# What is this weird support line doing in this print?

I am a newbie to 3D printing and ran into a weird infill line on my second 3D printing object on a new Qidi X-Pro machine (which works great). I've included a screenshot of the infill line, which is deliberately printed the full height of the object. I'm thinking this line has been deliberately inserted by the Qidi slicer for some reason, but I have no idea why. Do all slicers generate these kinds of lines? If so, why?

• Hello Kevin welcome to 3Dprinting stack exchange. Seeing your image seems to be your are printing with a high temperature with out retractions; there are a lot of melted points. Follow 0scar's recommendation. – Fernando Baltazar Sep 18 '18 at 6:54

I do not know the Qidi slicer, but if you look closely, you will see this line is thinner than the normal support infill lines. You could try to visualize the G-code in a viewer, usually this can be done in the slicer itself, but online viewers are available. The viewer will not only show the printed lines, but also show moves by the print head (usually in a different color). You can check whether this extra line is actually printed or a move. If it is a move, this extra line is caused by your hotend which is leaking when it moves. You need to properly tune the hotend with respect to the retraction settings and temperature. There are numerous retraction test print objects to find on the internet.

Depending on your slicer settings, some slicers are able to define where each layer starts printing (e.g. random, or start at sharp corner). The fact you see a support structure "printed the full height of the object" tells you that each layer starts at the same position. It is not uncommon in uniform simple parts where each layer starts at the same position (X/Y) as this is instructed by the slicer setting. In Ultimaker Cura such an option is called Z Seam Alignment.

Bottom line, all slicers will do this when your printer is improperly tuned (incorrect settings for e.g. print temperature, retraction, coasting, travel speed). It is up to you to find the correct settings, test print objects help you with that.

• I agree, that is not support but the leaking filament on the path from the end of infill to shell! – Trish Sep 18 '18 at 8:35
• Thank you to everyone for your help. This pic is from the second object print that I ever did. I was using the slicer defaults (plate 50C, nozzle 0.4mm @ 200C, 1.75mm PLA, and I think that retraction was set to 1.5mm by default.) I tried increasing the retraction to 2.0 mm (before this post), but it never made any difference. It's odd to see such a solid wall from a leaky nozzle using 200C and only in the one place (apparently moving from infill to outer wall, which is an interesting idea itself. – Kevin Sep 18 '18 at 19:27
• I switched slicers from Qidi to Cura and noticed a big difference in print quality using the same temperature settings for plate and nozzle. Print speed was 40mm on the Qidi slicer and I set Cura down to 40mm too (20mm on outer walls, 40 on the inside, and it uses 100mm/s !! on travels). Cura does better path planning and controlling but I still see odd walls in various places. I will try to collect and post more images. Thank you again for all your help. – Kevin Sep 18 '18 at 19:30
• @Kevin A higher travel speed also helps minimizing resulting stringing (I forgot about that one!), I'll add that to the answer – 0scar Sep 18 '18 at 19:45
• Hi Oscar, thank you for the tip! That's the opposite of what I've been trying. I reasoned that slowing the print head down would give better adhesion, etc., so I set it down to 80mm/s to see if that helps going forward. Please see my other post where I (possibly incorrectly) reason that a high travel speed prevents adhesion in one corner of two prints. I can see that tuning will take some time. Thank heavens Cura lets me save profiles! I read a book called 3D Printing Failures (very good book) to get an education, but I still get stuck! – Kevin Sep 18 '18 at 19:49

Here have a posible solution -> How to remove unwanted filament trails from sharp corners

I think, that can be a combination of z-hopping and combing-mode in the slicer that you use.

• Hi welcome to 3DPrinting.SE! Stack Exchange sites are not ordinary forums of threaded messages, but focussed on questions and answers. Your answer is sort of a link only answer with a hint to a possible solution without going into details why that might be the solution. Please take the tour for some more information. Thanks! – 0scar Jun 5 '20 at 22:00