Fabricate EDM

Since this is the only documented Post-Event activity, it has been moved to the general workshops area over here.

Among the labs toured during bootcamp Post-Event was Bitraf. There we met Jakob Rockenberger who is the author if the Fabricate EDM project. He was kind enough to brush the dust off it and explain how it works.

A first generation plywood Ultimaker 3-Axis system is at the core of it. A workpiece holder inside watertight container is mounted on the build plate. 3D printer extruder is replaced with custom-made TIG welding electrode holder. The electrode is driven using Rack-Robotics Powercore power supply, specifically designed for EDM machines. Jakob got the V1 via Kickstarter campaign.

Demineralized water from local Biltema hardware store is filled in the tank. It is also called deionized or distilled water, but the core property is that it is not conductive and is not causing electrolysis.

There were some gcode files left on the SD card of the printer and the latest one was used to figure out the essentials. Among the most important properties is the wear ratio, which was defined as 0.03. It is an amount in millimeters of z axis travel per one millimeter of xy axis travel. As with most NC machines, feedrate is of importance. The plunge rate defined was 20 mm/s and the cut rate 40 mm/s. A cut start parameter could be seen and it was -4 mm. In final G-Code the values are a bit different, and some more testing should be done to find the perfect values.

; Rapid Z:       7
; Start Z:       0
; Cut Start Z:   -4
; Plunge rate:   20 mm/min
; Cut rate:      40 mm/min
; Travel Speed:  1000 mm/min
; Tool Diameter: 1.5
; Wear Ratio:    0.03

It was unclear what CAM software was used to create toolpaths, but it was decided to stay at a low level. SolveSpace was used to create the initial drawing, and exported as G-Code. Python script would take that as input and add z axis values according to the wear ratio. The resulting G-Code of the last attempt. It was decided to make something that is not completely trivial. How about something 3D? How about a tetrahedron?

Here, construction lines were used to sketch the unfolded hedron in final size. Then, real lines were used to sketch the toolpath around it. This is a very early approach of defining toolpaths in the early APT programming language. A program definition is split in two parts: geometry definition and motion commands. Here, in SolveSpace, same approach was done in a visual way.

The final shape is the toolpath that can be exported as SolveSpace G-Code. The exported G-Code is generic and not ment for use with any specific machine. Each point in the drawing is translated to a G01 command with X and Y parameters. A Python script was used to take the SolveSpace G-Code file as input and generate Fabricate EDM G-Code output.

.add_wear_z.py input.txt output.gcode

The code can be found in Kris's Fabricate EDM Git repository.

Here, some more fun photos and videos. Jakob left some 0.2 mm aluminium sheets to play around with. It would have been nice to have more time to refine the process and play around with titanium or stainless steel. Next time.

To conclude, I never thought EDM machining can be this easy. With EDM I always thought it must be wire EDM. I like this Rack-Robotics aproach better as most of the parts and liquids needed can be sourced from a local hardware store. The power supply is the only part that is a bit cmplicated and it would be definitely an adventure to try to fabricate one.

Team Kris Nerdying