Introduction: 2.5D Laser Cut Gears
Laser cut gears are used in a wide variety of projects, from steampunk jewelry to the exposed mechanism of a wooden clock. By taking advantage of both the cutting and engraving capabilities of the laser, much more realistic and/or interesting gears can be created. Here I show how to create a basic laser cut gear (in traditional 2D), then how to use three different techniques for adding depth to the gear (a 2.5D effect). This is referred to as 2.5D because although it is adding a third dimension (essentially a Z axis) it is much more limited than the 3D you could obtain from a 3D printer or 4-6 axis milling machine.
I made this at TechShop www.techshop.ws
Step 1: Materials & Equipment
Vector drawing software (I used CorelDRAW)
Laser Cutter (my TechShop has a Trotec Speedy 300)
1/4" thick poplar, slightly larger than desired gear size
This instructable assumes some basic familiarity with CorelDRAW and a laser cutter
Step 2: Define Gear Regions
Each gear will have five distinct regions as shown in the image. Draw five concentric circles sized to your sense of aesthetics. In my case I chose diameters of 0.125", 0.5", 1.3", 1.7", and 2.0". This will result in a gear that is 2" in diameter that will fit a 1/8" shaft. You won't be cutting or engraving this pattern directly, rather it will be used as the basis for designing the gear shape and profile. Save this design, as you will use fresh copies in several of the upcoming steps.
Step 3: Create the Teeth
Start with a fresh copy of the concentric circles. Draw a rectangle that is 2.0" long and 0.2" wide, centered on the circles. I added a 0.05" x 0.05" chamfer to each corner. The portion between the two outer circles will form the teeth of the gear. Now, using the Rotate transformation make 6 copies of the rectangle at a 25.71 degree angle. This will evenly distribute the teeth around the gear. Since these particular gears are intended just to show the cosmetic aspects of 2.5D engraving, I am not too worried if the teeth and gaps mesh perfectly like you would for a functional gear. Finally, use the Virtual Segment Delete tool to remove all of the unnecessary line segments.
Step 4: Add the Spokes
Now you need to make the spokes, which occupy the region between the second and third circles. I decided that some curved spokes would be more interesting, so I used the B-Spline tool. To make sure that each spoke completely connects to the inner and outer circles, make the start and end points just outside the spoke region. Similar to the teeth creation, use the Rotate transformation to create 19 copies at an 18 degree angle. This will result in 10 spokes. Now you can use the Virtual Segment Delete tool to remove all of the extra line segments. Finally, use the Join Curves command on the overall design to connect all of the touching line segments. For example, an individual spoke cutout consists of four segments, but it will tend to cut better if all four segments are joined into a single curve. You now have a complete gear design!
Step 5: Standard Cut Gear
Now you can cut out the basic gear on the laser cutter. I found that 100% power and 0.8% speed worked well for my poplar. You now have your first 2D laser cut gear.
Step 6: Flat Engraved Gear
First let's try making the simplest of the engraved gears, the flat engrave. Here you will engrave both the spoke and tooth regions, leaving the hub and outer ring at the original height. Start with a fresh copy of the concentric circles design and enlarge the outermost circle to 2.2". This will make sure that you engrave past the outer edge of the teeth and prevent them from having a slight lip at the edge. Fill the tooth region with one color (here I used green) and the spoke region with a different color (here I used blue). This will allow you to individually set the depth of each region. You can use the same color if you want them both to be the same depth.
When you go to print the design, you have to make sure of two things. One, make sure that halftone is turned off or the two colors will be converted to a black and white pattern so you couldn't engrave them individually. Second, make sure that the Process Mode setting is configured to Standard as shown in the image.
Now you follow a three part process. First I configured the laser settings for the green color (100% power, 50% speed), disabled all other colors, and engraved that ring. You can make multiple passes until you achieve the desired depth. Then I configured the blue color for the same power and speed, disabled the green, and engraved the inner ring. Again, repeat until the desired depth is achieved. Finally, load and cut the gear outline right on top of the now engraved area of the poplar. You have your first flat engraved gear!
Step 7: Double Sided Gears
You don't have to stop at engraving just one side of the gear. Carefully remove the gear from the board, flip the gear over, and place it back into the original hole. The kerf of the laser is pretty narrow so the gear aligns fairly well in the original hole. Now you can load and print the green and blue rings on this side of the gear, giving you a double sided engraving. If you look carefully at the side view of this particular gear, you can see the effects of engraving to different depths. I made a single engraving pass on the left side of the gear and three engraving passes on the right side of the gear.
Step 8: Relief Cut Gear
Now you can try a more complex engraving that results in smooth profile changes across the face of the gear. So instead of just two flat regions, the teeth can start at one depth, smoothly transition up to the outer ring, smoothly back down to the spokes, and then finally smoothly back up to the hub.
Start with a fresh copy of the concentric circle design and once again grow the outer circle to 2.2". Now instead of filling in rings with solid colors, you will use the Interactive Fill tool to create different gradients. Start by making a Radial gradient from the outermost circle to the center of all the circles. This will result in a transition from black to white as you go from the outside to the center. Now you can add additional gradient points to the fill to create multiple transitions from black to white as shown in the image. Use the other red circles as guides so you can see how the gradients will overlap the different areas of the gear. Note that the black portions will be engraved the deepest and the pure white will not be engraved at all. The Interactive Fill tool can be a little confusing to use, so I recommend you read the CorelDRAW help for more guidance.
Similar to the flat engraved gear, you will first engrave the wood then cut out the gear shape. When you go to print, make sure the Process Mode setting is configured for the Relief option. The relief option tells the laser to make a single engraving pass, but to vary the power level of the laser to match the gradient of the image. This is what gives the smooth transition effect. If one pass doesn't achieve the desired depth, continue making engraving passes until it looks right to you. After engraving, load and cut the gear outline.
Step 9: Layer Cut Gear
Now you can try the last engraving type that results in the profile being cut as a series of flat layers. This creates an interesting stepped effect, but does take a fairly long time to engrave.
The process is almost identical to the relief cut gear, but with a slight difference in the print setting. Use the gradient image you created for the relief cut gear, but set the Process Mode to the Layer setting. You will then be able to set the number of passes to be engraved, I set mine to six passes. After engraving, load and cut the gear outline.
As you can see from the images, the laser alternates between horizontal and vertical passes. The darker areas of the gradient are engraved deeper on successive passes.
Step 10: All Together
Here you can see all four gear designs next to each other for comparison. That's all there is to it, so why not give your own design a try?