Elegoo Mars SLA-printer (resin printer)

The hacklab has a first-generation Elegoo Mars SLA resin printer. The printer is located inside a fume hood in the painting room.

Printing area: 120 x 68 x 155 mm
X/Y Resolution: 0.047 mm (2560 x 1440 pixels)
Layer height: Depends on resin; usually 0.05 mm

You can print any 3D model as long as it fits in the print area. The most common file format is STL. Models can be found online or created using CAD software, Blender, etc.

Models must be prepared using a slicing application before the printer can print them. ChiTuBox is the application used for slicing, but it is bad at auto-generating supports (it generates far too many of them, which wastes plastic and means a lot of extra cleanup work for you). If you need autogenerated supports, PrusaSlicer is far better at them and can also optimize the rotation of the printed body for minimum supporting. Both applications can be found on at least some of the computers at the lab (try the one next to the southern windows in the lounge labeled “Dragon”).

To generate supports in PrusaSlicer, make sure it is in SLA mode by selecting an SLA printer (either the custom Elegoo Mars profile or the Prusa SL1 profile). Then import your STL like you normally would, and use the tool palette on the left side of the screen to rotate it and add supports. Once you're done, go to File → Export → Export plate as STL including supports and save the file somewhere. You can then open this STL in ChiTuBox to finish the slicing.

Selecting the correct printer profile (Elegoo Mars) and the correct resin profile in ChiTuBox will give you workable default settings, but verify them by clicking on the big Settings button on the right anyway. One thing you will likely want to change here is the hollowing & infill setting – if the model is already hollowed, make sure the wall thickness on this page matches the wall thickness of the model or else ChiTuBox will generate detached infill structures and probably ruin your print. If there is no profile for the resin you are using, consult the resin bottle.

After the model is sliced, put it on the USB stick found attached to the printer, then plug the USB stick into the USB extension cable next to the printer.

ALWAYS WEAR SAFETY GOGGLES WHEN WORKING WITH RESIN. NO EXCUSES.

Resin is generally quite toxic (as the red warning symbols on the bottle suggest). Wear safety glasses at all times when working around the printer, and do not touch the resin with bare skin and definitely do not ingest it. In the short term, the resin causes chemical burns; it will not immediately burn skin, but it will immediately burn your eyes and mucous membranes. If you get it on your skin, wipe it off with paper and then wash it off with soap and water immediately. If you get it in your eye, rinse the eye under running water for 15 minutes and go to the hospital ASAP. In the long term, exposure to resin can develop an allergic sensitivity to it even with no previous history of allergy. This is another reason not to let it come in contact with your skin.

In a ventilated area the fumes from the resin are not a major concern and safety sheets for resins generally do not consider respirators necessary. IPA fumes are nastier, though, so if you must spend a long time cleaning up a print, you may want to wear a respirator. The paint room and 3D printing fume hood are ventilated, but the air in there is still stinky enough that a respirator is a good idea if you intend to spend more than 10 minutes in there anyway.

When working with resin and uncured prints, it is good to follow a clean hand & dirty hand hygiene practice. Wear a nitrile glove on one hand; this is the only hand that will ever touch resin, uncured prints, the working ends of tools, the build plate of the printer, and anything else that comes in direct contact with resin. Your other hand is the clean hand; this is the only hand that will ever touch tool handles, the printer or curing machine, or anything else that should not come in direct contact with resin.

With appropriate precautions resin is easy to work with, so don't be too afraid of it.

Turn the printer on using the power switch on the back side of the printer. Lift off the red plastic cover.

Make sure there is resin in the resin basin at the bottom. Odds are there already is resin in the basin; this is fine, as the resin will stay good for many days or weeks. However, it separates over time, so you will have to mix the resin in the basin before printing, as well as make sure there aren't any hard bits of resin floating around in it. The easiest way to do this is to wear a nitrile glove and mix the resin with your finger until it becomes uniform in colour (if it appears uniform already, mix it anyway; it could just be pretending).

If the resin in the basin has gone bad, you'll have to change it. TODO: how to change the resin

Make sure the build plate (the part at the top that dips in and out of the resin) is attached and tightened.

Set the red plastic cover back over the printer.

Select the file you want to print on the touchscreen. Verify that the preview looks about right and press start.

Observe the first couple of layers to make sure everything is going OK. The build plate should descend into the resin, reach the bottom, lift up a little, then descend again to touch the bottom. It will remain there for about 60 seconds (whatever you set the first layer exposure time at). It will then repeat this for another 4 layers (or whatever you set the bottom layer count at). After that each layer will only be exposed for 8 seconds (or whatever you set the exposure time at). If things are still looking alright at this point and there are no weird crunching noises and resin isn't leaking out and the printer isn't on fire, it is safe to leave the printer unattended. You won't be able to actually see the print for a long time anyway as it will be upside down suspended in the resin.

Once the print is finished, the build plate will lift out of the resin to its maximum height and stay there.

At this point put on your safety goggles and wear a nitrile glove on one hand as detailed in the resin hygiene section above. Loosen the big hand screw at the top of the printer using your clean hand, then detach the build plate by pulling it towards yourself – it will slide off horizontally. The build plate is covered in resin, so only touch it with your gloved dirty hand.

Using a scraper, carefully detach the part from the build plate. It is alright to scrape the build plate with a metal scraper, but do it gently at a low angle to not leave any deep marks and to avoid damaging your print. Remove any supports from the print and wipe off excess resin using a paper towel.

Next to the printer is an Anycubic Wash and Cure machine, which is used for washing and curing prints. Remove the yellow plastic cover of the machine. Do not touch the cover or any part of the machine or the container with your gloved dirty hand. Take the lid off the large cleaning fluid (the fluid is isopropyl alcohol) container and place it in the Anycubic. There are little grooves to help you align it, but there is no mechanical connection; the mixer at the bottom is rotated using magnets.

Put your print in the metal washing rack, then lower the rack into the cleaning fluid container. The handle fits into slots near the top of the machine. Put the yellow plastic cover on the machine. Set the machine to Wash mode using the control panel, and adjust the time to your liking (2 or 4 minutes should be enough). Start the machine and wait for the cleaning program to run. The machine will beep once the program is finished.

After the program is finished, lift the rack up, remove your print, and then rattle the rack against the edges of the container to get most cleaning fluid and loose pieces of plastic off of it before hanging it back up on the tool rack you found it on. Close the container lid tightly.

Finish cleaning your print up by hand by wiping off any remaining loose material and drying it using paper towels. Insert the acrylic platter into the Anycubic. It will slot into the axle at the bottom of the machine. Place your print on the acrylic platter and close the machine lid. Set the machine to Cure mode, adjust the timer to 6 minutes and press start. Once the program is done, flip your print upside down to expose the bottom and run it through the cure program again.

Your print should now be done.

Clean every tool you used with isopropyl alcohol and paper towels. Clean both sides of the build plate and reattach it to the printer. Clean off any spills, bits of plastic etc. Put used paper towels and nitrile gloves in the trash. Replace all the paper towels covering the work surfaces after you're done. You should leave the printer nicer than you found it.