It’s well known that ABS filament can be smoothed after printing by immersing the printed object in acetone. This process melts the surface of the object, blurring the layers together to produce a less accurate, but very much more smooth result. After the application of acetone, ABS frequently looks like it has not been printed.
Which is all very well for those who use ABS, but more and more printer manufacturers are turning to PLA as their filament of choice, for its superior printing qualities – it prints at a lower temperature, and generally doesn’t require a heated bed since there’s far less occurrence of the material curling up during the print process. The only problem with PLA is that acetone has little effect on it; there is, it seems, no way to smooth PLA in the same way.
And so we were particularly intrigued by the Kickstarter project for the 3D Refiner, which claims to “transform any 3D print into a high quality beautifully finished part in a fraction of the time” – the idea being that you can print a low resolution model, and then smooth it so it looks like a high resolution model. In the FAQ the developers explain how PLA can be smoothed using MEK (Methyl Ethyl Ketone), a high strength industrial solvent. Intrigued, we decided to try MEK out for ourselves to see if it worked.
Warning: Should you be planning to experiment with MEK yourself, be aware that it’s seriously nasty stuff. You should be sure to work in a well-ventilated environment, due to the unpleasant fumes, and to wear chemical-resistant gloves. Be especially careful not to splash it on your skin, and do wear protective eyewear.
A: The initial model
This is the model we started with – an elongated hand. You can clearly see the roughness on the left of the fingers, especially; these are the printing artefacts we were hoping to get rid of.
B: MEK painted on with a brush
Although it seemed at first that some smoothing was indeed taking place, once the hand was dried it became clear that very little smoothing was happening, if any. The white deposit instead served to exaggerate the unevenness of the surface.
C: One minute immersion in MEK
Immersing the whole hand in MEK did produce some slight smoothing of the surface – the fine lines between the printed layers are now slightly less apparent, and the hand feels quite a lot smoother to the touch. But the white deposit has now become worse, and the overall effect is very unappealing.
D: Five minute immersion in MEK
No significant improvement in smoothness was evident after a long immersion; the only real outcome was that the model became significantly weaker, to the extent that the index finger snapped off during the drying process.
MEK does not seem to be a viable solution. There may well be a smoothing agent that blends the layers of a PLA-printed object, but we haven’t found one yet. We’re still looking.