Random single "Zit" ruining every print...other than that perfect?

  • I have gone through dozens of rolls of carbon fiber filament, ASA, ABS+PC blends and I have landed on EzPC+Carbon and ABS+PC for our production parts we are trying to evaluate.

    I have spent time communicating with the folks over at Vision Miner and 3DXTech as we test out 3D printing as an option into our business model.

    I have the Pulse XE and I have moved from a .4 to a .6 hardened steel nozzle as we are trying to see if it improves the Carbon Fiber and time it takes to print our parts.

    I have spent weeks of printing 24/7 and am pretty impressed and happy with my current settings. It took us awhile but this thing is printing beautifully now EXCEPT for one thing that's happening that is ruining every print and I can't quite figure out what to change to fix it.

    Our original problem was we were not running nearly enough retraction. We are now at 6 retract/55 sec and have seen some of the most flawless prints with the calibration dialed with precision.

    We are getting no stringing at all. The retraction on our complicated parts has been perfect.

    Here is the problem...

    In at least one location, on an entirely flawless print, we are getting a "zit" along the travel path. This glob will build up until it bulges out the side and/or the nozzle will eventually hit it and shift the axis.

    We thought this was retraction as we originally had stringing leading up to it but we increased retraction length and speed until the stringing stopped but the zit still formed.

    On each 3-10 hour print I can identify that zit forming and I can reach in and "trim" it with the flush cuts (like I'm pruning a bush) and if I keep doing this every so often it will come out flawless...but obviously that is not fun or practical.

    I will attach some photos of it and its location on Mattercontrol. As you can see it is along a consistent travel path and not at an retraction/extraction point (as those are flawless/perfect).

    It is where a travel continuesly overlaps (I honestly wish you could stager this (alternate the travel paths)

    I am at the point, I am only making micro adjustments to the slice as the prints themselves are beautiful other than that one individual zit that forms on every print...

    I am pretty familiar now with all the settings other than wandering if a few I don't know would fix this issue

    • Extra length on restart (my thought is that it may be flowing to early as I tend to see it happening on the way to a extraction point but there is some distance in between where there is no oozing...maybe adding a -1mm "negative" but again its perfect traveling everywhere else. Always just one or maybe two zits on one print)
    • Time for extra length (maybe it is a longer travel..and this combined with adding a "negative" -1mm)

    Would love to figure this out as if we do this thing will be totally dialed!






  • MatterHackers

    This is likely due to slight overextrusion that causes filament to build up on the nozzle until it gets large enough to deposit itself randomly on your print.

    If you're printing with a 0.6mm nozzle, I would recommend you adjust your flow multiplier to 0.95 or .97 and try again with all the same settings.

  • @cope413 I am using a 0.4 nozzle with all default settings, i am getting some of the same zits. What are the multiplier settings?

  • Global Moderator

    @cope413 What are the multiplier settings?

    In MatterControl: Slice Settings > Filament > Advanced > Extrusion Multiplier ratio or %.

    If this does not fix the problem, it could also be a retraction issue. I use 8mm of retraction.

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