Dr. Lotfi K. Gaafar 2002

Dr. L. K. GaafarMENG 439

Chemical Machining

Dr. Lotfi K. Gaafar 2002

Chemical Machining

Was developed based on the observation that chemicals attack metals and etch them by using chemical dissolutions.

Is the oldest of nontraditional machining processes, and has been used to engrave metals and hard stones.

Can be classified into:Chemical

MillingChemical

Blanking

Dr. Lotfi K. Gaafar 2002

Chemical Milling

Shallow cavities on sheets, plates, etc… Selective attack by chemicals on workpiece Used in aerospace industry Used to fabricate microelectronic devices

Dr. Lotfi K. Gaafar 2002

Chemical Blanking

Blanking of sheet metals Material removed by chemical dissolution Used to produce fine screens, flat springs,

etc… Very cheap but efficient

Dr. Lotfi K. Gaafar 2002

Characteristics of Chemical Machining

Shallow removal of material(up to 12mm) Blanking of thin sheets Low tooling & equipment cost Suitable for low production runs Material removal rate(0.1mm/min)

Dr. Lotfi K. Gaafar 2002

Photo Chemical Machining (PCM)

PCM is a material removal process using chemicals (etchants) to produce high precision parts.

This process is also known as Photo Etching, Chemical Blanking and Photo Chemical Milling.

Dr. Lotfi K. Gaafar 2002

PCM Process

1. Artwork- generate design using CAD systems, then plot it using a high precision laser plotter to produce photo-tool.

2. Chemically clean the metal surface.

3. Coat both sides of the plate with photoresist. (photoresist is a polymer that adheres to the metal when exposed to UV light).

http://web.mit.edu/ndemarco/www/chemmilling/slide6.html

Dr. Lotfi K. Gaafar 2002

PCM Process Cont.

4. Expose plate and photo-tool to ensure image transfer.

5. Spray metal with etchant or dip it in hot acidic solution to etch all material other than part covered with photoresist (1-15 min.).

6. Rinse the plate to ensure photoresist and etchant removal.

http://web.mit.edu/ndemarco/www/chemmilling/slide6.html

Dr. Lotfi K. Gaafar 2002

Advantages

Low Tooling Cost- all tooling is produced by CAD systems at a low cost with a short creation time.

Low Modification Cost- short runs are possible at a low cost, thus, design can be easily modified.

Burr and Stress Free. Complex Designs. Thin Plates as thin as 0.005”.

Dr. Lotfi K. Gaafar 2002

Materials

Aluminum Chromium Copper (oxygen free, rolled…) Nickel Steel (carbon, stainless…) Lead Zinc

Dr. Lotfi K. Gaafar 2002

Applications

High Precision Partsand Decorative Items Gaskets Washers Sensors Nameplates Jewelry Microprocessor Chips

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