Aluminum is one of the harder metals to chemically etch. It’s reactive, and it etches in both acids and bases, so a process tuned for stainless steel or copper often breaks down once aluminum is on the line. Conard Corporation has spent decades perfecting the chemical etching process for aluminum, and achieving tight tolerances starts with manufacturability in the part design. Run a design through this aluminum etching checklist before it goes out for quote.

Factor in Etch Allowance and Undercut Limits

Chemical etching removes material omnidirectionally, both vertically through the sheet and laterally beneath the photoresist. This lateral removal, known as undercut, creates a subtle rounded profile (cusp) along the finished edge, typically measuring 10% to 20% of total material thickness.

To maintain dimensional accuracy:

  • Calculate the etch factor. Determine the ratio between etch depth and lateral undercut to predict edge geometry.
  • Incorporate dimensional allowances. Adjust CAD geometries for undercut rather than modeling strictly to nominal dimensions.
  • Prevent undersized features. Proactive compensation prevents parts from falling below lower tolerance limits post-etch.

Adhere to Minimum Feature Size & Spacing

Dimensional geometry in chemical etching directly correlates with raw material thickness. Applying proportional feature rules ensures chemical etchants flow evenly without causing structural failure or incomplete features.

Key design parameters include:

  • Minimum hole/slot widths. Maintain internal feature diameters equal to or greater than 100% of material thickness (1.0 x T).
  • Minimum land widths. Retain interconnecting metal webs (lands) of at least 75% of material thickness (0.75 x T).
  • Foil-gauge precautions. Apply strict minimums on ultra-thin stock to avoid complete edge breakdown or process rework.

Define Internal and External Radii

Sharp corners don’t survive etching the way they do in machining. Because the etchant works evenly outward from every edge, the smallest radius a corner can hold ties directly to material thickness: outside corners need roughly 75% of the thickness as a minimum radius, and inside corners need closer to 100%. A drawing can call out a true 90-degree corner, but the etchant will round it anyway, so it’s better to draw the radius the process will actually produce and keep the model and the part in agreement.

Optimize File Format and Artwork (Contrast)

Phototooling accuracy relies entirely on clean, high-contrast vector geometries provided in the initial design submission. Submitting production-ready CAD files eliminates conversion errors and accelerates tooling turnaround.

Adhere to these CAD file specifications:

  • Format requirements. Submit native vector formats (such as DXF or Gerber) rather than raster images to ensure precise line definition.
  • Polarity and polygons. Define geometries using binary black-and-white vector shapes, solid black representing retained metal and solid white representing etched regions.
  • Vector hygiene. Audit artwork for unclosed paths, overlapping lines, or stray hair-line gaps prior to quote submission.

Review Material Thickness and Tolerances

Aluminum etching covers a wide span of material thickness, from dead-soft foil around .001” up to sheet stock around .080”, and achievable tolerance changes across that span. Thinner material generally holds a tighter absolute tolerance, while thicker stock is usually toleranced as a percentage of thickness, often around ±10%. Confirming target thickness and tolerance early helps avoid a redesign once the part is quoted. For more on how aluminum compares with other fabrication options, Conard’s guide to precision aluminum components covers the trade-offs in more depth.

A quick summary of this aluminum etching checklist:

  • Etch factor. Build in allowance for undercut instead of drawing to nominal dimensions.
  • Feature size and spacing. Keep holes, slots, and land widths proportional to material thickness.
  • Radii. Draw corners at the radius the process will actually produce.
  • File format. Submit clean, high-contrast vector artwork with no stray gaps.
  • Thickness and tolerance. Confirm both early, since they shift together across the thickness span.

Streamline Your Production with Conard’s Aluminum Etching Expertise

Working through this aluminum etching checklist before a design is finalized saves time on both sides of the quote. Conard Corporation built its process specifically around aluminum’s quirks and handles material from foil to thicker sheet with tolerances that hold up in production.

Contact Conard to review a design, or request a free quote to get pricing on your next aluminum etching project.