I made it at TechShop.
As a novice user of the Epilog Helix Laser Engraver and Cutter, I decided to cut out some relatively simple stars and circles which will be used in a local elementary school for a Christmas art project. There were plenty of problems along the way, which I'm sharing so you can make different mistakes on your own version of the project.
For this instructable, I'm assuming that you've taken the Laser Cutting and Etching SBU class at TechShop or have equivalent knowledge if you're using a laser cutter elsewhere. This instructable only deals with cutting, and doesn't involve any etching.
The Epilog Helix uses a CO2 laser to cut and engrave non-metallic materials. Each laser cutting station at the TechShop is connected to a computer workstation where you'll load your design files.
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Step 1: Prepare the File
After deciding what to cut on the Epilog Helix, you need to create a drawing which lays out the shapes you want to produce. The TechShop recommends that you use CorelDraw to "print" to the Epilog Helix, so you should use a file format that CorelDraw can open. If you are going to work at the TechShop, prepare your file in advance and bring it on a flash drive. I used an open source CAD program called QCad to produce a dxf file, which is attached. Cutting many copies is straightforward, so I copied the original pattern to cover a 24" x 12" acrylic sheet.
Step 2: Materials
I purchased a 24" x 12" x 1/8" piece of fluorescent amber acrylic at a local plastic shop. More on that later. According to another person doing laser cutting, I should have also brought some paper to place between the Helix's grid and my acrylic. I used a second piece of acrylic with its protective paper still attached as a protective layer. It was not a great idea.
Step 3: Setting Up
If you think it's needed, place your protective paper on the grid and then place your acrylic on top. Make sure the acrylic sheet is flat on the grid. Align the top edge and left side with the rulers. Set the laser's focus and home position.
My acrylic wouldn't lay flat on the grid because the employee at the plastic shop cut the 24" dimension to 24.5". Unfortunately, I had failed to measure it before going to the TechShop. In order to have it lay flat, it had to be cut. Someone at the TechShop cut it for me on a panel saw, but he pushed the saw through the material very quickly. The right edge shattered as you can see in the photo.
Step 4: Open Your File and Set the Print Parameters
Open your file in CorelDraw on the computer which is attached to the Epilog Helix. Set the sheet size to fit the layout. The laser can cut right up to the edges of the grid, so you don't need any margins. You should zoom in on the edges, however, to make sure the objects aren't slightly over the edge like mine was on the left side. This caused a 1/8" gap in the cut of my leftmost leftmost circles, which I corrected in an extra cutting step.
This project uses only vectors and no raster images. Make sure the linewidth is set to hairline to produce vectors in the printing process. Select Print from the file menu.
Click the Preferences button in the Epilog Print dialog, which is where you will enter the appropriate speed, power and frequency settings for the laser. Look up the recommended settings on the chart provided near the laser cutter. For 1/8" acrylic the recommendations were, speed = 20, power = 90 and frequency = 5000. From previous experience with this laser cutter, I decided to reduce the speed to 17. Set the size in the dialog to match the sheet size you used in CorelDraw.
The speed setting determines how fast the optical head moves. The power setting determines how much power the CO2 laser will deliver, and must never be set above 90. The frequency setting determines how many pulses per second the CO2 laser will produce.
Step 5: Test Print Without Cutting
While keeping the lid up on the Epilog Helix, press the Print button on the computer's print dialog. When the lid is up, the CO2 cutting laser is switched off.
Make sure the red pointer is turned on and do a test run by pressing the GO button on the Helix. Watch that the laser seems to be doing what you expect. Be patient and let the whole job finish. Make any adjustments needed. I once failed to set the size in the print dialog (it defaults to a large size) and the laser started far from where I expected and went way past the edge of the acrylic.
After you make any corrections, do another test run! Test and correct until everything seems right then move on to the next step.
Step 6: Cut the Acrylic
Now that you know where the laser will cut, close the lid to activate the CO2 laser. Turn off the red dot pointer. Press GO and watch the machine cutting your material. If you see anything unexpected or alarming while cutting, lift the lid to turn off the CO2 laser. ALWAYS WATCH while you are cutting.
If the cut isn't going all the way through, stop the job and adjust your setting to a slower speed for more heat and a deeper cut. Keep in mind that different laser cutters may give slightly different results, and even one particular laser cutter may have some variation from one day to another.
Step 7: Finishing Up
Now that you've finished cutting, lift the lid and remove your material. If you are finished cutting, follow the instructions from the SBU class for putting the optical head in the correct location. Turn off the power.
Now it's time to remove your pieces from the scrap material. In the photo, you can see that at least one of the pieces wasn't cut all the way through in spite of my efforts to get the speed right. There was a very small bit of acrylic uncut, so it was easy to separate the scrap from the circles and stars by hand. Some small sharp edges had to be cleaned up to prevent children from scratching or cutting themselves.
i hope this Instructable will be helpful, useful or inspiring to you.