Assembly Process Analysis of Automobile Fastener connection (II)

In the previous article, we introduced the torque-tightening method of fasteners. In this article, Xinchi Fastener Company will continue to introduce to you the assembly process of automotive fastener connection, that is, the classification of automotive fastener connection, including the classification principle of fastener connection, the division of fastener connection pair, the space requirements of fastener assembly and the space requirements of the fastener assembly.

The classification principle of fastener connection

According to the degree of impact of the safety, regulatory and functional importance of the vehicle, the hazard that may occur when the vehicle fastener connection fails is defined as three risk levels. Different risk levels have different requirements for fastener assembly and documentation as well as installation tools. Specific risk levels are as follows.

1. High-risk class: direct or indirect body and life danger or operation hazard when fasteners fail;
2. Medium risk level: failure of fasteners leads to functional failure of vehicles;
3. Low-risk level: failure of fasteners, resulting in discomfort for drivers and passengers.

Among them, high-risk grade A is mainly used in the brake systems, safety system, power assembly, steering, fuel system and other important connection applications; Medium risk level B is mainly used in the automobile chassis, undercarriage body, opening and closing parts, electrical appliances and other important occasions; Low-risk grade C is usually applied to interior and exterior trim, body accessories, etc.

Division of connection pairs for fasteners

There are three kinds of fastener connection sub-states: hard connection, soft connection and joint connection. The ISO5393 standard has the following requirements for hard and soft connections.

1. Hard connection: refers to the connecting piece is a relatively large or rigid connection. Generally, the torque attenuation after the assembly of this kind of connection is little, and even the static torque will be greater than the dynamic torque of the assembly. When the fastener reaches the fitting point, the target torque can be reached after a 30° rotation.
2. Soft connection: refers to the connection part itself being relatively soft or there is elastic material between the connecting parts. The torque attenuation of this kind of connection is great after assembly. After reaching the fitting point, the target torque can be reached only by rotating more than 720°.
3. In daily use, most fasteners are connected between a hard connection and a soft connection, also known as a joint connection.

Space requirements for the fastener assembly

Fastener assembly is through a special sleeve or gun head under the drive of assembly tools, to achieve the designed torque value. In the design process of fastener products, it is necessary to take into account that the fastener needs to leave a certain distance from the peripheral parts in the assembly process. Fasteners should not interfere with other parts. And it needs to be easy to operate for assembly workers on the production site.

Boundary design requirements for the fastener assembly

In the design of fasteners, the installation space of tools should be considered. The following situations should not occur.

The position of the fastening point is in a confined space and cannot be seen by the operator. In this case, the tool and fastener are difficult to locate, and the fastener is not easy to take out after falling down.

There are other parts occluded above the fastening point (axial interference). There may be less room in the final installation position, but you also need to consider the length of the fastener and the interference of the initial state tool with the other parts above.

Xinchi Fastener Company is a trustworthy fastener company, especially in furniture nuts. And we are the designated fastener supplier to“STAPLE”. As a trusted fastener supplier,  Xinchi Fastener Company can offer a wide range of high-quality fasteners, including tee nuts, screws, bolts, rivets, washers, etc. If you want to know more about fasteners or want to wholesale fasteners, please feel free to contact us. And then our experienced and expert service team will reply to you as soon as possible.