UV Curing calculator

UV Shadowing Risk Calculator

UV cure assumes line-of-sight from lamp to part. The moment a part has 3D features, undercuts, or fixturing that blocks the lamp, that assumption breaks and dose at the affected surface drops dramatically — sometimes 50% or more. This calculator scores three independent contributors (geometry, fixture / lane setup, exposure angle / line speed) into a single risk score so DFM reviewers and process engineers can flag the parts that need an extra lamp, a redesigned fixture, or a chemistry change before they hit production.

What this calculator does

  • Score the cure risk on parts with 3D geometry, undercuts, or fixturing that blocks line-of-sight from the UV lamp.
  • Use it during DFM review of a new part, or when a defect spike traces to specific features (a bonded edge under a flange, an undercut adhesive joint).
  • Combines geometry, fixture, and exposure-angle scores into a single UV shadowing risk number, with a banded interpretation.

Formula used

  • Risk score = (geometry × 0.5) + (fixture × 0.3) + (exposure × 0.2)
  • Score 0–30 low, 30–60 medium, 60+ high — schedule a confirmation pass with a profiling radiometer in shadowed areas.

Inputs explained

  • Geometry exposure risk: 0 = flat top surface, 100 = deep undercut / interior cavity / blind hole.
  • Fixture / lane risk: 0 = open belt, 100 = part recessed in tight fixture or behind lane guides.
  • Exposure angle / speed risk: 0 = perpendicular, slow pass; 100 = steep angle of incidence or high line speed past lamp.

How to use the result

  • Use during DFM review on new parts, when adding a part to an existing line, after a fixture change, and as a triage step when defect data points to a specific feature.
  • It's a triage score, not a measurement. A high score warrants a profiling radiometer pass in the shadowed zone with a microprobe — that pass is what you actually trust. Don't make a release decision on score alone.

Common questions

  • How do I score geometry? Walk the CAD: 0 if the cure surface is flat and lamp-facing; 30 if there's a low boss or step; 60 if there's a vertical sidewall or partial undercut; 100 if cure is required inside a blind hole, deep cavity, or beneath a flange. Most adhesive joints in assembled products land 40–70.
  • What does a 'high' score actually mean for production? Score 60+ means at least one feature on the part is likely receiving <50% of the dose at the open belt position. Fix options in order of cost: re-orient the part, add a side-fire lamp, change to a chemistry with broader band sensitivity, redesign the joint to expose the bond line. Don't ignore it and hope the dose margin absorbs it.
  • Can the calc handle multi-lamp tunnels? Indirectly — score the worst-case shadow even with multiple lamps, because shadows cast by one lamp aren't always covered by the next. For a quantitative answer, run profile passes with each lamp on individually and use UV Multi-Lamp Dose to sum the contributions at the shadowed point.
  • Where does oxygen inhibition fit in? Separately. Shadowing reduces dose; oxygen inhibition reduces cure efficacy at exposed surfaces even with full dose. Run UV Oxygen Inhibition Risk for the surface effects and this calculator for the geometry effects — both can apply to the same part.

Last reviewed 2026-05-12.