LaserOrigami: laser-cutting 3D objects
Rapid prototyping with a laser cutter
Rapid prototyping, the fast-moving production of models or parts, is quickly expanding in manufacturing and other sectors. Researchers from the Hasso Plattner Institute, in Potsdam, Germany, have developed an innovative technique that does not use additive or subtractive processes, but a laser cutter to cut and bend material. They describe this procedure, which they have dubbed LaserOrigami, and outline its potential, benefits and limitations
Rapid prototyping and fast iteration
As its name indicates, a key requirement of rapid prototyping is speed: faster iteration allows for additional versions and thus for a better design within a given time frame.
Unlike software interfaces that may only need recompilation, physical objects require actual production—generally a much more time-consuming step. Generally, 3D printers, laser cutters and milling machines are used for the rapid prototyping of different design versions.
LaserOrigami is a single integrated rapid prototyping system that produces 3D objects by cutting and bending a single flat piece of acrylic material using a laser cutter. LaserOrigami is substantially faster than traditional rapid prototyping techniques, such as 3D printing and traditional laser cutting, as the resulting 3D objects do not require manual assembly.
Respective benefits and downsides
Using additive processes 3D printers offer maximum freedom in terms of the shapes they can produce, but they are slow as they assemble objects in layers from individual voxels (volumetric pixels).
Laser cutters achieve much higher speeds by generating objects from 2D plates rather than individual voxels. However, joints are generally needed to achieve three-dimensionality with the resulting pieces requiring assembly. This introduces repetitive manual labour or mechanical steps into production processes, also limiting how fast designers can iterate their project.
LaserOrigami is a novel rapid prototyping process that uses a laser to cut and shape 3D structures by bending the work piece rather than by using joints, thereby eliminating the need for assembly.
Bending with a defocused laser
The key idea behind LaserOrigami is that it achieves three-dimensionality by folding/bending material rather than by using joints. It does this by heating up selected areas until they soften and bend under the force of gravity.
The cutting laser is normally focused on the work piece causing the material to heat up so much that it evaporates. In contrast, LaserOrigami bends material by distributing the heat over a larger surface by moving the work piece away from the laser, thus defocusing it.
In addition, LaserOrigami distributes the laser’s heat further by running the laser repeatedly back and forth over the area to be bent. As a result, the work piece heats up only to the point where it turns pliable; it then bends under the influence of gravity. The result is a precise 90° corner. The part can be bent beyond 90° by using a servomotor that allows repeated rotation.
LaserOrigami modifies the laser's focus by moving up and down the cutting table under computer control. This allows cutting and bending to be executed in a single integrated process. When the user takes the work piece out of the equipment, it is already fully assembled. (See video of LaserOrigami process here).
LaserOrigami’s CAD user interface
LaserOrigami offers a traditional CAD-style interface, which was 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 to produce the respective shape, i.e. the lines that cut and the lines that drive the back-and-forth motion of the defocused laser. The back-and-forth motions of the defocused laser are encoded as pairs of lines of opposite orientation.
Switching between cutting and bending, that is moving the table up or down, is encoded in the line colours. In our cutter configuration we programmed red lines to mean cutting: whenever the laser encounters a red line the table will move to bring the laser into focus. In contrast, we configured green lines to move the table down, causing the laser to go into defocused mode, so heating up the material for bending.
The feature we manipulate here is called z-axis by our laser cutter. It is normally used to bring materials of different thicknesses into focus; with LaserOrigami it is used instead to defocus.
To make sure all features are executed in the proper sequence, the stacking order of all lines is set up within Visio; bottom lines are executed first, so that the cutting order can be arranged using "send forwards/backwards" commands when creating the master shapes. Since the laser cutter model used always executes all lines of one colour before moving on to the next colour, a new colour is used for each group of cuts or bends.
Finally, all lines of a master shape that encode laser cutter instructions are masked by moving them on a hidden layer in the drawing. This allows the user to work with only the information necessary, i.e., to determine where cuts and bends will be executed by the laser but not how, thereby preventing a cluttered interface.
LaserOrigami creates all designs from 3 basic actions: bending, suspending and stretching.
Bending only allows bends of up to 90°, limiting designs to "2,5D". However, using a servomotor to rotate the work piece repeatedly allows it to be bent beyond the vertical axis. Suspending an area of material in a controlled way is made possible by creating hangers that are designed to unfold when heated up with the laser. The depth of the suspended area is defined by the length of the hangers.
Creating a hanger requires making a hole in the work piece. This is one of the limitations of this approach, although it does offer the opportunity to steer the hangers into place. This allows them to be positioned so as to minimize interference with the rest of the work piece.
Stretching is used to create other objects, such as a paint holder. This requires the use of closed containers to hold the liquid paint. To achieve this, the outline of an area is heated until it becomes loose and stretches under the weight of the suspended patch. If the latter is too light, weights can be added to it before suspending. Stretching causes the inside surfaces of the suspended area to get thinner, limiting the maximum suspension depth, although this is also dependent on the material’s thickness and on the width of the stretched area.
Benefits and limitations
LaserOrigami is a truly rapid prototyping system that allows users to create 3D objects in a single fast and integrated process. As it uses a laser cutter to bend rather than joining, no additional manual or mechanical handling is required. In addition, it produces parts that are sturdier because they are made of a single piece and have no joints.
However, LaserOrigami currently presents certain limitations. They include:
- the length of material that can be bent: a certain minimum temperature must be retained over the entire length to allow the piece to bend
- the thickness of the material: the thicker the material, the longer it takes to bend
- Use of materials that have thermoforming properties, such as acrylic; others are not suitable.
As a new rapid-prototyping technique LaserOrigami presents many advantages and is set to prove useful in many industrial and other domains, such as architecture. A number of manufacturers in the plastic parts sector have expressed interest in this process.
International Standards for the safe use of equipment (including systems) incorporating lasers, such as the Universal Laser Systems PLS6.150D used for LaserOrigami, are prepared by IEC TC (Technical Committee) 76: Optical radiation safety and laser equipment.
- Focusing and defocusing a laser beam to cut or bend materials with thermoforming properties
- LaserOrigami is faster than 3D printing (left) and requires less handling than laser cutting and assembling (right)
- IEC TC 76 Standards for the safety of laser equipment include recommendations for proper labelling
Improving safety for users
The operation of laser equipment presents risks for users, in particular eye and skin injuries, as laser light can result in permanent and serious eye injuries. As lasers find their way in a growing number of industrial and even consumer applications, safety is of paramount importance.
IEC TC 76: Optical radiation safety and laser equipment, is recognized as the leading body on laser standardization in this technical area. It prepares Standards applying limits to human exposure to optical radiation (100 nm to 1 mm) from artificial sources.
As the different types of laser sources and applications require a need for basic and product safety standards IEC TC 76 developed the IEC 60825 series of Standards for the Safety of laser products. Part 1 of the series covers Equipment classification and requirements, such as engineering specifications, labelling, the classification of laser products and additional requirements for specific laser products.