This is a follow-on to http://www.thingiverse.com/thing:904

It is a cylinder with a helical channel. The channel is designed so that the part can be printed without any internal support material. This was printed on a Dimension uPrint with zero internal support material.

The hollow channel can then be filled with low-melting-temperature metal alloy to form an electromagnet.

Due to the low number of turns, the performance of the electromagnet is poor. This is really just a proof-of-principle of the fabrication method, not much of a practical electromagnet.

Malone and Lipson report better results using similar materials with a layer-by-layer approach in the paper "Multi-material Freeform Fabrication of Active Systems" which can be found here: http://creativemachines.cornell.edu/publications

The SpoolHead is another promising approach for making embedded conductors. Info here: http://reprap.org/wiki/SpoolHead

UPDATE June 27 2011 - Also be sure to check out Rhys Jones' new results on the RepRap page here: http://blog.reprap.org/2011/06/new-approach-to-printing-metals.html

After the part is printed, it can be heated in a water bath and filled with molten alloy using a plastic syringe (see pictures). The process is described in more detail over at http://www.thingiverse.com/thing:904

Be careful if you actually try to do anything with low-melt alloy. It is messy, toxic, and hot enough to cause burns. Use it only if you are experienced working in a lab environment.

STLs and Alibre source files are provided.