Printing

Begins with raster graphic (JPEG) of logo. I needed a good challenge, and there was no existing vector graphic of this logo available.

Vectorization of raster is performed automatically in Inkscape (or Adobe Illustrator), resulting in several sets of paths instead of a grid of pixels. Also I have added a frame based on the convex hull of the pink section, along with union with a manually drawn extension for the keyring hole. The set of paths is saved as a vector graphics file (SVG)

The three sets of paths are exported as three DXF path files, one for the letters, one for the pink frame, and one for the overall frame. Functionally, they are 2 dimensional polygons of straight line segments.

Using OpenSCAD, with its own scripting language, an SCAD compilation file is created which pulls in these vectored polygons and extrudes them to configurable depth, resulting in a to-scale viewable model of the key ring. This file can be exported as a closed-form tessellated 3d polygon file (STL).

A slicing engine (Cura in this case) is used to compile the STL model into 3D Printer commands - a text format of instructions (move here, squirt plastic now, then move here), known as a GCODE file. The GCODE file is compiled towards a given set of printer / filament characteristics.

The key ring itself can be arbitrarily scaled up or down from its original engineered size, even from only the finalized STL format.

The GCODE file is uploaded to the Raspberry Pi based print server connected to the Lulzbot Mini 3d Printer. The print server allows for real-time monitoring of the print process from any other device on the network.

A single copy is printed first with first-cut configuration of printer settings / GCODE compiler parameters. From this, changes are made to the SCAD model, both in terms of shape itself as well as overall scale, and to the extrusion parameters in the Slicer. In this case - changes were made to make the pink more apparent, the part more durable, and the key ring hole stronger and larger.

2.5 hours printing time for a set of 12 key chains. Material costs for prints: $0.12 per unit. Key rings are $0.10 each when bought in sets of 100, and easily applied with key ring pliers to any given batch. Like cookies, they pop off the plate still warm to the touch.

Testing of durability by wearing one of the first batches on a key ring. Finishing options are being explored including fine sanding, acetone vapor bathing, and acetone brushing, each of which add a nominal time for overall build process.