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Improve print quality PLA


alexanderswo
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Posted · Improve print quality PLA

Hi out there,

I'm trying to improve the surface quality of my PLA prints. I keep having these really tiny artefacts on the surface. Any advise how I can improve this?

You can see them in the pictures on the surface of the cone. -and it might be the same problem that causes the extra material on the small top parts with the holes.

 

IMG 6339

 

IMG 6340

Thanks!

 

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    Posted · Improve print quality PLA

    Hi

    It is generally around overhangs, this might help:

    - Use thicker layer.

    Extension of the cooling time of individual layers:

    - Reduced print speed,

    - Reduced print temperature.

    - Two objects simultaneously printing.

    Heat from below (construction area) reduce:

    Adhesive aids such as: Glue Pen, Blue Tape, Kapton, or special printing plates could help, since usually less heat is required.

    General things:

    - Avoid possible overhangs at own designs, especially in the vicinity of the construction surface.

    - Other materials such as Fila Linen should have fewer problems with overhangs.

    - The fans for object-cooling should start early and work with maximum Performance.

    Markus

     

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    Posted · Improve print quality PLA

    In addition to what Markus already mentioned, you may set the minimum layer time to 7s and enable the cool head lift feature for the top.

    You also may play around a bit with the print orientation as cooling and air flow are the essential factors for this print.

     

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    Posted · Improve print quality PLA

    Any advise how I can improve this?

     

    Yes. Get rid of all overhangs. :)

    Seriously, I'm just going to say the same thing as mnis. Shell thickness .8mm. print speed 20mm/sec if you really want god like perfection but 35mm/sec should improve what you see. Lower your print temp by another 10C or try 200C. Fans must be 100% by the time the overhang starts which is, um, layer zero. Bed is much too hot and causing that curve in the bottom 3mm of your part - that is fixed by lowering bed temp to 60C or even 50C. 60C should be fine. Increase minimum layer time a little like dimensioneer says.

    With fans at 100% at layer 0 you may have trouble getting the PLA to stick so actually you should print the first layer hot (240C) and then cool to 200C gradually so it doesn't overshoot to 190C (set to 210C and then wait for it to overshoot to 200-205C or so then set to 200C).

     

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    Posted · Improve print quality PLA

    On small parts like that, printing PLA on a room-temperature bed with glue stick for adhesion generally works fine. This allows much faster cooling of part as it is printed.

    As to bed temps for larger pieces, I'd suggest starting at 65C for PLA, which helps with adhesion, then reduce to 55C after the first layer or two to allow the first layer to become firmer to resist warping caused by subsequent layers contracting.

     

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    Posted · Improve print quality PLA

    Superb guys, thanks for all the advise! Meanwhile I switched to colorfabb xt and the prints look much better. I'll try your suggestions next time I'm onto the red PLA.

    Thanks a lot!

     

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    Posted · Improve print quality PLA

    At room temp I found the glass doesn't stick very well. It doesn't take much force at all to get it off. Much more details and experimental results here:

    http://umforum.ultimaker.com/index.php?/topic/3404-printing-on-glass/

     

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    Posted · Improve print quality PLA

    I'm still trying different settings, but am already using the following printed fan duct, which improved the print on the right side significantly:

    - https://www.youmagine.com/designs/fanduct-another-idea

    Furthermore I'm using cheap hairspray to keep the print fixated on the glass bed.

     

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    Posted · Improve print quality PLA

    Fans must be 100% by the time the overhang starts which is, um, layer zero.

    With fans at 100% at layer 0 you may have trouble getting the PLA to stick so actually you should print the first layer hot (240C) and then cool to 200C gradually so it doesn't overshoot to 190C (set to 210C and then wait for it to overshoot to 200-205C or so then set to 200C).

     

    Why not turn the fans on at 1 mm instead of 0? I would think 10 layers should be enough to adhere to the glass well, more so if there is glue. It seems a bit overkill to push the temperature that high since the PLA is suppose to melt at 190C. I agree with EldRick that a room temp bed with glue would help small parts adhere instead of doing a heated bed. Mind you, I've only recently gotten the UM2 myself and am still tweaking things to get the best results.

     

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    Posted · Improve print quality PLA

    And if the seller specifies the print temperature to be 210C?

     

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    Posted · Improve print quality PLA

    Well, I'm still using the PLA Ultimaker provided me which melts fine at 190C even though the default preset was 210C.

    PLA's melting point is actually 170C, which can be raised about 50-60C by blending other polymers. Typically most filaments are within the 180-210C range.

    However, if we're trying to optimize printing and reduce the stringing effect in overhangs, you want that sweet spot where the plastic can extrude but cool quickly. If you set the temperature too high then it'll be more like a liquid, allowing it to spread/stretch/string out before it sets.

    So it doesn't matter what the manufacturer says, you need to test this yourself to find the sweet spot.

    However, for my earlier comment about adhesion, you want the plastic to be hot and liquid so it adheres to the glass better. I suggested turning on the fans after ~10 layers instead because it's something you can enter in as a setting. I think it'd be much harder to manually try to get the temperature where you want it by dynamically modifying the set point while the nozzle is heating and cooling. More room for mistakes.

     

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