Photochemical Machining Prepress
Updated August 2026
Photochemical Machining & Acid Metal Etching Undercut Calculator
Calculate alloy etch factors ($EF$), lateral acid undercut ($U$), phototool artwork compensation offsets, minimum manufacturable slot/land widths, and hourglass cross-section profiles for chemical milling and precision metal etching.
1. Etching Parameters & Material
Double-sided halves the etch depth per side, dramatically reducing undercut.
0.010 in (10.0 mil / 250 µm)
Desired final physical finished dimension.
2. Undercut & Phototool Artwork Compensation
Effective Etch Factor (EF)
2.00 : 1
Vertical Etch Depth per Side
0.125 mm (4.9 mil)
Lateral Undercut per Edge (U)
0.063 mm (2.5 mil)
Total Feature Width Compensation
± 0.125 mm (± 4.9 mil)
Photo-Tool Vector Artwork Dimensions
Target Physical Part Size
1.000 mm
Phototool Artwork Feature Size
0.875 mm
Artwork Adjustment Direction
Shrink Aperture by 0.125 mm
Min Manufacturable Slot Width
0.275 mm (11.0 mil)
Min Metal Land / Bridge Width
0.225 mm (9.0 mil)
Natural Inside Corner Fillet (R)
0.094 mm (3.7 mil)
Hourglass Cross-Section & Acid Undercut Geometry
Preparing Vector DXF Phototools for Chemical Milling?
Photochemical machining photoplotters operate at 16,000+ to 40,000 DPI. Raster images (PNG, JPG, scanned blueprints) suffer from fuzzy, anti-aliased edge transitions that degrade photoresist exposure and create ragged acid etching. SpotItLive converts your sketches and technical drawings into mathematically exact 1-bit DXF, SVG, and PDF phototool masters.
Vectorize Phototool Artwork →Photochemical Machining Metal Etch Factor & Design Rules
Reference guide for material etch factors, typical tolerances, standard photo-resist resolutions, and chemical etchants.
| Alloy Group | Standard Chemistry | Double-Sided Etch Factor | Single-Sided Etch Factor | Standard Tolerance (±) |
|---|---|---|---|---|
| Stainless Steel (301, 304, 316) | Ferric Chloride ($FeCl_3$) | 1.8 - 2.2 : 1 | 1.0 - 1.2 : 1 | ± 10% of Sheet Thickness |
| Copper & Brass (C110, C260) | Cupric Chloride / Ferric | 2.2 - 2.8 : 1 | 1.2 - 1.4 : 1 | ± 8% of Sheet Thickness |
| Beryllium Copper (C17200) | Ferric Chloride | 2.0 - 2.4 : 1 | 1.1 - 1.3 : 1 | ± 10% of Sheet Thickness |
| Nickel & Inconel Alloys | Ferric Chloride / Acidified | 1.4 - 1.8 : 1 | 0.8 - 1.0 : 1 | ± 12% of Sheet Thickness |
| Aluminum (5052, 6061) | Alkaline / Acid Mix | 1.2 - 1.6 : 1 | 0.7 - 0.9 : 1 | ± 15% of Sheet Thickness |
| Titanium Grade 2 / 5 | Hydrofluoric / Nitric Mix | 1.0 - 1.4 : 1 | 0.6 - 0.8 : 1 | ± 15% of Sheet Thickness |
Key CAD & Prepress Rules for Chemical Milling Phototools
- No Anti-Aliasing: Phototools must be pure binary (1-bit black/clear). Any gray anti-aliased gradient will cause semi-polymerized photoresist that sloughs off during acid spray, causing pitting.
- Hourglass Break-In Compensation: In double-sided etching, the top and bottom acid sprays meet in the center of the sheet thickness, creating a narrow knife-edge waist. The opening at the metal surface is wider than the center.
- Tie-Bar & Tab Geometry: To prevent etched parts from falling into the acid sump, include micro-tabs (half-etched or full-thickness tabs with 0.5x sheet thickness width) connecting components to the runner frame.
- Closed Loop Vector Polylines: All apertures and part outlines must be zero-gap, tangent-continuous vector polylines formatted as DXF R12/2000 or high-resolution PDF for laser photoplotter RIPs.