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Measuring system cables for large machining centers

The complete machining of large components such as diesel engines, turbines, generators, and ships’ propellers is resulting in ever larger machining centers. This also affects the machine technology. The constructor of these highly complex systems generally uses the latest generation control units for which a special overall solution with a measuring system cable has been developed. This can securely transmit signals over even large distances and ensures good machine availability.

WALDRICH COBURG GmbH is a global leader in the field of large machine tool construction. "Our guiding principles are to maintain the highest quality standards and a consistent focus on customers", states Dipl.-Ing. (TH) Thomas Bätz, Group Manager for Electrical Design. The Coburg site manufactures horizontal and vertical milling machines, vertical turning machines, and grinding machines. "We regard ourselves as a reliable partner for our customers throughout the world when specific requirements arise in terms of complex technologies, precision, machining performance, workpiece dimensions, and productivity." “

Demand for the machining centers is continually rising and the number of employees has grown from 500 to approximately 850 over the last few years, of which around 10% are apprentices. "This enables us to safeguard our need for specialists in the long term." To machine parts economically, general, production, and application engineers all work hand in hand. "We are committed to a high vertical range of manufacture as this enables us to guarantee the best quality for our customers", explains Thomas Bätz. "For example, all key components such as spindle and milling units are produced and assembled on site. Even the most complex switch cabinets are created by our in-house team." “

Measuring system cables for large transmission ranges

Energy chains and chainflex® cables from igus® GmbH in Cologne have been used in large machining centers for many years. In smaller versions of the portal machining centers, the company also opts for pre-assembled energy supply systems operated under the name readychain®. "Our customers often use the machines for 20-30 years or more and require at least 95% availability throughout this period", states the Group Manager.

Picture of a machine tool with a E4 e-chain from igus®

WALDRICH COBURG machine tool during assembly. Foreground: An igus® E4 energy chain supplies the moving machine table with signals and media.

 
Picture of the involved persons

Oliver Köhler, Andreas Muckes (both igus® GmbH), Thomas Bätz, and Thomas Bischoff (both WALDRICH COBURG GmbH).

 

"This means that all components must function impeccably under all circumstances and at all times", comments the Group Manager, highlighting the high requirements profile. "In this context, we have had great experiences with igus® chainflex® cables over the years." “
 
In 2010, the specialist in large machining centers decided to use new control technology in its machines. The modern control unit is equipped with the open encoder interface Drive-CLiQ. This is a drive-internal interface that permits the interconnection of components from different manufacturers and reliably transmits the measuring system signal in real time. The changeover also involved a need for new measuring system cables. As the Coburg machine engineers had already experienced good results with the CF113.D cable series in their machines’ energy chains, the decision was made to connect the Drive CLiQ systems to CF113.028.D, a cable that was specially developed for this interface.

When it comes to machining centers, the aim is to appropriately design the cables, plugs, and number of coupling joints. "That makes it extremely complicated", states Thomas Bischoff from the Electrical Design Department. "Every coupling joint is an obstacle for the signal. As a result, the length specified by the control unit manufacturer is additionally restricted with each coupling joint." “

CF113.D cables have a PUR jacket. When used in energy chains, they offer an optimized braid and shield structure for a longer service life. Further to being halogen-free and flame-resistant, they also fulfill further important criteria established by the machine tool manufacturer, including being UL and NFPA79.2012 approved.

chainflex® measuring system cables are available for medium to high stress levels. They are generally tested in energy chains with many million cycles. PVC, PUR, and TPW measuring system cables for systems from all prestigious manufacturers worldwide can be selected. Depending on their type, the cables are flame, coolant, and oil resistant, can be used at high speeds and acceleration levels, and fulfill the diverse requirements established by the drive technology manufacturer. This means that almost all drive manufacturers can find the perfect cable for them in stock.

Growing signal distances

In the first instance, the technical specifications of the control unit manufacturer have been fulfilled. "However, we quickly realized that the cables weren’t long enough for our large machines. The reason for this was simple. If the technical specifications provided by a control unit manufacturer indicate that a measuring system signal can be transmitted over a maximum distance of 50 m, we quickly hit boundaries as lengths of up to 100 m have to be overcome with our large machines", explains Thomas Bätz.

When it comes to machining centers, the aim is to appropriately design the cables, plugs, and number of coupling joints. "That makes it extremely complicated", states Thomas Bischoff from the Electrical Design Department. "Every coupling joint is an obstacle for the signal. As a result, the length specified by the control unit manufacturer is additionally restricted with each coupling joint." “

Picture of plug connector and measuring system cable for large machining centers.

