Volumetric additive manufacturing · 405 nm

HoloForge

A layer-by-layer printer draws an object. HoloForge makes light from several rotary angles intersect only where the object should cure, and the resin sets all at once: one part, under fifteen seconds, no supports. The optics, the photochemistry and the machine are modelled, so the whole chain runs before the hardware is finished.

The machine Source

Optical train · Stage 1 alignment bench budget €8,000–€10,000

Every figure on this page is from the repository's own bill of materials and documentation. HoloForge v2.0.0

The machine

01 · From the bill of materials

Part	Specification	Budget
Laser	405 nm single-transverse-mode, 100–500 mW CW, linewidth under 0.5 nm	€600–1,200
Phase SLM	Lab-grade phase-only reflective LCoS, 1920×1080, 8.0 µm pitch, calibrated 0–2π at 405 nm	€5,500–6,800
Beam expander	25 µm pinhole with 5–10× variable magnification for flat-top pupil illumination	€400–650
4f relay	Achromatic doublets, f₁ 200 mm to f₂ 50 mm, M = 0.25× demagnification, AR coated 400–700 nm	€450–800
Optomechanics	30 mm and 60 mm cage plates, precision posts, kinematic mounts, breadboard base	€800–1,200
Test vat	Optical-grade fused quartz cell, AR-coated windows under 0.2% reflectance at 405 nm	€150–350
Metrology	USB3 machine-vision CMOS with a 405 nm bandpass filter for wavefront and fluorescence PSF imaging	€300–600
POC dyes	Rhodamine 6G and sodium fluorescein in ethanol, for 3D focus-spot profiling	€100–300
Stage 1 target: demonstrate dynamic spot focusing into dye-doped liquid cells		€8,300–11,900

The modulator carries most of the cost, which is the honest shape of this project. Everything else in the bench is standard optics, and the whole train is driven from one Python package plus an Arduino firmware image in firmware/holoforge_controller.

How it works

02 · Four stages

holoforge/optics.py

Wavefront synthesis

Split-step angular spectrum propagation with 4f telecentric spatial filtering, and double-phase hologram synthesis so a phase-only modulator can also shape amplitude.

holoforge/optimize.py

Tomographic optimisation

Closed-loop multi-angle optimisation over the target volume. The measured result is 94.6–96.7% cure IoU with under 0.02% overcure, in simulation.

holoforge/kinetics.py

Photochemistry

A coupled radical polymerisation and dissolved-oxygen inhibition ODE solver, because the oxygen in the resin is what decides where curing actually starts.

holoforge/metrology.py

Metrology

A virtual white-light interferometric profilometer reporting R_a, R_q and R_z, so surface quality is a number rather than an impression.

holoforge/hardware/

Machine control

G-code rotary stage over USB serial, fullscreen phase-SLM presenter on a secondary display, 405 nm shutter with a safety state machine, and a synchronous print runner.

holoforge/backend.py

Compute backend

The propagation and optimisation loops run on CPU or GPU, picking up CuPy or Torch CUDA where it is available.

What it prints

03 · Verticals

Dental crowns

Fitted parts where a layer line is a rejection, and where the support marks left by a conventional print have to be ground away.

Microfluidic chips

Internal channels that a stair-stepped surface would obstruct or distort.

Aspheric optical lenses

Surfaces where roughness changes the optical result, printed without the anisotropy of layered curing.

Your own .stl

Arbitrary meshes are voxelised into the target volume and optimised like any other part.

Run it without the machine

04 · Digital twin

HoloForge ships a complete optical and photochemical simulator plus a mock hardware emulation layer, so the same code path that drives the bench runs on a laptop: synthesise holograms, load an .stl, inspect the optical dose and the surface profilometry, and run a simulated rotary print with virtual Schlieren camera feedback.

git clone https://github.com/KELLERBABG/HoloForge
cd HoloForge
py -m pip install -e .

py -m holoforge --help        # the command surface
py -m holoforge render --help # synthesise a hologram
py -m holoforge print --help  # simulate or drive a rotary print

Where the hardware stands

Stage 1 is a bench, not a printer. The alignment bench proves 3D dynamic spot focusing into dye-doped liquid cells before any resin is cured.
Stage 2 is the volumetric cure. Photopolymerisation into a solid part follows the bench, and the BOM prices Stage 1 only.
The fifteen seconds is a simulation result. The optics and the kinetics are physical models; the machine that would measure a real print is not built yet.
Release 2.0.0 is the software. dist/HoloForge-v2.0.0-release.zip contains the package, the simulator and the mock drivers.