Nov 16, 2015 | By Benedict

Luke Taylor of 3D printing filament company Polymaker has published an article in which he demonstrates some effective methods for joining, sanding and painting 3D printed parts, using a 3D printed Iron Man bust as an example.

Polymaker knows a thing or two about 3D printing. When the experts in filament production and finishing procedures offer advice on how to turn your prints into professional plastic products, it’s advice worth taking. In his guide to post processing techniques, Taylor, a Creative Technician at Polymaker, pulls no punches about the limitations of 3D printing. In spite of the significant efficiency, rapidity and affordability of additive manufacturing, Taylor points to the geometry flaws and rough surfaces of 3D prints as noticeable weaknesses of the process. The technician observes that for some additive newcomers, having heard the praises for 3D printing sung loudly and frequently, its rough end products can actually seem a little disappointing compared to the flawless plastic products made using subtractive manufacturing.

Rather than accept this difference in quality as inevitable, Taylor has outlined some techniques for turning 3D prints into professional looking plastic products. Using a 3D printed Iron Man bust as a model, Taylor has demonstrated how to achieve a professional finish using only 3D printed parts, filler and paint. The creative technician details three key steps of the post processing stage: joining, sanding and painting, and the results are extremely impressive. “By post processing a 3D printed object you transform it into a finished part,” Taylor explains. “This is what consumers have come to expect from plastic objects. However, what you can produce with 3D printing is a unique part, possibly even designed by the end user. The ability to rival the aesthetics of a mass produced part but keep the anonymity of a personally printed object is a hugely rewarding process.”

Because 3D prints such as Taylor’s Iron Man bust are larger than most 3D printer build areas, they need to be divided into parts, which are joined together after the printing is complete. However, there are several ways in which makers can assemble their 3D printed parts, some more effective than others. Taylor discovered that superglue was ineffective at bonding PolyMax, his filament of choice for the Iron Man bust. A two part epoxy resin glue proved more effective at keeping the parts attached, but its noxious fumes made it tricky to worth with. The best method turned out to be a friction welding technique, which uses a short length of the filament used to produce the prints, spun in a rotary tool. The fast spinning filament is then fed into the seam line between the printed parts to be joined. The heat generated by the friction of the spinning causes the plastic to soften, allowing the two printed parts to be welded together. This method produces a strong joint, with no foreign material used.

A good joining technique combats the issue of limited print dimensions, but the coarseness of 3D printed components is another issue that must be tackled in order to produce a high quality plastic product. Taylor’s advised method is sanding, for which a 3D printed part must be printed with at least 3 shells. When sanding PLA prints, Taylor advises taking frequent breaks to allow the plastic to cool, whilst also adding water to the surface of the plastic for the same purpose. The technician recommends using a 240 grit sand paper, in order to remove visible traces of joints. The Polymaker guru also recommends using very small quantities of a two part body filler, to eliminate the minor fluctuations between printed parts. When the 3D printed model has been fully sanded and all filler has been applied, the next step is to apply a primer for painting.

For his Iron Man bust, Taylor applied a very thin layer of high build modelers’ primer. The trick is to move your hand fast, making swiping passes at a distance of around 30cm. Never hold the can pointing at a single spot for a prolonged period of time. It isn’t deodorant! Thin coats should be applied every 10 minutes or so, before leaving the 3D print to dry overnight. The primer can then be sanded, using a 400 grit sand paper with water. The final sanding should be done with a 1000 grit sand paper, for the smoothest finish possible. Now that the 3D print is smooth as can be, the top coat can be applied. Taylor’s Iron Man bust required just gold and red paint, but some prints may require several colors. It is crucial to pick the right color to apply first. Generally, it is best to go from light to dark, since darker colors are harder to cover up. Applying a light yellow over a dark blue, for example, will result in the blue showing through. Applying the color can be done in a similar way to the primer: move your hand quickly, at a distance of around 30cm. Once the first color has been applied, masking tape should be used to cover up the necessary areas, before the next color can be applied. This process is repeated until the whole 3D print is appropriately colored. For his Iron Man print, Taylor added a few final highlights and low lights to really bring the model to life.

Taylor’s tips should prove invaluable to all makers looking to add a professional touch to their 3D prints. “At Polymaker we encourage people to test our filaments to the limits,” stated Aaron Jennings, Design & Communications Manager. “Nonetheless, we are well aware of the limitations that extrusion based technology suffers from. We want to enable our customers and show them how to accomplish a fantastic finish with minimal effort.  We aim to carry on researching into post processing widening the horizon of extrusion based 3D printing.”

Take Polymaker’s advice on board next time you’re planning a big 3D printing project, and see if you can produce a professional quality print like Taylor’s stunning Iron Man bust.



Posted in 3D Printing Application



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