Intro: Creating Illuminated 3D Objects With a Laser Cutter
Although I used these techniques to create art, the real beauty of this is that you can create any 3D object you want with a laser cutter, whether it's the object itself, or a negative of the object encased in a block, as I did. In essence, you're turning your laser cutter into a 3D printer with a resolution limited only by the thickness of your material.
Have you ever seen acrylic that’s been edge-lit using LEDs or similar? The light normally just passes through, but wherever there’s a scratch you’ll find that the light refracts and it appears quite brightly. People engrave messages and patterns onto plastic sheeting to make it really stand out when lit. Well, what if you did the same thing, but instead of just etching the surface, you cut sections out of it and then scuffed up the parts that had been cut? Now the entire thickness of the sheet begins to glow in those areas!
In a natural progression, this led me to realize that you could apply this technique in layers, allowing you to create a 3D object in the sheets of stacked acrylic, so that it appears to be frozen in the stack and glow brightly. What I’ll explain below is exactly how I went about this, and how you can easily replicate my results. It may seem complicated, but if you follow along one step at a time you can make it appear that anything you want is “frozen” in light in a stack of plastic sheets!
Before I begin, allow me to thank my fellow members at LVL1, Louisville’s Hackerspace. We have all kinds of cool tools, like 3D printers, 3-axis CNC machines, and the laser cutter I used to make this. However, the people you will find there are the most incredible resource you will ever come across. In particular, this project would not have been possible without my good friend Blenster, who stayed and helped me with this over the course of days, and only offered encouragement when the first version didn’t work out and I had only 24 hours left. He’s like a real-life Good Guy Greg. Also, thanks to Tyler for his technical help and to Chris for providing me with the acrylic glue that the White Star Balloon team had not yet huffed. If you’re anywhere near Louisville, you’re truly doing yourself a disservice by not checking it out.
Anyway, on to the project!
Step 1: Step 1: What Youll Need
You’re going to need the following items to make this project:
1. Google Sketchup – the free version is fine.
2. Sketchup plugins from sketchucation.com – Slicemodeler, Export to DXF or STL, and STL Importer are all free
3. Lots of acrylic sheets -- my project used about $30 worth.
4. Acrylic glue/cement
5. A Dremel-type rotary tool and burr bit.
6. Whatever lighting you desire – LED, CFL, etc.
Step 2: Step 2: Make a Model!
In order to make the slices we can cut on a laser cutter (or by hand, I suppose), we’re going to need some sort of 3D modeling program. There are many fine options out there, but I chose to go with Sketchup. Blender is very powerful, as are the commercial offerings, but I chose to go with Sketchup because it’s highly intuitive and the non-Pro version is free. If you draw a square, it automatically becomes a face, and using the Push/Pull tool let’s you give it volume by simply clicking on that face and pulling up or down. Although it is actually a surface modeler and not a solid modeler, we can still use it perfectly well because of the ability to extend its functionality with plugins.
The Sketchucation forums have hundreds of different free plugins that provide incredible functionality. For our purpose, we need SliceModeler, at http://forums.sketchucation.com/viewtopic.php?t=15313, STL Importer, at http://sites.google.com/site/jimfoltz/sketchup/my-sketchup-plugins/stl-importer, and Export to DXF or STL, available at http://www.guitar-list.com/download-software/convert-sketchup-skp-files-dxf-or-stl. You’ll need to make an account to see the files. Once you have them, extract out the .rb files and copy them into the Plugins subdirectory of wherever you installed Sketchup. So, if you have yours installed in C:\Sketchup, drop the files into C:\Sketchup\plugins, and they will automatically show up the next time you start Sketchup.
For my project, I found a free model of a virus that I liked at http://www.turbosquid.com. If you set the price range from $0 to $0, all of the free models will show up and you can search through them. It was in STL format, commonly used for 3D printing, so I used the STL Importer plugin we installed earlier by going to the File/Import menu and selecting the file I downloaded. This brought the model into Sketchup.
Now, in order to make slices of it, we need to cut the model OUT of something else, or else the slices would be of the virus itself. You can of course do this as well, but for this project we’ll be cutting the virus out of something else to make it look like it’s frozen in the acrylic. To do this, I drew a box 5”x5”x5” around it. There are many sketchup resources out there, but essentially I drew a square base and used the push tool give it volume. With this in place, I moved the model into the box, trying to center it as best as I could, as you can see in the second picture.
The Sketchup model is available below.
Step 3: Slice It Up!
In order to slice it up, we must make it into one group. Use the cursor to select both the box and the model, and then right click on both of them. Click on “Make Group”, as seen in the first picture. Next, go under plugins and click on “SliceModeler”. There are other, newer plugins that accomplish this task, but because our model is hollow, or not manifold, they fail. SliceModeler doesn’t care that our object is actually empty.
A box will open asking for parameters. For slice spacing, I used .08", because that’s how thick my acrylic was. For slice thickness, I used 0, since I want each slice to be right next to each other with no gaps, giving me the highest resolution possible. SliceModeler tends to approximate to the nearest fraction, so it actually used ~5/16th of an inch for the thickness. However, since this is very close to the .08 I wanted, it didn’t make an appreciable difference. Depending on how you want your project to appear, pick an axis. I found that the X-axis worked well for me. Click on OK . A box will open up asking you to confirm your parameters, and will show you the number of slices that it will make. Click OK and let it run. Although it shows the number of the current slice it’s working on, don’t kill the process if it appears to freeze! It will actually finish, but may take a few minutes depending on the complexity. When it's finished, it will offer to slice everything along another axis. Click cancel.
