Breaking New Ground in Robotic Printing

"It was the most complex integrated process we’ve done, by far," says Woodrow Wiest, laboratory engineer at RISE Application Center for Additive Manufacturing, and continues:

“Using large-format robots for printing and machining, in one constant motion, is extremely rare. For us it is brand new. We know that there have been robotic mills for a long time, and robotic printing has been around for a few years. But combining the two, that process is quite novel.”

When Melker of Sweden approached RISE with their new kayak concept, it offered a valuable chance to explore the limits of robotic printing and multi-tooling. Transforming this concept into a finalized prototype became a joint effort between RISE and Adaxis. Adaxis provided both the expertise and software solution needed for a seamless integration of 3D printing and machining. Biofiber Tech contributed with their bio-based materials, while ABB's software was utilized to generate the robot's printing program. Apart from its pioneering complexity, the procedure involved several innovative sub-processes, such as printing on the hatch rings.

“Printing on prints is not an easy thing to do. It’s a very new technology that opens so many more possibilities with printing. Large-scale printing poses limitations when dealing with angles exceeding 45 degrees. If we start printing sideways, the layers won't align, leading to their eventual collapse. As a result, add-ons are typically produced separately and glued on by hand,” Woodrow Wiest explains.  

Creating New Research Opportunities

According to Woodrow Wiest, being able to print on a print has unlocked several new research opportunities. How to improve the adhesion of the second print is one of them.

“How do you get the new print to stick to the previous print, when the previous print is cold and it’s no longer a continuous process? That’s not solved yet. It has been done, but mainly due to luck and coincidence. You get to the right point where it works and keep your settings there, rather than having proper simulations in place that actually show that it’s possible.”

Another unconventional procedure was to vary the extrusion process automatically on certain surfaces, during the single perimeter print. This was to increase the thickness of the hull bottom, and thereby ensure that enough stock was available for milling. The milling spindle was integrated during spring, and this was only the fourth time it had ever been used in a process.

“It’s quite a big leap from professional milling software to printing software. This is also an area for research: at what point is the usability of the software good for printing, how far do we have to take the mill as an in-situ process, and when do we want to separate the two processes?”

The Print's Success Redefining Boundaries

Beyond the fresh avenues for research, the triumph of this print will unquestionably open new doors for the manufacturing industry.

“If any part of the industry needs a large and rapidly produced part, with drilled holes and milled surfaces, it can be done. The system is very flexible; because it’s a robot arm on a track, we can reach many different places and tailor the robot to specific products. Whether it’s plastic, cement, or metal, all those materials can be printed, and then milled, polished, or painted afterwards by the robot,” says Woodrow Wiest.

A specific domain where this emerging technology could find notable applicability is in crafting negative moulds.

“These things are often produced using giant blocks of foamed thermoset plastic, which are not easily recycled. A whole lot of material is milled away to get to one small piece in the middle. Using our method, we could just print the material we need with the supports we need, mill the surface we need, and drill the holes we need. And in theory the mould could be ground down and reused again as feedstock for a new mould, hence reducing the environmental footprint on mould making.”

Onwards and Upwards

Despite the intricate nature of the process and the multitude of new elements involved, the print turned out to be a success — an outcome that took Woodrow Wiest by surprise:

“Things don’t usually work on the first try with robotic printing. It’s easy to share successes and not failures, so people tend to think that the technology is much more advanced than it really is. It is of course very capable, and you can get wonderful parts off of it, but there’s still a lot of work to be done with large format printing.”

Woodrow Wiest believes that initiatives such as the kayak are pivotal in propelling development and yielding fresh insights.

“We need to work with the process non-stop, and increase our printing and milling activities. Real-world use cases is essential to tune in the system and discover its utility. Undoubtedly, by nurturing our strong relationship with the industry and continually seek new collaborative prospects, we will uncover a multitude of applications for this technology.”