Chemical milling is a process used to remove material from metal by using acidic or caustic chemicals. It is widely used to make parts with complex or precise shapes, like in aerospace, electronics, and automotive industries. It is a non-mechanical method, and it works well for creating fine details or thin-walled components.
Steps in the Chemical Milling Process:
1. Cleaning the Workpiece:
First, clean the metal workpiece to remove any dirt, oils, or rust that could affect the etching process.
2. Masking or Coating with Resist:
Coat the metal surface with a photoresist or protective material. This light-sensitive material is used in photochemical etching. Apply the resist layer evenly by spray coating or spin coating, depending on the level of precision required.
3. Exposure (for Photochemical Etching):
Expose the photoresist-coated surface to ultraviolet (UV) light through a photomask. The photomask holds the pattern you want to etch. UV light will interact with the resist and harden it in the areas that receive light (depending on whether it’s a positive or negative resist). In positive resists, the exposed areas become soluble, and in negative resists, the exposed areas become insoluble. Carefully control the exposure time to ensure proper resist development.
4. Developing the Resist Pattern:
After exposure, submerge the workpiece in a developer solution. This will remove the unexposed (or exposed) areas of the resist, leaving the pattern you created with the photomask.
5. Chemical Etching:
Immerse or spray the workpiece with a chemical etchant, such as ferric chloride for copper or nitric acid for aluminum. The etchant will dissolve the exposed, unprotected metal, leaving the protected pattern intact. Carefully control the etching to make sure it removes material evenly and doesn’t over-etch or under-etch.
6. Stripping Rinsing and Inspection:
After etching, rinse the workpiece thoroughly to remove any leftover etchant and resist. Inspect the component to make sure the pattern is correctly etched and matches the design.
Advantages of Chemical Milling:
– Precision:Chemical milling lets you create very fine details and tight tolerances.
– Cost-Effective: It is often cheaper than mechanical processes, especially for complex shapes and thin materials.
– No Mechanical Stress: Since it is a non-mechanical process, there is no risk of causing stress or distortion in the material.
– Complex Shapes: Chemical milling can make very complex shapes that may be hard or impossible to create with traditional machining methods.
Applications:
– Aerospace: Lightweight parts with complex shapes, such as brackets, panels, and structural components.
– Electronics: Creating fine features or parts for printed circuit boards (PCBs).
– Medical: Making precise components like implants or surgical tools with intricate patterns.
– Automotive: Parts with thin walls or complex shapes, such as heat shields and other lightweight components.
Chemical milling is a flexible and effective method that is useful in industries where precision and material savings are important.
