CourseWiki/Machining/Production and Nontraditional Processes

Chemical Milling and Etching

A mask protects selected areas while an etchant dissolves exposed metal; sideways etching limits the detail.

A mask defines where chemical removal occurs

Chemical machining uses a chemical reaction to dissolve exposed material. A protective mask covers areas that should remain. Chemical milling can make shallow recesses or reduce a metal part's weight. Photochemical etching uses a patterned resist and can produce intricate thin-sheet parts, including through openings.

Unlike ECM, ordinary chemical etching does not use an external machining current between a tool and the work. Select an etchant compatible with the particular material; “chemical machining” does not name one chemistry that works on everything.

Allow for sideways etching beneath the mask

Etching can spread sideways beneath the mask edge as well as into the surface. This undercut limits narrow lands, corner sharpness and dimensional control, especially as etch depth increases. The mask design must compensate for the etching behavior. Surface finish depends on the material and chemistry. Chemical removal avoids a cutting-induced thermal HAZ, but that is not the same as saying the chemical bath has no temperature requirements.

Why thin-sheet patterns are a useful application

A mask can define many features at once without a separate shaped cutting tool for each opening. Fotofab describes partial and through etching.

Compare Electrochemical Machining and Selecting a Material-Removal Process. Safety reference: Chemicals and Safety Data Sheets.

Appears in

DET 330 DET Nontraditional Machining