After Having experimented in Making Perfectly Smooth Surfaces for about a Year now within the Print Process itself, Its time I Capitulate and start putting in some more Work and Sand it all smooth!
Just a bit of an Issue… Whenever I sand Coloured PETG, it looses its Colour and turns into that Broken Plastic White.
As someone who hasn’t had to Fix something like that before, I’m not sure where to even start Fixing this? Can it be Avoided in the Sanding Process, or can the Colour be Regained afterwards?
I have heard of People Treating it with Heat and Vasaline to get the Colour Back, what kind of Methods do you all use and how reliable are they?
There is a product that is used to restore car headlights.
The clear plastic on headlights gets foggy and yellow over time.
It’s not expensive. You can get it online. Lots of names and brands.
I used some on pla and it did make it look like it had not been sanded.
I actually documented it.
So here you go. https://imgur.com/gallery/J01PA0o
I just use a heat gun or a quick pass with a torch. Sanding makes small imperfections that light reflects into, giving it that matte look. Heating it melts those little scratches back together so it reflects light properly again
The Prints I’m working on at the moment are rather small, I think a Torch or Heatgun could also melt other spots that aren’t supposed to be melted because of needed Surface Patterns… I wonder if there is something a bit more Controlled?
There are lighters with a blue flame, these work quite well and controlled.
Practice on a scrap piece.
Couldn’t you use a soldering air gun? Actually I don’t know if there are cheap ones that can get a nice low temp, but the nozzle tends to be a fine tip.
I have tried using a Regular Soldering Iron to smooth out the surfaces, to not a lotta luck tho. At what temps can the Plastic Colouring be regained? Because I think I had mine set too high
I’ve used my soldering iron at 200c to re-attach broken off pieces, to much success.
Edit: it strengthened the layer to layer lines as well. Pretty neat for small bits.
I got a cheap 862D combo soldering iron from Amazon for $50 about 5 years ago. It goes down to 200°C.
Just remember to put it on a separate power strip and turn off the strip when you are done. These are super cheap, and I wouldn’t recommend leaving them plugged in unattended.
I’ve polished to a practically mirror shine with progressively finer and finer grit sandpaper. Took an eternity. Worked for the purple I was using, but it might not work for all colours.
I’ve also tried heating PETG with a butane lighter out of pure frustration. It does work, but the line between restoring the surface finish and deforming the print is very thin.
I see, thats quite interessting… I do wonder since my Main Concern are Flat Top Surfaces, if putting the rough Print surface on a Heated Surface of Sorts would do something simular? Thinking like a Heated Pan or Metal Sheet?
I think a heat gun would probably work, as suggested elsewhere. A hot surface might transfer its texture to the print?
Oh! I wonder if your printbed could get hot enough to do it?
Otherwise, yeah, 220 -> 400 -> 600 -> 1000 -> 2000 -> 4000 -> 8000 -> 10000 grit might do it.
Hmmm my Heatbed goes to 100°c and I do have a Smooth surface plate around… what do you think?
I would say clear coat it, but if you’re doing that, you might as well paint it and I know that may be more than you want to get into.
My process is covering with a light coat of plastruct, sand it (around 800 grit usually gets it done), prime it, then clear coat and it usually looks better than new. Clear coat alone will go a long way.
How fine are you sanding it? Coarse sandpaper makes the PETG turn white and fuzzy. That goes away after wet sanding with 400 to 600 grit. I usually go up to 2000 grit to get a smooth surface. The color is still quite a bit lighter after sanding though.
I have been using more Coarse ones thus far yes… I do wanna achieve the same colour as the original Plastic tho
+1 for heat gun. Doesn’t need a lot of heat and you should be able to get rid of the white without deforming the print
a MEK vapor bath would likely give you a smooth finish. But, Uhm, personally the raw print is probably preferable as MEK is some nasty shit. (not so nasty you can’t buy it at your local big box hardware store, but it’s not something you can just pour into a kitchen pot and be safe around.)
it would work similar to an acetone vapor bath for ABS.
don’t work with MEK unless you have industrial venting.
Soooo I did actually try Vapor Smoothing with MEK Before! Infact I still got a Litre of that Stuff Around now, but even after leaving the print in there for Days at 50°C the Results where… honestly no big Changes at all…
I do suspect there is an Error in my Methodology… but turns out there isnt a lot of Info out there on Vapor Smoothing with MEK… Have you used MEK for Vapor Smoothing before?
I’ve not used MEK personally, all of my petg parts are structural. What I’m seeing online says 60-80c.
What I’d do is kick it up by 5c at a time.
swap in failed test prints and see how that changes things. Keep in mind if you stay in the cold range and give it more time, it might create a better finish.
Too hot and it’ll start melting.
Maybe also “priming” the chamber with a heat gun so the air is also warm. (Do this before placing the MEK!)
Also, a small hole someplace that’ll get covered and a toothpick to lift the part will help retain its shape.
The main thing I’m wondering right now, is the MEK supposed to Boil? I feel like it should be, but at that point im also working with e Pressurised Vessel with very much Dangerous chemicals… thought’s?
i;ve never used pressurized vapor baths, for anything. I’d certainly stay away from pressurized vapor baths using heated solvents that are also rather flammable (that’s… got some exciting possibilities that I would let my worst enemy do first.) I’d use picture glass (or cheap ikea mirrors.) to build up a box. set it up outside where the vapors aren’t a problem.
alternatively, a cheap-ass-fuck stock pot with a glass lid will also work fine, but don’t seal it… and certainly don’t use it for food when you’re done.
as for if it should boil, it’s boinling point is about 80 deg. C, so if you’re seeing boiling, you either have somewhat impure MEK (which is fine,) or your temp measurement is off. It should still put enough vapor into the box that you can see it working though… it’ll just work faster. its less advised to boil it off because, well. it works too fast usually.
please tell me you’re doing all of this outside or with a ginormous fume hood that goes outside. (seriously, MEK is not to be underestimated.)
For what it’s worth, if you have a pressure vessel and you want to make it go differently, reducing the pressure will have better effect (or so I’m told.)
I mean it wasn’t boiling which I thought was the issue. The setup I got rn is a Very Solid glass Jar that was fully Sealed and heated to around 50°C on my Printer bed. Left my Prints in there for between 30 Minutes to a Whole day, and while it was a lot shinier afterwards, no changes in the lines or or layers where to be seen.
Safety wise I got a Gas Mask, Fitting Clothes and some other Saftey stuff around
I habe never used mek, but acetone on abs. Works like a charm.
Have you tried epoxy resin? No sanding and layer lines disappear with shiny finish looks
The Shiny look it something I try to somewhat avoid im afraid
