What are the differences between chemical etching and other metal shaping methods?

A Cambridge University Journal published research revealing that manufacturing process selection (MPS) influences product design outcomes but is often guided by experience rather than a structured evaluation of alternatives

Different metal shaping methods remove material in different ways. Mechanical processes use force, thermal methods use heat, and chemical etching uses controlled chemical reactions. These differences directly affect material integrity and reliability.

You can model the perfect geometry in computer-aided design (CAD), but how you cut or form it can change what the surface and near-surface layers actually look like and how they perform.

Reviews of machining “surface integrity” show that material-removal processes can alter microstructure, introduce residual stress, and create surface anomalies, making it important to carefully assess manufacturing options.

Mechanical methods

Stamping, punching, and CNC machining remain widely used due to their scalability. Once tooling is established, they can produce large volumes of consistent components quickly and cost-effectively.

This is why they are widely used in the automotive and electronics industries. However, these processes rely on physical force to cut, form or remove material, and that interaction inevitably affects the metal itself.

When a punch or cutting tool shears material, it plastically deforms. This is the permanent alteration of the material structure, usually affecting the surrounding region, where it produces burrs, edge deformation, and localised strain.

Surface integrity studies state that machining and shearing processes introduce mechanical and thermal loads that can alter subsurface material properties and introduce residual stress, which may affect fatigue performance and long-term reliability.

These effects usually require additional finishing operations, like deburring, grinding or polishing to meet functional requirements. Burr formation is a recognised and largely unavoidable outcome of machining, with research in Light Metal Alloys Applications highlighting that deburring is a necessary but non-value-adding process that can significantly increase production effort and cost.

Residual stress is another consideration. The UK National Physical Laboratory (NPL) confirms that machining and forming processes introduce internal stresses that can lead to distortion, reduced fatigue life and dimensional instability, particularly in precision components.

In addition, mechanical processes can impose practical limits on achievable geometry. Producing very fine features, sharp internal corners, or thin, delicate structures may require specialised tooling or secondary machining operations.

Tool wear further complicates production over time, affecting dimensional accuracy and process consistency. The aforementioned research also highlights that tool wear can significantly affect machining performance, especially in precision applications requiring tight tolerances.

Thermal shaping

Another approach to shaping metal is thermal processing. Instead of physically cutting or deforming the material, these methods use concentrated energy. This is typically in the form of a laser, plasma arc or electrical discharge, to melt or vaporise material along a defined path.

This allows engineers to produce intricate geometries, fine features and complex internal profiles that would be difficult or impractical to achieve using conventional mechanical tooling.

Because thermal processes do not rely on physical cutting forces, they avoid many of the deformation effects associated with punching or machining. However, introducing heat creates its own set of material considerations.

When a laser or electrical discharge interacts with a metal surface, it generates a highly localised thermal cycle. This produces a heat-affected zone (HAZ), a region where the material has been exposed to elevated temperatures and undergoes microstructural changes, even though it does not melt.

These microstructural changes can directly influence mechanical performance. A 2021 survey of existing research found that heat-affected zones can significantly reduce material strength in certain alloys. This includes reductions of up to 50 per cent in aluminium alloys and proof stress reductions of up to 70 per cent, depending on material condition and thermal exposure.

The NPL also found that residual stresses generated during machining can reach extremely high levels, typically around 500 MPa and up to several gigapascals in hard materials. These are levels that are more than sufficient to influence flexural strength and long-term component performance.

What’s more, thermal cutting processes can produce recast layers. These are thin layers of resolidified material that form when molten metal cools rapidly at the cut surface.

Such altered surface layers often differ in microstructure and mechanical properties from the original base material, requiring secondary finishing processes to restore optimal surface integrity.

Chemical machining

An alternative option is chemical etching. Also known as photochemical machining (PCM), this process removes material using controlled chemical reactions rather than mechanical force or thermal energy.

A photoresist mask is applied to define the component geometry before the exposed metal is selectively dissolved using etchants. Because material is removed chemically rather than physically, the process avoids the deformation and thermal effects associated with conventional shaping methods.

A recent manufacturing review revealed that PCM is a stress-free process that doesn’t introduce residual stress, burrs or deformation. Neither does it alter hardness, grain structure or ductility, because no cutting forces or thermal loads are applied.

Research published in 2025 in the Journal of Tribology also suggests that photochemical machining is a viable option for producing microstructures and precision components. This is while maintaining material integrity and avoiding the stress and deformation associated with conventional manufacturing methods.

Another advantage is tooling flexibility. Chemical etching uses phototools rather than hard tooling like dies or punches, which can be created quickly and modified easily for faster design iterations and lower tooling costs. Because phototools do not experience mechanical wear, they also maintain accuracy throughout production.

From an engineering perspective, this supports faster product development and allows manufacturers to adapt quickly to changing design requirements, which brings us back to the start of this article.

Manufacturing process selection influences component performance and reliability. Mechanical shaping introduces force, thermal shaping introduces heat, and both can affect material integrity. Meanwhile, chemical etching removes material without introducing either, allowing engineers to preserve material properties while achieving precise geometries.

Understanding these differences helps make informed process selection decisions, ensuring that manufacturing supports rather than compromises design intent. That’s why design outcomes should be guided by a structured evaluation of alternatives rather than experience.

Contributed by Ben Kitson, head of business development at Precision Micro.