Once complete, it will offer to hide the original, unsliced, model. Hit OK to do this.
The last picture shows the model after it has been turned into slices.
Step 4: Prepare the Slices
Cool, huh? We now have a bunch of slices stacked together with the model cut out if it! All of those places where the virus was removed will be available for us to abrade, letting the light really glow brightly when they're all stacked together.
In order to use these, we need to separate them. Right click on group of slices and click on "Explode". This will separate all the slices into individual components. Use the Move tool on the first slice and move it aside, and then continue with the rest. To avoid one long row, I made a long group of slices and then moved them along a different axis.
Be careful you move the slices in order! Just clicking on the one that looks closest may not actually select the one you want, especially if it doesn’t form a closed structure. Sketchup doesn’t interpret these as faces and tends to select the nearest closed face.
After ordering your slices, use the Rotate tool to flip all the slices on to the X-Y plane. I selected each row of slices by dragging the cursor around a group and then letting go. Use the Rotate tool to have the slices lay flat along the X-Y plane. Don’t worry, it’s a fairly intuitive process.
Once you have them all there, click under Camera/Standard Views/ and select top. This allows us to look down on them. Go to the first slice and select it by clicking on it or drawing a box around it. To save just that slice, click under Tools/ and select Export to DXF or STL, the plugin we installed earlier. It will ask you for a unit of measure, such as inches, feet, etc. and then ask you to pick how you want the lines interpreted as. Click on “Lines”.
Pick a file name and save the first image. Do the same for the rest of the slices. It helps to assign a shortcut key to make this faster. There is a plugin that exports directly to SVG, but it tends to re-arrange the different features of the slice, so we can’t use it.
Once you have your files, you’ll need to inspect each one individually and clean up any errors. The size and dimensions will be exactly as you made it, but because the slicer is “cutting” through the virtual model, there may be gaps in the drawings. Use any vector editing program, like Inkscape, or Corel Draw to clean these up if you find any errors.
Step 5: Cut Them Out and Start Grinding.
Depending on how your laser printer works, you will need to print these images. With ours, we can use Inkscape or any viewer, so I just loaded up each file one at a time and began cutting. Plan in advance, because this will take many hours! As you laser out each one, use a marker to add the number of the slice to it so that things don’t get confused. The acrylic usually has a thin plastic sheet on it, so it will be removed later. You’re going to end up with quite a pile of scraps! If you look to the bottom left of the first image, you'll see a stack of pieces that have been cut out., as well as scrap pieces next to them.
Next, we need to roughen up the areas we cut out so that the light will refract and appear bright. To do this, use a Dremel rotary tool or similar. We didn’t have the right burr I needed at the space, but luckily my cheapo Harbor Freight rotary tool came with a ton of accessories, so I found the tiny, needle-like burr I needed. Just run the bit across the interior surfaces until it’s clearly scuffed up well, as shown in the second picture.
This will also take quite a while to do right, so be patient, because the outcome is worth it. After burring each slice, clean it off with a brush to get rid of any debris that has accumulated.
Step 6: Glue Them Together.
Now it’s time to glue! Use a bottle of acrylic cement or glue that works well for you. I find that IPS Weld-on 3 or 4 works rather well. Unfortunately, I didn’t have as much as I needed, so I only glued the corners together, which leaves ugly bubbles. If you have enough, coat the entire surface. When it dries, it’s completely transparent and you won’t be able to tell it’s even there. After removing the protective film, use a soft brush to remove any residue or grit left over from scuffing it up. Then use a syringe applicator, like shown in the photo, to either cover the entire surface or just the corners. Start with gluing one sheet to another. As those first ones dry, glue the sheets of two together, and then the sheets of four to each other, etc. This allows you to keep working as the sheets get dry enough to hold together firmly. Work quickly, though, because the cement evaporates.
As you progress, you’ll begin to see the details of the model emerge from the stack of acrylic sheets. If you look closely at the third picture, you can see the details of the arms and spikes beginning to show as the stack builds. In the fourth picture, the details really begin to emerge as the stack grows taller. Keep cementing sheets until you’re completely done.
Step 7: Avoid My Mistakes!
Now, in order for the real details to emerge, you need to light it very well. I originally had planned on edge-lighting every single pane with PCBs I home etched using the TLC5940 PWN driver. Unfortunately, I ran out of time as my original design didn’t work out too well. I originally had the virus model suspended inside of a human head, and spent approximately 20 hours cutting them all out. When I started to stack them a large problem became evident.
What emerged was that while you can see the model from the sides, you can’t see it from the front of the face! This is because the staggering of the plates didn’t create a uniform enough surface to see anything. Each one of those side cuts reflected light in a different way, so it made seeing the model straight on impossible. I considered sanding and polishing it, but there was no way I could make the deadline in time, and it would have not been as clear on how to replicate what I did.
So, remember: Make sure you have a uniform viewing surface. It could be a box, cylinder, etc. or anything else, as long as it maintains a uniform edge across the viewing surface. Otherwise, you just wasted 3 days and lots of money like me!
Step 8: Light Up and Enjoy!
Now that you have all the sheets stacked, you can enjoy your new artwork. Although good, colored lighting makes it really shine, it's easily viewable in normal lighting. To highlight the way it looks, I used an LED light bulb from Lowe’s that cycled through different colors.
Placing the finished object in front of the light, you get the final result! It looks rather pixelated when photographed for some reason, but when viewing it in person the object looks very smooth, with fluid transitions from one slice to the next. I’ll post video soon that I hope will clarify this.
I hope you enjoy this project and feel free to vote for me!