Fori Automation (Shelby, MI) manufactures assembly equipment for automakers throughout the world. To get its new tire assembly machines to market that much quicker, the company uses a control system incorporating the SM-EZMotion servo programming module and Unidrive SP from Emerson Control Techniques (Eden Prairie, MN). This combination cuts application development times to just a few hours. The Unidrive SP's universal feedback device support system also facilitates the use of absolute encoders, which increase the machines' productivity once they are in place on the shop floor.

Tire assembly machines put tires on rims, inflate the tires to correct pressure, and palletize them for shipment to auto and truck assembly lines. Servomotors are used because of their accurate speed and torque control, as well as their small footprint. Servos also make the machines flexible because of their programmability, giving them the capacity for rapid product changeover.

According to Fori controls project engineer Kevin Sproat, absolute encoders operating via the Stegman Hiperface protocol eliminate downtime for adjusting the machine homing upon restart or after E-stops. In addition, absolute encoders don't need to home to a sensor on every power cycle. This avoids the problems that result when sensors fail or are moved out of positional tolerance due to machine vibration.

"The use of absolute encoders more than pays for itself, as we estimate their use could save about an hour of downtime a week," Sproat says. With the tire assembly cycle being 10 seconds, that translates into 300 additional tires being produced each week.

The SM-EZMotion module uses Windows-based PowerTools Pro software, which allows Fori to program a new application with very few lines of code. Specifically, "drag and drop" and "point and click" tools simplify integration of the DeviceNet fieldbus for plug-and-play communication with the PLC and HMI.

Both the SM-EZMotion and SM-DeviceNet modules snap into place inside the Unidrive SP, which can accommodate up to three modules. Because of the Unidrive SP heatsink configuration, Fori was able to achieve optimal thermal design by using through-hole panel mounting. This allowed Fori engineers the flexibility to place drive panels where they wanted on the machine and avoid the expense of adding panel air conditioning.

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