Distech Systems Inc. (Rochester, NY), an original equipment manufacturer of robotic machine tool tray loaders, designs their equipment to interface with machining centers and automation equipment for the machine tool industry. Distech Systems uses a tray stacking system and robotic technology to load and unload parts from trays or heat treat racks and feed them directly into a machine tool's internal loader.
Inside a Distech machine tool loader, various tasks are performed simultaneously. A typical sequence of operation starts with the automated tray system that accepts stacks of trays from carts. An elevator transfers the top tray in the stack. The elevator raises the top tray and locks it into position. A robotic arm empties or fills the tray depending on the application, and the completed tray is then transferred to a restack station.
 Distech sets themselves apart from other companies by offering a plug-and-play design configuration that allows the company to properly size a system to best meet their customers' needs. "We use a different approach in designing our systems," says Dan Schwab, owner of Distech Systems. "Our equipment is modular with an integrated robot on a 7-axis slide." By using an articulating robot with a 360° range of motion, Distech's machine tool loader has more flexibility than traditional gantry style robots. The articulating robot eliminates the need for very specific alignment with the host and increases the flexibility of the system.
Hardwiring was expensive and space consuming.
While Distech's modular approach enables speed and flexibility for the machine tool process, handling the hardwired connections of multiple inputs inside the machine was time consuming and labor intensive. Hardwiring was Distech's standard. Every discrete input - hundreds of them - required a cable that traveled back to the junction block and to the control panel. This was both expensive and space consuming.
Connecting the articulating robot was a challenge as well. Robot manufacturers provide only a limited number of conductors to control end of arm (EOA) tooling which was restrictive for Distech because the company offers many options at EOA. The company experienced higher labor time in wiring and required a large amount of mounting space for so many conductors. "We needed to find a better solution," says Schwab.
Schwab and his team of engineers looked at various bus systems to reduce the amount of cables running through a machine. Seeing the advantage in alternative networking, they tried the Actuator-Sensor interface (AS-i) bus system. "We tried the AS-i bit-level bus system on one machine, and we never looked back," says Schwab.
Distech chooses the AS-i system for networking.
AS-i is the lowest-level, potentially least-expensive open network available for sensors and simple actuators. It was founded in 1990 as a non-profit independent organization by a consortium consisting mainly of sensor manufacturers and is now supported by more than 100 vendors worldwide.
The philosophy behind the AS-i network is its simplicity. A basic AS-i system structure consists four main components: a controller, a power supply, standard I/O modules and a trapezoidal "flat" cable that carries both power and data to a controller. To setup a system, the flat cable is positioned along the path of the I/O points. The I/Os are then connected to the cable using AS-i's snap-and-go piercing technology. One cable can connect an entire network of I/O points. If needed, a user can connect additional splitter modules to branch and lengthen the network as well as add safety functionality. The controller controls all communication over the AS-i cable without the need for special software. A power supply feeds a symmetrical supply voltage into the AS-i cable which provides communication and power to the sensors.
Numerous companies offer the AS-i networking system, but each differs in its own style of connection components such as controllers, power supplies and modules. Distech tried several suppliers' systems until finally deciding on the AS-i system from ifm efector (Exton, PA), one of the original founding members of the AS-i consortium.
 A selling feature for Distech was the compatibility of ifm's I/O field modules with their machines. The low-profile I/O module has a smaller form factor than most and fits easily inside the machine tool loader. A quick-mount slide enables the flat cable to be sandwiched between the upper module and its base without the need for mounting screws. The module can rotate in three directions with a simple twist to accept the cable vertically or horizontally. This allows Distech to stock fewer parts. The width of the AS-i block mates perfectly to the structure of their machine. Distech uses Bosch rail throughout their machines and the width of the AS-i block - exactly 45mm - matches the rail perfectly. Highly visible LEDs on the upper module indicate signal status. Unlike many suppliers who charge separately for the top and base of an I/O module, the cost for an ifm I/O module includes both components.
One of the biggest benefits of the AS-i network was the ease of adding and subtracting components. The AS-i network is not limited by topology and structure. AS-i has no restrictions in terms of adding or subtracting components. "Other systems keep you very regimented and can be very complex," says Schwab. "The AS-i network allows our group to wire any way they want. We can snap on a block wherever we want. Clip on a splitter. Add branches where we deem necessary."
Although referred to as a flat-cable network, AS-i allows users to choose the best cable for their application. Distech can easily transition from a flat cable at the block, to a high-flex round cable, and back to a flat cable wherever needed, without restrictions. This is important for Distech who often has different requirements in any given area of a system.
While there are many advantages to the simplicity of networking I/O points, Distech found the ease of programming an added benefit. Since the actual program is a function of the main PLC, Distech's control engineers found it simple to address the blocks during initial setup. AS-i's simple format allowed their staff to understand and incorporate it immediately. "AS-i allows us to increase the number of options at EOA by adding addresses instead of conductors. This offers us much more flexibility in complex applications," says Schwab.
ifm's Controller-E PLC/gateway integrates an Ethernet IP node and controller in a single housing.
For data exchange with higher-level Ethernet IP networks, Distech uses ifm's Controller-E PLC/gateway that integrates an Ethernet IP node and controller in a single housing. The network interface enables structured data acquisition of the digital and analog inputs from the connected AS-i system. The Controller-E can connect up to two full AS-i systems, up to 868 I/O points, as one node on a higher-level bus system. Information is passed transparently from the AS-i system to the higher-level network without the need for additional software. A highly visible four-line LCD display lets users instantly check operational status or diagnostic information. Pushbutton programming and a configurable menu structure provide quick setup, and the integrated display can change languages.
In cases of troubleshooting, the AS-i system is very intuitive. The system indicates when a fault occurs. If there is a problem on the machine, the AS-i network applies its auto-addressing feature. The bad block is taken off and a new block is attached which programs itself. Schwab states, "Our engineers snip off one block. Upstream is dead, and downstream is still on." He adds, "It's plug and play; someone can't make a mistake. And, if there is a mistake, the system can take you to where the problem is without closing down the entire network."
 For position detection inside the tray loader, ifm proximity sensors are used to locate pneumatic slides, monitor elevator lifts, detect trays, and monitor inputs. Although Distech considers proximity sensors a commodity, he uses ifm sensors because the company offers high quality products, good pricing, and the products are familiar to his customer base. When a problem arises, ifm's customer support team provides immediate service and stand by their products.
Distech realizes large savings in labor.
Schwab has seen a 38% reduction in labor savings and is moving closer to a 50% savings as his team gains more experience with AS-i. Distech electricians are no longer needed to cable the machine. "The mechanics are wiring the machine, not the electricians. They layout all blocks, plug in all sensors. The electricians are back in the panel doing what they should be doing," says Schwab.
For some of Distech customers, the AS-i network is not well known. But, according to Schwab, everyone they have introduced it to is now using it as a standard. If their customer needs to make changes or additions, they go to their cabinet and snap it on a new component.
"As simple as AS-i is, it still has the diagnosis tools that you would associate with high level systems," says Schwab. "It is seamless, transparent, and a delight to use."
For more information about Distech Systems Inc., visit www.distechsystems.com. Click here for more information about ifm efector's AS-i Networking System.
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