PRINT METHODOLOGY AND REFERENCES - Lactic Acid (CAS 50-21-5) - ANT HOUSE 2026-10-29 (procedure v7)

1. WHAT THIS MODEL IS
  A one-piece ball-and-stick model for material-extrusion (FDM/FFF) printing.
  Atom positions and bond geometry come unchanged from the molecular structure
  record; the design never moves or deforms the molecule (checked on every
  build: every source point within 0.001 mm of the printed surface outside the
  pencil and cup zones) [Z]. Everything added for printing - base, pencils,
  cups, raised logo - is a separate solid joined to the molecule.
  Element symbols are engraved on the spheres facing the viewer.

2. DESIGN DECISIONS AND WHY
  a) Vertical pencils only. 7 hexagonal posts stand straight up from the
     base under atoms that have a free vertical path. Diameter grows with length
     (3.5 mm and 5.0 mm) so no pencil is slender enough for the slicer to flag it as a
     "thin fragile part" [Z]. Tilted posts were rejected (design decision).
  b) 45-degree cups. A neck under a sphere supports only a small cap of it:
     a neck of radius r under a sphere of radius R reaches asin(r/R) from the pole
     (10-21 degrees here). Each pencil therefore ends in a cone at 45 degrees,
     tangent to the sphere and cut at 50 degrees, so the lower sphere surface is
     never steeper than the self-supporting limit of about 45 degrees [R 1][P 11][Z].
  c) Slicer supports for the rest. Spheres without a free vertical path are
     supported by the slicer's organic (tree) supports [M 8]. Settings keep every
     tree on the base, never on the bed beside it (molecule fitted inside a
     circle of radius 44 mm over the flat top, branch angle at most 25 degrees,
     bridges not supported) [Z].
  d) Molecule centred on its minimum enclosing circle (Shapely), which allows
     the largest scale that still fits the base: 20.49 mm per angstrom [Z].
  e) Raised MolGod logo across the top of the base: symbol 1.4 mm, lettering
     1.0 mm, 45-degree bevel on every edge so it needs no support [R 1][Z];
     thinnest lettering stroke 1.89 mm (nozzle 0.4 mm).
  f) Base lettering on the vertical front face has a 45-degree chamfer (no flat
     ceiling that would need support) [R 1][Z].
  g) Profile for the thin upper part (cooling, minimum layer time, z-hop,
     acceleration): PRINT_INSTRUCTIONS.txt section 4. Interlayer bond strength
     in extruded polymers depends on the temperature history of the layers
     [R 4][R 5]; the specific values are practitioner recommendations
     [M 6][P 15][P 16] and HYPOTHESES until confirmed by our test prints.

3. HOW WE VERIFIED THIS FILE (before any physical print)  [Z]
  Slicer: PrusaSlicer 2.8.1 (command line), profile slicer_profile.ini.
  B0 heating   bed >= 50 C and nozzle >= 190 C before the first layer ...... PASS
  B1 stability slicer reports no floating or thin fragile part ............. PASS
  B2 mid-air   G-code analysed layer by layer (0.1 mm raster): extrusion in
               the molecule with nothing underneath .......................... PASS (molecule 0, base 0)
  B3 on base   slicer support moves outside the round base ................. PASS (sides/back 0, front 0)
  B4 logo      raised logo present in the G-code ........................... PASS
  Geometry     molecule untouched, one watertight solid, base dimensions,
               engraving depth, QR code, author mark ....................... PASS
  Each instrument is checked both ways before it is trusted (e.g. a cube must
  pass B1 and a floating sphere must fail it; the same model without supports
  must show mid-air regions in B2).

4. WHAT WE DO NOT KNOW YET
  - No physical test print of this release has been reported yet.
  - Peer-reviewed limits for pencil diameter versus height, neck diameter for
    clean cutting and engraving depth on small spheres were not found; the
    values used are our measurements and practitioner reports.
  - Other slicers may treat the 3MF settings differently (PRINT_INSTRUCTIONS 2).

