The High Velocity Oxygen Fuel (HVOF) coating thermal spray coating process improves or restores a component’s surface properties or dimensions, extending equipment life by increasing erosion and wear resistance. Part spraying usually takes 3 hours to 4 hours, with spraying in 1-minute to 2-minute intervals followed by a 2 minute cool down period with cold air provided by a pneumatic cooler (the blue pipe on the left).

t simply looked too clean,” Juan Puente thought when he saw Universal Robots (UR)’s collaborative robot (cobot).

The thermal spray supervisor at Aircraft Tooling Inc. (ATI) in Dallas, Texas, needed a rugged system – something tough enough to handle the dust and heat of high velocity oxygen fuel (HVOF) and plasma spray to coat aviation parts. He didn’t think the delicate-looking UR systems could outperform traditional industrial robots.

However, he needed an option that the traditional systems could provide as ATI sought to automate aviation repair tasks.

The UR robots can be programmed through the arrow keys on the robot’s touch screen or by grabbing the robot arm and moving it through way points.

“The cost [of a traditional robot] was outrageous. The cast iron models we looked at were too bulky; we could not easily move them between cells; they were hard to program; and all required safety guarding, which would not work in our small spray cells,” says the supervisor, who stumbled upon UR in a YouTube video.

“The UR10 robot had the required reach for the spray distance and the cost was about half of everything else we looked at. It was very user-friendly and portable. Because of its collaborative safety features we did not need to fence it in,” Puente explains. UR robots are classified as cobots due to their built-in safety system that makes the robot arm automatically stop operating if it encounters objects or people within its route.

Nick Armenta (left), automation engineer with UR robot distributor Olympus Controls, and Juan Puente, thermal spray supervisor at ATI, discuss the HVOF spray process. The spray cell is an open booth that allows suction flow through the work cell to keep the robot cool. Robots can be programmed using arrow keys on the robot’s touch screen or by grabbing the robot arm and moving it through waypoints.

Though Puente readily admits that the UR10 “won their hearts,” there was significant hesitation at ATI as to whether the robot would operate reliably in the spray booth’s hot and dusty environment.

Didn’t believe it

“We were very surprised. I actually thought the robot wouldn’t stand it. Some of these powder coatings are tungsten carbide which is a hard metal coating. If it seeps into the bearings of the robot, we were afraid it would destroy them,” he explains. ATI opened the seals on the UR10 and found the bearings intact.

“There were no particles in there, three years of operation, it doesn’t show,” says Puente, adding that recoil from the spray gun was another concern. “We were nervous that the recoil would trip the robot or interfere with the servo capabilities. We went as high as the pressures would take to make it bounce, and it wouldn’t do it. The robot simply stayed in position.”

Initial setup and programming of the UR10 robot took ATI four hours by using the touch screen.

Nick Armenta, automation engineer with Olympus Controls, the UR robot distributor working with ATI, explains that the company’s experience with the robot’s durability is common. “We often see the robots operate in harsh environments, taking over jobs that humans don’t want to perform,” Armenta says. “Many think of cobots as being fragile but the opposite is true, this is an extremely durable robot; it’s sealed against dust, rated for high temperatures, and works just as well in extreme environments as in a cleanroom.”

Maintenance friendly

ATI staff was also surprised to find that no preventive maintenance is required with the UR robots.

“All we do is dust the robot arm off and keep on going,” Puente says, adding that he did not have to pay for a licensing or service agreement. “That was really unusual compared to other solutions we looked at. With the UR robot, everything was included in the purchase price.”

ATI was initially concerned that the UR10 robot would not be able to withstand the recoil from the spray gun attached at the end of arm. They tested it with the highest pressures possible, but the robot stayed in position.

Armenta explains that service calls with the UR robots are not typical.

“We do have to make them occasionally, and that is something we provide free of charge. If there is any kind of issue with the robot and it’s under warranty, we can get a part the next day, if we don’t have it in stock,” he says, recalling how his company has been able to get customers’ robots up and running again the same day by exchanging joints in the robot arms.

Inverted installation

The UR10 robot ATI chose is the largest of the three collaborative robot models – UR3, UR5, and UR10 – Universal Robots offers. The cobots are named after their payload in kilos and span in reach from 19.7" to 51.2".

“We chose the UR10 because of its length, being able to hang it upside down, walk underneath it. Keeping the floor clear of anything was always an advantage to us,” says Puente, who now uses two UR10 robots with a third being installed. The robots’ payload and speed (39.4ips) was more than sufficient for ATI.

Most of the speed comes from turntables making sure that the coating is being applied at a certain velocity,” Puente explains.

“Our spray guns aren’t that heavy, so payload wasn’t an issue.

Fast programming

It took the ATI team about four hours to unpack the robot, get it going and programmed.

“It was a simple, user-friendly process as opposed to other robots with a much more complex, multi-step programming interface,” says the ATI supervisor, who also received a day of free training from Olympus Controls. Programming the UR10’s spray path was done using the teach method that allows the user to grab the robot arm and move it through waypoints inserted directly on the robot’s touch screen. “We used a red laser to indicate exactly where we wanted the robot to move. Once the waypoints were set, we just hit ‘play’ and the robot moved through that trajectory,” Puente says. He looks forward to adding more complex application tasks next. “We’re looking into adding a vision camera, so we can have the robot perform quality inspection of coated parts, locating areas that need an extra coating. There are so many things we can do with these robots that we have only started to explore,” he says.

Aircraft Tooling Inc.
www.atirepairstation.com

Universal Robots USA Inc.
www.universal-robots.com
IMTS 2018 Booth #236861