Schematic of the new setup [1] by N. Holt et al. Researchers in the AM3 lab, at the university of Arkansas, have demonstrated the potential for a new low-costs powder bed AM technique for the manufacturing of micro-components made of low-melting temperature (~600C) powders [1]. Unlike Selective Laser Sintering and Selective Laser Melting that employ a laser beam scanned across the powder bed, the new concept, referred to as MAPS for Micro-Array Powder Sintering, employs arrays of micro-heaters as energy sources. This proof-of-concept could increase build speeds and reduce powder waste and running costs.
Two of the most versatile additive manufacturing (AM) processes are selective laser sintering (SLS) and Selective laser melting (SLM) where a laser beam scans a 2D pattern across the flat and homogeneous surface of a powder bed. The powder particles are incrementally fused layer by layer to form 3D objects.
SLS and SLM use point-wise scanning strategies where the build speed is directly dependent of the scan speed as well as of the size of the 2D areas to be scanned. It also requires comparatively expensive high-power lasers.
To compensate for the limiting aspect of the point-wise scanning strategy, several technologies have been developed such as multi-beam laser additive manufacturing [2] that uses two or more laser beams to scan across the layer simultaneously.
Sintering process with MAPS [1]
By contrast, MAPS replaces the laser beam with an array of microheaters used as an energy source to sinter the powder particles. This layer-wise sintering, where the 2D layer pattern is processed in a single step, has the potential to significantly increase the building speed. Given the relatively low costs of the micro-heaters arrays compared to a high-power laser, this could also decrease the power consumption of the setup, reducing not only the buying costs but also the running costs: the heaters can provide 1.2W power and melt powders at up to 600C in 1.2ms.
 Micro-heaters array [1] |  Packaged MAPS prototype [1] |
MAPS uses an array of micro-heaters to create and apply a 2D heat pattern directly to the powder particles in a non-contact mode by placing the array in close proximity to the substrate in an atmospheric environment at room temperature. It is also linearly scalable by increasing the numbers of micro-heaters.
Track width [1] Preliminary results show that heating efficiency through the air gap between powder and array must be kept to a minimum to maximise heat transfer to the material. This technique is particularly well suited for use with nanoparticles that exhibit low layer surface roughness that help keep the air gap to <1um. Tracks width of ~140um resolution can be reliably achieved by playing with the various parameters, such as exposure time and air gap distance, and varying the maximum temperature achievable with various type of heaters.
Application
Flexible electronics printing
One anticipated application is the printing of flexible electronics that require metallic ink nanoparticles to create conductive circuits on flexible substrates.
The current technology requires inkjet or screen printing (non-digital method) to print a circuit which then needs to be sintered at high temperature to achieve high electrical conductivity without damaging the plastic substrate [3].
The MAPS technology can provide a digital version of screen printing and removes the need for post processing. The very short heating cycle keeps temperature of the flexible substrates to a minimum and prevents damages to the plastic films.
The current technology requires inkjet or screen printing (non-digital method) to print a circuit which then needs to be sintered at high temperature to achieve high electrical conductivity without damaging the plastic substrate [3].
The MAPS technology can provide a digital version of screen printing and removes the need for post processing. The very short heating cycle keeps temperature of the flexible substrates to a minimum and prevents damages to the plastic films.
3D printing of low melting metals (and plastics)
A second application can be 3D printing of low-melting metals (and polymers) where MAPS shows the advantage of being more energy efficient. For instance, comparing MAPS to a commercial SLS printer shows that MAPS consumes 14times less power than SLS [4]. The heater may also provide an in-situ monitoring setup by way of measuring the resistance of the heater [1].
Takeaway
Still at an early development stage, MAPS is a cheap and scalable new proof-of-concept with a dual printing and in-situ monitoring potential. The technique exhibits fine resolution and low power consumption and could easily be automated to manufacture affordable flexible and wearable electronics.
References
[1] N. Holt et al. / Journal of Manufacturing Processes 31 (2018) 536–551
[2] R. Patwa, H. Herfurth, J. Chae, J. Mazumder, Multi-beam laser additive manufacturing, 32nd International congress on applications of lasers and electro-optics 2013
[3] Guillot MJ, McCool SC, Schroder KA, Simulating the thermal response of thin films during photonic curing, Houston, ASME 2012 International mechanical engineering congress and exposition
[4] https://www.prodways.com/en/industrial-3D-printers/promaker-p1000/
[1] N. Holt et al. / Journal of Manufacturing Processes 31 (2018) 536–551
[2] R. Patwa, H. Herfurth, J. Chae, J. Mazumder, Multi-beam laser additive manufacturing, 32nd International congress on applications of lasers and electro-optics 2013
[3] Guillot MJ, McCool SC, Schroder KA, Simulating the thermal response of thin films during photonic curing, Houston, ASME 2012 International mechanical engineering congress and exposition
[4] https://www.prodways.com/en/industrial-3D-printers/promaker-p1000/