Thursday, October 24, 2013

Tutorial: Laser Cutting Techniques and Projects

Tutorial: Laser Cutting Techniques and Projects

As a long time designer and maker, watching a computer-controlled laser cut out my project was a transformative experience. Until that moment, many of my designs had been trapped inside the computer. The only output available was a mere paper printout to guide my traditional woodworking tools. Since that fateful day, I’ve spent a lot of time dreaming of and designing projects to exploit the strengths of the machine and systems to make it all go smoothly.
Here are three projects, each of which demonstrates techniques and systems I’ve developed specifically for this form of digital fabrication.
Designing for Laser Cutters’ Strengths – Project 1: Map Puzzles
Like all tools, laser cutters have strengths and limitations. Understanding and designing for them will allow you to exploit the former and minimize the latter. At the same time, I believe clever design can turn a tool’s limitations into opportunities. For me, daydreaming about how to use the machine to easily cut things that are difficult or impossible to cut using other methods gave birth to a whole line of products, my Map Puzzles. Here are some primary strengths and limitations as I see them and what they mean for your projects.
Africa USA
Laser cutters have a lot going for them. Their incredible engineering allows them to cut and etch with an accuracy measured in thousandths of an inch. With some careful measuring, this allows for the production of very accurate parts and perfect fits. They can cut out the same shape all day long and do so with incredible repeatability. Besides accuracy, their ability to cut complex shapes easily is something else they’re known for. This was a primary source of inspiration for my Map Puzzles. How else could you accurately and quickly cut out such complex shapes? In addition to geographic lines, other complex shapes like gears also worked their way into my projects. This free, online Gear Generator became very useful for generating all kinds of different gears.
Safety is another huge benefit of laser cutting that doesn’t get much mention. While it’s possible to start a fire or otherwise hurt yourself while operating the machine, it’s almost certainly safer to use than traditional woodworking tools. Nearly every time I’m finished using my table saw I find myself being thankful that my fingers still remain on my hands.
Unlike other digital fabrication methods like 3D printing, laser cutting is generally much faster. Not only does the machine cut fairly rapidly, many of the other tasks typically required in traditional woodworking are spared. For instance, work like clamping your material down, making sure the table saw’s blade is square and cleaning up the saw dust afterward is eliminated
But like all tools, laser cutters have significant limitations. For at least the majority of consumer-level machines they only cut perpendicularly through sheet material. While this still allows for an enormous array of options, certain things, like corner dovetail connections are impossible (at least as far as I know!). While this limitation exists, there are many clever ideas out there to push the limits. Living hinges allow rigid materials like wood to bend. Laser Origami uses out-of-focus lasers to heat and bend acrylic all within the machine.
The range of suitable materials and thickness appropriate for laser cutting are other limitations. Most consumer level machines can cut through a host of natural and synthetic materials (wood, paper, cardboard, rubber, leather, acrylic etc) but not metal, ceramics, stone, glass and certain plastics. Furthermore, most consumer machines can cut through at most about ½” material which makes things like furniture somewhat difficult.
Iterative Design Made Easy with 3D Modeling - Project 2: Smoking Pipes
As a maker, something profound I learned as a student in architecture was to approach design and prototyping as an iterative process. Just like in evolution, changes are made and tested and slowly the design transforms and improves. This method meshes particularly nicely with digital fabrication since it’s relatively easy to produce an updated design and evaluate the changes made to it. I give myself room for my first iteration to fail because although it may not work the way I’d like, there are almost certainly a number of things about it that do work. Usually by the third or fourth iteration the design becomes quite solid and the light at the end of the tunnel grows brighter.
PipeFamily SnapEnlarged
One of my first projects for the laser cutter was a smoking pipe. An iterative process worked beautifully since each time I finished assembling a pipe, new ideas and changes came to mind. Eventually, this process resulted in a whole family of related pipes, each of which had gone through dozens of iterations.
To facilitate this iterative process, I’ve developed a system of 3D modeling and easy 2D exporting of the cut files. While there are many software programs out there to do this, I find SketchUp Pro to be quite adequate for most of my needs when working on primarily orthogonal projects. My system requires only a basic knowledge of SketchUp. The Pro version is useful because it allows you to export DWG, EPS and other vector formats, but there are free SVG exporter plugins that allow you to do the same without paying for the Pro version.
Here’s how it works. Roughly model the major pieces of your project and make each piece a component. Navigate to a nice 3D view of your project and make a new scene of that 3D view. I call this scene my perspective scene. Next, drag a copy of your entire project to one side and rotate each piece until it’s flat. Switch to the parallel projections view and make a new scene looking straight down at your newly flattened parts. I call this scene cut. If you’re like me, I prefer to model primarily in perspective. Now, when you make changes to the model in the perspective view those changes are automatically updated in the cut view. We’ve essentially tricked SketchUp to behave like BIM, Building Information Modeling, which is transforming architecture since it allows plans, elevations and sections to generate automatically from the 3D building. Likewise, when changes are made to the 3D model, those changes are automatically updated in the 2D cut view. When you’re finished designing and ready to export your cut scene, you can arrange your flattened pieces to efficiently use your material. Export your cut view and you’re ready to cut.
Edge Quality & Kerf – Project 3: Containers
Making boxes and other containers is as old as time, but with laser cutting it can be done anew. For instance, I’ve made finger jointed boxes where the fingers are 1/16″ thick. How else could that be done besides on a laser cutter? Not only can this provide for a very strong joint, it also creates a visual element that is quite striking.
Toolbox3 DSC08741 copy
Another reality of laser cutting that I attempt to integrate is that wood’s cut edges become darkened. I think of this as a two-toned color scheme and attempt to integrate it into my work to create a pleasing aesthetic appeal. This is especially noticeable when using light colored woods like Baltic birch plywood. Experimenting with the power, speed and frequency settings can make the edges either lighter or darker.
In traditional woodworking the blade’s kerf is fixed and something you have to keep in mind. In laser cutting, the kerf is variable since it depends on your power and speed settings. For thin materials and for many projects it can be neglected, but not always. How important the kerf may be to your project depends largely on what material and thickness you’re cutting from and how much accuracy or how tight of a fit your project requires. For good fits on inlays, for instance, you may find that you’ll need to enlarge the inlay piece by a few percent for a perfect fit.
Other free, web-based resources for those interested in making boxes are Box Maker and MakerCase. Enter the dimensions and select the type of joint you’d like and the software will create the cut files for you. They even allow you to enter a kerf thickness too.
With the plethora of web-based laser cutting services, anyone with a passion for Making can turn their digital designs into cut reality. Now go out there and get cutting!