[Adran] wanted to be able to accurately cut out a bunch of the same parts out of wood but didn’t have the cash to spend on buying or building an automated CNC machine. After thinking about it for a while he decided to build a mechanical device that will allow him to duplicate objects by tracing them in 3 dimensions. This type of duplicator uses a stylus to trace over the surface of an object while the cutting tool is also moved over a piece of raw material, cutting as it goes. The end result is a newly carved object that is the same shape as the original. The idea is like a pantograph that works in 3 dimensions.
The wood frame is constructed to move freely front to back and left to right. To control the height of the cutting tool, in this case a Dremel, the frame pivots up and down and the X-axis rail. A screw driver is mounted off the side of the Dremel that acts as a stylus. It is mounted in the same orientation as the Dremel bit and is constrained such that it and the Dremel move in the same direction and amount at all times. When the tip of the screwdriver is traced over a 3D part, the Dremel moves the exact same amount carving a part out of a block of material.
Although the machine works, [Adran] admits there is some room for improvement. The left to right motion is a little choppy as the wood frame is riding directly on steel rails. He plans on adding linear bearings for the next revision to smooth things out.