Grinding help

Automating the weld grinding process with a robotic grinding cell proves beneficial

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The Fab-Pak OmniClean robotic grinding cell features 3M’s Servo Rotary Tool that ensures consistent speed at varying force loads.

Two companies that are each more than 100 years old and both giants in their fields have come together in recent years to collaborate on an automated grinding solution for weld removal. Robotic grinding provides an opportunity for manufacturers to increase productivity and ease the challenges of a shrinking labor force. Grinding is considered one of the last hurdles for robotics in manufacturing as it requires a light touch.

A new turnkey robotic grinding cell from Lincoln Electric and 3M addresses this concern to provide confidence in robotic weld prep and grinding. It helps that the Fab-Pak OmniClean is backed by 3M’s experience in abrasive material removal and application engineering support and Lincoln Electric’s welding and robotic integration expertise.

The partnership began “a couple of years ago when we were contacted by 3M through our robotics supplier, Fanuc Robotics,” says Shawn Vincel, general manager, Lincoln Electric Automation. “We are both leaders in our respective industries so we were looking to develop solutions for material removal systems, specifically weld removal using robotics. The two companies discussed the potential opportunity and in what markets we could potentially sell automated material removal systems. That formulated high potential and we’ve been in collaboration ever since.

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The 3M Active Compliant Tool ensures the robot applies the right amount of force for optimal grinding performance in the weld removal process.

“On the welding side of our automation business, as our customers grow, they want to automate more of their processes, whether its assembly, material handling or others,” he adds. “So, material removal is an extension of the tangential operations to welding, and we are very interested in that.”

3M comes into play on the abrasives side of things. “We’ve had a robotics team for more than 30 years,” says Tyler Naatz, senior global application engineer, 3M. “We have a lot of abrasive knowledge, experience and expertise on how to optimally set up an automated process using 3M abrasives. Lincoln is an expert in bringing the automation to life. Using our abrasives know-how and their automation skills, it really is a great pairing.”

The right force

There are a few challenges with robotic grinding for weld removal. For a robot to be able to apply the right amount of force for optimal grinding and required finishes is probably the biggest. This, however, is addressed in the Fab-Pak OmniClean with 3M’s Active Compliant Tool.

“Having force control is very important because the media wears away,” Naatz says. “Over time, it’s not going to cut as fast as it was at the beginning so having force control and being able to adapt forces as grinding is taking place is very important. The Active Compliant Tool allows this.”

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The all-in-one Fab-Pak OmniClean solution includes application support from robotics experts at 3M and Lincoln Electric Automation.

Consistency in the amount of weld needed to be removed can also be a challenge. If the workpiece is coming from a robotic welding system, typically consistency is not a problem.

However, “even if the welds are not super consistent, they can still be removed successfully,” Naatz says. “Robots are much more rigid than an operator, making robots more capable of handling higher torques. This means a disc on the robot, with a servo motor and Active Compliant Tool, can be used at a lower angle. Constant force at a lower angle allows more of the abrasive on the disc to be used, creating more contact time on the weld for faster removal and better blending once the weld is removed.

“When the disc is on the weld at a constant force, there is a small contact width on the disc creating a high unit pressure and fast cut rate,” he continues. “When the weld is removed, the disc has the same amount of force applied to it, but now on a much larger contact area, drastically lowering the unit pressure on the disc, which allows for a nice blend. The lower the angle the disc can run, the better the finish. As long as the welds are not drastically different, the angle of the disc and use of the Active Compliant Tool can compensate for the difference without an issue.”

And on the welding side, Vincel says Lincoln has the ability to try and tailor the welds produced knowing what the finished product needs to look like. “We have processes in our welding capability that can help simplify the grinding process.”

The Fab-Pak OmniClean can be used for weld prep as well. The one robotic grinding cell can be used for both processes.

Unique cell

The Fab-Pak OmniClean comes with everything needed for robotic weld removal by grinding. The turnkey system comes pre-engineered to automate and optimize grinding without the added time and expense of a custom-built cell.

The grinding cell requires minimal assembly, installation and setup. The single-station headstock and tailstock system includes a Fanuc robot equipped with 3M’s servo rotary tool that ensures consistent speed at varying force loads. A fully integrated software package is used to adjust parameters and maintain safety features of the Active Compliant Tool.

Available in 3-hp or 5-hp models, the Active Compliant Tool allows constant force throughout the grinding process.

“Active force control is super important for consistent finishing and adapting to different areas of a part,” Naatz says. “It compensates for gravity so if the robot is working on the top or bottom or the left or right side of a part, the forces will be the same and create consistent finishes.”

For built-in, tool-changing functionality, a custom tool drawer was developed to allow for a quick changeout of grinding media. The drawer is also removable to allow the operator to change out media while the unit is working, which provides a lot of flexibility.

Even though grinding is inherently different than welding, programming the operations is the same.

“Looking at the back-and-forth motion an operator uses for grinding, it seems like it would be difficult to program,” Naatz says. “But with the robot, we can run it more consistently and use a single pass, in most cases. It’s a simple path of straight lines and easy to program. It is essentially the same as welding; it just looks a little different. Grinding is all about the angles, and that is similar to a weld torch.”

Each grinding cell comes with an abrasives starter pack with discs designed to quickly remove and clean welds. This is helpful for startups and the first couple of days in the initial runs.

Customer response

For customers interested in the robotic grinding cell, 3M offers testing on parts to show the process works.

“We are able to offer a proof of concept to the customer,” Naatz says. “We like to show the customers the process – the tooling and the sequence. There haven’t been a lot of automated systems out there to show people that robotic grinding is possible, so it helps for people to visually see that it can be done.”

One reason customers might be particularly receptive to robotic grinding is the labor shortage.

“A huge challenge in the abrasives world is finding workers who are willing to run a grinder all day long; It is a dusty, dirty environment and running a grinder is difficult and not very fun,” Naatz says. “Becoming an experienced operator takes time, and due to the challenges of the job, it is tough to hire and retain workers. The robotic grinding cell is a great alternative.”

Vincel sums up the Lincoln and 3M partnership this way: “The combination of 3M’s expertise in application of abrasives coupled with Lincoln’s strength in developing automation solutions offers our customers the best robotic system for material removal. It’s been a great partnership and we rely heavily on each other to provide the best solution for the customer.”

3M

Lincoln Electric Automation

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