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There are several concepts that must be understood in order appreciate the workings of a computer controlled (CNC(Computer Numeric Control)) routing machine.
Picture yourself floating above and looking down at a piece of 48 inch by 96 inch plywood with the long dimension running horizontally (from left to right) and the short dimension running away from you, yikes! The long dimension is referred to as the “x” axis, the short one as the “y” axis. So..... if you wanted to refer to a point that was 10 inches along the x axis it would be x=10. This position runs from the top to the bottom of the sheet so wherever you measure 10” from the left edge of the table to the right is always x=10. Anywhere along this line is how we refer to the “y” axis. So... if you went from the bottom of the table up the x=10 line to 24 inches you would be at y=24 and also at x=10. These values are referred to as coordinate points. In this case the bottom left corner of the table is the x=0, y=0 position as it is x=0 AND y=0. In the case of the cnc router system that we use we can access an area that is 49 inches in the ‘Y” direction and 98” in the “X” direction. So we can access any area on the table from 0,0 to 98,49. Simple, eh?
The other axis that we have available is the “z” axis which is the up and down axis. This provides for vertical movement of the router bit spinning in the router. This allows us to pierce the material to whatever depth the bit and the carriage will allow (from about 1/4” to 21/2”) and then to move through the material cutting our choice of 2 dimensional shapes. In the case of Vcarving (2 1/2D) the software moves the v shaped bit up and down in the material in order to suit the width criteria of the object that it is carving. As an example, a drawing of a 3” high bowling pin will be cut deeper at the larger base than at the narrower top as the bit simply satisfies the width requirement and therefore must raise and lower the bit in order to satisfy the drawing criteria!
Then we have 3D. This is harder to explain than to use. In 2D you can cut out the shape of a half of a sphere, but it will simply be a flat circular shaped object.
With 3 dimensional cutting the most wonderful things can be created but you need more expensive software. A 3D drawing and/or CAD (Computer Aided Drawing) package and a 3D cutting program are then required (no changes to the machine are necessary). When you draw the sphere, and want to cut half of it, the top side, let’s say a 10 inch diameter ball to be generated, so the dimensions will be 10 by 10 by 5 inches. The machine then generates the code and uses this height to cut the sphere shape in the Z direction as well creating a half of a ball.
In general 3D cutting tends to be very expensive, especially when compared to 2D cutout shapes!
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