What is a lithophane (lith-uh-feyn) you ask? It is an etched or molded artwork made of a thin translucent material that can only be seen clearly when back lit with a light source. Traditionally these are made of porcelain, often masterfully crafted into the bottoms of teacups, but for several years people have been creating lithophanes with 3d printers.

Since the first time I experienced the magic of a lithophane I thought it would be a perfect accessory for a nightlight, but my knowledge of how to create the lithophanes was lacking. Recently I stumbled upon an item on Thingiverse by user poor_red_neck that described how to use a modeling software to combine a part he designed with a generated lithophane. I used his guide to make a few of these, but wanted mine shaped a bit differently so I started trying a few different things to improve the process.

Follow along to find out how I use free software to create the models to 3d print your very own custom lithophane night light. You will need a night light to backlight the lithophane. I use these LED night lights but have used some incandescent lights as well.

I encourage you to vote for this instructable as I will be entering it into the Lights contest.

For those of you who don't like reading, I have demonstrated this method in the video linked below.

https://www.youtube.com/watch?v=EagvYFY-VUM

Step 1: Create the Lithophane Model

There are many different methods for creating lithophanes, but the easiest that I've found for making night lights is a web-based utility called Image to Lithophane. It can be found at http://3dp.rocks/lithophane/

Open the website and select the Images tab at the top. Here you can upload the image that you want to use for the lithophane. I've found that portrait layout photos work the best, so those are the settings that I'll be showing. If you want to use a landscape photo, you'll need to experiment with the settings a bit to get it sized correctly.
Once your image is uploaded, select Settings > Image Settings. Here you will want to select 'Positive Image', as the default setting is set to 'Negative Image'. I leave the remaining Image Settings on their defaults.
Next select Settings > Model Settings. Here you will need to change a few settings. My "go to" settings are as follows (changes from defaults highlighted):
- Maximum Size = 80 (this will limit the height of a portrait image to 80mm tall, which works well for a nightlight)
- Border = 0 (adjust as desired)
- Thinnest Layer = 0.8 (a majority of printers are sold with a 0.4mm nozzle, so this will give you 2 perimeters)
- Vectors Per Pixel = 4 or 5 (simply put, the more vectors per pixel, the smoother the transition between high/low areas. Keep in mind more vectors = more processing time)
- Base/Stand Depth = 0
- Curve = 180 (in degrees)
- Thickness = 2.5 - 3 (this is the maximum thickness of the litho)
Once you have your Settings adjusted, click the Model tab. At the bottom of the screen you want to select 'Outer Curve' and then click the 'Refresh' button. Once the model is generated and looks acceptable click the Download button.

Step 2: Determine the Size

Once you have your lithophane model downloaded, you'll need a program that can open the .stl file. The program that I use is called Cura. It can be downloaded from here. It is a slicing software that slices a 3d model into all the separate layers that get deposited by the 3d printer. The functionality that is demonstrated in the remaining steps is available in Cura 2.3 and higher. The current release is 2.5, and that is what I use.

Open Cura and then open the .stl file you downloaded. In the lower right corner you will see the dimensions of the model. These dimensions will be used to create the base that will slide onto the night light.

Step 3: Prepare the Modeling Software

To create the base that will slide onto the night light you'll need a 3d modeling software. There are many to choose from, some free, some paid, but I'm most familiar with Sketchup. If you don't have it, you can download it here. You will also need to create an account, or login with a Google account to download an extension used to export .stl files.

Open Sketchup and choose a template with mm measurements. In the 'Windows' menu, select 'Extension Warehouse'. Click 'Sign In' in the top right corner. Use a Google account (or create a Trimble account) to sign in. Once signed in, type 'STL' in the search bar and hit enter. Select the SketchUp STL extension by SketchupTeam and then click Install.

