Why Universal Robots redesigned its industry-standard cobot flange
Universal Robots recently unveiled its UR30 cobot, designed to take on heavy payloads and workloads and support high torque screw driving. The UR30 shares its architecture with the UR20, already an industry leader.
However, rather than using the existing flange from their current line of cobots, Universal Robots completely redesigned the component for the UR20 and the UR30. But why redesign a flange that has essentially become the de facto industry standard for cobots? Why fix what is already working?
“It was a fairly large decision for us to say we were going to abandon [these] flanges,” said Anders Billesø Beck, Vice President for Innovation and Strategy at Universal Robots. “We’ve built an ecosystem with more than 460 products that are tailored to the design we have today. But we decided we needed to take that one step up, to decide what high payload cobots need.”
The limitations of an already well-designed component
The standard flange, such as the one used in the company’s UR10, is used in machines designed for lower payloads. It can, however, accommodate up to 20 kilograms—if it is positioned and secured properly. The increased torques and speeds of the robot at that payload weight, along with sudden changes in speed and momentum, place significant stress on the flange, eliminating the room for any error in its operation.
“You need to be really careful using the small flange with a 20 kilo payload,” said Carsten Nommensen, Technology Leader, Cobot Arm at Universal Robots. “Remember that when you’re moving things with a robot, it’s not just a vertical pull, you might have a lot of momentum as you move things around dynamically, and you might have some lever effects as well.”
While Universal Robots offers an adaptation plate for the UR20 to better enable it to handle those loads, the company recognized that a long-term solution would require redefining the standard for tool flanges on high payload cobots. “It is important for us that every application we are building is safe and works smoothly out of the box,” said Nommensen.
Using simulations to design the new flange
Universal Robots had rolled out an extensive research, testing and prototyping campaign even before making the decision to design a new flange. In fact, the company had conducted physical simulations of the screws that hold the existing flange in place, including the shear forces in the screws and the moment the screws bend, to ensure they could withstand the UR20’s workload. That’s where they originally identified that payloads exceeding 20 kilos needed a new component.
“We have a build and simulation model for the tool flange where we take our alloy into account,” said Nommensen. “We simulate with the stresses in all directions and we also rotate the stresses around in space in order to ensure that there is no weak point in any of the directions. We do fatigue tests on physical models to compare it with the simulation model, which helps us understand that our models are actually also correct.”
Running digital simulations enable the designers to factor in many complex variables—and they can run a new simulation every two minutes. These variables include the dynamics of longer robot arms versus shorter ones: even if the torques are the same, the dynamics can be significantly different. This enables the simulations to accurately portray the flange’s behavior as the cobot moves a heavy payload around in space.
Universal Robots uses Ansys for simulation, and relies on Siemens products for lifecycle management. The company also deploys AI for software development and test pipelines, and uses custom equipment as well for its simulation work.
Breaking robots to make a better robot
Digital simulations aren’t the only tool in Universal Robot’s flange redesign toolkit. The company also relied on extensive prototyping to make sure its new flange design worked.
The company typically has two or three different iterations of all its prototypes in development, and builds 50 to 60 complete units for testing. Universal Robots also conducts sub-component testing or subsystem testing; one example is testing fatigue strengths of the tool flange.
“We have a test team that shows up whistling going to work every morning, because all they do is break robots,” said Beck. “They just love that.”
The company can run a couple hundred tests, from small components to the full arm in the entirety of its motion; some of the tests are multi-month and even multi-quarter tests to monitor long-term wear on the parts. This is done to ensure that the cobots can withstand the years and decades of their service life, and uses both virtual and real-world models—especially for modelling and testing complex interactions such as how friction evolves over time, or how microsecond changes in timing affect the robot’s performance.
For this reason, Universal Robots implemented full traceability in its testing pipelines. “We try to test as much as we can as close to the source of the error as possible,” said Beck. “We can identify the origin of those challenges and have a super quick turnaround to get them resolved. While it gets more and more expensive to fix as we go downstream in the test pipelines, and it gets harder to identify the problem, it also identifies when some of the bigger issues may be cross-functional. That’s often some of the things that we discover later on in those test pipelines.”
This rigorous testing regime not only helped identify the limitations of the existing flange, and therefore the need for a new one, it also enabled the company to conduct exhaustive design, development and testing on the new flange—so that the new flange could be rolled out to market with confidence.
In-house and industry-wide collaboration
Redesigning a crucial component that has become the industry standard is not done on a whim. It requires close collaboration by different teams inside the company, as well as open and extensive partnership with the companies that rely on Universal Robots’ products.
“When we started selling cobots 15 years ago or so, we managed to standardize on one flange design, which has become the de facto standard for collaborative robots,” said Beck. “It allowed us to standardize an ecosystem. And as soon as you become a standard in an ecosystem, of course you need to be very careful when you change the specifications.”
At Universal Robots, product teams are enabled to work independently on their components, while having holistic and cross-functional leadership to ensure each component fits into the bigger picture.
The company had extensive dialogue with its partners and clients about the proposed flange redesign—and found the industry was supportive.
“We didn’t want customers to needing an engineering degree in mechanics to decide which screws to use on their flange,” said Beck. “Or even just being concerned that a product mighh fall apart or even put customers at risk. So our ecosystem was actually quite excited about us taking this, the right technical decision.”
Creating a new flange enables companies to differentiate between lighter and heavier payload products. With the new flange and the UR30, companies can specialize in heavier payload products. Or, they can continue to use the UR20 and UR30 with the adapter flange if their work falls under that weight restriction, and the company will still provide support for them.
Identifying the need for a change, and developing a new flange to address that need, has been a long road for Universal Robots.
“It was a long process, but it can be beneficial to give it that time, to really step back, and think slow,” said Beck. “And then as soon as we knew exactly what to do, then we could create the design and scale it out.”
While the new flange has only recently entered the market, Universal Robots is confident that, given time, it will find widespread adoption in the industry. “I do expect a number of the other heavier payload cobots to adopt it as a standard,” said Beck. The company’s partners are already developing and building tools that will use the design.
