Upgrading machine components to boost productivity

No machine lasts forever, and every manufacturer recognizes that its production equipment has a finite life cycle. Product lifecycle management and establishing a plan for retiring and replacing equipment is critical to sustain the highest levels of productivity, uptime, and product quality.

Cummins Inc., a global company that designs, manufactures, sells, and services diesel engines and related technologies, recently consulted with Hoffman Estates, Illinois-based Bosch Rexroth Corp. and determined that some Bosch Rexroth drive units used on machine tools at its Jamestown Engine Plant in Jamestown, New York, were reaching the end of their life cycle. The companies have worked together on a regular basis for servicing Rexroth products and equipment life cycle planning for the Jamestown plant.

The plant has eight high-speed camshaft contour grinders that use Rexroth RAC spindle drives on the machine tools’ rotating axis. The contour grinders are 3-axis machines that grind parts based on a machine-generated path – the spindle rotates the part being ground at high speeds while the other two axes move around it to grind the required part.

Cummins has been able to keep these older Rexroth spindle drives operational for more than 15 years by sending the equipment out for repair. However, replacement components were no longer available, and a more permanent solution was needed. Keeping the contour grinders operating was important, so a solution that allowed for this was critical.

“Everything we build here is already sold,” says Cummins plant machine electrician Michael McLaughlin. “We don’t inventory engines, so we can’t afford to have a grinding machine go down.”
 

Equipment upgrade schedule

Plant management was interested in the most cost-effective and efficient migration path for replacing other legacy machine components. The grinders were part of an installed base of 50 machine tools and other production systems that were identified as potentially needing component upgrades, retrofits, or complete replacement during the next several years.

When Cummins contacted the original equipment manufacturer (OEM) to inquire about replacement parts or upgrade options, the tool builder proposed an extensive solution that would replace most of each of the machines and take one year per machine to implement – an approach Cummins rejected.

Cummins turned to Bosch Rexroth, which offered a solution to sustain the performance of the machines – without an extensive or expensive overhaul – and could interface with the existing third-party motor in each machine.

After discussions, it was jointly determined that a retrofit program for the contour grinding machine RAC spindle drives was the right solution. The RAC drives were no longer supported, so Bosch Rexroth engineers had already created a plan for migrating older equipment to current technology to extend the life of machines, so that solution needed to be tailored to meet Cummins’ needs.

According to McLaughlin, four of the eight contour grinders are older machines that Cummins has scheduled to be replaced within the next five years. Rexroth came up with a custom solution that would extend the life of the newest grinders while keeping the older machines in operation until their scheduled replacement.

“We decided to upgrade the four newer machines with the current Rexroth drive technology (the DKR), which would provide us with four more spares of the obsolete RAC drive to keep the older grinders operating until their scheduled replacement,” McLaughlin says.
 

Integrating new drives

Naser Suleiman, the Bosch Rexroth applications engineer who worked with McLaughlin on the Jamestown plant retrofit, recommended the Rexroth DKR AC drive as the replacement for the legacy RAC drives. Part of the Rexroth DIAX03 family of drives and drive controllers, the DKR drive is a modular AC drive that combines AC servo and spindle drive performance into a compact package suited for machine tools.

The DKR drive has a similar footprint to the RAC drives, enabling easy replacement. In addition, it features similar parameter sets, and there is no need to change the spindle motor’s encoder – easing the RAC-to-DKR upgrade. It also provides a power regeneration option – any excess power generated by the machine’s duty cycle is fed back into the contour grinder’s power bus.

Using the Rexroth DKR drive meant there was no need to change either the motor or encoder on the axis. In addition, the DKR features an adapter cable that eliminates the need to rewire interfaces, saving time on installation.

The final requirement from Cummins was that the Rexroth DKR drives interface with third-party Reuland AC motors. Rexroth’s Suleiman was able to reach out to the motor manufacturer and obtain the required specifications to configure the new Rexroth drives for installation, saving time and limiting any technical complications with the retrofit.
 

Machine service

With the technical requirements satisfied, Rexroth personnel set up a schedule to install the new DKR drives that would have minimal impact on Cummins’ operations. Instead of a year-long process that might have been required to upgrade an entire machine, retrofit installation took only two days per machine.

The four new DKR drives have been installed on the contour grinders, extending their drive service lives to 2019.

Cummins can enter a Rexroth program that would extend service life to 2024.

Suleiman’s decision to reach out to get the necessary motor specifications was an example of the support Rexroth delivered to Cummins, says McLaughlin.

“Rexroth’s service and retrofit departments always do an outstanding job communicating to us when products are reaching end-of-service, and presenting us with options for drives and controls migration, whether it’s for retrofits, upgrades, or remanufactured solutions,” he adds. “They’re not just salespeople; they’re engineers who’ve been out in the field who really know their business. I like being able to pick up the phone for support, or schedule someone to come in and help us when our electrician staff can’t resolve the issue.”

Bosh Rexroth
www.boschrexroth-us.com

Cummins
www.cummins.com