Chemical milling (also known as photo etching, wet etching, photochemical etching, & chemical etching) is a photo-lithographic process that uses a phototool to block UV light from exposing the area of a sheet of metal that has first been cleaned and laminated with photoresist.
The sheet then gets developed, which washes away the unexposed photoresist leaving a very precise mask of hardened photoresist behind. This patterned sheet gets exposed to concentrated etchants that dissolve any exposed material.
The affordable pricing, quick speed, and high precision of chemical milling make it is the quintessential method for both production and prototyping of metal parts.
Chemical Etching Process
This process has several steps including:
- Phototooling - The process begins with an engineering drawing or sketch. CAD software and laser plot technology generate an image of the part on a set of photographic films, called a Phototool. Depending upon the size of the part, the Phototool may contain from one to serval thousand exacting images of a part.
- Exposing - Using the phototool, UV lamps expose the image of the part onto the photoresist.
- Coating - Extremely flat and clean sheets of metal are coated on both sides with a polymer called photoresist that is UV light sensitive and resistant to acids. The coated sheet of metal is vacuum-sealed between the top and bottom layers of the phototool.
- Developing - Developing solution washes away the unexposed coating, leaving a mask in the shape of the part with only the material that is to be etched away left uncoated.
- Etching - The uncoated areas are etched away, leaving the precisely defined features of the part.
- Stripping - An alkaline solution is used to remove the mask from the metal surface.
- Forming - If applicable, forming presses are utilized to bend the etched blank into precise three-dimensional shapes.
- Inspection - Calibrated measuring instruments, including state of the art inspection machines, are used to ensure your part meets your specifications.
Benefits of Chemical Milling
This process offers many benefits for a variety of industries including:
- Works on a variety of metal alloys
- Easily produces complex design
- No stress to the metal
- Produces uniform, burr-free parts
- Fast tooling, production, and shipping
The efficiency of chemical milling is great for various applications including:
Photochemical etching is the most economical option if you:
- Want to invest in tooling
- Want to make a series of prototypes
- Want to etch thin metal alloys
- Want complex parts with intricate designs
Chemical etching rivals:
- Laser cutting metal
- Metal Stamping
- Water Jet Cutting
- Electrical Discharge Machining