Odd issues on taller cylindrical parts

[corsecprops]

So I've seen an issue when printing taller cylinders. There are vertical strips that are rougher than the rest of the part. They seem to be random and can last for 1/2" to 2" or so. They don't seem to be the layer start area and can happen in several spots at one time. Any thoughts on whats going on?

[ednisley]

They don't seem to be the layer start area and can happen in several spots at one time

They look a lot like retraction zits that appear where the nozzle stops, retracts, and moves elsewhere. Peering at the picture, they (seem to) appear on every other layer, which means you'll find a similar column somewhere else around the perimeter: each layer has one zit, with adjacent layers having them in different places.

Tweaking the retraction / coasting settings can minimize the zits, but, in addition, select whatever option tucks the layer start into a concave corner to make them pretty much invisible.

[3dPrintingMD]

Ed is spot on (of course)!

Tweaking the settings will in my experience never fully eliminate it, but as Ed suggested you can select in Simplify 3D, on the Layer Tab, Start Points, and chose starting points, this will but that seam all in one column.

Then what you want to do is find somewhere on the print that hides it. For example, if you were doing a square, you could have it on the corner, and it wouldn't be noticeable.

[corsecprops]

Thanks guys! One question. Is there a way to force it into the center of the part? These all had holes in the middle because a pvc pipe will go through them. Is it happening once per layer or does it happen once per outer edge per layer? Also is there an easy way to find the coordinates of a specific part of the model?

[jsc]

Every perimeter of every layer is concentric, so there will be one seam per perimeter, although of course any perimeters that aren't exposed to the outside or inside won't be visible.

To precisely locate a position in S3D or other slicer, you can use a model of a thin cylinder or square, move it around the slicing view, and read the coordinates off of the object. Remember to get rid of it before printing.