Background & Introduction

Hexagonal crimp is the most common type of crimping for copper and aluminum cables, lugs and connectors, as it is suitable for both copper and aluminium conductors.

The central force of a hexagonal crimp is applied consistently from all directions during the crimping operation. And the individual strands of the conductor are being homogeneously compressed preventing any damage, which produces a consistent electrical field and consequently has a positive impact as to an unwanted field scattering, as shown in following figure 1.

Due to a strong mechanical connection and an even compression, the hexagonal crimps are also suitable for application in medium and high voltage cable terminations, connections and joints.

Hexagonal Crimping- Din types

The range of copper lugs is approximately corresponding with the cross sections from 6sqmm to 400sqmm.

LV Lugs & Connectors 

– complete range of copper crimp connectors suitable for use with joints and terminations for low voltage cables, as shown in following figure 2.

HV Lugs & Connectors 

– complete range of copper crimp connectors suitable for use with joints and terminations for medium/high voltage cables , as shown in following figure 3.

Apart from mechanical pull out tests and cross-section analyzing, also electrical durability tests are included.

The Correct Crimping

An incorrect crimping can lead to low compression  or excess compression crimps, which may cause potentially fatal consequences. Defective cable crimps and lugs can lead to rise of temperatures because of increased contact resistance, which, in the worst case, can cause fire, as shown in following  figure 4.

Prior to the cable crimping operation,  the operator must ensure that the conductors or cable joint be brushed to achieve a metallic clean surface if necessary.

While stripping cable conductors, it can not being damaged. And the bared length of cable lug or connector is more or less identical with insertion length. Crimping dies need to be clean and metallic bright.

Tip: HongHao recommends to start crimping operations on cable lugs always from the palm towards the cable. In this case the compressed material can slide towards the cable end which hasn’t been crimped.

Only a sufficient degree of compression is being achieved to insure optimum contact properties, as shown in above  figure 5.

Practices

In the previous content, regular hexagonal crimping is defined in detail, and it is generally used in the following cases:

1.The hexagonal crimping machine with the integrated non-changing die, as shown in figure 6.

2. The large tonnage terminal crimping machine is equipped with a non-changing die separately to form a combined hexagonal crimping machine, as shown in figure 7.

Non-changing Die has the following benefits:

A. One Die can be suitable for crimping of terminals in a range of different specifications; for example, if the die is 10 to 120 mm², then the terminals in this range can be crimped.

B. At the same time, it can also be slightly adjusted for any terminal in the specification to meet the crimping requirements (cross-sectional area, compression ratio, etc.), this is especially helpful for terminals of the same specification but different styles.

For example, two 70 mm² terminals with different parameters or cross-sections, may have different effects as fine-tuning based on the standard parameters is applied.

Because of this, the die is designed with straight edges and does not need any additional bump structure.

As a result, there are the following disadvantages: because the blade movement stroke is very small, the maximum size of the crimping hole is not large, and it is not convenient to operate for some connectors (such as the elbow in figure 9 or the connector / terminal size is too large).

Under such circumstances, there is a good solution on the market:

Non-changing Die of Opening & Closing Type: it can be opened from the side to avoid the restriction of joint size, as long as the entrance size is larger than the crimping part, it can be put into it for crimping.

From the above, it can be seen that the blades of the non-changing die is movable, and the crimping size of the die can be adjusted arbitrarily, so there is no problem in the design of the die.

The crimping blades of the non-changing die are actually six ones, each of which represents an edge of the crimping section, the corresponding steping time is consistent with the feed distance.

Therefore, in the process of crimping, the six edges are synchronously contracted toward the center to form a regular hexagon, which is scaled proportionally in the crimping process.

Therefore, the calculation of compression ratio is one of the main quantitative criteria to help confirm the crimping quality, but it is not the only one.

It must also be confirmed with the cross-sectional analyzing.