LinkageFab: Linkage Converter For Fabrication

This tool allows the creation of ready-to-cut linkages from a given linkage configuration. It parses a given linkage, creates a immediate graph representation and generates an output file which can be used for fabricating the linkage.

Input

The main objective when creating this tool was to have a way of fabricating linkage systems designed within solvespace. The linkage can be provided as solvespace document (.slvs file) where all line segments will be treated as rigid links and joints will be created from spatial proximity.

Output

Currently the only supported output format is a svg cutting plan for creating an easy to produce prototype from e.g. wood (using a laser cutter) or cardboard (using a cutting plotter). See Fabrication section for detailed guidance on how to cut and assemble.

How to use

Install dependencies

Install all dependencies necessary to run this tool by calling: ```

pip install -r requirements.txt

(requires python3)

Run

• create svg file for fabrication with:

python3 src/linkage_fab.py sample/saxena.slvs --output linkages.svg

• this creates two files:
  • linkages.svg --> can be sent to laser cutter directly for fabrication, (geometry red should be cut, labels in blue engraved )
  • linkages_assembly_manual.svg --> a rendering of the assembled linkage showing the position for each hub

Fabricate

• The exported svg can be cut using a laser cutter or cutting plotter.
• Different materials can be used, e.g. cardboard or wood. Make sure the picked material is stiff enough for the linkages to stay rigid.
• The blue letters contained within the cutting layout should be engraved or drawn onto the fabricated linkages to simplify assembly.

Assemble

• Depending on the material used, pick a suitable method for connecting the linkages.
• You need to connect the linkages tightly but leave enough freedom to rotate around an axes.
• Suitable conenction systems could be bolts or rivets (for paper/fabric).
• The created assembly manual will help identifying matching linkages.

Example Linkages

• Parallelogram: a simple linkage system forming a parallelogram
• Saxena: a sophisticated linkage system as described in Kempe’s Linkages and the Universality Theorem (by Anupam Saxena)
• Mulitplicator Gadget: a linkage modeling Kempes multiplicator gadget
• Peaucellier Lipkin linkage

Future Work

• implement angle constraints
• find a way for modeling fixed hubs/joints
• svg postprocessing (e.g. remove duplicate paths for hubs)
• extend assembly manual by assembly order
• come up with temporary assembly aid (for holding linkages in place before connecting finally)
• take material thickness into account (important for thicker materials, like wood)