen spring is not too high, so as to avoid instability and complicated structure when installing on the mold. The larger the stroke, the higher the price of nitrogen spring. This is particularly important for independent nitrogen spring. If the stroke is really large due to process requirements, it is recommended to use nitrogen spring seat plate system, which can reduce the mold height and improve the stability and reliability of nitrogen spring. Sometimes, in order to avoid accidents, the safety stroke of 3-5 mm should be increased when selecting nitrogen spring.
1. Selection of nitrogen spring stroke in blanking process nitrogen spring is used as ejector and discharge in separation process. The stroke requirement is small and can be satisfied with 10 mm. However, when selecting the nitrogen spring in practice, it is better to select the stroke of 20-30 mm, because the minimum stroke of the specification of nitrogen spring is 20 mm. The working stroke of the mold is small, and the selection of the nitrogen spring with a large stroke does not affect its structure. After the mold is used for a certain time, the working area of the nitrogen spring can be changed, which is conducive to the use of a nitrogen spring in various molds, so as to improve the service life of the nitrogen spring.
2. Selection of nitrogen spring stroke in the drawing process, nitrogen spring dog is mostly used to obtain blank holder force, and the blank holder force is required to be basically constant. When selecting the stroke of nitrogen spring, factors such as drawing depth of parts, radius of die fillet and safety margin of stroke should be considered For the drawing and shaping process, the stroke of nitrogen spring is equal to the height of the part plus 3-5 mm, because the finite position device is designed in the shaping die to limit the shaping stroke. There is no need to choose too large a journey to avoid waste. For cylinder drawing, the stroke of nitrogen spring is equal to the height of the part plus 8-10 mm in order to take the part conveniently, ensure the quality of the drawing part and improve the dimensional accuracy of the drawing part. In short, nitrogen spring blank holder is used in the drawing process, and its stroke is equal to the height of the part plus 3-i0 mm. If the nitrogen spring is used to eject the deep drawing workpiece, the selection of the stroke is not so strictly limited, which can be determined according to the specific situation.
3. In the bending and flanging process, the selection of nitrogen spring has a large stroke in the bending and flanging process. In addition to the height of the parts, a margin of 10-20 IQ] m should be added to reduce the springback of the workpiece. The preload of the die can also be adjusted by using this allowance. Using its characteristic curve, we can obtain different forces by adjusting its starting position on the press. Practice has proved that this point is convenient for ensuring the quality of parts and adjusting the die.