Best way to polish and smooth PLA prints

[301584]

Hi, so I’m printing this vase for a girl I like. The thing is, you can clearly see the 3D print lines and the surface is kind of rough. What is the best way to get rid of this? I am printing in PLA btw.

[SOC3D]

The best way is quite subjective. It depends on the person, the skillset, the budget etc. Xtc-3d by smooth on along with similar two part casting resins can coat a print and give it a clean smooth surface. Priming and painting. Glazing compound. Sanding and polishing with buffing wheel and compound. Rock tumbling with various media and polish. I’m sure wax dipping is a thing though it may warp the PLA…

[3dpGeek]

I thought I had a youtube video for you but I don’t so I will try to explain in text.

You want to use sand paper as acetone doesn’t work on PLA. Depending on the thickness of the model walls depends on what grit sandpaper you use. If its a single layer wall its going to be hard. If the wall is 2 or 3 layers thick and is 300+ microns than start with 150 grit. If 250- microns start with 250 grit and work your way down. I print with 250 micron layers and 2-3 layer wall thickness and start sanding with 250 grit and work my way up to 2000 grit. I go 250,400, 800, 4000 grit. WHEN YOU SAND MAKER SURE YOU SAND IN A CIRCULAR MOTION as the purpose of sanding is to make smaller and smaller scratches until they are invisible to the eye.

[301584]

Ah, I see. The first few models I tested on I sanded back and forth causing the scratches you speak of. I will try sanding in a circular motion.

[301584]

I’d like to use Xtc-3D but its so expensive lol. I heard there is a alcohol solution you can soak prints in or is it the xtc?

[3dpGeek]

Don’t push very hard you want the grit of the paper to do all the work. You can use the 4 grits I said or you can add an additional in between 450 and 800.

[Arnoldas]

Hey @301584,

Do you have some pictures?

[CMDRReservoir]

If you are using PLA, sanding or XTC-3D is definitely the way to go! As a side note, if this is for a girl you like, XTC-3D is definitely worth the expense. Regardless, I’d use an electric sander if you have one, just to make things easier. There is already some solid sanding advice in here already, so I’ll just tack onto it: Make sure you aren’t sanding too hard/fast. If you do, the plastic will heat up again and you start scraping off large flakes and bits rather than fine material, and you’ll have to sand THOSE blemishes off.

Let’s not forget safety and PPE! Wear a respirator and safety glasses, especially if you are using an electric sander. If you are using one of those, you may also want to wear earplugs.

[3dpGeek]

I forgot that part, definitely wear a mask! And not it in a well ventilated area.

[Enza3D]

Hi there! You are very right that XTC-3D is expensive! XTC-3D, also know as Smooth-On, is really just an epoxy resin with a fancy name. That being the case, I’ve had great success by using other epoxy resins that are available at home improvement stores or Amazon. I’m really partial to this one https://www.amazon.com/Clear-Epoxy-Encapsulating-Casting-Gallon/dp/B00IT0APVM, and as a nice little bonus, the epoxy includes UV inhibitors so it won’t yellow that quickly and protects the PLA a bit.

For finishing PLA, I start with 80 grit sandpaper (60 is too abrasive for most part in my opinion, but I will use it if there are noticeable flaws) and work my way up to 400 grit (80, 120, 200, 400). From 400 grit to 1000 grit (400, 600, 800, 1000), I wet sand to prevent buildup of heat in the PLA . I just stick the part in an appropriately sized bowl/container and sand the part under the surface of distilled water, and change the water between grits or when it becomes dirty. After sanding, I clean the part with water and coat with the epoxy resin. If the color of the part got to distorted while sanding, I’ll very lightly apply heat with a heat gun until the color is restored.

Is this a lot of work? Yes, but it produces really nice results.

[jfield]

Of the vase or the girl?

Or both!

[MakeCoolThings]

Sanding, definitely sanding. But WET SANDING. It keeps the paper from getting loaded up, and it cools the plastic. (If you try to sand PLA too aggressively, it’ll get too hot and the dust loaded up in the paper will actually fuse itself back to the part, making it feel all crusty!)

Here’s what I do: just have a tupperware type container or some other sort of small bucket or tub on your workbench with water in it, and keep running your sandpaper through it to rinse the particles off, periodically dunking the part, wiping the part off with a towel, and wetting it again… Obviously you’ll need sandpaper that can take being wet. (I use 3M Wetordry, their automotive sandpaper…another benefit of this is it’s manufactured to produce a much more uniform scratch pattern.)

If you’re printing at 0.2mm or smaller layers, you probably don’t need to start with 2xx (200, 220, 250 are common, depends on brand) grit and can get away with starting at 400… Then it’s 800, 1000, 2000. If you want to get really super-shiny you can try 3M Trizact in 3000 and 5000 grit. (You should be able to achieve a mirror finish at this level.)

Of course, this is just if you want to polish up something printed-in-color, as-is… Painting is a much more practical approach, because a good high-build automotive primer can take most of the work out of surface prep. Example: (Skip to 2:57) Prop: Shop - Mister Handy Scale Model Build - YouTube (Although this is about making a mold master from a 3D print, you can skip the molding/casting and just paint it at that point…you get the idea.)

[mariankeller]

How do you polish complex surfaces with an electric sander?

[Filmdesigner]

I have been having a lot of success with warm Epoxy resin on PLA (I haven’t tried it on ABS as PLA is my primary filament). If you use it directly form the mixing bowl its way too thick. By adding 10 degrees of heat the epoxy starts to run like thin honey. Too much heat and it forms lumpy skins.

An additional process is to use a VERY low power blowtorch - I use those little modellers pen-like blow torches - and wave the flame lightly back and forth over the epoxy resin you have just laid-down. This softens the epoxy and smoothes it.

Obviously this doesnt work on smaller or thin elements but works very well on everything else. Its easy to sand afterwards.

[jazzlee37]

May I ask your detailed procedure? How to heat resin? Use hot water or heat directly? Do you heat the resin before or after mixing the hardender? Thanks.