How Metal Embossing Stencils Are Made
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Computer-Aided Design (CAD)
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First, the artist creates either a two-dimensional drawing or a three-dimensional sculpture of the design to be made into a metal stencil. Drawings are loaded into an optical scanner and uploaded as a digital image. Sculptures or carvings are passed under a laser scanner which measures the angle of light deflected across the entire surface to read its exact three-dimensional shape.
Then, special computer-aided design (CAD) rendering software converts this data into a scalable, three-dimensional chart of surface elevations.
Computer Numercial Control (CNC) Milling Machine
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Once the CAD software has generated the surface chart file for the design, the file is sent to a high-precision milling machine. "Milling" is a general term for the metalworking technique of cutting away metal with a rotating, toothed cutter. In CNC milling, each design is expressed as a grid with a finite number of points. Each point has a numerical value that represents the height/thickness of the grid. The CNC milling machine shifts the target metal plate around and grinds each point on the plate down to its corresponding height in the digital file. Several different cutters are used, from tiny, cup-shaped heads to thick, saw-like blades.
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Materials
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Given its strength and resistance to deforming after repeated use, brass is the alloy most commonly used for embossing stencils. The stencil starts as a 1- or 2-inch thick plate of solid brass purchased from a foundry. Although there's only one design, two different, interlocking stencils must be made: a male, positive stencil (a.k.a. the "debossing die") and a female, reverse stencil (a.k.a. the "embossing die"). Therefore the CAD software creates two files: the original, debossing chart based on the scanner image and a negative embossing chart which is nothing more than a perfect inverse of the former.
The two stencils are then CNC milled from two separate plates, rinsed with water, dried and coated with a special oil film to prevent corrosion.
Once complete, the two stencils are packaged and shipped to the client.
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