applications feature | 3D printing
colour and texture for additional solutions. Eastman has been focusing on bringing new
materials to the “prosumer” market since 2013. Users in this market are using relatively low-cost machines – many under US$5,000, often desktop types from companies like Stacker – that fit in the space below and slightly overlapping that occupied by the likes of Stratasys. Dudall says there is considerable growth among start-ups using desk-top fused filament fabrication (FFF) technology. He expects materials and processing technology
developments to continue at a high pace, although any expectations of 3D printing gaining a substantial foothold in the market for commercial production of finished parts are likely to remain unmet in the short-term. “It will still be focused more on prototyping for now,” he says. “The education market will be an important growth driver though.”
The isotropic challenge Dudall points out that one of the reasons that 3D printing has not grown as quickly as some may have anticipated is because it is still very difficult, if not impossible, to produce parts with the same level of isotropy that can be achieved with injection moulding. Because 3D printing builds up parts in layers, it is inevitable that in-plane mechanical properties are different from through-plane properties. Eastman’s material is claimed to have better inter-layer adhesion than PLA and ABS grades used for prosumer 3D printing, which goes some way to ameliorating this problem. “These copolyesters are naturally more sticky,” Dudall says. Eastman is working to further improve properties and also to develop property data for use in 3D printing,
3D print terminology
l Fused Filament Fabrication (FFF)/Fused Deposition Modelling (FDM): The base material here is in the form of a plastic filament on a reel. The material is extruded, heated via a freely moveable hot nozzle and applied in liquid form. During cooling, the individual layers fuse together to form the three-dimensional part. If necessary, supporting structures can be implemented using a second hot nozzle. l Selective Laser Sintering (SLS): Here, the part is melted, or sintered, layer-by-layer in a bed of a powdered material. The unmelted powder acts as a supporting structure for projecting parts. Following manufac- ture, downstream operations are necessary that require additional infrastructure. The plastic part is removed from the powder bed and cleaned. The unmelted powder is then removed and reprocessed.
44 COMPOUNDING WORLD | May 2015
Eastman and Helian have developed a carbon-
fibre-reinforced Amphora filament for 3D printing
since data obtained through tests on injection moulded test bars according to current international standards can be misleading. Dudall believes compounding technology has an
important role to play in the advancement of 3D printing. “There is a lot of interest in bringing unique functionalities into 3D printing materials—conductivity for example,” he says. As to what properties are important for materials used in 3D printing, Dudall says that, at least for prosumer printers, materials need to be fairly stiff so that they can be fed into the printer. “There’s a lot of interest in flexible and elastomeric materials in the market, but this is a challenge since it is difficult to feed these types of materials into the printer. You also need materials that process at quite low temperatures too, which is why you currently don’t see many engineering thermoplastics used in 3D printing. PLA and ABS are easy to print with, and Amphora is the same in this respect.”
Bring in the reinforcements Helian has recently added to its range with a 20% carbon-fibre-reinforced material based on Amphora. This has extra stiffness, but the toughness of the Amphora resin still enables the filaments to be fed into the printer without breaking. Dudall says more grades will be added in the future. Amphora will also be available for use by other filament producers. Helian has also been working with German bioplas-
tics compounder FKuR to develop a 3D printing filament made from PLA reinforced with natural fibres. PLA is already widely used for 3D printing because of its relatively narrow melt window at low temperatures. However, a disadvantage of unmodified PLA is its brittleness and low impact strength, which Helian is aiming to overcome through the use of natural fibre reinforcements. The use of filled and reinforced plastics in 3D printing is nowhere near as common as it is in injection moulding. Now it looks as if a new phase is beginning
www.compoundingworld.com
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