Plug connector and measuring system cable for large machining centers.

 
Picture of a warehouse has multiple chainflex® cables in stock.

The Coburg warehouse has multiple chainflex® cables in stock.

 

Furthermore, the machine manufacturers have to guarantee that all individual components can be easily installed and removed even on their high-tech machines. "This leads to multiple coupling joints and thus a reduction in the signal distance specified by the control unit manufacturer." “
 
Further to the above, the cables must withstand the continuous movement in the energy chains and the sometimes harsh environmental conditions associated with metalworking without becoming damaged. Thomas Bischoff comments: "Cables and plugs must be robust and fulfill the mechanical, electrical, and chemical requirements. They must also be easy to process during production without having to procure additional specialist tools. Where possible, we also wanted to continue using the same cable and plug material so as to avoid problems during the changeover." “

Multiple advance tests

Presenting a solution is not only about the proper functioning of a cable but also about the number and properties of the individual connection points. "It isn’t possible for the solution to be a standard product from the catalog", explains igus® Product Manager Andreas Muckes. "We looked at every last detail before qualifying an appropriate solution. " Test series were conducted in the in-house test laboratory in Cologne to find the optimized connection solution. The cables then went to the user, who connected them to an original control unit. Realistic machine loads were next simulated to test the everyday suitability of the cable concept found.

All the work eventually led to the desired result: Today, the measuring system cables perform well in all machining centers with the new control unit generation - even when retrofit to older machines. They have worked seamlessly from day one. A major advantage for installation is that the familiar M23 round connectors can be used as default components.

"The results are impressive. The necessary durability and signal quality have been achieved. A total cable length of 90 to 100 m is currently possible without issue and a length of 120 m is even conceivable", states Thomas Bätz. A maximum of five connection points are also used. "This plug/cable combination enables us to realize extremely low dampening properties. These are far lower than with the original from the control unit manufacturer", adds Thomas Bischoff.

Seven basic features of durable cables chainflex® cables prevent cable failures in energy chain applications. To this end, igus® has prepared the cables with seven design tricks: They comprise a core with high tensile strength that stabilizes the composite stranding inside the cable and thereby prevents corkscrewing and core breakages. A special copper litz wire prevents core breakages thereby creating durability in continuous movement, even for small bending radii. The litz wire is adapted to meet all requirements. For example, in the field of measuring systems, there are many different cross sections. The cross section is therefore customized for each application to achieve the best result.

Only high-quality materials are used for core insulation - ones that have stood the test of time in millions of core kilometers in energy chain applications. Stranding in bundles strengthens the core braid and relieves it in the radius due to lower tensile/pressure stressing. Corkscrewing and core breakages are therefore prevented. The gusset-filling, extruded inner jacket provides sustainable external support for the composite stranding. An overall shield with optimized shield braiding prevents shield breakage and clearly enhances the EMC properties of a cable. The narrow braid angle and redistributions or shield pairs influence the signal range, i.e. the signal’s sensitivity to interference after a certain number of meters.

There is also a highly abrasion-resistant, pressure extruded outer jacket for attaching the shield braiding. This ensures minimum abrasion in the energy chain and thereby demonstrably a longer service life, even under highly dynamic loads.

In a measuring system cable, the core cross section combination is specified by the manufacturer of the measuring system or control unit.

Picture of measuring system cable for the new generation of control units.

Measuring system cable for the new generation of control units.

 
Picture of igus® chainflex® cables in the energy chain.

igus® chainflex® cables in the energy chain. They withstand all thermal, chemical, and electrical requirements.

 
Picture of a tight shield concept with narrow braid angle and narrow redistributions.

Tight shield concept with narrow braid angle and narrow redistributions. This affects the cable’s robustness.

 

That means that there is a direct interdependency between the number of cores of a particular size that are braided together and the electrical capacity signal properties. There is absolutely no leeway. "Finding a compromise in which both the necessary electrical properties and the necessary durability could be achieved required a great deal of experience, which we could invest in this and many other applications", states Andreas Muckes.

Complete stock

Measuring system cables are basically aligned with the relevant measuring system from the various providers. They must remain functional at all times. "Our requirements in relation to robustness against external influences and stability have been fulfilled from the start", reiterates Thomas Bischoff. "That can be attributed to the close and successful cooperation during the development process." “
 
WALDRICH COBURG exclusively uses the broadest range of chainflex® cables in its machining centers. These guarantee the centers’ long service lives and must therefore be available from stock. "We’ve no problems to report in this regard either", concludes Thomas Bätz. "As there are no shortages, quick response times are achieved when cables are required." “

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