The rivet nut is a new generation of riveting fastener products on the market. It changes the traditional method of installing parts on thin plates, and is a new breakthrough in the joining process of plates. At present, in the sheet metal industry, the rivet nut fixed by riveting method is generally used to fix the threaded connection nut on the sheet metal part. There are two kinds of riveting methods and tools. One is to use riveting gun riveting, which is mainly used for riveting. The riveting of sheet metal parts with small batches of various types and repairs; the other is the riveting of sheet metal stamping die, which is mainly used for riveting of single type of sheet metal parts in large quantities. Both of these two riveting methods have fatal defects - low production efficiency, high labor intensity and poor stability of riveting quality. Another riveting method is active riveting. This riveting method has a simple operation process, which can just compensate for the above two methods.

1. Riveting method of riveting gun

The riveting process of the riveting gun is: take the part → insert the nut → screw the riveting head into the nut → pull riveting → unscrew the nut with the riveting head → product. The defects of the riveting method of the riveting gun: the process is cumbersome, the efficiency of manual nut insertion is low, the production efficiency is low, the technical requirements of employees are high, the service life of the riveting gun is short, and the service life of the riveting gun head is short.

2. Mold riveting method

Mold riveting process: take parts → insert nuts → position on the mold → press riveting → products. The defects of the die riveting method: the process is cumbersome, the artificial nut insertion power is low, the production efficiency is low, the fixed stroke riveting method has poor compatibility with the nut length deviation, and the riveting quality is unstable.

3. Active riveting scheme design

Active plug-in equipment has been widely used in the sheet metal industry, and the skills are quite mature, but because the riveting nut selected by the automatic plug-in equipment is a pressure riveting nut, there is no precedent for using a rivet nut. Compared with pull riveting, pressure riveting still has the following defects:

(1) For the same standard riveting nut, the pressure riveting mother is more expensive than the riveting nut (at the market price).

(2) Press riveting has strict requirements on the thickness of the sheet (material thickness ≥ 1.0mm), so it is not suitable for parts that require the use of thin materials (material thickness<1.0nm). Thickness will greatly increase the production cost. At the same time, the structural parameters of the pressure riveting nuts selected for different plate thicknesses are not consistent. If the pressure riveting nuts are used for production, the types and standards of the nuts will be increased, which will eventually lead to increased production management and quality management costs.

The primary reason for the rolling of the rivet nut is that the round rivet nut cannot form a structure that avoids rolling after riveting. After analysis, if the method of matching the hexagonal riveting nut hole with the circular riveting nut is selected, a part of the material of the riveting nut will flow to the gap between the circular riveting nut and the hexagonal riveting nut hole during the riveting process, forming a hexagonal shaped boss. The boss can play the role of preventing the nut from rolling.

The working process of the mold is:

① The parts are positioned on the positioning pins to ensure that the riveting surfaces of the parts are level;

②The upper die presses the riveting nut into the cavity of the lower die, and the positioning pin moves downward with the pressing of the nut;

③When the positioning pin touches the fixed seat, the nut wall is plastically deformed, and the deformed nut and the parts are tightly combined to achieve riveting;

④The upper die continues to descend, the lower die shaft sleeve cooperates with the upper die to re-press the deformed part of the nut, and part of the material of the deformed part of the nut is pressed into the gap of the hexagonal riveting hole of the part to form a regular hexagonal structure to prevent the nut from rolling. effect;

⑤ The upper die goes up, the positioning pins hold up the parts, and the riveting process is completed.