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Interactive Fabrication of Functional Mechanical Devices

constructable_01 copy 2

Created by Stefanie Mueller, Pedro Lopes, and Patrick Baudisch at Hasso Plattner Institute – Potsdam, the project introduces a new way of working with fabrication tools such as laser cutters and 3D printers by removing the CAD system from the process. Using a hand-held laser pointer, the constructable – an interactive drafting table, allows users to interact directly with the laser cutter by drafting directly on the workpiece.

The system tracks the pointer using a camera mounted above, beautifies its path, and implements its effect by cutting the workpiece using a fast high-powered laser cutter. Constructable achieves precision through tool-specific constraints, user-defined sketch lines, and by using the laser cutter itself for all visual feedback, rather than using a screen or projection.

A key element of interactive fabrication systems is that they provide output to users not at the end of the process, but after every editing step. This allows users to validate their designs earlier and build sub- sequent work steps on the result of earlier steps. The related work suggests that this offers value to artists and designers, as their creative process is often inspired by seeing the partially completed workpiece.

Each proxy laser features three barrel buttons. While held depressed, the middle button activates the laser beam, allowing the system and the user to see where the tool is pointed. The visual feedback allows users to determine a starting point with precision before starting to cut. Polyline, Circle, and Freehand are constructable’ tools for creating objects from scratch. The circle tool, for example, al- ways produces a perfect circle, but diameter and location remain freehand. The freehand tool is not subject to any constraints. Likewise there are additional tools such as the copy tool, results in the creation of new objects.

When you take out a pen tool (a normal laser pointer) an arduino MEGA microcontroller detects that the pen was taken out. While you draw, an over head camera tracks the red laser pointer dot using a custom color tracker implemented in OpenCV in C++. The path is smoothed using a Kalman Filter and converted into the coordinates of the laser cutter space and then the sketch that you made is vectorized and beautified. The sketch is converted into perfect lines using PaleoSketch (open source library) and generates smoothed shapes. The final sketch is sent to an OpenDraw document (open office APIl) using a custom OSC to OpenDraw java server team implemented. Lastly, the documented is printed using a robot program (java, open source libs) that controls the operating system pointer and clicks on “print” on the laser cutter software.

Constructable is useful for some design prob- lems and less so for others. While constructable extends the range of problems that can be tackled interactively, it is obviously a CAD system. As with traditional some types of projects can be tackled tool- in-hand, while more advanced problems require users to sit down with a piece of paper first. The same applies here, constructable cannot replace CAD but does offer a new way of interacting with fabrication devices.

More information including a paper can be found on the Project Page.

Stefanie Mueller | Pedro Lopes | Patrick Baudisch

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