hand trace to gcode

hard to measure slopes and curves

Update: Fusion 360 has improved spline sketching since this blog post was created

Anyone reading a CNC blog will be familiar with creating a drawing in CAD but what if the aim is to reproduce an item that's difficult to define with a few caliper measurements ? The picture on the left is part of a toy truck.

It's possible to trace the photo itself in software.  It's also possible place a 3D object on a flat bed scanner.  In this example a quick trace was was done with fine tip marker.  The trace was placed on the scanner and the resulting b+w image opened in Inkscape

vector graphic on left, imported scan on right

Inkscape can autotrace a bitmap but the idea was to improve the original felt marker trace.  Use the bezier tool in spiro path mode to make the trace,  left mouse clicks create nodes and dragging creates the lines/curves.  The fewer the nodes the smoother the curves.  It may take a bit of practice to get a feel for the process.  When satisfied with the result drag the vector trace to the side and save (export) as a dxf file.

The dxf can be imported into CAM software to create the gcode file.  Fusion 360 was used for CAM.  As mentioned earlier the digital camera image can be imported directly into Fusion for tracing,  I am simply more comfortable with the Inkscape tracing features.  The picture below is a test cut done in a piece of scrap.

pictures or it didn't happen

  A sharp eye will notice the reproduction varies a bit from the original.  It was an attempt  at a beefier look in the handle area.