Easy Way to Smooth PLA | No Sanding

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First of all, Thank you for checking out my tutorial! You are awesome.

Second, I put a lot of time into the YouTube video so watch it too, it explains it all.

So currently, there is no easily accessible chemical to smooth PLA the same way acetone does to ABS.

But here I will show you how I fill in the layered build lines.

Video:

Step 1: Materials

You will need:

A 3D printed model with visible layer lines.

Any can of spray paint that bonds well to plastic.

Fast Drying Polyurethane - Clear Satin.

If you like this skull you can download it here: https://www.thingiverse.com/thing:2951822

Do read and follow all safety warnings on all spray cans and 3D printers.

Step 2: The Magic Steps

First clean the model of any dust and make sure it's clean.

Next spray the model with your selected color of spray paint.

Then quickly spray a layer of Polyurethane.

Then place it under a fan to prevent drips and to make dry faster.

The paint and Polyurethane will mix and fill the layers, any holes, and printed flaws.

The thinner each layers and the longer you let each layer dry the better.

I waited 20 minutes between layers and then waited an entire day before spraying the final coat of spray paint to cover any discoloration.

Step 3: Finished!

And that's really it!

I like this method because you can print in larger layer lines without worrying and it will print much faster,

you can print in any color and paint the final color you want, it doesn't need sanding, it can fill holes or flaws, and its pretty easy to do.

Note: I did print the skull at a layer height of 0.3 which means detail was lost during printing. A height 0.1 would have been better and taken less time to smooth but I needed an extreme layer height to show how much this method can do!

The final result looks much cleaner and more professional. People wont believe it's 3D printed!

Feel free to check out my YouTube channel - 3DSage. I create lots of different and fun videos!

Thank you and see you next time!

www.youtube.com/c/3dsage

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    59 Discussions

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    gomibakou

    9 months ago

    Aren't paint and polyurethane chemicals? I'm scratching my head.

    6 replies
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    3DSagegomibakou

    Reply 9 months ago

    The point I was trying to make in the shortest title is that for years I have searched how to melt or smooth filament and the results people would post were to use chemicals like Methylene Chloride, Dichlorometane, chloroform, Tetra Hydro Furan, Sodium Hydroxide, Oxolan and many other weird and hard to find chemicals.
    So my way uses spray paint and spray polyurethane which are two very common and widely used products that yes contain chemical (technically everything is chemicals) but are so much less dangerous than the alternatives listed above that I feel my way is different.

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    chrwei3DSage

    Reply 9 months ago

    then say "less toxic chemicals" because spray paint is still a toxic man made chemical, it's just not corrosive or poisonous when used as directed.

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    corski67chrwei

    Reply 9 months ago

    Seems like you're missing the point cherwei. Paint is a common item available even at some grocery stores. Most of us would not consider these to be "chemicals" as typically used for this purpose so I fail to see the need for criticism.

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    chrweicorski67

    Reply 9 months ago

    if you don't consider paint a toxic chemical then you are missing the point. you can buy lots of toxic items a grocery store. portraying spray paint as an inert substance is just irresponsible. in many places you even have to show an ID and be over 18 years to buy it.

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    RicksterInstructableschrwei

    Reply 2 months ago

    I’m pretty sure the requirement for ID to purchase spray paint is to help discourage “tagging” (graffiti). Though it may be to reduce the use of spray paint for “huffing” (inhaling for “intoxication” high). Which reinforces your concern that it’s toxic...

    Used in a well ventilated area should prevent inhalation of the toxic VOCs.

    Once dried, I think spray paint is pretty inert.

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    Dangerously Explosivechrwei

    Reply 9 months ago

    Y'all know that the PLA is "toxic", too, right? In the right quantities, anything can be.

    The point of the project is to show an easy way to smooth PLA with readily available materials, without the need for anything other than a backing surface (to keep the paint off everything else) and perhaps a fan.

    It is less labor intensive than sanding, and some would argue that sanding creates toxic PLA micro-particles that could potentially damage your respiratory system if inhaled.

