A few weeks ago we celebrated Victoria Day here in Canada and enjoyed a leisurely three-day weekend. With the extra time I opted to do some May-Long Making at home and play around with XTC-3D by Smooth On.
For those of you who are unfamiliar, XTC-3D is an epoxy coating made specifically for 3D printing! The coating allows you to smooth layer lines to the touch and gives your models a glossy finish in one easy application.
This coating is relatively well documented inforums and on YouTube, so I did a bit of research and compiled some notes. I “borrowed” a few demo models from the office. I chose to try a couple of phone booths (green and red) with some hard to reach corners, and an anatomical heart with some organic surfaces, to see how the coating fared in different situations.
A WORD OF WARNING: the product comes with several pages of safety advisories and emergency instructions, which advise gloves and eye protection, covered skin, the use of tinfoil trays, and a well ventilated area to coat your parts. It is advised that you read all of the included literature prior to use.
When you buy the box you get: a large bottle of solution A, a small bottle of solution B, a stir stick, a foam brush, a graduated medicine cup and the aforementioned literature. You will also need gloves and tinfoil in order to safely use XTC-3D.
Following the instructions, I mixed 2 parts (20 ml) of bottle A with 1 part (10 ml) of bottle B in the medicine cup for 1 minute and transferred it to the tinfoil tray, scraping the sides of the cup thoroughly. Transferring the fluid to a larger vessel helps increase the working time of the epoxy (10-15minutes) and allows you to more thoroughly mix the liquid.
Next was time to apply the epoxy! Using the included brush I globed the epoxy onto the model and spread it out over the surface. The heart model was easy to cover, simply pressing the brush into the crevasses covered those sections of the model. The phone booths presented more of a challenge for clean coverage. I had difficulty applying the coating to the internal corners on the windows, and had to settle for the pools of epoxy.
To dry the models, I made mounting posts from tooth picks so that the excess epoxy would drip off the lowest corner instead of laying them directly on the tinfoil and having to remove and sand the extra material that would dry onto the model. I let the parts sit for the prescribed 2 hours and then removed them from their posts. I found that the coating was still slightly “gummy,” that is it was solid and dry, but I could press a fingernail into the surface. This may have been due to slight imbalance in the 2 components, though other have apparently experienced the same result. Allowing the parts to set for another few hours gave the epoxy time to harden completely.
The end result was more or less as advertised. The surfaces were smooth to the touch, though some lines were still evidently visible through the clear coating. I also fount that peaks or apexes In the models did not hold the material as well and the coating was a little thin. The resin pools in the closed corners of the phone booth stayed put and cured in place, however, the flat surfaces took the epoxy well and were almost without flaws!
I also tried a model of a handle that had cracked along a layer line when removing it from one of our printers. I applied the coating generously to this area and allowed it to harden yielding an invisible fracture line and a very solid and repaired handle!
In future, I will intend on applying more coats, perhaps sanding in between, to ensure even coverage. I would also advise that you use a very fine brush to carefully apply to internal corners, which would hopefully eliminate unsightly pools of epoxy in your final product! Lastly, a little bit of epoxy goes a long way! I mixed 30 ml of the coating and the 4 models I coated used less than half of the fluid! Unless you have a lot of material to cover, I would suggest doing a 10/5 ml mix to start.