How we made a 1300C 3D printer hotend for printing metals on the Creality Ender3
Channel: Rotoforge
Date: 03/03/2024

This is part of an ongoing open source project for printing metals, and ceramics on the home desktop at low cost.
By community demand I have a Kofi if you want to support my work with a donation:
https://ko-fi.com/michaellynn
Also, money is great, but frankly, instead of paying me, I would much prefer if you used it to run some experiment you are interested in.
like any of those "hey you should try this" type thoughts, or anything else in order to build sustainable low cost infrastructure for metal and ceramic 3D printing on the home desktop. 
We will have a community fund in future if we are successful and need  money to support additional development. 

We have a discord channel where others contribute to the project here:
https://discord.gg/Hdz8JkdSHP

We have a github here:
https://github.com/Sindry-Manufacturing/rotoforge
It is in desperate need of update and will be updated soon.

I blog in greater details about the technical aspects of the project here:
https://dailyrotoforge.blogspot.com/2023/12/rotoforge-2023-11-30-cold-working-and.html

A blog post more on the basic physical and engineering details of how and why this ceramic glow plug hotend(and similar techniques) works, will be published soon.

I have published additional details on the ceramic glowplugs, including thermal and electrical characteristics, and 3D models on my printables page:
https://www.printables.com/model/635347-beru-glow-plug-cgp-002

i have also provided a set of models and details about the EDM drill rig we used on printables:
https://www.printables.com/model/628848-alie-express-edm-drill-spindle

Our workholding is also on printables:
https://www.printables.com/model/791527-edm-drill-workholding-for-ceramic-glowplug-hotends

While it is possible to preprocess glowplugs with a rotary tool it is difficult to get good results. we opted to use the Proxxon FD150E mini lathe for our machining operations.
https://www.proxxon.com/us/micromot/34150.php

We use the dremel 4300 to cut off the  top electrodes. 
https://www.dremel.com/us/en/p/4300-5-40-f0134300ad

We use Mcmaster EDM oil for drilling the glow plugs, because they cannot be drilled in water.
https://www.mcmaster.com/products/edm-oil/

Our EDM spindle and pump combination are based on the ones seen in Ben Krasnow's video on applied science:
https://www.youtube.com/watch?v=rpHYBz7ToII&t=368s

We used the open source, rack robotics powercore V1 for our EDM pulse generator:
https://rackrobo.io/

G-EDM might have been a good choice for this as well:
https://github.com/G-EDM/G-EDM

the direct drive belt extruder we use for printing:
https://kevinakasam.com/papilio/

We used ruby fluid zinc chlorid flux on the glowplug contacts:
https://superiorflux.com/products/industrial-soldering-flux/rubyfluid-flux/

What is this video about:
We want to print metals and ceramics on the home desktop at affordable cost for a student.  So we decided to build our own hotend purpose built for the task. this video is about what we did, a tiny bit about why we did it, but mostly about how we did it. 

Why would you need to do this?:
 Conventional hotends have a large hotblock, and a large nozzle thermal mass which limits how quickly they can respond to changes in temperature. More importantly, their relatively large surface area means a large amount of heat from the typical cartridge heater is lost to convection. 
This is fine for printing plastics, but a nonstarter when printing metals.

Metals have high melting points compared to plastics. Metals also typically have narrow ranges of temperature in which they are thixotropic and thus printable, and are highly thermally conductive, which means that steep thermal gradients exist between the heated material and the buildplate and other elements of the hotend and printer.  One way to resolve this issue is to use a relatively power dense(1-10 watts/square millimeter) source of heat positioned directly at the deposition region where material is being deposited(IE ceramic glowplug tip). In this way we can ensure that no steep thermal gradient is formed in a nozzle where  a jam or clog can occur. further positioning the heater at the nozzle tip ensures sufficient power is always available to maintain constant thixotropic viscosity conditions at the deposition region. The glowplug heater has a volume of about ~14 cubic millimeters, which enables rapidly adjusting the amount of power available in response to flow rate changes which is critical for printing materials, like metals, with narrow deposition windows. 

The deposition window we refer to is the temperature region in many alloys, where they are "semisolid", that is, between the solidus and liquidus, where one alloy phase is suspended in the melt of another metallic phase. Such as solid copper suspended in molten tin, as in 510 phosphor bronze between 949 and 1043 C.  Many brazers/solderers/welders may be familiar with this "pasty" behavior of many materials.