Running third-party devices through the network (sidebar)

Dec. 1, 2004
One of the benefits of an open-source network protocol is you can run a mixed collection of devices on the same centralized network.

One company that can attest to that is JVH Engineering Inc., Grandville, Mich., which helps automotive suppliers retrofit injection molding machines (IMM). JVH worked with one auto supplier to retrofit an IMM that used a Bosch Rexroth digital injection controller and a Bosch Rexroth closed loop clamp controller. This needed to be integrated with an Allen-Bradley SLC 5/05 programmable logic controller that communicates to the Bosch equipment.

The DeviceNet network JVH installed allowed the auto supplier to communicate with the Bosch Rexroth closed-loop controllers and download all the setpoints for the process control. The SLC can then trigger the different parts of the process such as starting the machine clamp “close” process. Diagnostic information is also available. Once the cycle is complete, the Bosch Rexroth controllers provide actual data that help determine how well the machine performed.

“To retrofit the IMM, we utilized more of the functionality of DeviceNet than the typical user,” explains Jason Cassiday, project engineer at JVH. “The third-party modules have explicit messaging, so we were doing messages within the logic.” Cassiday explains that the most difficult hurdles were making sure the messages communicated correctly. The result of blending the third-party devices into the automation system is a reduction in scrap rate by nearly 90 percent, and the retrofitted machine is 5 percent more efficient in cycle time. The cycle time savings alone are $25,000 per year.

See the story that goes with this sidebar: Automation Networking: Stable Protocols and Changing Device Language