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Funny Bumps in Printout


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Posted · Funny Bumps in Printout

I've got these funny looking bumps in the middle of an otherwise super smooth print (see photo).


I've isolated the cause to these movements. Example:


G1 X144.768 Y124.427 E6874.67709  ; Print to Point (50mm/s)G0 F9000 X144.768 Y125.025	; Fast Travel .589mm (150mm/s)G1 F2400 E6870.17709		; Retract Filament 4.5mmG0 F9000 X140.715 Y134.515	; Fast Travel 10.39mm (150mm/s)


By Line:

1. The Printer prints the outer shell and stop at the point of the funny bump

2. It then Fast travels inward for about .5 mm

3. Then retracts filament for 4.5mm

4. Then Fast travels to new print position

I think the second line is causing the funny little bubbles where it fast-travels inwards before retracting and moving away. It's either pulling or oozing extra filament when it does that.

Has someone run into a similar issue and where you able to resolve it?

I'm thinking maybe I'm printing to hot? (215c PLA)

Fast-traveling too fast? (150mm/s)

Retracting too much? (4.5mm)

sure, I can shotgun try all these things, but I'm hoping someone already has and knows the answer.

If so, THANK YOU, ahead of time!!


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    Posted · Funny Bumps in Printout

    OK, I have tried different hot-end temperatures: 190 - 215 in 5c increments. No Joy.

    I have tried different retraction speeds and lengths. No Joy

    I tried disabling retraction altogether. No Joy

    I am now trying the extreme change of a whole different slicer: Cura 2.1.1

    Yipes! It is a whole different slicer. It took me a couple hours just to figure out how to set it up and create a new printer profile (since my Aurora A3 doesn't match any existing profiles). But I do like it!

    Fingers crossed.

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    Posted · Funny Bumps in Printout

    Try printing much slower. I think it's the fact that it stops and has nothing to do with the .5mm move nor the retraction. I've seen those bumps and slowing to down to 35mm/sec or even 25mm/sec makes a huge difference. Usually I can make them disappear completely.

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    Posted (edited) · Funny Bumps in Printout

    The funny bumps disappeared with Cura 2.1.1 beta (when I got it to work). And from your suggestion, I notices the print speeds were much slower for the outer shell speeds in particular. (30mm/s)

    So I copied all those setting from Cura 2.1.1 to Cura 15.04.4 and did another test print. No Joy. Still lumpy and in the exact same spots. :(

    So I'm still stuck with the lumps on the only version that works with my printer and no idea how to set up the json files to get my JG Aurora A3 configured properly on Cura 2.1.1

    I think I'll go eat some worms.

    Edited by Guest
    wrong version number
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    Posted · Funny Bumps in Printout

    Dear Dahai 8,

    Depending on your original *.stl model, it can be caused by several reasons;

    When your model has a shell itself, it can be that the shell is slightly thinner than your given shellsize in Cura, or nozzlesize. Adjusting either your original shell or given shell/nozzle size in Cura could make a difference. In this case, you could change the flowrate a bit, while printing.

    If you print with an infill, bumps could also be caused by a retractionmoment. In expertsettings you could go for the option; "infill prints after perimeters". I think it is called "infill before walls" in the Beta version 2.1

    Finally it could be caused by the retraction setting, you could play with that a bit.

    At this moment I want a lot of bumps in my print, so far a came to this conclusions.

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    Posted · Funny Bumps in Printout

    Nozzle size is .4mm and wall is 2mm thick. I've tried shell thickness of .8 and 1.2 with 15% and 100% infill. No Joy.

    I did play around with lots of different retractions, even disabled retractions. Still no joy and still bumps where the head rapid-moved from one area to the next.

    I will try "Infill Prints after perimeters" that would make the rapid head moves from one side to the other happen within the walls and may just work!

    I'll let you know.


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    Posted · Funny Bumps in Printout
    Nozzle size is .4mm and wall is 2mm thick

    Some times I noticed that the legacy cura is a bit "bitchy" on some parts where the wall is whole-number from the nozzle size. In this cases helped me either to make the wall a tiny bit larger (e.g. 2.01mm) or "fake" the nozzle size (e.g. 0.39mm) ...

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    Posted · Funny Bumps in Printout

    Dear Dahai 8,

    And? Did the "Infill Prints after perimeters" made any difference?

    Kind regards,


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    Posted · Funny Bumps in Printout


    Sorry. I got on another project and totally forgot!


    The movement now happens inside the walls and is not reflected on the surface.

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