How to clean 3D parts

What is the best way to clean 3D parts?

As in “clean up printing defects and artifacts” or “clean up uncured printing resin left on the surfaces?”

Post-print cleaning of excess resin is usually done by immersing the parts in isopropyl alcohol (90% or higher is recommended). Other cleaning solutions have been used with some success, like Simple Green or acetone, but generally 90% IPA is what is most often used.

Cleaning up printing artifacts like print support nubs is done by mostly normal tooling methods of filing, sanding or buffing. The cured resin is often quite brittle and prone to chip-out and cracking if supports are aggressively cut away using nippers or by “carving” with a craft knife. Supports can be sawn off quite effectively. If flush or side cutting nippers are used, but sure to leave plenty of extra material and not cutting too close to the desired finished surface.

Basically, the same tooling methods as used for cast urethane resin parts work on resin 3D printed parts. FDM 3D parts are tooled like any other plastic object made from the same type of filament plastic.

I use Flexi Files, normal needle files, sandpaper and sanding sticks. 4x0 steel wool can be used to buff away tooling marks from the filing or sanding.

To reach into very tight places, small sanding sticks can be fabricated with thin strips cut from wet-or-dry sandpaper and glued using rubber cement or contact cement to wooden toothpicks that have been shaped to fit the area concerned. (To cut the sandpaper, flip it over and cut from the back side using a craft knife and a straight edge.)

3D resin printed parts can be washed in warm soapy water to get rid of finger oils, sanding dust, and cutting swarf in preparation for painting. In my experience, no special painting precautions or preparations are needed, and normal model paints of all types seem perfectly suitable for 3D printed parts.

To help reduce the brittleness I use a blend of 85% Elegoo ABS-Like and 15% Siraya Tenacious. 100% Tenacious is completely flexible, like polyethylene, but the 15% imparts some flexiblity that has saved a lot of parts breakage, especially if I drop them on the concrete. You have to experiment with your exposure time since Tenacious needs longer exposure than standard resins. I added about 20% more exposure and get great detail reproduction.

For cleaning I use a three-step process and it’s messy. I have a “dirty” isopropyl 99% bath, a “clean” bath of the same and an ultrasonic cleaner using a small quantity of Simple Green (not to much since you don’t want it to foam.)

You don’t leave the parts in IPA too long. it can really soften the resin. I run the ultrasonic for 15 minutes, then rinse with clean water before drying with a hot air gun. You shouldn’t post cure when the parts are wet.

Thank you guys. I was talking about cleaning the uncured resin on the surfaces. Sorry about that. I bought some parts from Model Monkey that I will be using on the SMS Emden. I have never used 3D parts before and I didn’t know if my usual washing in soapy water would be good enough. Would soaking in IPA for 15 minutes be about the right time?

You might have to give the parts the “soak and scrub” treatment a couple of times. Depending on how the printer cleaned the parts, there may be some residue on them from a “dirty cleaning” solution. There are more components in the resin than just the UV light curable stuff (things like the different pigments, etc.). Even IPA that has been allowed to cure in the sun and precipitate the cured resins out will still have stuff left in solution that can contaminate the surface of the printed parts.

Like @Builder2010, I also use a two-bath alcohol cleaning process for my own printed parts. I also print most of my stuff using Elegoo ABS-like standard gray resin, but given usual my print jobs, don’t feel the need to mix resins for additional shock resistance.

For “scrubbing” the parts, I don’t recommend using a toothbrush as is so often suggested. Depending on the resin and the printing exposure times, the semi-cured resin is subject to abrasion and damage if scrubbed too hard. (This can mute or obliterate fine surface details.) I use a large, squirrel hair watercolor brush to agitate the surface while immersed in the alcohol or while still wet (preparatory to another dunk).

After cleaning with the alcohol (or acetone perhaps), maybe allow the parts to dry in sunlight if they still don’t feel clean. It’s possible that they may need a little extra post-printing cure time. You do want to clean any excess resin off, first, or that will also cure on the surface of the parts.

However, be cautious that you don’t just leave them in the sun for an extended period. About 20-30 minutes to a side while rotating to get all-round exposure is adequate. If you just allow the parts to “bake” in the sun, you risk warping them as they post-print cure unevenly.

I’m guessing that Model Monkey uses a true SLA printer that has a UV laser vice the DLP-type printer that I use. These true SLA printers use different resins with different exposure times. However, they also cure under 405nm UV light, so a dose of sunlight will eventually post-print cure even these types of parts.

I don’t think I have seen a squirrel hair brush but I will look. Would another type of brush work, such as sable or ox hair (in case I can’t find squirrel hair)? Truth be told, I was going to use an old toothbrush but I am glad you told me about the problems of using it. Are the parts I purchased semi-cured and the cleaning and sunlight part of the post-print cure process?

Basically, for a brush, just any big and soft watercolor brush will work. Most such watercolor brushes are “natural” hair and, although not advertised as such, they are made with squirrel hair.

However, even a large, soft artificial fiber watercolor brush will work.

The one I use just happened to be at hand when I needed it. Nothing too special or particular about it. Like many, I had been following the advice on a number of 3D printing forums and FB pages to use a toothbrush, but I noticed that it was excessively abrasive and was muting the sharp edges on details. Once I saw that, I just reached for the largest, softest, CHEAPEST brush in my shop that would work.