As you can see, we are printing smaller and smaller spots on the object as we are also increasing heat retaining bulk. Thus, I believe, the normal cooling process is slowed a bit with each added layer. And, the amount the cooling is affected is probably impacted by the density of the infill we have selected.
The fact that the more dense the object becomes the more filament cooling is slowed probably also explains why we see more cooling with 50 micron layers than with 250 micron layers. While 3D printers get blamed for stringing issue, in fact, our designs and the choices we make with layer resolution and infill selection are also critical factors. And that is because the speed with which filament cools is, at some level, dependent on the bulk of the filament that has already been laid down.
The tests that we have already done, seem to validate this theory, with a twist when it comes to the 300 micron test. Let's review.
We compared 300 microns / Hollow Thick, 250 microns / Low and 150 microns / Medium.
Of the three test objects, the 250 microns / Low infill appeared to have the least amount of stringing. If our theory about infill is correct, them why wouldn't the 300 micron object that was hollow not have come out on top. I think that it, too, had bulk heat retention issues. The operative word is THICK. Yes, it had no infill; but, the walls themselves were thicker than usual adding to the overall bulk and heat retention. With the 150 micron version, perhaps increasing the number of layers added to the overall bulk, offsetting the benefits of the Medium infill setting.
With this in mind, let's start with our best result so far, which was 250 micron layers / Low Infill and compare that with other infill settings at than same print resolution.
|250 Microns / Low Infill|
|250 Microns / Medium Infill|
|250 Microns / High Infill|
While you have to open the images to full resolution to see it clearly, the object printed at 250 microns / High infill does validate our basic working premise. It shows a considerable amount of stringing compared to the other 250 micron examples. It also displays more surface blemishes where the print jet lifts away from a point to travel to another point.
So, for now, we can probably conclude that when printing Tough 3D Ink, at a print resolution of 250 microns, a good setting with which to start is an infill of Medium.
So, 250 microns / Medium infill becomes our new baseline for further string testing at 200 microns, whic we will cover in the next installment of our string test series.