User:B.viswanathan89/sandbox

Chemical Grinding In this process metal is removed from the workpiece by controlled attack or etching. The metal can be removed from selected regions or from the entire of the workpiece as per requirements. Selective machining can also be carried out if required, by covering the portion which are to be left unmachined with a resistant material, called a resist or maskant, which can be removed after the machining operation is completed. The chemical machining process can be classified as follows: 1.	Chemical Blanking: It used for cutting out parts from thin sheet metal. 2.	Chemical Contour Machining: It is also known as ‘Chemical Milling’, in this process selective or complete metal removal is carried out from thicker workpieces. 3.	Chemical Engraving: This process whenever conventional machining process is either impractical or extremely difficult to carry out due to the extremely thin sections or complex shapes of parts to be machined or high hardness, brittleness or toughness of the workpiece material. The types of resists used are: 1.	Cut and Peel type: These are used when very critical dimensional tolerances are not required. They are applied by either dip or spray method. 2.	Photographic Resists: They used when closer dimensional tolerance are required. They can be applied by dip coating, spray method or roll coating. 3.	Screen Resists: These are generally used for relatively shorter parts having flat surfaces or otherwise simple contours.

Advantages of the process: •	Tooling cost is very low. •	Both faces of the workpiece can be machined simultaneously. •	Due to the absence of mechanical working, the workpiece is not subjected to usual defects like work gardening, cracks, etc; •	The part produced is free of burrs •	Complex contours can be machined easily. •	Hard and brittle material can be easily machined. •	The cost of design change is very low.

Disadvantages of the process: 1.	High manufacturing cost. 2.	Low metal removal rate. Hence, process is slower. 3.	Metal thickness that can be machined is limited. 4.	Sharp corners can’t be produced. 5.	Larger floor space is required 6.	Skilled workers are required.