Sep 7, 2015 | By Alec

While desktop FDM 3D printers are steadily becoming more available and affordable than ever before, many users are still impatiently glancing over at all the SLS metal 3D printers out there. However, as any economist out there will tell you, competition drives down prices and in that respect it is fantastic to learn about a brand new metal 3D printing technology. It’s called LBDMD (short for laser-based direct metal deposition) 3D printing and has been developed by a team of researchers from the Southern Methodist University, led by Professor Radovan Kovacevic at the Research Center for Advanced Manufacturing (RCAM). This promising metal manufacturing solution seems to combine FDM principles with laser technology and is perfect for manufacturing high quality metal parts for a variety of high-end industries.

Fig. 1 Prototype of Multi Fabrication (MultiFab) System at SMU (US Patent no. 7,020,539).

This promising approach to metal 3D printing has been under development for some time, as the Southern Methodist University (or SMU) has been specializing in laser- and plasma-based advanced manufacturing since 2005, when they were awarded a grant from the National Science Foundation. A further grant was added in 2010. However, the result is very promising indeed, as PhD Candidate Yaoyu Ding, from the team of professor Kovacevic explains to As he explains, LBDMD 3D printing essentially relies on a so-called multi-fabrication (or MultiFab) system of metal deposition and subtractive operation. They have already been awarded two patents for their innovations: US no. 7,020,539; 7,045,738 and 6,995,334.

While still under development in some respects, this promising additive manufacturing technology has already proven to be an excellent option for the 3D printing of complex metal structures at low volumes, and even for the repair or modification of existing components. Partners from various industries, including the automotive, biomedical and aerospace have already expressed their great interest, the PhD candidate explains.

Fig. 2 Samples built on MultiFab (a) hollow spiral, (b) slender spiral, (c) gear

So how does it work? ‘It is a promising additive manufacturing technology that builds metal components layer upon layer by forming a molten pool on substrate using a laser beam and feeding metal powder/wire into the molten pool in combination with subtractive operations,’ Yaoyu Ding tells us. ‘Thanks to the high spatial resolution of the well-defined laser beam, the state-of-the-art LBDMD has been growing to build near net shape components from their CAD files.’ To illustrate this, they have already shared footage of a 3D printed propeller component with their MultiFab setup (in which the technology has been embedded), which you can see below.

While it does work very well, we are obviously most curious about the exact differences between this technology and that of laser sintering 3D printers (which is the current industry standard. ‘The main advantage of our approach is that a multi-axially positioning system allows us to build up components without using the support structure and the size of buildups is not a limitation like in the DMLS systems. Plus possibility to use machining during the buildup allows us to build the internal cavities and improve the surface quality,’ Yaoyu Ding says.

Fig. 3 Setup of the LBDMD system. (a) schematic, (b) photo of the system in action

However, that doesn’t mean that this technology isn’t faced with difficult challenges that the rest of us deal with. Taking the example of the propeller, Yaoyu Ding explains that 3D printing it takes careful planning to deal with the complex geometric characteristics. Most of the existing LBDMD techniques are based on building the components layer by layer in a horizontal plane, and the fabrication of complex parts with overhangs requires the support structures. The support structures are then removed by machining or chemical treatment. It makes the process invariably time-consuming, inefficient, and involving human intervention at multiple steps,’ he explains.

Fig. 4 (a) CAD model of the propeller and (b) printed propeller at the LBDMD system.

So to optimize the use of their LBDMD 3D printing technology, the research team is working on a robotized 8-axis system that does away with typical time-consuming steps. ‘ In our system, multiple-directional deposition was developed to eliminate the requirement for the support structures by using a multi-axis positioning system to orientate the substrate with respect to the laser cladding head. Owing to the synchronized motions of the robot and the positioning system, such system has potential to simplify the process planning and reduce production time,’ he says of the solution they found. ‘To achieve the process reliability and the repeatability of finished components, we also developed a sensing and control system for the powder flow rate and the molten pool size during the printing process.’

Fig. 5 Comparison between non-controlled and controlled LBDMD (the power of the laser beam is controlled based on the measured size of the molten pool in rea-time)

In short, the SMU team is thus still working on tackling a number of process-related steps, including process planning, state sensing and control, microstructure optimization, expansion of build volume, reduction of production time, and production of fine graded composition, but that is exactly what this 8-axis system is for. While nothing is yet known about bringing this technology to commercial indsutries, it definitely seems like we are looking at the next-generation of metal 3D printing.



Posted in 3D Printing Technology



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Feign wrote at 9/8/2015 9:41:01 PM:

Those lines are so smooth, and precisely controllable. It looks like it would be a dream to do welding with that laser, even without the robot attached.

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