Resin 3D Printers – A very entry level primer (Part Five)

As a recap, what we’ve discussed so far:

  • The differences between filament and resin printing
  • Obtaining models for printing
  • Software used, supports, and infill

Now that we have a .CTB file saved to a USB drive, we should be ready to print. First, following manufacturer directions, the print bed/plate will need to be levelled.

The way I level mine (and it’s not how the Elegoo says to do it, so proceed with caution), is to loosen off the print bed set-screws so the plate can move up/down & left/right freely. (Leaving the top black set-screw tightened, so the build plate is still firmly attached to the piece that moves up/down on the back). Then I go into the settings and (with the resin tank installed) tell the build plate to return to home position. The plate will move down fully and the build plate will rest against the FEP film. I then tighten the two screws I loosened earlier, and under the settings use the “Set Z=0” option to set this as my new home position. Where this differs from the official instructions is I’m using the FEP film to set home versus the sheet of paper method that Elegoo recommends. Personally I tried it their way first, and found this way worked better. Your mileage may vary.

If the resin tank is empty, with the lid securely closed, shake the resin to make sure it’s well mixed. Pour some into the resin tank, making sure to keep it below the “max” line. Note: You’ll need a lot less than you think; I’ve let mine run on a print for 8 hours and the resin level was below half in the tank. Then we need to load the USB key with the .CTB file saved on it. There’s a test print on the key that comes with the Mars; if nothing else you could try printing this file. With the USB key loaded, it’s a matter of going into “print”, and locating the file with the touchscreen. Select the file and confirm you want to print.

At this point it’s a waiting game. Make sure to put the red cover back on as this helps restrict fume leakage, and minimizes exposure to errant UV rays. For my setup I actually keep the printer in a pitch black room, with an exhaust fan going. Total blackness isn’t needed, but the room isn’t being used otherwise so why bother leaving a light on. For the first handful of layers you won’t see anything happening other than the build plate moving up and down as it dunks into the resin. Eventually, you’ll be able to see the model emerging as the print grows. If needed, you can press the Pause button to make the build plate lift up, and then you can see what’s happening with the print.

One thing that I’ve added to this stage, that I mentioned in my first post, are the Elegoo active charcoal filters. They’re battery rechargeable, and have a fan that actively sucks surrounding air in to pass it through the charcoal filter. There’s a spot inside the printer that I put mine on, and it seems to be helping cut the smell down. Whenever I’m checking a print with the cover off, loading resin, or cleaning the final print however I’m also wearing a respirator that’s rated for paint fumes. Better safe than sorry!

Once the print has finished, you’ll need to get it off of the build plate. Since I’m new at this, I’m still working out an effective technique. What I’ve found that seems to work well is taking the build plate fully off of the printer, and then using the metal putty-knife to remove the print by sliding it gently under the edge of the print where it connects to the base. In some cases, this is significantly easier said than done. There has been some prints that absolutely did not want to come off of the plate and I didn’t want to leave a large gouge in the plate itself. In these cases, I ran warm water over the plate (with a container underneath to catch the resin that runs off), and used the putty knife at the same time.

One extra word of caution; it can be very easy to try and force the knife under the print with lots of pressure. This will work, eventually – but as I’ve found out, it can also slip and ram the business edge of the putty-knife into your hand. Obviously, this is not recommended. I recognized that when I did this, I was in a rush because I wanted to start another print and was short on time. In retrospect, I should’ve just waited because I hurt myself, and I damaged the print. All-in, a colossal waste of time.

After the print has been successfully removed from the build plate, I dunk it into a container of warm water. Using a large brush I clean as much excess resin off as possible. I also start snapping off the supports (since the contact point is usually very small, this is easy to do by hand). Over time the water will become pretty gross – I transition this to the large glass jars I have, and refresh with new water. Eventually, the print will be clean and mostly support free. The remaining support chunks I’ll remove after final curing.

Update 04/22/2021: I’ve been doing some reading on this process, and most guides seem to agree always use fresh water and continually flush the model. Some recommend also giving it a quick dunk in Isopropyl alcohol, even if you’re using water washable resin. Resin particles that makes the water cloudy will accumulate on the print if you aren’t using clean water, and cause surface imperfections.

I then lay the pieces out to dry, removing excess water with a paper towel. I’ll let these dry fully before the final curing process. Once they’re dried, I use the Elegoo Mercury to final cure the pieces. Basically, there’s a sunlight powered turntable inside and when the UV strips turn on, the turntable spins automatically. You tell the Mercury how much time you want, and press go. Once the curing is done, the print should be ready for sanding and paint if desired.

How much time to use for the Mercury/curing process? This also seems to be heavily opinion based. Personally, I let the final curing go for 2.5 minutes to 5 minutes, depending on the size of the print. I’ve read of people recommending longer or shorter curing time; it’s one of those “you’ll have to see what works for you” things. I do know that everyone seems to agree that too long will make your print go yellow and make the resin very brittle. I’d recommend no more than 5 minutes, but I think it’d also depend on how large and complex the print is. Would love to hear if there’s an actual formula for this beyond “it depends”.

Something to note: Preparation is everything in this stage. If you leave excess liquid resin on the print during cleaning, it will turn hard during the curing process. Take the time to clean the print fully, and make sure to properly handle the resin and water when doing so. Obviously the temptation will be to just hold the print under the running tap, but this is extremely bad for the environment and should never be done.

Up next; a final recap of what I’ve learned and what I have planned for the future.

Throughout this series, I’ve been showing off the Barbarian Chieftan sculpt by Matt Gubser of Prophet Miniatures. I’m not affiliated with Matt or Prophet in any way, I just think it’s a great sculpt that prints well. You can find the .STL at Matt’s page on MyMiniFactory.

Author: Greg

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