Stefanie Mueller, Bastian Kruck, Patrick Baudisch
Personal fabrication tools, such as 3D printers, milling machines, and laser cutters, allow users to create one-off physical objects. In the field of human-computer interaction, these tools are mainly used to prototype casings, mounts, and other parts for interactive prototypes. A key requirement of rapid prototyping is speed, as faster iteration allows for additional versions and thus for a better design within a given time frame . Unlike software interfaces, which may need only to be recompiled, physical objects require actual production—a generally much more time-consuming step.
Additive fabrication methods, such as 3D printers, offer the most freedom in the shapes they can produce, but as they assemble objects from individual voxels, the time required grows cubed according to the size of the workpiece—thus, they are slow. Laser cutters achieve much higher speeds by assembling the object from 2D plates rather than individual voxels. However, laser cutters generally achieve three-dimensionality through the use of joints. These require assembly, which introduces repetitive manual labor into fabrication. This also limits how fast designers can iterate.
With our system LaserOrigami, we demonstrate how to overcome this limitation. LaserOrigami allows users to laser cut 3D structures by bending the workpiece rather than by means of joints, thereby eliminating the need for manual assembly. Inspired by a technique used to shape steel , LaserOrigami allows users to create 3D objects in a single, fast, and integrated process. Figure 1 shows an example object created using LaserOrigami—a mobile phone screen-cam holder that allows tracking a user's finger for usability studies. This example was fabricated using five "bends," one of the three basic elements of LaserOrigami.
The key idea behind LaserOrigami is that it achieves three-dimensionality by bending the workpiece. LaserOrigami accomplishes this by heating selected regions of the workpiece until they turn compliant and bend under the forces of gravity.
As shown in Figure 2, the cutting laser is normally focused on the workpiece, which causes the material to turn so hot that it evaporates. In contrast, LaserOrigami bends the workpiece by distributing the heat over a larger surface. By moving the workpiece away from the laser, it defocuses the laser; this distributes the laser's heat over a larger region. In addition, LaserOrigami further distributes the laser's heat by repeatedly running the laser back and forth over the region to be bent. As a result, the workpiece heats up only to the point where it turns compliant; it then bends under the influence of gravity. The result is a precise 90-degree bend.
LaserOrigami modifies focus by moving the cutting table up and down. The cutter we used (model PLS6.150D) allows this to happen via computer control; cutting and bending can occur in a single, integrated process. When users take the workpiece out of the cutter, it is already fully assembled.
LaserOrigami offers two types of interfaces. The first one is a traditional CAD-style interface, which we created as a master shape library for Microsoft Visio. The shapes in the LaserOrigami master shape library encode all the instructions that the laser cutter requires in order to fabricate the respective shape—the lines that cut and the lines that implement the back-and-forth motion of the defocused laser. As shown in Figure 3, we encode the back-and-forth motion of the defocused laser as pairs of lines of opposite orientation.
Switching between cutting and bending (moving the table up and down) is encoded in the line colors. As an example, Figure 3 shows the lines that implement a simple bend. In the configuration dialogue of our cutter, we configured red lines to mean cutting: Whenever the laser encounters a red line, the table will move the laser into focus. In contrast, we configured green lines so as to move the table down, causing the laser to go into defocused mode and heating up the material for bending. The property we manipulate here is called z-axis for our PLS6.150D laser cutter. It is normally used to move materials of different thicknesses into focus; with LaserOrigami we instead use it to defocus.
To make sure all features are executed in proper order, we arrange the stacking order of all lines within Visio; bottom lines are executed first, so we can arrange cutting order using "send forward/backward" commands when creating the master shapes. Also, since this cutter model always executes all lines of one color before moving on to the next color, we use a new line color for each group of cuts or bends.
In addition to the CAD-style interaction, LaserOrigami is fast enough to allow for interactive fabrication of 3D objects . In interactive fabrication, users work directly on the workpiece and see immediate physical change of the workpiece after every editing step. We integrated LaserOrigami into our interactive fabrication platform constructable , which is also based on a laser cutter. In constructable, users use laser pointers to draw directly on the workpiece through the safety-glass enclosure of the laser cutter. Constructable then tracks the path using an overhead camera, beautifies the sketch, and immediately cuts the workpiece with the laser (Figure 4).
