As ExOne boldly declares on the latest cover of TCT Magazine, 2021 is shaping up to be the year of binder jet additive manufacturing (AM). With a stream of new machines from the likes of GE Additive, Desktop Metal and HP making their way onto the market, we spoke to a number of companies within the space to find out how software is shaping up to address the complexities of this technology and maximise its production capabilities.
For the binder jet pioneer, software plays a key role at ExOne before, during and after printing. Factoring in part shrinkage to binder quantity and drying times, the company has developed tools both in-house and with external partners like Siemens, Ansys and Altair to tackle design, live in-process monitoring, control and analysis. To mitigate the effects of sintering, a necessary post-processing step that has been successfully deployed in the metal injection moulding (MIM) industry for decades but the effects of which remain hard to predict, ExOne tells TCT it has created “complete software-controlled recipes” and anticipates a wave of commercial software solutions to arrive as binder jet demand increases.
Rick Lucas, ExOne Chief Technology Officer and VP, New Markets, continued: “That will certainly help simplify the process and increase adoption going forward, but it’s truly an exciting time in binder jetting and that’s helping pull a variety of software players into the market to help support this key sustainable manufacturing technology.”
Lucas may well be on to something. Simulation specialist Simufact recently introduced a metal binder jet tool which allows prediction and prevention of the distortion caused during sintering. The tool, found in Simufact Additive, addresses this key challenge in the binder jet process which can sometimes see parts shrink by up to a third in size. Now, Simufact says users without specialist simulation knowledge can manage sintering effects such as thermal strain, friction, gravity, and sintering-induced mechanical stress, and compensate for those factors at the design level.
“We see process simulation as a fundamental enabling technology that will help drive the industrialisation of metal binder jet AM,” Jeff Robertson, Technical Business Development, Simufact, part of Hexagon’s Manufacturing Intelligence division told TCT. “It stands to reason that without a robust sintering simulation capability, it will be difficult for companies to take full advantage of MBJ as the scalable production technology we need it to become.”
Robertson says the most requested functionality is this ability to perform geometry compensation and if binder jet continues to rack up the kinds of customers it's currently attracting across industry - Cummins, Wabtec and Sandvik in the case of GE Additive or Volkswagen and U.S. Marine Corp for HP – the significance of those capabilities will become all the more prominent.
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“It’s clear that MBJ has the potential to bring the benefits of AM to new automotive and industrial applications by sufficiently lowering cost and processing time compared to L-PBF, and there is a race to get it right,” Robertson added. “There are only a few printer OEMs that can achieve this initial breakthrough and software that helps make sense of the data and guides the user through the necessary steps to achieve repeatable quality is a vital component.”
But several OEMs are also building tools internally. Desktop Metal, known for its bound deposition technology, recently launched its Live Sinter platform in a bid to remove the trial-and-error process of sintering and improve part shape and dimensional tolerances. To do that, the software uses proprietary algorithms to generate negative offset geometries by filling the part design with “cells” which go through the process of shrinking and distorting in the same way they would in a furnace to eliminate the need for supports and ensure parts come out within 1% of their final geometry. Live Sinter also improves on the use of setters, typically deployed to prop parts up inside the furnace, by minimising the requirements for expert sintering knowledge.
“If you know exactly what that shrinkage is, then you can put a part in the furnace and essentially scale it up first so that when it shrinks, it comes out the right size,” Andy Roberts, Desktop Metal VP of Software, said. “Unfortunately, it's not that easy because not only does the part shrink in different amounts in different directions but it also has friction drag against the setter and because there's friction with the part as it shrinks, the setter doesn't shrink. So, what will happen is, the part will drag against the setter and as it shrinks, it will warp and deform and sometimes even crack.”
Live Sinter
Negative offset in Live Sinter and final MBJ part.
Live Sinter runs on a GPU-accelerated multi-physics engine with a set of Nvidia physics tools, borrowed from the gaming world, in combination with meshless finite element analysis (FEA) to rapidly deal with thousands of cells within in a part. Roberts shared how the team is constantly fine-tuning parameters and discovering new resolutions for additional challenges such as how asymmetrical parts with cut-outs can open up and deform as they shrink or how the powder spreader can cause uneven densities.
“It's almost like a street cleaner in some sense that it has a counter rotating brush and it's pushing a mound of powder ahead of it,” Roberts explained, pointing to an example of a printed fuel swirler. “What we found is that when the layer of powder goes across a prior layer where there's printed material, it's almost like hitting a manhole cover on a street and that causes that density to spike up on the leading faces of the parts.
“What Live Sinter does is simulate the behaviour of the part as it exists after printing with density being messed up inside the part and in sintering where you've got friction and variable warping […]. So it's really not just simulating the sintering but simulating the printer and resulting furnace effects.”
Aiding Live Sinter, Materialise, known for its software expertise having provided the backbone to many leading AM hardware vendors through its custom build processors, recently developed a specific platform for Desktop Metal. Through this collaboration, Materialise is providing additional sintering support generation and metal binder jetting enhanced 3D nesting capabilities as part of its Magics SG+ module.
“Out-of-the box software often doesn’t meet the unique and specific requirements of binder jetting technology,” Stefaan Motte, Vice President and Managing Director of Materialise Software, told TCT. “In addition, with its large platform, typically smaller parts and high print rates, binder jetting typically also requires greater parts and data management. In combination with a build processor, which manages the communication between software and machine, Streamics, our AM management software, can facilitate this.”
Motte explained how Materialise’s build processors create standardised workflows for all print technologies, deemed crucial for companies working with diverse manufacturing environments. But he also cautioned that there’s a fundamental difference when it comes to binder jet, and that’s down to the way part data is communicated to the machine by images rather than tool paths.
Motte elaborated: “There are two ways of delivering content to the binder jetting machine. The first way is by providing slices to the machine that are converted into images or immediately provide images to the machine. Materialise currently provides slices to the Desktop Metal machines but we are currently also looking into providing images directly from the build processor.”
Despite being around for more than two decades, binder jet remains a complex process yet its advantages in terms of speed, material diversity and perhaps most relevant today, sustainability, make a compelling proposition for production applications.
Simufact’s Robertson added: “The industry needs a tool that is useful and enables AM specialists and engineers to build parts successfully and repeatably. If we can do that well, then everyone wins.”
