Microwave furnace

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This is a page to document my proposal to build a massive microwave furnace at Noisebridge. I have already acquired all of the parts and supplies, but assembling everything, testing, safety checks, and coordinating on training new users will be quite a process. Please message me on Discord if you're interested in getting involved! You can also check out my website project page covering this effort. MAINTAINER: Lucy (Discord: @autopoieesis)

Why would we want this

You can make highly detailed metal parts with complex geometries!

The process goes something like

• Print the part in wax castable resin on an mSLA printer.
• Make a mold with petrobond and a casting box, add a hole, and melt out the wax
• Load you metal(s) of choice into a silicone carbide crucible, wrap them in some insulation, and load them into the microwave to blast
• Carefully unload the crucible and pour your molten metal into the mold

What's involved in building a 10kW microwave furnace

At a high level, you need to put together a magnetron, a (10kW 2kV) AC->DC PSU, a high power chiller for the cooling loop, and an assortment of tubing and fittings. We will need to build an enclosure which incorporates the waveguide/heating chamber, work area to unload the crucible, and various control and safety systems. The 2kV out of the sputtering PSU will need to be stepped up to the 9kV 1.6A required by the magnetron head, which we will do with a beefy full bridge LLC step up converter (WIP). Making sure everything is safe to operate in a community space is going to be quite a bit of work. We are gonna need to sort out HV isolation, interlock systems, overtemp protections, ground fault and rf leakage detection, etc

LLC Step Up Converter

The LLC converter is necessary to step the output from the AC/DC PSU up to 9kV 1.6A we need to drive the magnetron head.

• LLC component selection math
• References and component datasheets
• Approximation and design reference

Interlock System

The interlock system is responsible for shutting down the system in the event any failure conditions are detected. The failure conditions we are worried about are:

• Grounding errors
• RF leakage
• Overheating (driver components, heating chamber, or cooling loop)
• Excessive power draw

TO DO

• LLC step up construction (values selected, components acquired, harmonic approximations and spice sims seem good)
• Fill out more HV relay sample requests for the interlock
• Figure out the most reliable possible way to detect grounding errors and RF leakage