3D Printing 102

Class Resources:

Class slides: https://docs.google.com/presentation/d/1CDXfT0D10Ap_I4goh0198Uu-BOqhTGTyO1uojcEkcaE/edit?usp=sharing
Datasheets: https://docs.google.com/spreadsheets/d/1pK5aVEyTf-aOrXQpK6-OapwI8Xo1nazsSsVLVB3yv1Q/edit?usp=sharing

ChiTuBox Basic download: https://www.chitubox.com/en/download/chitubox-free
MakerLabs Default Profile: https://drive.google.com/file/d/1cUI1LJFlo9xH0F7C3FY79-gvHonQk2ZJ/view?usp=sharing

Safety

Photopolymer resin is a skin irritant, lung irritant, and a serious eye irritant
- Can cause contact dermatitis, a skin rash which can develop into an allergic reaction down the line
- Can also irritate the lungs if breathed in
- Should always wear gloves and a VOCs respirator when handling resin
It’s also toxic to aquatic life with long-lasting effects
- Rather than pouring resin down the drain, cure it with UV light or sunlight before throwing into trash
Clean resin spills with 99% iso alcohol and cure papers in UV light before disposing in the trash

Parts of Printer

Image taken from ELEGOO MARS 3 User Manual

How SLA Printers Work

(image taken from https://grauonline.de/wordpress/?page_id=1767)

A: The build plate hovers mere nanometers above the FEP screen
B: UV lamp comes on and passes through the 4K LCD screen, which selectively allows UV light to pass in some places but not others (as determined by the design you are trying to print). This cures the resin at those points to both the build plate and the FEP screen.
C: The resin vat pulls away from the build plate, with the intention that the cured resin sticks to the build plate and not the FEP screen.
D: Build plate advances further away and prepares to expose the next layer.
E: as in steps B and C, the UV lamp comes on. This time, with a different image corresponding to layer 2 of your design.
F: Steps B, C, and D are repeated over and over again until the object is fully printed, layer by layer.

Preparing Your Model for Print

- Some Limitations
  - Resin needs to be shielded from environmental UV whenever possible
  - Avoid unsupported islands
  - Avoid large flat surfaces
- Best Practices
  - Lean models back
  - Use supports
  - Use drain holes and UV pen for larger prints if you want to save on resin (models roughly... say, 300ml in volume or greater as a rough start)

ChiTuBox Specifics

The ELEGOO MARS 3 uses ChiTuBox as its slicer.

If you haven't configured the ELEGOO MARS 3 in ChiTuBox yet, do so by clicking the gray Settings button above the blue Slice button.
- Add a new printer: ELEGOO MARS 3 (not the Pro but the Regular)
- Refer to this datasheet when filling out the Machine, Resin, Print and Advanced Tabs
  - The resin settings inputted here will be the default to auto-populate when you slice a job.
  - Print Time Compensation is highly recommended, as default settings tend to under-estimate print times by 33%. See datasheet.

Once your environment is set up:

Import your model. Feel free to rotate it in a way that minimizes overhangs and supports, especially ones on the prominent parts of your model.
Once you're happy, add supports.
1. - The auto-support feature is trustworthy enough to use as a starting point for beginners
  - If your part doesn't have a large flat bottom (and/or if you want to avoid the elephant's foot effect), it's highly recommended to set a Z-lift of 2-5mm with a raft enabled for good bed adhesion
Add as many models as you like on the build plate. SLA printing time is dictated by the tallest object on the build plate, and adding additional models that are shorter do not extend your print time!
Click Slice.
1. - Vital Statistics (such as volume, weight, and printing time) will be displayed on the right hand side
  - Resin settings are displayed at the bottom, which you can temporarily change for this one job
    - e.g. if you're using a special resin, or want to experiment
Use the slider and verify that there are no issues with your setup
1. - Resin settings are correct
  - No overhanging islands
  - Parts are adequately supported
  - No concerns about parts prying loose due to gravity or suction cup effects
Click Save, and save the resulting .CTB file onto a USB drive. You are now ready to go to the machine!

optional: if this is a job you see yourself returning to, you can save your workspace (as well as your supports) as a project. Exit out of the Slice screen, click the three horizontal bars in the top left corner of your screen, click Save Project > All Models. The .CTB file extension indicates the slicer file that you take to the printer, and the .chitubox file extension indicates the project workspace file that helps you manage your 3D models and supports for printing.

At the Printer

Ensure you have booked the tool out on our website
Load your USB stick
Level the bed (consult the clipboard or the manual if you don't remember the steps)
Load your resin
Hit Print, and ensure that the machine is able to begin exposing the first couple of layers
- There's an issue sometimes where the optical sensor will muck up and the Z zeroing process will fail
recommended: check back after the first half hour or so to ensure your print hasn't failed
- if it has, make sure there aren't half-cured bits floating in your resin before resetting - these little rocks may dent and scratch the screen when the build plate comes down to within 5nm of the FEP screen
Come back and grab your prints
Wipe them down as much as possible with a paper towel before washing, so that the alcohol bath can remain effective for longer

Washing Your Print

Following instructions summarized from Mercury Plus 2.0 Wash/Cure Station Manual

Mercury Plus 2.0 has a Wash and Cure mode.
- For Wash mode, remove turntable and put on wash bucket and basket
- For Cure mode, put back turntable
“Forbidden to put part in bucket directly - must put in cleaning basket”
- Otherwise damage may occur to model and/or cleaning bucket
Wash print with 95% ethyl alcohol (isopropanol also okay)
Recommended cure time is 2 minutes for model with diameter <30mm
Increase curing time for larger models
If model is less than 124 x 90 x 110mm, can wash model with build platform
If greater, should clean model without platform
Let model air dry afterwards

Curing Your Print

ELEGOO recommends 10mins, but we have found that models come out looking yellowed and photo-aged, especially if they are small 1" figurines
Start with 2-5mins for miniatures about 1" high and assess tackiness
If under-cured, model will not come to full strength
If over-cured, model will turn yellow.

Cleaning Your Station

Reclaim whatever resin is leftover in the vat
- Use a funnel with a filter to pour the resin into the same container it came from
- Some purists online worry about reused resin being lower quality and will pour used resin into a separate bottle, but we haven't noticed any quality issues yet with ours.
Clean all resin-contaminated parts and wipe down all resin-contaminated surfaces (this easily can happen while you wait for your parts to wash and cure)
Throw any resin-contaminated paper and waste into the UV bin below. Turn on the UV lamp and expose contaminated materials for at least 10mins as a start point.
- Ensure resin has cured before transferring materials out of the UV bin and into the trash.

Congratulations on your new resin prints!