Critical Process Steps in Crimping

Crimping & Crimp Quality - Issue 7

With both semi-automatic and fully-automatic crimping, the critical process steps begin before the actual crimping process and end with verification of the crimp quality.

Crimping is a complex procedure requiring an optimal interaction of different processes and processing media. Depending on the final product and the required quality, the ability to automate the process must be taken into consideration early in the terminal design stage. Although the choice of appropriate materials (conductor type, wire cross-section, crimp terminal design, etc) is strongly related to the end product, the ability to automate the process should also be considered in the early stages of development. 

fully automatic processing:
CrimpCenter 64

At first sight, it is not possible to tell whether a crimped wire was processed using semi- or fully-automatic equipment.  Therefore, important issues to consider are the quality to be achieved and the necessary expense and effort during the process. Since the basic processing steps are identical for both processing types, the same quality requirements apply. The main difference is in how the wire is moved between the individual processing steps.  It can be moved automatically (=high process security, short cycle times) or manually (=high flexibility).

Some types of terminals can not be crimped automatically, or can only be automated with considerable expense and effort. An example is crimping of loose-piece closed barrel terminals onto battery cables.

Example of processed tube type terminal

Here, the terminal must first be manually placed onto the stripped cable end, whereby all individual strands must be covered by the barrel/sheath. This process requires “fingertip touch” and is therefore usually carried out manually.  This type of terminal is often crimped using hexagonal form (cable cross-sections >25 mm²). Battery cables are large and heavy, making them difficult to handle.  They are often fitted with loose-piece closed barrel terminals or battery connectors and run in small production quantities. In most cases, special heavy duty crimp applicators are used for the different designs.

Quality Assurance

Fault recognition and fault prevention processes are also critical steps of the crimping process.  Crimp force monitoring (CFM) is the "in-process" quality control method used to monitor the quality of the crimping process during production.  The CFM measures the crimping force during the crimping process.  It compares the force/time curve of each terminal being crimped against the stored reference curve.  If the measured values are outside of the specified tolerance limits, the crimp is identified as bad.  Today, two out of three crimping presses have a CFM system installed on them.   

In modern production environments, early recognition of production faults is generally standardized and supported by numerous measuring methods. Follow-up costs can be reduced, but only after a few faulty wires have already been produced. It is better to avoid faults in the first place. Alongside internal organizational measures, faults can also be avoided through the use of modern technology. Most measures can be used in both semi-automatic and fully-automatic processing.

Human Factor

With semi-automatic processing, the individual processes are carried out using different machines (in different places). This requires additional processing steps and thereby creates additional potential for error. Through the combination of processing steps (e.g. Stripper-Crimper) and a targeted quality assurance, the highest quality requirements can also be realized here. 

The human factor is not just important during semi-automatic processing. Specialist competency in setting up, operation, and maintenance is just as important as material quality and precision of the processing medium. In the end, the interplay of people and technology determines the crimp quality.