Defect on small feature

[SilverV]

Hello all,

I am new to the forum and happy to be a part of this helpful community . Read a lot of helpful things here. I am not new to 3D printing, but I am new to FDM.

I printed a fender vertically and it seems to have some defects at the top end (see Figure 1). I can only assume that this is a too fast and not enough time for heat dissipation issue, but just want a second opinion from the pro's. I noticed some of the profiles posted for ultra quality had the speed at 4800, which surprised me, I had this set at (S3D):

-speed (slightly under) 3000.
-layer height of .1mm
-PLA @ 215C
-Fan 100%


Figure 1.Top Defects


Figure 2. Retract Artifact (one of them)

The artifacts on the side happen when my nozzle was retracting and repositioning the filament for next layer, I suppose the distance was too much.


Figure 3. S3D Orientation

Thanks in advance for your opinions (only the good ones though! ),

-Val

EDIT:

Just though about this, surface area there is very small so the extruder doesn't really shift away and probably gives a lot of conductive heat transfer to the area below (with the fan not capable of cooling it since the nozzle doesn't move away from that area). Is there a way to get the nozzle to shift off that area after every layer?

[jsc]

The point defect does appear to be a cooling issue. What do you have for cooling settings? Having it slow down the print on fast layers can help, but if you slow it down too much that can create issues as well.

There is no real easy way to force the hot end to take a break for cooling. What I would do is create a separate process for the area that is giving you trouble and add a layer change gcode script that will move the extruder away, optionally dwell a short time, and come back. Or you could print two at once, or put on a tower the height of your print and print that simultaneously. Any increased idle time may cause ooze issues, though.

[Tim]

I've had the best luck with Jin's last comment about creating a separate piece. I had the same problem with my chess set ("glChess chess set" on Thingiverse)---you can find my "cooling tower" there, which is just a simple extruded square about a half-centimeter on a side and 1-filament (maybe 2) thickness, as tall as the piece being printed. It doesn't require much filament to make the tower; it's just necessary to be sturdy enough not to fall over, and to be placed away from the other piece so that the extruder has to move back and forth between the two, which keeps the hot end from lingering over the piece and melting it.

[SilverV]

Thanks guys, sounds good. I was looking into the wipe and tower functions but didn't understand what that meant as far as S3D's capabilities, sounds like you create an artificial tower along with your print job. Is it a good idea to create a separate process for that tower which includes the wipe function? I guess I was thinking of a hard wipe that PolyJet machines do on the wiper/flush assemblies.

[jsc]

What wipe and tower functions are you referring to? In S3D?

I was suggesting that you just plop on a tower model onto the bed alongside your print that will get built up at the same time as your model, and be big enough/far away enough to allow for extra cooling time for the tip. If you don't mind the filament waste, you can just set Skirt Layers to some huge number, which will build a wall around your model and act as a time extender for cooling.

[SilverV]

Oh, no, I'm sorry I didn't write that correctly. I meant that I was looking into some of the functions other software packages seem to offer. I printed two at once and that particular problem definitely went away. I did get some drool around the edges (cleaned up ok though) from the nozzle moving around (see pic below) but I suppose a little tweaking with the temp and coasting may help. Perhaps even the wipe function? The wall thickness on this is theoretically .5mm so a nozzle and half's width, I measure the parts to roughly two nozzle widths (2x.35mm) on average. Just out of curiosity, have you guys tried a .25mm nozzle yet? I'm curious if there is major tweaking needed to get it running or just pretty much setting up the base layer.

Thanks for your input, much appreciated.

[ednisley]

The wall thickness on this is theoretically .5mm so a nozzle and half's width, I measure the parts to roughly two nozzle widths (2x.35mm) on average

You may get better results by designing the walls to accommodate two (or slightly more) threads, which is the absolute minimum required for a peninsula. Some slicers can produce a single-wall strip when you specify 0 perimeter threads, so the single remaining thread will be infill; that tends to produce visible steps as the infill changes from the normal pattern, through successively fewer parallel threads, to 3, 2, 1 ...

Changing to a 0.25 mm nozzle will reduce the minimum peninsula wall to about 0.6 mm, while increasing the likelihood of clogging on random debris in / on the filament and requiring much more attention to detail. As with everything, it's a tradeoff.

[SilverV]

so the single remaining thread will be infill

Ah, I see, good to know. I was wondering how it would accommodate for a continuous value of layer widths, makes sense. As far as the 0.25 mm nozzle, is there a particular type of resin that is better (least impurities) that you've had experience with? I've only printed with MG PLA so far, so I have pretty much zero experience.

[jsc]

You shouldn't be worried about impurities in the filament, as long as you stick with quality filament from reputable sources. "Quality" is correlated somewhat to price. I've had some poor experiences with bottom dollar brands off Amazon, but that is more likely due to their formulations and manufacturing tolerances than outright impurities.

What you should be concerned about is impurities that get introduced ON your filament, specifically dust. Your roll is picking up dust every day, and it will be carried into your print head unless you filter it out. There are a number of filament wipers on thingiverse that you can try, but I've found just bulldog clipping a microfiber cloth loosely around the filament before it enters the guide tube works without any special hardware. Once you finish a roll, take a look at all the stuff that didn't make it into your extruder.