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Crimp Force Monitoring Improves Crimp Quality
The CK 01 Crimpforce Monitor, developed specifically for Z + F AM/CR series crimping machines, provides high-speed, high-precision crimp quality analysis.
 

Crimp connection technology is widely used in the electrical and electronics industry. Compared to alternative means of making interconnections, advantages include excellent electrical performance and high mechanical reliability, assuming that the crimping operation is carried out correctly. Proper inspection of crimp connections can ensure that high quality is maintained, and the the Zoller + Frohlich CK 01 Crimpforce Monitor is an invaluable tool for visual monitoring of crimp connection quality. When teamed with a display module from Electronic Assembly GmbH (www.lcd-module.de), the combination provides reliable crimp-connection inspection capabilities

Founded in 1963 in Wangen, Germany, Zoller + Frohlich GmbH (www.zofre.de) brings more than 50 years of experience in cable crimping to customers in need of repeatable inspection capability. At the company site in Wangen, Germany, the firm designs and manufactures high-performance components and systems and also makes machines for high-precision production of these components and systems. The company's recently introduced model CK 01 Crimpforce Monitor helps ensure consistently high quality during wire stripping and crimping operations. The CK 01 provides real-time monitoring of crimping connections along with graphic analysis. Together with the model eDIPTFT43-ATP color display from Electronic Assembly (EA), a long-time business partner of Zoller + Fröhlich, cable crimping monitoring can be performed efficiently and effectively.

With the growth of international quality standards, such as those developed by the International Organization for Standardization (ISO), process monitoring and documentation are becoming increasingly important. For example, in the aircraft industry, every crimp connection must be checked for integrity. This type of inspection helps ensure that crimp functionality is not impaired in any way, such as due to missing cable strands, poor insulation in the crimp contact, incorrect crimp depth, the wrong wire gauge, or inadequate stripping.

Verifying Crimp Quality
Inspection of crimp connections can be accomplished in a number of different ways. One is by means of complex tomography analysis, in this case microfocus computer tomography (CT). A specimen for inspection is rotated through 360° at constant intervals in front of a detector. The multiple images acquired in this process are then converted to an integrated three-dimensional (3D) image on a personal computer (PC). Due to the high operating costs, technical complexity, and large investment of time required (several minutes per crimp), this technique is not suitable for volume production.

Another approach to inspecting crimp connections is so-called micrograph analysis. With this technique, a sample is cut open at a right angle to the cable axis and then deburred and polished. The sample is then treated with acid etching of the surface to improve visibility. A microscope can then be used to determine whether the crimp is conforming or non-conforming. This method has several disadvantages. For one, 100 percent inspection is not feasible because nondestructive inspection is not possible. The cost and time factors are further disadvantages, precluding the use of this approach for high-volume production in most cases.

Tensile testing is yet another crimp inspection technique which is not nondestructive. With tensile testing, a crimped cable is inserted into a machine which measures the force necessary to pull the crimp connection away from the cable, and the resulting force can be compared to nominal (reference) value. Again, this approach is not feasible for 100 percent inspection, and not suitable for production applications.

The simplest method for checking crimp connections is by means of visual inspection by a worker. It is the lowest-cost approach, but it is prone to errors and imprecision. For example, an inspector may spot the complete absence of a crimp, but may miss the absence of individual strands in a crimp connection. This approach can be improved through the use of a crimp height gauge. The height of the crimp is determined and compared with a standard. This method is also very time-intensive, because every contact must be inspected and checked manually following the crimping operation.

The Zoller + Frohlich Solution
Zoller + Frohlich offers a practical solution which is suitable for high-volume production and eliminates all of the disadvantages of visual inspections. The CK 01 Crimpforce Monitor provides 100 percent quality test for just-in-time inspection and documentation of every contact without adding any time to the production process. Force-time analysis is performed during the crimping operation. Teach-in is required on the CK 01 system, and the resulting reference curve is compared with the actual crimp. The CK 01 system is essentially a low-power system, and does not require an additional, dedicated PC for control and a long learning curve of software tools for effective operation.

The CK 01 Crimpforce Monitor handles wire gauges between 0.14mm2 and 6mm2 (wire gauges of AWG26 through AWG10). Using high-precision piezo force sensors, the CK 01 performs high-speed force analysis during the actual crimping operation. The results of every crimp operation can be saved to a Universal Serial Bus (USB) memory stick or PC for documentation and archiving. Information about a crimp is communicated to the operator on a companion 4.3-in. (109mm) touchscreen from Electronic Assembly GmbH which connects to the crimp system using a serial port. If a defect is detected, the force curve shown on the display provides an indication of what has gone wrong. The operator can intervene directly in the process, improve the quality and reduce the reject rate, saving both time and money. In addition to the 4.3-in. touchscreen display, Electronic Assembly also offers 3.2-, 5.7-, and 7.0-in. (81, 145, and 178mm) TFT display screens that connect by with RS-232, I2C, or SPI communications ports and run by 5V DC power.

The CK 01 Crimpforce Monitor is designed for use with the firm's AM/CM and CR series crimping machines, which handle different wire gauges. The CK 01 can store as many as 50 different inspection programs and their associated parameters, for managing many different projects. These different parameters can be clearly shown on the Electronic Assembly's thin-film-transistor (TFT) display screen. As Hans Schneider from the Zoller + Frohlich development team explains, "The Electronic Assembly EA eDIPTFT43-ATP display gives us variable multilanguage design capability without the need for an extra graphics processor. The result is a lean, high-speed system." Another member of the Zoller + Frohlich development team, Gregor Koch, added that "a large set of tools and good support drastically reduced the development time."

By concentrating on the task at hand, namely, high-precision force detection during ongoing production, the design team succeeded in developing hardware tailored specifically for force detection. The EA eDIPTFT43-ATP graphic display presents essential information and provides a mechanism for user interaction. All the main processor must do is send the process data to the display. Rapid implementation, good legibility, and the precision touchscreen make the easy-to-read display module a major feature of the machine design. According to Zoller + Frohlich Chief Executive Officer (CEO) Christoph Frohlich, "Highly intuitive operation of the Crimpforce Monitor on the production floor was a major design priority. Naturally, cost is not a negligible factor. It would have been much more expensive for us to design the display hardware and software in house and then procure and maintain the necessary stock of individual components. Buying into the complete embedded display module was the better option."

The AM/CM and CR series crimping machines together with the CK 01 Crimpforce Monitor and the EA eDIPTFT43-ATP graphic display form a highly integrated solution well suited for crimp connection inspection. It is also cost effective, not adding time to the crimping production process. Inclusion of the Electronic Assembly display module reduced development time by a substantial margin and helped to achieve an unusually fast time to market for a project of this complexity.

 

Contact: Zoller + Frohlich GmbH, Simoniusstrasse 22, 88239 Wangen im Allgau, Germany +49 7522 930800 fax: 49 7522 9308-252 E-mail: info@zofre.de Web:
http://www.zofre.de

 
 
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