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Synchronizing Servos

Liquid filling machines designed for pharmaceutical users benefit from 12 to 24 axes of servo control.

The servo drives and MKD washdown servo motors (above) are part of a control system that uses up to 24 axes of servo control per
The servo drives and MKD washdown servo motors (above) are part of a control system that uses up to 24 axes of servo control per


Leading U.S. pharmaceutical manufacturers around the world are using Bosch Packaging’s FLM-Series machines to fill prescription liquids into glass and plastic bottles and vials. Critical to the performance of these filling machines is a Rexroth Power PC motion controller that governs up to 24 axes of motion.

“We chose the Rexroth servo controls because of their strong support, both for us and our customers,” says Jeff Jackson, product manager, Pharmaceutical Division, Bosch Packaging North America.

The Rexroth controls package is also compatible with Rockwell Automation’s Allen-Bradley ControlLogix programmable logic controllers (PLCs) and human-machine interfaces (HMIs) that Bosch Packaging uses for the FLM machinery.

Jackson notes, “We structure the FLM fillers so that the Rexroth controls ‘report’ to the Allen-Bradley PLC. It doesn’t have to be done that way, but we do it that way because of the benefits in validation.”

The U.S. Food and Drug Administration, he says, “is looking for proof that [the process] is in control. Every customer has its own way of doing that, and we have to meet each customer’s requirements. We don’t deal with the FDA, but we can assist our customers. We offer validation services and stay in tune with the FDA requirements.”

The controls architecture looks something like this: The PLC sends signals to the Rexroth multi-axis motion controller, which in turn signals the drives that actuate the servo motors. The HMI uses Ethernet to connect to the Allen-Bradley ControlLogix PLC. The PLC uses ControlNet to communicate to the Power PC. Serial Real-Time Communication System (SERCOS) is used for all digital drive communications, servo drives and servo motors.

The Rexroth controls perform electronic line shafting, camming and registration functions. They’re critical in several areas, including the two four-axis robotic units that execute high-precision vial picking and placing functions at the filler.

Jackson says the FLM machines can be configured with four to 16 filling heads. Top speed is 600/min.

The liquid filling machines fill either glass or plastic vials or bottles with injectable drugs administered by a doctor, typically at a hospital or clinic.

The Rexroth servo controls synchronize functions including the infeed starwheel, transport system, nozzle motion, in-process control check-weighing, pumps, stopper and outfeed starwheels.

The Rexroth controls, Jackson says, “benefit Bosch Packaging because of the flexibility we can design into the machine

for different customers and different applications.” He says Bosch Packaging is trying to use its controls proficiency as a sales tool, though he admits it depends a little bit on if the customer has a reluctance with the new technology. “We try to work with them, and teach them. We’ve had Rexroth people come in here and talk to them, we can go to the customer and we can put customers in touch with other customers already using these.” The latter, he says, does happen, even in the competitive pharmaceutical business.

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