I printed an enclosure box by PLA, and wanted to use it outdoor. I coated with Epoxy resin, and I wanted to use Rust-Oleum 2X Ultra Cover to protect it over UV.
My question is should I sand the coated surface first then apply the spray? 1200 grit sanding sheet is fine or should I use something else?
I have applied the resin by a brush and it has been almost 24h.
I know that I should have use other material for printing, but prefered to use PLA because was easy for me as a beginner to print with.
Please see the details of the material being or going to be used, added below (didnāt know if it is fine to add link or not, so just added the details).
The purpose of doing coating is just to make sure it is water and UV proof (kind of).
I would appreciate if you could please give me some advice.
Thanks
Boyle Crafty Resin 1L (500ml+500ml) Kit - Bunnings, Australia
canāt go wrong with a light scuffing and especially if it doesnāt have to look beautiful. You always want the base code to grab the material and if thereās not lots of chemical bonding then physical bonding is always better than no bonding.
Something I learned from my brother who own a sailboat is that black paint lasts the longest in UV exposure because it has the most pigment and blocks light from getting to lower layers of material. Tough for plastic though since black also means heating. So maybe black layers topped with a couple of white layers.
Thanks @dougl! I printed the enclosure with a gray PLA. The coating spray is clear. I think adding black paint layer could cause heating as you mentioned. Thanks for your comment again.
An update: I just used 1200grit sanding paper and didnāt work as expected, so did 400 first gently, then did one time 1200, and applied the spray on top. Looks fine and hopefully should be fine for what I am expecting.
Most āblackā pigment used in paints and plastic is just ācarbon blackā, and my understanding is that this is totally UV opaque and resistant, wonāt fade, and protects the surface underneath it. Eg heavy carbon black parts will hold up better than colors.
Anecdotally; I have some black pla parts on my boat that have held up well for a few years of harsh exposure and show no signs of deterioration.
Iāve seen a bunch of videos on Youtube of people whoāve made thigs like electrical outlet boxes or covers out of PLA and left them outside for a couple of years without having any real problems.
Usually surface preparation is done for cosmetic reasons more than anything else.
I usually use a much courser grit. 350-400, you need a much tougher sand to really reduce the layer lines. I tend to prefer wet/dry paper as it keeps the dust down and it lasts longer without clogging.
I then use a generic automotive filler primer on top to further reduce the layer lines. Depending on what kind of finish you want you can either sand it again with 350-400, and then give it a second coat and sand it with 1200, or go straight to 1200.
Use a tough automotive paint on top of that, and maybe also a lacquer.
Coating in 3D printer resin is also possible. Iāve tried it, but you end up with a finish a little like melted wax with less definition on corners etc.
You can try printing with PETG next time. PETG is not much harder to print than PLA, there is not much difference. You can ask ChatGPT to know the conditions for printing PETG, you will see that it is also easy and PETG allows for outdoor weather conditions. Good luck.
Printing successfully with PETG requires keeping the filament dry. In some climates, this can be easy; in others (like mine) you will not be successful without a filament dryer. Iāve removed 8g of water from a kilo of new PETG filament, fresh out of the bag from the vendor. Most of it arrives dry; occasionally it doesnāt. It adsorbs water greedily.
Donāt think I donāt encounter this problem, I live near Barcelona and the sea is not too far away, the humidity levels in Barcelona are not ideal for 3D printing either, in fact I have to use an environmental dehumidifier to lower the environmental humidity to 50% or 40% during the winter. I also use a filament dryer box, since even if I keep the rolls I started in a plastic bag, they always pick up moisture.
Just calling it out as a difference relative to PLA, which is much more forgiving here ā though it gets brittle and can snap after adsorbing water and can also benefit from a trip through a filament dryer.
Thanks a lot All for your comments! I got PETG and want to give it try, I did some tests and found the proper speed and temp (using speed and temp auto towers). I am not sure how good would be the output but will try as everyone suggesting PETG for outdoor. If I couldnāt manage it, then prob will try PLA again with what you suggested @Aaargh_Zombies
I have tried PETG, did temp and speed auto towers, and looks fine, but when I started to print my design and didnāt go well, problem with sticking the first layer to the bed. So, tried different adjustments, and still have issues. Currently I am using retraction speed of 50 mm/s with 4 mm distance, travel speed 120, print speed 15 mm/s for first layer, and 80 mm/s print speed, tried bed temp 80 and 85. The temp tower was ok with 220 - 245C and speed tower was ok with 60 - 100 mm/s print speed. I donāt have a PEI bed (I have a PC spring steel bed), so used blue painterās tape. Found some suggestions to clean the tape because it might be covered with kind of wax. At the end, still not getting good results. Do you think could be the moisture causing the issue? I did the towers right after I unpacked the filament, and after 2 days I am trying to print the design, and filament was left on printer not in a bag etc. I can put the filament into an oven (lab oven) on 60C for couple of hours and try it, if you think that could be the issue. Thanks
Wet PETG filament will typically pop and snap as it prints. But I weigh my PETG before putting it away and when I pull it back out, and if it has gained weight I dry it. Unless you have a fan in your oven, Iād do at least 5-6 hours. A fan can make it dry quicker than without. I often dried filament overnight before I put a fan in my oven, and I still dry for 5ā6 hours. Iād rather go too long than too short.
Bed adhesion is a common challenge with PETG. You are right to print the first layer slow. The bed temperature might be relative to the surface. I think that I used 70Ā°C for PETG most of the time, but I was printed on PEI. I thought that PETG actually could adhere too strongly to PC, even to the point of damaging the surface. I used non-scented acrylic hairspray on the bed surface when I printed PETG much of the time. (I rarely do anymore now that I have printers that print ABS well.) I would clean the bed very well with alcohol (I used 70ā99% isopropyl alcohol), then put a layer of hairspray on after it was dry. The hairspray seemed to help with bad adhesion, but also was a release agent for things that stuck too well.
PLA often does well if it is āsquishedā onto the bed; PETG definitely doesnāt. It doesnāt adhere quickly, so if it is squished, that drags the filament around and makes a mess. Use ābaby steppingā to increase your base Z offset until adjacent lines donāt come loose while printing next to them.
While epoxy helps with water resistance, PLA is still susceptible to heat and deformation outdoors, especially in direct sunlight. If long-term outdoor use is critical, consider a different filament like PETG or ASA for future prints.
