FabLab Synchrotron Project

This project is about building a model of a particle acclerator, specifically the Diamond Radiation Light Source. The model will hopefully use a ball-bearing to represent the photons in the ring, with holding solenoids used to draw it around. LED strips will be used to represent the beam-lines, and both the accelerator and storage rings will be represented.

The purpose of the model is demonstrate to the public the operation of synchrotron radiation light-sources as they relate to some of the work carried out by the Manchester Organic Geochemistry Group.

Current status: building/planning

Designing the base in LibreCAD

Constructing a base from the design in OpenSCAD

Rendering the base in Blender

Setting up tool paths on ShopBot's software

Preview of the base on ShopBot's software

ShopBot cutting the base

ShopBot cutting the base

The finished base

Files

The following files were produced as part of this project:

  1. synchrotron.dxf - the 2D design of the model base, constructed in LibreCAD
  2. synchrotron.scad - an OpenSCAD script performing extrusion of the 2D design into the 3D model
  3. synchrotron.stl - this is the 3D output of the OpenSCAD script
  4. synchrotron.blend - this is a Blender scene containing the extruded 3D model with some textures and a light and camera for rendering
  5. synchrotron.crv - this is the model after importing into the ShopBot PartWorks software. It's basically the DXF file after some scaling and with the addition of tabs and toolpaths
  6. pocket_and_cutout_1-2_dwn_18k.sbp - this is the ShopBot router code that we actually ran to cut the model from 25mm thick MDF (about 1.2m by 1.2m)

All files in this project are also available from GitHub.

Software

The following software was used in this project:

  1. LibreCAD - for 2D design work
  2. OpenSCAD - for 2D to 3D extrusion
  3. Inkscape - for post-processing 2D design
  4. Blender - for 3D rendering
  5. Ubuntu Linux - everything was run under Ubuntu Linux (specifically 12.04 LTS)

Video

Here's some video of FabLab Manchester's ShopBot CNC router cutting the base of the synchrotron model:

Observations

Originally, I started the design for this project in Blender, intending to produce the 3D model then use slicing or projection to produce the 2D files required for the CNC router. However, after doing so it became quickly apparent that this is entirely the wrong way to go about things:

  1. Blender isn't a CAD package. While it is quite brilliant for producing artistic 3D models (easily out-stripping simpler tools like SketchUp), if you wish to produce something which is largely based on simple geometric shapes it is overly complex.
  2. When going from 3D to 2D you have all sorts of annoying things like normal directions to worry about (otherwise your STL files won't work as expected). If you go 2D to 3D all such problems disappear (yes, there are other problems to solve but they're a lot simpler!)
  3. The DXF standard is either poorly specified or poorly adhered to by several applications; loading the DXF file from LibreCAD into the ShopBot software produced several errors, but was ultimately successful (specifically it complained several times about a missing .drw file, but skipping the errors was successful)
  4. It is preferable to have completely joined the segments of each contour prior to loading the file into ShopBot's software (PartWorks); the latter is capable of doing this automatically but the algorithm is naturally fairly crude and thus there is some minor danger of getting it wrong. That said, I'm not yet sure the proper procedure for doing this in LibreCAD (although it's trivial in Inkscape - simply use the "Join selected nodes" tool)

Design

Here is a reasonable method (some parts of this method are currently untested -I'll revise accordingly after my next ShopBot encounter!):

  1. Create the layers of your design in a CAD package like LibreCAD, saving the results in its native DXF format
  2. Load the resulting DXF file into Inkscape. With a little luck (and a recent version!) it should import the layers of your DXF as layers in the resulting SVG file (you may need to change the page size to encompass the drawing)
  3. Select all the lines and arcs that you wish to combine into a single path and use the Path / Combine menu option to make a single path out of them, then under the Node editing tool, use the Join selected nodes icon to combine segments into one
  4. Save the results as SVG in case further editing is required, and create a PDF export for importing into ShopBot's PartWorks software
  5. If you only require the 2D design for CNC purposes, stop here
  6. If you would like to see a 3D model to check your design, use an OpenSCAD script to extrude the 2D design into 3D (using CSG operations to cut things out as necessary)
  7. Import the resulting STL model into Blender for texturing and rendering
  8. Should you require additional vector overlays, import the DXF into Inkscape for post-processing

Construction

The base of the synchrotron model was cut from 25mm MDF with a 1/2" bit at 18krpm on ShopBot using the files available above. The process (after software setup) took approximately 25 minutes with a few minutes afterward for popping the bits out and filing down the tabs.

The next phase is to get the solenoid and ball-bearing setup working. After spending some of the weekend playing with a variety of solenoids and some 10mm steel ball bearings I've concluded that the 12V solenoids aren't sufficiently powerful to draw the bearing around. The large 55lb 24V solenoid that I purchased probably will be but I could only find an 18V power supply to test it with. The proper 24V power supply for it should arrive sometime this week and I can resume testing!

Electonics

Under construction!

Acknowledgements

We are extremely grateful to the helpful community at FabLab Manchester for their help so far. Hopefully with a bit more, we can build something pretty impressive!