The first thing you'll need to do is purchase the components. The bill of materials can be found on the github page

This metal extruding system is meant to be an upgrade to existing 3D printers, so it is assumed that you already have a 3D printer to modify. On the Github page you will find 3D models for attaching the extruder to various common printers (for prototyping purposes at the moment, only Prusa I2 MK2 is supported, but feel free to submit a pull request for your type of printer), and configuration files for various firmware and slicing settings. Eventually the plan is to clean and package these up and submit pull requests on the respective projects.

The printer I am testing with has 200 step motors for the Z axis, and 400 step for all other axes, so you may need to multiply my steps per rev by 2 if using Marlin. My setup uses Prusa Mendel I2 MK2, Rambo, Marlin, Prusa Slicer and Octoprint, all of which have been around for a while and have excellent documentation, and some have large communities around them where you can potentially find support if something's not working properly. I've been out of the loop for quite a while with Marlin 2.0 updates, but it seems like more recent versions of Marlin are no longer compatible with Arduino IDE, and since I don't have time to figure out all the new features before the end of the Hackaday Prize, I'll be sticking with Marlin 1.8.15 for now. I'll sit down and add Marlin 2 compatibility afterwards.

While you wait for your materials to arrive, you can make sure your printing system has everything it needs to be compatible with the metal extruder.

For low temperature metals, aluminum or steel extruder components will work. Molybdenum and Tungsten tool steels can be used to print silver and its alloys at around 900C. 3D models for the extruder can be found on Github. The long bore that goes through the center is meant to be drill pressed all the way through by hand after CNC machining because I was unsure if the CNC I was using could do it. I can add a model later that has the bore actually going all the way through instead of just with pilot holes. Generally I have found that for mild steels and HSLA steels, a high spindle speed and low pressure with machining oil and titanium nitride drill bits on a hand-controlled drill press does fine, but low speed high torque kills 2mm drill bits if they get even a little stuck. High spindle speeds aren't great for drill bits either, but the nitride coating and the oil mitigate any abrasion or accidental annealing that would otherwise occur. Drilling down from the top is better, because the melt chamber further down can handle a bit less precision. Drilling from the top and bottom to meet in the middle is probably best though.

The two holes on the top of the heat sink off center are meant to be tapped with an M3 tap. The hole on the bottom of the heat sink and the centered holes on the heater blocks are meant to be tapped with an M6 tap.

You will then need to anodize or black oxide coat some of the parts: that process is described in detail in this project log. More detail on the way in the future.

This is all specific to the printer you want to use. In the future, instructions will be included with each calibration file or set of 3D prints. For the time being, refer to the project logs while I get something better sorted out. It should be pretty obvious which screws go where when fitting everything together from the pictures provided, but feel free to reach out with questions in the comments section.

To make the liquid glass gasket material, simply mix about 18 grams borax (hydrated) with 20 grams glycerol and bring to a boil until the bubbles become less frequent. Cooking at 300C for 30 minutes after mixing well seems to do the trick.

Do not add the liquid glass gasket to the extruder until the Xpando has had time to set in all the M6 screw threads: it will mix with the Xpando and prevent it from setting properly. After the Xpando is cured they are fine to use together though.

At present I also use a Bondtech extruder and added a custom heated bed, which might not ultimately be necessary. It makes the prototype system more reliable and versatile for testing, but also more expensive than a final solution would be. They're also a bit ad-hoc so if it becomes clear they are necessary, I'll improve the documentation about them. With all those modifications it seems like it would be difficult to keep the upgrade cost below $500 like I'm targeting, so hopefully at least the Bondtech extruder is overkill, if not both features.

Since I don't think I've mentioned it elsewhere, in case they are needed, bristles can be added to the nozzle aperature with one of those new portable spot welders Tesla uses to build their battery packs. They can be spot welded to the back of the nozzle and then run through the tip of the nozzle and cut to the preferred length. In practice they shouldn't stick out of the nozzle more than a millimeter or so: the thermal gradient outside the nozzle tends to be steep.

There's an immense diversity of printer firmwares and slicing softwares nowadays, and each of them has its own documentation, but for Marlin I like Triffid Hunter's old calibration guide: it'll get you on the right track. There does seem to be a newer and more thorough reference for 3D printer manual calibration here. For Prusa Slicer all you have to do is import the config file on the github page into Prusa Slicer.

There are no suppliers for metal filament for this yet, which is something I'm working on and it should be ready soon, but in the meantime I show how to make small quantities of wire for printing by hand in my second project log. Sn75Zn25 by weight works fine.