    So really, toxicity has nothing to do with it (as far as the point goes), but rather this project is about reducing labor and pointing out easily accessible everyday fixes for a common problem so that everyone can get slightly higher quality prints.

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    jpfalt

    2 months ago

    Low build automotive surfacer primer also works very well and dries quickly. I use this for printing master patterns for foundry work. This also allows easy and light sanding to get perfectly flat surfaces and sharp edges. After surfacer primer, any automotive laquer or finish makes a photo ready finished part.

    1 reply
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    adamtimm1jpfalt

    Reply 2 months ago

    This was an exciting idea but from a standpoint of safety I agree with one of the commenters. Chemicals in the house and on the stove can be improved upon. I have not tried this but as a chemist it should work. I am busy residing my house so I hope someone will give it a try and give feed back.

    As I understand it the point is to envelope the PLA in EtA vapors so temp is a small thing. Longer exposure should compensate for heat on the PLA. The vapor pressure of Ethyl Acetate is 70 degrees C (158 F) at 760 mm of mercury EG sea level. Just for comparison the pressure at 1 mile high is 640 mm of mercury so the temperature of vaporization is lower. That is low enough that this may work well and get the chemicals off of the stove and out of the house.

    I suggest that a deep (deeper the better) jet black pot large enough for your parts can be used in the sun to vaporize the EtA. A couple of blocks set on the bottom of the pot can be used to support an aluminum screen on which to place the parts. Leave the lid slightly off of the pot as you would for popcorn. The heat from the sun should be enough to vaporize the EtA . My wife says I make things much more complicated.

    PLA smoothing diagram.jpg
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    aidanruff

    9 months ago

    I use Ethyl Acetate to vapour finish and smooth PLA. I use a vegetable steamer - put a couple of table spoons of EE into the bottom, model goes in the top. Heat it on a stove - preferably electric, not gas, unless you're outside. Wait until the EE vapourisesand then leave it for a minute or so on the heat. Remove it and place outside, removing the lid.

    It's not quite as effective as acetone on ABS, but not a bad result. Plus it improves model strength

    3 replies
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    zootalawsaidanruff

    Reply 2 months ago

    You can use paint stripper designed for acrylic paint - it’s main chemical constituent is ethyl acetate, is safe and you can just brush it on, wash it off.

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    adamtimm1zootalaws

    Reply 2 months ago

    Great tip! I hope I can find ETA. The Fed just nixed MEK and I can't find it on a shelf.

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    p0laris

    2 months ago

    Thanks. I will definitely be trying this on parts where dimension accuracy and detail aren't a big concern. It is, however, worth mentioning that each applied layer is losing more and more of both those things.

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    zootalaws

    2 months ago on Step 3

    “So currently, there is no easily accessible chemical to smooth PLA the same way acetone does to ABS.”

    Heaps of them.

    Probably the easiest is paint stripper for acrylic paint. Safe, easy to use. Cheap.

    Then there’s MEK. Get it just about anywhere in the world.

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    Azahrens

    8 months ago

    This is EXACTLY what I’ve been looking for! Trying to sand PLA and not only will you quickly be pulling your hair in utter frustration but you loose a lot of fine detail

    One tip: a fan with an AC filter to it will screen those cat hairs out!

    Question: when dealing with a cube print, would you recommend alternating sides in the layering steps or to finish one set of sides and then do the other set?

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    SherylinRM

    9 months ago

    The very reason I have not gotten into 3d printing is because of "dangerous" chemicals. Unlike some of the comments here I understand the risk involved and this is the lowest risk.

    I do have one question however.

    How many layers did you use to fill in all of the gaps?

    Not including the last layer the next day.

    Thank you :)

    2 replies
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    moeinSherylinRM

    Reply 8 months ago

    it depends on layer height, the part shape and geometry and the quality you need to reach. but it's somewhere between 2-5 layers of filler.

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    SherylinRMmoein

    Reply 8 months ago

    That seems reasonable. Had it been something like 10 or more then it would have been silly because it would start to change the shape of what you are doing and become way too thick I would think.

    Having made a few things and covered them in varnish, I was using that as a guide idea for layer thicknesses.

    Thank you for your reply :)