Chen Biao, General Manager of Dongguan Tengfei Hardware Mould Co., Ltd., the member of the Alliance, was specially invited by the Hot Forming Industry Alliance to make a technical sharing on the "failure and safety of nitrogen spring". Tengfei is a domestic first-class enterprise that focuses on the research and development, production, and sales of nitrogen springs. It mainly provides professional solutions for nitrogen springs and oil cylinders for industries such as automotive molds, household appliances, railways, and copiers.
What is the function of a nitrogen spring?
The application of nitrogen springs in stamping products is very extensive, generally used for blanking, stretching forming, cutting edge materials, etc. of cold stamping products; In hot stamping molds, nitrogen springs mainly serve to compress the insert, ensuring a small rebound coefficient of product size during the holding time; In hot forging molds, it mainly plays a role in buffering and cutting edge materials; In the Injection mold construction, it mainly plays the role of assisting the ejection mechanism to reset. The correct use of nitrogen springs is very important in the stamping process, as they not only exert the effect of elasticity, but also give a helping hand to the stamping process.
The safety function of the product is very important during the use of nitrogen springs. The component group of nitrogen spring mainly consists of four parts: cylinder body, plunger, guide sleeve, and sealing parts. After assembly, a circular circlip is used to clamp the guide sleeve, and after inflation, the plunger displacement is compressed, causing a reaction force to be generated by the changes in high-pressure nitrogen space inside the cylinder, achieving a large rebound force. In practical applications, the safety of using nitrogen springs should be fully considered in the design structure. Generally divided into overtravel use, overload use, and overpressure use; Failure to use according to operating standards can easily cause nitrogen spring failure, which can occur in three ways:
(1) Pressure drop
The decrease in air pressure is the most common problem when using nitrogen springs. The structure of nitrogen springs is plunger sealing and piston sealing. During stamping use, the sealing ring will rub against the plunger rod or piston rod. After a certain number of repeated movements, the inner diameter of the seal will gradually increase, and the sealing function will gradually decay, causing a decrease in air pressure. Non vertical fixed use can also cause a decrease in air pressure.
(2) Plunger rod separated from cylinder body
The separation of the plunger rod from the cylinder body is the most dangerous failure mode in nitrogen springs. The reason is that during the stamping process, the mold insert is stuck, unable to reset normally, and the stuck insert bears the ultimate force of the nitrogen spring's use stroke. After human intervention in the insert reset, the nitrogen spring instantly rebounds and resets. In the case of unreasonable design strength of the plunger rod hanging platform or defects in the heat treatment process, the plunger rod hanging platform fractures, This can cause the plunger rod to detach and pop out, causing a safety accident. When the insert is stuck, it springs back instantly, and the heat treatment process of the plunger rod is defective. If you hit the plunger rod hard to check whether the air pressure is normal, it will also cause instant springback. So when stamping products, try to avoid this situation to reduce safety accidents.
(3) Extrusion deformation of nitrogen spring cylinder body
The main reason for this is that the closing distance of the stamping mold exceeds the effective stroke of the nitrogen spring, causing the insert to press against the upper end of the nitrogen spring cylinder, causing deformation and fracture of the cylinder plunger. Therefore, when designing the mold, it is necessary to add a limit block to prevent excessive stroke use.
