My limited knowledge of plastics has bitten me, as I had half expected (hoped) that I could just run the NIP ABS through the Stratasys and have things ‘just work’. As noted previously, I had used the exact same extruder temperature on the ABS from New Image Plastics as with the Stratasys ABS, but had sagging filaments as a result. Nophead (who is easily one of the most experienced RepRappers out there) guessed that I likely was using too high of a temperature, which made sense. But shouldn’t ABS run just like ABS? Not a chance, as I found out – I had mistakenly assumed that ‘ABS‘ referred to a specific polymer composition, when in fact you can tweak the ratios of the components (Acrylonitrile, Butadiene and Styrene) to achieve certain properties. Obviously, NIP is using a different formulation than Stratasys is. Additionally, Erik de Bruijn noted that he had seen different colors of ABS require different temperatures for optimal extrusion. Stratasys is apparently doing a great deal of work to make all of their P400 ABS colors act identically at 270° C. Out of interest, here’s the sticker from a Stratasys reel that lists recommended temperatures for various materials:
E20/E20R is an elastomer (and corresponding support material), ICW06/ICW06R is an investment casting wax and support, P400R (high-impact polystyrene) is the support for P400 ABS, and P400SR is a soluble support material. It’s interesting that the 0.010″ tip suggests a higher temperature (for one material, anyhow) than the 0.012″ or 0.016″ tips, but I suppose this makes sense – you’d need a less viscous fluid when pumping through a smaller orifice in order to maintain the same linear flowrate.
My latest plate of Mendel parts completed with the NIP ABS, but the results were not as good as with the Stratasys ABS, I’m sorry to say. I had severe warping on the larger parts, though this could be due in part to me dropping the extrusion temperature down by 15° C early on in the build as a result of nophead’s suggestion. On the plus side, the NIP peels off of the support material just beautifully (perhaps a little too well, as one of the drive-pulley_3off parts became detached from the raft near the end of the build). I’m wondering if the lower adhesion between the two materials may have also contributed to the warping – keeping the corners held down more securely may be part of the secret of getting more accurate prints.
I also notice a lot of fine feathery filaments with the NIP ABS at the end of an extrusion path. Whereas the Stratasys ABS acts like a microscale toothpaste, the NIP ABS acts like a microscale silicone caulk. The NIP ABS also shows its displeasure at the higher temperatures by turning brown after sticking to the nozzle for a while (meanwhile the Stratasys ABS would simply lose a bit of color, but not appear to actually be charring). So, time for some testing to see if there is a magic temperature at which the NIP ABS acts like the Stratasys ABS.
I adjusted the white balance on this photo to better capture the filament detail – the parts really do not look this grubby, although it’s interesting to note that the highest temperature pass does look a bit browner than the others. I created a box with the 0.15″ crosshatch fill in Quickslice, and ran it at ever decreasing temperatures on the Stratasys. At the recommended 270° C for Stratasys ABS, the NIP ABS is practically dripping off of lower layers. As the extrusion temperature drops, the filaments droop less, but even at 240° C there is still a reasonable amount of droop. At this point I started having slippage on the drive wheels (I think this was due more to buildup of tiny ABS fragments than due to lowering the temperature), and more importantly, I was entirely out of Stratasys support material. As such, the next phase will be to play with the HIPS from New Image Plastics and see how it differs from the Stratasys support material.