Constructable implements functionality as laser tools, such as the polyline tool for drawing straight lines. Extending the constructable tool set with the LaserOrigami design elements thus meant turning each of the shape library elements into a separate laser tool, such as the bend, suspend, and stretch tools. Figure 4 illustrates how to bend interactively by drawing a stroke across a part of the workpiece using the bend tool.
The main contribution of LaserOrigami is the concept of the rapid prototyping of 3D objects using a laser cutter, so as not to require manual assembly. Our approach is substantially faster than traditional 3D-fabrication techniques such as 3D printing, and unlike traditional laser cutting, the resulting 3D objects require no manual assembly.
The bending concept behind LaserOrigami offers the following four advantages:
- Faster than 3D printing, eliminates need for assembly from laser cutting
- Sturdier result than finger joints, because bending allows fabricating objects in one piece
- Easier calibration: Traditional finger joints require a very precise calibration to achieve the desired tight fit; bending does not.
- Cheaper than 3D printing.
On the other hand, LaserOrigami is also subject to four limitations:
- LaserOrigami is limited to object shapes that can be constructed by cutting, folding, and stretching the material.
- Works only with materials that become compliant when heated up
- Limited length of what can be bent or suspended in one piece. If a bend is too long, it cools down faster than the laser can heat it up.
- Limited material thickness, again limited by the power of the laser.
LaserOrigami assembles all designs from the three basic design elements: the bend, the suspender, and the stretch, which we will discuss in the following sections.
The bend element allows bending only up to 90 degrees, which limits our designs to 2.5D. We can bend past the vertical axis using a servomotor, which also allows rotating the workpiece repeatedly, for instance, to make the card holder shown in Figure 6.
Suspenders. Suspenders allow suspending a patch of material in a controlled way. Suspenders are designed to unfold when heated with the laser, as shown in the opening image on page 36. The length of the suspenders defines how deeply the patch will be suspended.
Stretching. Suspenders are our general mechanism for suspending a patch of material. However, in some cases, the material for the suspenders is required, such as for the paint holder shown in Figure 7. In this case, we can suspend by stretching.
LaserOrigami eliminates the need for manual assembly since it produces 3D-folded objects in a single integrated process.
Stretching causes the walls of the suspended patch to get thinner, which limits the maximum suspension depth. How deep a patch can be suspended by stretching depends on the material thickness as well as the width of the stretched region.
Here, we presented LaserOrigami, a rapid prototyping system that produces physical 3D objects using a laser cutter by bending rather than joining. Based on this mechanism, LaserOrigami eliminates the need for manual assembly since it produces 3D-folded objects in a single integrated process.
Using LaserOrigami's approach, users can iterate faster and thus achieve a better design in a given time span. This is especially important for users who prototype a design under many external constraints, such as changing customer needs or tight deadlines.
As future work, we plan to eliminate the need for pre-programming laser-cutter behavior by instead programmatically monitoring the workpiece with a webcam or heatcam. For more detailed information on LaserOrigami, please see our CHI 2013 full paper .
We thank Mike Sinclair for his wisdom on laser-cutting techniques, Mark Gross for his feedback, and Raf Ramakers for guiding us on the shape library.
Stefanie Mueller is a Ph.D. student working with Patrick Baudisch in the Human Computer Interaction Lab at Hasso Plattner Institute. In her research she develops interfaces for personal fabrication that allow the user to work directly on the workpiece rather than through a digital editor. email@example.com
Bastian Kruck is an undergraduate student in IT-systems engineering at the Hasso Plattner Institute who enjoys working on personal fabrication projects in the Human Computer Interaction Lab. firstname.lastname@example.org
Patrick Baudisch is a professor in computer science at Hasso Plattner Institute at Potsdam University and chair of the Human Computer Interaction Lab. His research focuses on natural user interfaces and interactive devices, including miniature mobile devices, touch input, interactive floors and rooms, and most recently, interactive fabrication. email@example.com
Figure 1. LaserOrigami fabricates 3D structures by bending, rather than using joints, thereby eliminating the need for manual assembly. Here it fabricates a mobile phone screen-cam holder by cutting the contour lines and heating up the bend paths until the material becomes compliant and bends down under the influence of gravity. When the user retrieves the object, it is already assembled and ready to be deployed.
Figure 4. We integrated LaserOrigami into the interactive fabrication platform constructable : Users interact by drafting directly on the workpiece with handheld lasers. Here the user draws a bend path using the bend laser. The system responds by bending the selected piece using the defocused laser.
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