Cobots Empower Donnelly Custom Manufacturing to Optimize People‑Automation Balance

Donnelly Custom Manufacturing is a short‑run, high‑mix custom molder that performs more than 40 mold changes a day on its 37 injection machines to serve customers’ low‑to‑mid‑volume needs (see previous articles in March ’15 and Sept. ’12). One of its key challenges is learning where and how to automate jobs that may run only a few hours.

As president Ron Kirscht explains, this ongoing learning curve is driven by a string of record sales years—$36.2 million in 2018—which keeps Donnelly’s Alexandria, Minn., plant busy, even with the addition of two new presses last year. “We need to be agile while leveraging our short‑run expertise to manage effectively and save time in critical processes, both setups and production runs,” he says.

For more than a decade, Donnelly has been adding robotics, installing Cartesian‑style part removers on all machines above 140 tons. These robots free employees for higher‑value tasks such as welding, decorating, and machining. In the last five years, the company has explored collaborative robots, or cobots. It began by installing two Baxter cobots from the former Rethink Robotics (now out of business; its technology was acquired by the Hahn Group of Germany). Donnelly uses them for simple pick‑and‑place tasks, such as packing or clipping sprues. “Packing boxes takes the equivalent of half an operator’s time,” Kirscht notes. “The Baxter can do it and keep count without the need for weighing the boxes.”

GOING COLLABORATIVE

Last year, Donnelly explored what further potential cobots could offer in more sophisticated sequential operations. The firm bought its first UR5 cobot from Universal Robots. “We visited CNC machining shops in our area that use several UR cobots. We could see that they are more capable than the Baxter in speed, precision, and ease of programming,” says Jerry Bienias, Donnelly’s vice‑president of operations.

Donnelly put the UR5 to work loading two tiny inserts into a two‑cavity mold, then removing the parts, clipping the gates, and dropping the parts into tubes in a box—five parts per tube. The entire sequence is completed within a 40‑second cycle, thanks to end‑of‑arm tooling (EOAT) developed by Donnelly to allow the cobot to perform all operations with a single EOAT. As a result, a cell that formerly required one and a half operators now requires only half an operator’s time. (See it in action here.)

Bienias says Donnelly will likely continue to use UR cobots for future purchases. The Baxter cobot, no longer on the market, was not suitable for insert loading due to arm shake. “We still love the Baxter. It was our launching pad into a new world of collaborative robotics,” he says.

While cobots are praised for their safety around people, Donnelly has hard guarding around the EOAT area because the parts being molded have sharp edges that could cause injury through accidental contact.

Cobots are also touted for their ease of programming using a “lead‑through teach” method. Accurate setup of the UR5 is essential for insert loading. One factor is the mold, heated to 380 °F, which expands as it warms. The UR5, mounted on wheels, is bolted to the press, and a special setup EOAT that closely matches the production version is used to “teach” the robot where the mold is in space by locating pegs on the mold. Within five to ten minutes, the cobot is oriented precisely enough to place the inserts within a couple of mils.

Although Donnelly is pleased with its evolving use of cobots, Kirscht points out that “people continue to perform the majority of critical manufacturing tasks here. Automation helps us better understand the nature of the tasks performed by humans so that we can identify opportunities to strike the right balance between people and automation.”