Build Instructions

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• 1

  Step 1 — Parts and Laser Safety

  Parts can be found in the Components section or on the GitHub

  Total cost lands around 750 €, dominated by the filters, surplus spectrometer and laser safety glasses.

  Notes on the two "wildcard" parts:

  • Spectrometer: the BTC100-2S is the cost compromise of this build. Its 100 µm slit is the main resolution bottleneck. Any spectrometer covering roughly 500–650 nm will work — a better one yields sharper peaks, though often at significant cost.
  • Objective: must be infinity-corrected — the design places the dichroic and longpass filter in collimated space and uses the achromat as the tube lens. A finite (160 mm) objective will not work without redesign! Also keep in mind that anything >20x often features a working distance too short for measuring inside containers or a cuvette (though at higher NA = more signal). 20x is the best compromise, from my experience at least.

  This build uses a 532 nm laser at >30 mW — a Class 3B laser. Direct exposure and even specular reflections can cause permanent eye damage before you can blink.

  • Certified laser safety glasses rated for 532 nm are mandatory. Buy from a reputable supplier, not AliExpress. I use these from Protect Laserschutz (~130 €).
  • Keep the laser disconnected from power during the entire assembly. It is only powered once fully enclosed in the cube.
  • Never look into the beam path or the objective, even with protection on.
  • Remove watches and rings while aligning — stray reflections mostly come as a surprise.
  • Know your local regulations for Class 3B laser operation.
• 2

  Step 2 — 3D Printing Notes

  All parts print without supports, and each is printed only once (except where noted in the parts table on GitHub). I printed on a Bambu P1S with a 0.4 mm hardened steel nozzle, sliced in BambuStudio.

  Material: ideally dark, non-reflective, and stiff. I used black PETG-CF (matte, my favorite); PLA-CF is a sensible alternative.

  Settings:

  • Layer height 0.12 mm — at least for anything with threads or fine features
  • 4 walls, 50 % gyroid infill
  • Seam position Nearest (or Random) for better thread fit
  • "Precision" parameters set to 0.001 mm (may just be placebo)

  Orientation: print faces flat / perpendicular to the build plate — especially threads, which must be printed vertically for clean engagement. "Auto-Orient" should always do the trick.

  Overview Graphic; be aware that parts might have been slightly modified!

  Order & tips:

  1. Print Base-Cube, Base-Cube-Top and the four Cube-Inserts (Sample, Dump, Laser, FilterFocus) first, then the remaining grouped parts.
  2. The Base-Cube is the most demanding part due to overhangs — everything else is easy.
  3. For the Cube-Inserts and Cube-Lid, let the build plate cool fully before removal, or you risk permanently warping the part.
  4. Also print the two spanner tools (Spanner_SM1RR, Spanner_SM05RR) — they make tightening the retaining rings much easier later.
• 3

  Step 3 — Base Cube

  Printed: Base-Cube, Base-Cube-Top 

  Sourced: 24× M3 heat-set inserts (4 mm length, Ø4 mm), 24× M3×8 screws

  1. Melt the heat-set inserts into the bosses of the Base-Cube using a soldering iron. Keep the iron perpendicular and let the plastic — not force — do the work.
  2. Fasten Base-Cube-Top with M3×8 screws.

  You don't have to populate every insert at first. I initially left out the bottom row and one full side — the side that later takes the Beam Dump — because that opening doubles as access to the adjustment screws of the 45° mirror inside. The Cube-Insert clearances are relatively tight (tighter still if the cube's overhangs sagged a little), and during testing I ran most inserts on just 2 screws (top-left + bottom-right).

  The following sub-assemblies (Steps 4–7) don't need to be built in order.

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