I ran some more parts with the New Image Plastics ABS, and noticed something odd:
No, not the horrific brightness/contrast I needed to apply (natural ABS does not photograph well if you’re trying to capture detail) – the sunken, spongelike top surfaces of the parts. I had been using a crosshatch fill pattern for parts within the Quickslice software which worked just fine with the Stratasys ABS, but the NIP ABS acts a little differently. Here’s what the internal crosshatch fill should look like:
The pattern is about 0.15″ square – the important part is that the filaments are entirely straight and do not sag. Unfortunately, this isn’t what happened with the NIP ABS:
In this case, the extruded filament did not stay taut, and the insides of the parts resembled the world’s smallest Golden Gate Bridge convention. When the final top layers were laid down, they draped over the peaks in the internal fill, leaving a lumpy final top surface (though the outer contours were just fine). None of the process parameters were changed from the Stratasys material, so I’ve started to wonder what the difference in formulation or processing might be?
In any case, I’m not about to lose sleep over it – the order of magnitude difference in price between Stratasys and NIP materials means that I can dispense with the crosshatch interior fill and use the standard ‘fast’ fill. Sure, it takes longer to build, but the parts are notably stiffer with the extra density, and the Stratasys has proven to operate reliably when run unattended.
Perhaps tweaking the parameters will help some, but if I have to run with standard fast fill instead of full crosshatch, I can certainly survive. It’s not as if I currently have a need for ultra low density parts.