The old saying, “garbage in, garbage out” may need to be re-evaluated. Students at Victoria University of Wellington are developing a machine that recycles old milk jugs, extruding an HDPE plastic filament that can then be fed into a MakerBot for 3D printing.

The process involves grinding the plastic into small pieces, then pressing these through a heater and extruder plate to produce a continuous bead of the proper diameter for the MakerBot. Nichrome wire — the stuff of hair dryers and toasters — forms the heating element, and this must be regulated within a specific temperature range for different plastics. The initial grinder design is hand-cranked, but they are working toward a fully automated system. It appears that the machine could also recycle old MakerBot output, provided the grinder has sufficient torque.

[MkMan's] LEGO spider robot combines pieces from a Mindstorm kit with a few milled plastic parts. The legs are a locomotive concept called a Klann Linkage. They operate in pairs and convert the rotational force from one motor into movement for two legs. Here, a total of four rotating gears moves eight legs, besting the hexapods we saw a couple of weeks ago in both leg count and motor economy.

Each limb is made up of five pieces plus one base for each pair. That makes eleven pieces per pair and a total of 44 for the entire robot. [MkMan] milled these parts out of 3/8″ HDPE stock. He’s made videos of forward motion and turning which we’ve embedded after the break. Even on a polished surface the bot looks fairly efficient at getting around.

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The RepRap project has been working on bringing 3D printing to the masses by creating a extrusion printer that can also make the majority of its own parts. For the most part, these print ABS or HDPE plastics which are strong and recyclable. In order to create these replicating printers, similar machines called RepStraps are built out of either laser-cut parts or machined elements. They are functionally equivalent to RepRap printers, but are not made of printed parts. [nophead] documented his RepStrap, HydraRaptor, that is based off a milling machine. He had already printed a set of RepRap parts, and he documented printing a second set. The machine worked for about 100 hours over the course of 2 weeks, printing about 1.5 kg of parts. He made a few adjustments, such as replacing ABS bearings with HDPE to reduce friction. The parts are for Factor e Farm so they can get started with 3D printing.

Related: RepRap pinch wheel extruder