5. COMPARABLE WORK
  Published one-piece ball-and-stick FDM models with built-in supports were not
  found; published approaches split the model into parts [R 22] or print with
  slicer supports [R 21]. See also [R 23].

6. REFERENCES (accessed 2026-10-21; DOIs verified in Crossref)
  Peer-reviewed [R]
  [R 1] Jiang J., Xu X., Stringer J. (2018). Support Structures for Additive
        Manufacturing: A Review. Journal of Manufacturing and Materials
        Processing 2(4), 64. https://doi.org/10.3390/jmmp2040064
  [R 4] Seppala J. E., Hoon Han S., Hillgartner K. E., Davis C. S., Migler K. B.
        (2017). Weld formation during material extrusion additive manufacturing.
        Soft Matter 13, 6761-6769. https://doi.org/10.1039/c7sm00950j
  [R 5] Kuznetsov V. E., Tavitov A. G., Urzhumtsev O. D. et al. (2019).
        Hardware factors influencing strength of parts obtained by fused
        filament fabrication. Polymers 11(11), 1870.
        https://doi.org/10.3390/polym11111870
  [R 21] Scalfani V. F., Vaid T. P. (2014). Journal of Chemical Education 91,
        1174-1180. https://doi.org/10.1021/ed400887t
  [R 22] Paukstelis P. J. (2018). MolPrint3D. Journal of Chemical Education 95,
        169-172. https://doi.org/10.1021/acs.jchemed.7b00549
  [R 23] Penny M. R. et al. (2017). Journal of Chemical Education 94,
        1265-1271. https://doi.org/10.1021/acs.jchemed.6b00953

  Manufacturer documentation [M]
  [M 6] Prusa Research, Knowledge Base: Cooling.
        https://help.prusa3d.com/en/article/cooling_127569
  [M 7] Prusa Research, Knowledge Base: Stringing.
        https://help.prusa3d.com/article/stringing_1805
  [M 8] Prusa Research, Knowledge Base: Organic supports.
        https://help.prusa3d.com/article/organic-supports_480131

  Practitioner reports [P] (grey literature: opinions, not measurements)
  [P 11] LulzBot forum: Suggestions for printing a small ball shape.
        https://forum.lulzbot.com/t/suggestions-for-printing-a-small-ball-shape/3948
  [P 12] Prusa forum: Round base won't print right.
        https://forum.prusa3d.com/forum/how-do-i-print-this-printing-help/round-base-wont-print-right-photos-settings-3mf
  [P 13] Printables: Pin Support Sphere Challenge (comments).
        https://www.printables.com/model/310666
  [P 14] Dreaming3D: Design your own supports in CAD.
        https://dreaming3d.net/blogs/news/stop-fighting-your-slicer-design-your-own-supports-in-cad
  [P 15] Printables: Pin Torture Test (comments).
        https://www.printables.com/model/490899
  [P 16] Bambu Lab forum: How to fix layer wobble for tall and skinny parts.
        https://forum.bambulab.com/t/how-to-fix-layer-wobble-for-tall-and-skinny-parts/56301
  [P 17] Printables: DNA helix (comments on z-hop).
        https://www.printables.com/model/29825
  [P 18] Prusa forum: Bed flinger - slower Y movement as a function of Z.
        https://forum.prusa3d.com/forum/prusaslicer/bed-flinger-slower-y-movement-as-function-of-z
  [P 19] Prusa forum: Issue with debossed text.
        https://forum.prusa3d.com/forum/english-forum-original-prusa-i3-mk4s-how-do-i-print-this/issue-with-debossed-text
  [P 20] MyMiniFactory: 3D print caffeine necklace (hydrogen atoms broke off
        with the supports).
        https://www.myminifactory.com/object/3d-print-caffeine-necklace-43955

  [Z] MolGod.org own measurements for this release (build report and slicer
      analysis included in this package).
