Solving 3D Printing’s Hidden Problem: Vibration

As with any other type of machine that involves moving parts, 3D printers deal with vibration. But users often don’t recognize how much of an impact vibration has on their machines. “When you ask people, ‘Does your machine vibrate?’ they’ll say no,” says University of Michigan mechanical engineering professor Chinedum Okwudire. This is because machine vibration has an easy solution. “You just slow down and you don’t see vibration anymore,” he explains. “That’s why it’s actually a hidden problem.”

This means machines aren’t reaching their full potential. “People have not tried to push their machines to the limit,” he notes. “They just take the default parameters and say, ‘That’s the speed I’m supposed to use.’” OEMs can make other adjustments to their machines to counteract the effects of vibration and enable increased speed. Damping can help reduce vibration, but it adds mass, requiring more energy to run the machine and increasing wear and tear. Machines can also be made of stiffer materials, but OEMs have reached the limits of what they can do to design their machines to deal with vibration.

“People have not tried to push their machines to the limit. They just take the default parameters and say, ‘That’s the speed I’m supposed to use.’”

Okwudire studied the effects of vibration in machine tools while earning his PhD, and encountered the issue again when working for machine tool builder DMG MORI. “That's where the idea came to consider using software to compensate for vibration so that we can speed up the machines without sacrificing the quality of the parts that we're making,” he says.

When Okwudire joined the University of Michigan, he started researching how software could be used to compensate for machine tool vibration, eventually developing an algorithm called Filtered B Splines, or FBS. At the suggestion of one of his students, he applied the algorithm to 3D printers. “3D printers are close to our wheelhouse because they are manufacturing machines,” he notes. As they looked into FFF 3D printing, they saw quality issues that could be caused by vibration. And when they applied FBS to an FFF 3D printer, they were able to double the speed of the machine without compromising part quality or changing the machine’s hardware.

Okwudire has founded a company called Ulendo to make FBS available to the manufacturing industry. Beyond 3D printing, the algorithm is applicable to subtractive machine tools and robotics, but the company is focusing on FFF 3D printing as its entry point into manufacturing.

Vibration Compensation

3D printers, like robots and other machine tools, work by sending motion commands to the machine or equipment. FBS “tricks” the machine and modifies the motion commands based on how the machine vibrates. “Say you want the machine to travel straight, but due to vibration, it veers upward,” Okwudire explains. “What FBS does is that it asks the machine to move downward.” The downward motion cancels out the upward vibration so the machine travels straight.

Before the software can be applied to a machine, it needs to be able to predict how the machine is going to vibrate. This is accomplished by measuring the machine’s vibration behavior and creating a model called a calibration map. “With that calibration map, we're able to predict how the machine vibrates without our algorithm, and then determine what we should do to compensate for that motion,” Okwudire says. For 3D printers, this is a one-time process. For example, a 3D printer manufacturer would send one machine to Ulendo. The company then creates a calibration map of the machine, which can be deployed on all machines of that make and model.

After the calibration map is created, FBS is installed within the printer’s firmware (the software that controls the machine’s motors), and this is where all of the compensations are made — not in the G code. “It takes in the original commands, and then it modifies them and sends those modified commands down to the motors of the 3D printer,” Okwudire explains.

Faster Print Times

For the first test, the team printed a scale model of the US Capitol on what Okwudire describes as a “low-cost desktop printer.” Results showed that FBS reduced print time by 50%, from four hours to two, without impacting quality. These results (doubled print speed) have been consistent across multiple brands of FFF printers, including what would be considered “higher end” models. “It doesn't surprise me because I worked in an industry that manufactures high end machines and I knew that those machines had vibration problems,” he says. “It’s not a low-cost machine problem. It is a problem that is shared across the board at different levels.”

Faster print speeds means higher throughput, which could translate to a number of benefits. For example, “We've spoken to people who say they have to buy a second or a third printer just to keep up with the demands,” Okwudire says. But if their existing printer can produce parts twice as fast, they won’t need to add more machines as frequently.

It could also open up new business opportunities for on-demand printing. For example, say there’s a kiosk that scans a person’s feet and prints custom insoles. If it ordinarily takes four hours to print the insoles, that’s half the day. But if FBS reduces the print time to two hours, that’s much more feasible for on demand manufacturing. Customers could finish their shopping and come back to pick up their insoles. “Four hours to two hours can make a big difference in in the production value or the end benefit of 3D printing in a particular industry taking off or not,” Okwudire notes.

Beyond FFF

Although Ulendo is starting with FFF 3D printing, the technology is applicable to many different manufacturing applications. “FBS is agnostic to the actual process that is happening at the end,” Okwudire says. “It makes whatever you’re doing more capable.”

This includes other 3D printing processes, such as directed energy deposition (DED). “I would expect more or less the same results for DED because the machines carry heavy masses that move quite aggressively,” he notes. “So I think the vibration problem is equally as bad.” FBS could also be applied to powder bed fusion (PBF), particularly machines that use a gantry to drive the lasers, because they’re relatively similar to FFF, though it could also possibly benefit PBF machines that use mirrors.   

Outside of 3D printing, FBS could also be applied to machine tools, which have a similar platform to FFF printers. However, these machines have the added factor of cutting forces. During roughing passes, where the machine tool is removing a lot of material, the cutting forces work against the vibration, and accuracy and surface finish are less important at this stage. But during finishing passes, where small amounts of material are being removed, cutting forces are lower and the machine tool can start to leave vibration marks on the part that affect the surface finish. FBS could improve speed and part quality in these applications.

Robotics is another area that Ulendo is closely investigating. This would be more complex than a 3D printer because a 3D printer gantry’s “payload” (the nozzle) is constant, and the motion is limited. A robot’s vibration changes depending on the motion and the payload, plus it has more axes of motion, so the team is working on a version of FBS where the calibration map changes as these factors change. Similar to 3D printers and machine tools, FBS could allow robots to move faster, but it could also allow collaborative robots to handle heavier payloads.

New Machine Possibilities

Okwudire says that a major opportunity for FBS is how it could enable new machine designs and configurations. When machine OEMs don’t have to be so concerned with designing machines to reduce vibration, it opens new possibilities such as machines with smaller belts and motors. “You could have lower cost 3D printers or robots that are more capable,” Okwudire says. “It will open up precise 3D printing to a different class of people who might benefit from these machines.” There’s also the potential to add more functionality to machines. For example, FFF 3D printers could have multiple nozzles without sacrificing print speed.

In the short term, however, Ulendo is working with 3D printer OEMs to add FBS to machines. “We decided as a company for efficiency’s sake to start with 3D printer manufacturers,” says CEO Brenda Jones. It recently announced that Flashforge is including FBS on two of its printers. One, the Adventurer 4, is Flashforge’s best-selling desktop printer, and the other, the Creator 4, is a new industrial model, so Ulendo will get exposure to both the maker and industrial 3D printing spaces. The company is in the process of onboarding the software onto the printers, and hopes that they’ll be available by the end of the year. Longer term, Ulendo plans to offer FBS as an aftermarket option for a variety of machines. “There are millions of printers already out there this could help,” Jones notes.