Specific layers present underextrusion

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jerrymenm
Posts: 2
Joined: 08 Sep 2016, 20:25

Specific layers present underextrusion

Post by jerrymenm »

Hey guys!
So I've been 3D printing for about 6 months on a KOSSEL XL and I feel like I've gotten a lot of experience. However, this is my first time posting because this is a very abnormal issue for me.
I designed a part with 3Ds Max for medical sector and was getting near perfect results with Verbatim PLA (which is imo the best PLA out there, at least the best of the ones I've tried); however after switching to Purement FDA anti bacterial PLA, a very strange problem of some cylindrical layers not closing up properly began ocurring. Below are pictures of the problem:

White part is Purement, Blue is Verbatim before switching to Purement and Orange is Verbatim after switching back to Verbatim.
IMG_0268.JPG
IMG_0276.JPG
IMG_0273.JPG
IMG_0275.JPG
IMG_0271.JPG
IMG_0274.JPG
As you can see, the problem stops at a specific height of the print.

I've tried fixing it reducing the Seam hiding gap all the way down to .6 (tried other settings too) and depth to like 0.3, increasing the temperature, adjusting the flow teak to a higher and lower value and even printing with 0 retractions or very low retraction values but it just wouldn't work.
After this, I retightened the belts, the bed and pretty much every screw and replaced my former Johann's extruder with an aluminum all metal MK8 extruder using a Planetary geared Nema 17 Motor, which did present some improvements but was still failing.
I decided to switch back to Verbatim to try and find what the root of the problem was, thinking that if verbatim printed perfectly like it did, then the Purement filament was faulty. To my surprise, it also started presenting the problem with Verbatim PLA and now I have no idea what to do.
The 3D model I used for all of the tests were always the same, even when it printed nicely on Verbatim.

These are my settings for both Verbatim and Purement filaments. I've run them both on 150 micron layers on 0.38 extrusion width (0.40 nozzle), 33% infill, 1 loop and infill extrusion width of 0.4
Settings Verbatim.png
Settings Verbatim.png (27.66 KiB) Viewed 1518 times
Settings Purement.png
Settings Purement.png (31.89 KiB) Viewed 1518 times
Hope you guys can help me!
Thanks a lot in advance.
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Bobby O'Seal
Posts: 7
Joined: 13 Nov 2014, 14:56
Location: So.Calif

Re: Specific layers present underextrusion

Post by Bobby O'Seal »

I see 17C temp difference, could that be it??
dorbar
Posts: 12
Joined: 01 Sep 2016, 15:34

Re: Specific layers present underextrusion

Post by dorbar »

I would also suggest you to play with a Seam Hiding (a feature in KS v1.5) this way you can scatter the seams around and not in a straight line as it is now.

About your problem; It might also be that your nozzle is obstructed. Because from the picture you sent it seems that the flow is not constant... Kind of a jerky and not with a steady flow.
Try cleaning your nozzle.
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