Terminal Crimping to Wires and Application

In a wire harness, a terminal is crimped onto the end of each wire. The crimping quality of terminals and wires plays a vital role in the overall quality of the wire harness; at the same time, the control of the crimping quality of this area has also been recognized by all wire harness manufacturers. Therefore, it is very meaningful to conduct in-depth research on the crimping here.
We know that most of the terminals crimped at the end of the wire harness are open crimped terminals. The typical structure is shown in Figure 1. For such terminals, due to their large usage, every wire harness factory has conducted in-depth research on its crimping methods and formulated specific work instructions to control the crimping quality of this part of the terminals.

Typical construction of crimp terminal blocks

Figure 1. Typical structure of open crimp terminal
However, with the development of automobile manufacturing technology, especially the development of hybrid and pure electric vehicles, closed terminals are increasingly used in automobile wiring harnesses. For closed terminals, since they were rarely used in automotive wiring harnesses in the past, many wiring harness factories now do not know how to start with the crimping process and quality control of this terminal. Therefore, it is particularly important to conduct systematic research on the crimping forms of closed terminals and the situations where various crimping forms are suitable. The author below introduces several crimping forms of closed terminals.

01, diamond crimping of terminal blocks
The typical structure of diamond crimping is shown in Figure 2a, and the cross-sectional shape after crimping is shown in Figure 2b. This crimping method is suitable for situations where the wall thickness of the crimping terminal is very thin and the crimping quality requirements are not high. In order to increase the force of pulling the wire out of the terminal, the terminal is composed of multiple rhombuses in the longitudinal direction, and each rhombus is evenly distributed, and the direction of the rhombus is staggered.

Diamond crimping of terminal blocks

Figure 2 Diamond crimping
Since the wall thickness of this type of terminal is very thin, the crimping force is not strong, so the crimping can be achieved with a special manual crimping pliers. Of course, there are also dedicated crimping machines, but the investment cost is relatively high, making it uneconomical to do so. This crimping method is commonly used on household appliance wiring harnesses. It is used to fix the head of the wire, and then fix it in the line by squeezing the screw. Now this crimping method is also seen in automobile wiring harnesses, but because the quality of this form of crimping is not very high, it is rarely used and is generally used in less important parts of automobile wiring harnesses.

02, one point crimping of terminal block
This crimping method is mainly suitable for hole-type joints and crimping barrels with relatively thick wall thickness. The typical structure is shown in Figure 3a, and the cross-sectional shape after crimping is shown in Figure 3b. As you can see from the cross section, it is pressed down from a

One point crimping of terminal blocks

Figure 3 One point crimping

Since the wall thickness of this type of terminal is relatively thick, the crimping force is a bit large, and the crimping cannot be achieved with manual crimping pliers. This can only be achieved with special hydraulic pliers, but the crimping quality of hydraulic pliers is not high and the efficiency is extremely low. Wire harness factories generally use special molds to achieve this crimping on a punch machine, so that the height of the crimping can be accurately controlled, and the crimping quality and efficiency are better than those of hydraulic pliers.
This form of terminal is mainly used in the main circuit of automobiles to transmit power to the automobile circuit, so it has high requirements for crimping quality.

03. Two-point crimping of terminal blocks
This crimping form is also suitable for hole-type joints and crimping barrels with relatively thick wall thickness. This form of crimping is used only because the size of the socket connector and the crimping barrel are larger, and the crimping method with one point is not enough to fully deform the crimped terminal. The cross-sectional shape after crimping is shown in Figure 4.

Two-point crimping of terminal blocks

Figure 4, two-point crimping
This form of crimping is very powerful. Wire harness factories generally implement this crimping using a special mold on a punch machine, thereby achieving precise control over the crimping height.

04, Four-point crimping of terminal blocks
This crimping form is suitable for aviation plug pins with relatively thick walls and relatively small volumes. The typical structure of the adaptable terminal is shown in Figure 5a, and the cross-sectional shape after crimping is shown in Figure 5b. The crimping of this terminal is forced from all four sides, forming 4 dimples.

Four-point crimping of terminal blocks

Figure 5, four-point crimping
In this form of crimping, force is applied from all sides, the force is received evenly, and the excess material of the terminal has a place to escape. The force of crimping is not very large, and it is the form of crimping with the best effect. However, this crimping form requires a relatively complex structure of the crimping mold, and of course the investment cost is relatively high. At the same time, due to the complex structure of the crimping mold, it is very difficult to design the crimping mold for larger terminals. Therefore, this type of crimping is only suitable for crimping smaller terminals.
This type of crimping is mainly used in automotive wiring harnesses where aviation plugs are used, and is not widely used in automotive wiring harnesses.

05, Hexagonal crimping of terminal blocks
This crimp form accommodates very thick wall thicknesses. If the terminal cannot be fully deformed by any of the above forms of crimping, its crimped shape will be close to a regular hexagon. The typical structure is shown in Figure 6a, and the cross-sectional shape after crimping is shown in Figure 6b.
Since this form of compression has no place for the extruded material to escape, the terminal should not be deformed, so the matching between the terminal and the wire is required to be very good. If the matching is not good, some holes will be found during cross-sectional analysis of the crimped terminals, which is unqualified. Sometimes in order to make up for this problem, a point will be added on the top and bottom of the hexagon during design to enhance the compactness of the crimping and increase the pull-out force.

Hexagonal crimping of terminal blocks

Figure 6, Hexagonal Crimp of Terminal Block

This form of crimping force is also very large, and it also requires a special mold on a punch machine to achieve precise control of the crimping height. In addition, some special terminals have two holes for crimping two wires. The typical structure is shown in Figure 6c. We can also achieve this by pressing a hexagon, but the upper and lower sides need to be longer.
With the development of modern automobile technology, especially the application of electric drive technology in automobiles, more and more closed terminals have been widely used in automobile wiring harnesses. Through the research on closed terminal crimping, it is very meaningful to fully master this technology and make the performance of automotive wiring harness more stable, both now and in the future.