May 26, 2014

We Found the Perfect Solution For Us

Single wire connection? Passive distribution boxes? Fieldbus? This question sparks intense discussions in the electrical departments of many companies. Schuster Maschinenbau GmbH from Denklingen, Germany has an excellent solution for solving the problem of finding the ideal installation concept. They found that passive distribution boxes are the most practical solution for most of the machines. A universal pluggable design based on Murrelektronik's Exact12 distribution boxes simplifies installation also in the cabinet.

Schuster Maschinenbau GmbH is headquartered in Denklingen, Germany, about 60 kilometers from Munich in beautiful Bavaria. The company was founded 1979 and presently has 65 employees.

Currently, the company has four main pillars: it produces and develops vertical turning machines, impact cutting systems, automation solutions and custom machines.  Schuster Maschinenbau GmbH delivers about 35 machines and systems a year. The majority of them - about 30 machines - are vertical turning machines. The company distinguishes three different types of turning machines: flexible turning cells (F series), pick-up lathes (P series) and vertical turning cells with integrated fast handling systems (V series).

Schuster Maschinenbau GmbH is a mid-sized company with strong customer orientation: many machines are designed according to customer requirements. These customers are often mid-sized companies in the automotive supply industry.

Herbert Assner is the manager of the electrical department at Schuster Maschinenbau GmbH. One of his tasks is installing and connecting the I/O points of the machines and systems in a very simple, reliable and cost-effective manner into the cabinet and connecting them to the control.

Three different concepts are established in the market: conventional parallel wiring, passive distribution technology and fieldbus technology. An important criteria for selecting the right installation concept is the relationship between the I/O points and their distance to the machine. With a very small number of I/O points, conventional 1-to-1 wiring may be the most cost-effective solution. However, this requires a lot of installation time, even when the number of I/O points is small. This makes the installation with passive distribution technology a more cost-effective solution. Pluggable or molded homerun cables of distribution boxes are quickly installed and they prevent wiring errors in the field. LED displays show the status of operating voltage and signals. The time required for installation, commissioning and service is significantly shorter, because the I/O level is designed in a pluggable way which results in lower total costs. In case of extensive installations with a high I/O density that also require comprehensive diagnostic options, an active fieldbus system may be the right solution.

Schuster Maschinenbau GmbH also uses fieldbus technology, that is Murrelektronik's modular fieldbus system Cube67. This system is used in impact cutting machines, because it's the most cost-effective solution. Mr. Herbert Assner and his colleagues have worked out, however, that passive distribution is the best solution for many other machines that Schuster GmbH produces.  The reason is that about 50 I/O points is the typical number for a Schuster machine, and they are located in a rather compact space. Passive distributors gather the I/O signals directly in the field into the cabinet and connect them to the control.

Murrelektronik's unique, new distributor concept with passive distribution boxes from the Exact12 series allow Schuster Maschinenbau GmbH to engineer installations in their machines with overall pluggable connection from the control cabinet into the field. If the I/O points are farther away from the cabinet, they are connected with a distributor cap with pre-wired or molded cables.  Distributors for rear mounting are used for I/O signals that are located near the cabinet.

For safety applications, Mr. Assner and his colleagues use Exact12 safety distribution boxes. Additionally to eight standard sensors, up to eight actuators for safe shut-off can be connected to these boxes. The relevant ports are marked by yellow rings (360° marking). These yellow rings make it easy for the workers in the production and the machine operators to clearly recognize the safety ports. Safety distribution boxes of the Exact12 series are approved according to EN ISO 13849-2. Up to performance level d can be achieved with safety distributors. This standard refers to fault exclusion in case of short circuits of adjacent conductors, terminals and multipole connections. Herbert Assner explains: "Most of all in the field of hydraulics, for example with main drain valves, we use a two-channel switch off for safety reasons.

By implementing the well-engineered distribution concept based on Exact12, Schuster GmbH can do completely without terminal boxes that take a lot of space in the machine and require time-consuming, error-prone and expensive installation.

The system offers even more benefits: eleven- and twelve-pole power strips have been pre-wired to the homerun cables of the distribution boxes to simplify installation. "In the cabinet, they are transferred with a transfer module with spring clamp terminals," says Herbert Assner. "This goes very fast, because it's no longer necessary to connect up to 23 terminal points to terminal blocks by hand." When installing the distribution boxes it is not necessary to connect the ferrule ends. And implying the solution with pre-wired terminals, Schuster Maschinenbau GmbH can be certain that the components used are already 100% tested. This is a huge relief especially for safety applications. "This way, one possible error source is already eliminated, when the machine is commissioned.", Herbert Assner explains. A service adapter offers an additional option to visually check all I/O signals. If all connections are error-free, the test LED on this control component light up and directly show the signal states. "This installation concept creates a clear separation between control cabinet and machine peripherals", Herbert Assner continues and he explains another advantage: "With this system of transfer adapters in the cabinet we also have a simple separation for transport that facilitates on-site commissioning. The additional connectors that otherwise are used to separate the machine are also no longer required." The manager of the electrical department says: "With this distribution system, we have found the optimum solution."

The Torque Wrench: A Clever Tool

Herbert Assner appreciates installations based on M12 connectors, because they have proved to be very durable and they are easy to handle by the operators. "And the torque wrench is also an additional help", the manager of the electrical department explains, "especially with fully populated distribution boxes we can be sure that really all connections are made with the correct torque - and therefore IP67 sealed. Tightly connected, no wobbling."

And if space is extremely scarce, Schuster Maschinenbau GmbH also uses M8 distribution boxes. This is often the case in robotic applications or in the field of handling and assembly. "Murrelektronik's M8 distribution boxes feature different mounting holes that allow horizontal and vertical mounting, this is another advantage for us", says Herbert Assner and he is very pleased about this additional flexibility.

And talking about flexibility: When integrating hydraulic power units that are often separately delivered to the end customers, Schuster Maschinenbau GmbH also relies on a distribution solution from Murrelektronik. "Here we prefer the cap models of the Exact12 series," explains Herbert Assner, "this solution helps us to create a simple and quick transport separation."

Exact12 - durable because completely molded

  • Highly resistant and durable with TPU molding
  • Vibration resistant up to 50 g, tested with vibrations and free fall
  • IP65 and IP67 tested
  • Approvals according to multi-norm standard (RoHS, UL, CSA, Gost)
  • With two cables that are suitable for C-track applications: PUR/PVC (with 2 million bending cycles) and only PUR (5 million bending cycles)