Methodology, Equations & Data Sources

1. G-Code Extrusion Mass & Unit Costing

When you load a `.gcode` file on G-Code Time Estimator, the parser tracks axis mode commands (`G20` inches / `G21` millimeters, `G90` absolute / `G91` relative XYZ, `M82` absolute / `M83` relative extruder, and `G92` coordinate resets). Net extruded filament length E_total_mm is converted to mass in grams:

grams = (E_total_mm / 10) × π × (d_cm / 2)² × density_g_cm3

At 1.75 mm diameter (`d_cm = 0.175`), the cross-sectional volume is `0.024053 cm³` per centimeter of filament length. Unit cost and commercial pricing are calculated as:

material_cost = (grams / 1000) × price_per_kg
energy_cost   = (watts / 1000) × hours × kwh_rate
wear_cost     = hours × wear_rate_per_hour
unit_cost     = (material_cost + energy_cost + wear_cost) × (1 + failure_pct / 100)
selling_price = (unit_cost × markup + channel_fixed_fee) / (1 − channel_fee_pct / 100)

2. STL Edge Topology & Signed Volume

On STL Repair Online, binary STL detection checks whether `file.byteLength === 84 + 50 × N`, where `N` is the 32-bit unsigned integer at byte offset 80. Vertices are welded using spatial quantization with `epsilon = 1e-6 × bbox_diagonal`. Undirected edges used by 1 triangle are counted as boundary edges (forming boundary hole loops); edges used by more than 2 triangles are non-manifold. Signed volume is computed via tetrahedral divergence:

signed_volume_mm3 = Σ [ v0 · (v1 × v2) ] / 6

3. SLA / MSLA Resin Volume, Consumables & Exposure Time

On Resin Print Cost Calculator, resin draw accounts for hollow shell retention and support volume overhead, while exposure time accounts for both normal layers and bottom burn-in layers:

resin_ml = solid_volume_ml × retained_fraction × (1 + support_pct / 100)
layers   = ceil(height_mm / layer_height_mm)
seconds  = layers × (exposure_s + lift_s) + bottom_layers × (bottom_exposure_s − exposure_s)

4. Spool Tare Subtraction & Linear Mass Density

On Filament Spool Weight Calculator and Empty Spool Weight Database, empty spool tare values represent typical dry weights recorded on `2026-11-01`. Because cardboard and injection-molded spools vary by production batch and humidity, weighing an empty spool of the same brand once is recommended.