cylinder has corrugated look

[jimc]

also, is the filament staying a consistent diameter.

what is the diameter of this cylinder? is it the only thing being printed? could it be getting heat soaked? try printing 3 or 4 of these cylinders at the same time and see if the same thing happens.

[ednisley]

explain your last 3 suggestions a little more in detail

Yeah, I worded those points kinda-sorta inside out... [sigh]

The general idea is that the infill pattern can affect the perimeter layer: when you see a repetitive pattern on the outside, see if it's caused by what's inside. Remember that you're producing a plastic object by squeezing thin ribbons of molten goo into intricate shapes: effects that can't be easily measured will be easily seen.

- Infill pattern dense enough to not affect perimeter -- no periodic voids

A sparse infill pattern won't contact the perimeter thread over wide areas, so you're basically building a thin vase between the infill contacts; that can be several layers for some infill patterns. Typically, whenever the infill touches the perimeter, the perimeter will bulge outward more than it does when it's standing by itself.

A dense infill will contact the perimeter often enough (spatially speaking) to prevent that or, more accurately, the perimeter will be consistently bulged outward.

- Too few perimeter threads for infill pattern -- collapses in sparse sections

A single perimeter thread doesn't hide what's going on inside very well at all: infill that works fine behind three perimeter threads will probably produce visible artifacts through a single perimeter thread.

- Too many perimeter threads for infill pattern -- bulges in dense sections

The converse happens when you have many (say, three) perimeter threads and dense infill: at the places where everything comes together, you get a solid lump of plastic that looks different than the places where it's backed by air.

All of those problems will be exacerbated when the extruder produces a thread that's either narrower or wider than the expected value, so you must begin by calibrating the Extrusion Multiplier.

For example, if the slicer thinks the extruder is producing a 0.40 mm wide thread, but the filament diameter is slightly larger than nominal and it's coming out 0.44 mm wide, you have 10% too much plastic. The slicer lays down threads on 0.40 mm centers, but that extra plastic must go somewhere: the new, gooey thread will bulge to the side.

I set the slicer to lay down the infill pattern first, so that the perimeter thread can attach to it and overhangs fuse better. Other folks prefer doing the perimeter first, thinking that it'll harden in the proper position. Your mileage will definitely vary, so it's worth trying both sequences.

Temperature matters: the plastic will be more gooey at higher temperatures, so an unsupported thin-wall section will tend to slump more than at lower temperatures. If you're printing that vase rapidly, the whole thing may not have time to cool: the thicker sections will stay hotter and slump more. In the limiting case, you wind up with a blob surrounding the nozzle...

Make more sense?

[Deereengineer]

I don't think it's a geometry issue. In playing around with it I reduced the percentage of outline overlap and also changed the print speed. After that it printed really well. Onviously the slower print speed caused less heat to build up but can someone explain why the outline overlap would have an effect?

[jimc]

The more the outline iverlaps the more overextrusion there will be. The overlap should be just enougj so that the infill just grabs ahold of the perimeters. Basically its not so much the overlap setting as it is over extrusion. The more plastic thats pushed out the more it will build up and bulge out. Its just hard to tell from your pic exactly whats going on.

[ednisley]

why the outline overlap would have an effect?

The overlap determines how much the infill and the perimeter threads try to occupy the same space. A 0% overlap means the infill just touches the perimeter, 100% means the infill tries to sit right atop the perimeter.

So too much overlap produces too much plastic in the spots where the infill hits the perimeters, which is pretty much what you were seeing.

Something on the order of 10% should work well. What setting caused the problem and what did you end up with?

If you haven't calibrated the Extrusion Multiplier and it's extruding more plastic than the slicer expects, then the overlap will be worse than the setting indicates. Similarly, if the actual filament diameter is larger than the setting you gave the slicer, the extruder will produce more plastic than expected. Did you set both of those values before twiddling the overlap?

[willnewton]

Found this article on Z-axis artifacts on the 3D printing FB group. https://www.evernote.com/shard/s211/sh/ ... dcdd2d687e