In preparing to draw the model, you have to keep in mind the origin of the model. The origin of the lithophane model will be directly in the middle of all axis (X,Y,Z). I'd suggest either drawing the base so that the origin point (0,0,0) is positioned in the center of your model, or draw the model and move it so the center point is positioned at 0,0,0. Also, I'm a big fan of keyboard shortcuts, so if you see bold square brackets around an uppercase letter/key combination, that is the keyboard entry to use for a specific tool (i.e. [C] = circle tool).

Step 4: Start Drawing...

Remember those dimensions you got a couple steps back? Here's where you'll need those. We know that the lithophane is a 180° half circle, therefore the X dimension of your lithophane should be roughly twice the Y dimension, which should be the radius of the circle. In my instance, the width = 47mm and the depth = 24mm, so I need to start by drawing a half circle with a 47mm diameter. Since the center of a half circle is NOT the same as the center of a whole circle, I start by using the tape measure tool [T] to layout some construction lines. First I double click on both the red axis and the green axis. This will place a construction line directly on the axis lines. These will come in handy later. Click on the green axis and drag your mouse to the left. You can enter a specific distance by typing the numbers and pressing enter. I entered 47/2 to draw a construction line that was 23.5mm to the left of center. I repeated this to the right. I repeated the same steps dragging the line back and forward of the red axis, using 24/2 for the direct entry measurement.

**Direct entry in sketchup can handle mathematical equations of whole numbers. Unfortunately it cannot handle a decimal on either side of an operator (+,-,*, or /). For example 2.5/2 will not result in a 1.25 distance.

Now that the working area is defined by the dashed lines, I set the radius to 1.5mm less than the original radius. I do this by dragging another construction line 1.5mm from the front construction line towards the center. You can then draw a circle [C] using the intersection of the rear construction line and the green axis as the center point.

**Circles in sketchup are made up of a bunch of short, straight sides. By default, a circle in sketchup has 36 sides. This can often result in flat spots in a curve. To smooth out the curves you need to increase the number or sides. I typically use 100 because it's a number that is divisible by 4. To set the new number of sides, start to draw a circle by clicking where the center point of the circle should be and then type the desired number of sides followed by a 's' and press enter (i.e. 100s).

Drag the edge of the circle and click on the intersection of the 1.5mm offset line and the green axis. Now draw a line [L] along the rear construction line. This should go through the middle of the circle. You can then use the eraser tool [E] to erase the back half of the circle. You can erase most of the construction lines at this point, too.

Most of the typical night lights have a D-shaped section that the original lens slides around. The width of this section is just under 17mm. To allow for a little wiggle room, I find that making a slot 17.4mm wide slot into the base makes a good fit. Working out from the center, draw construction lines 8.7mm to each side of the green axis. Depending on the depth of the lithophane you're using, you'll need to establish the front of the D-section. I typically offset from the front of the curve 3mm. From that point, I can draw a construction line 8.7mm from the offset line to get the center point of the D-section.

Using the arc tool, click the center point defined by the construction lines. Next click the intersection of the 8.7mm construction line to the right of the center point and drag the arc around to form a half circle. Next use the line tool [L] to draw from the ends of the arc along the green axis to the back edge of the base. Use the eraser tool [E] to erase the line that closes the end of the D-shaped slot. You can also erase all the construction lines now.

Now that the shape of the base is established, we need to give it some thickness. Use the push/pull tool [P] and click the face of the shape drawn and drag upward to extrude the shape. Type 1.6 and hit enter to give it the appropriate thickness.

If you want to bevel the edges of the opening to make it easier to get onto the night light, you can, but I'm not going to cover that here. I do show how to do it in my video if you want to see how to do it. Otherwise it's time to export the model in a format that can be opened with the slicing software. This is where the SketchUp STL extension is used.

Press the [spacebar] to activate the selection tool. Click and drag a window around the entire part to select it. Go to the File menu and select 'Export STL...', when the dialog pops up, check the box for 'Export selected geometry only' and select 'Model units' in the drop down box. Save the file.

Step 5: Mash 'em Together

Go back into Cura and click Preferences > Configure Cura... In the General settings, uncheck the 'Ensure models are kept apart'. This will allow you to overlap two models.

Open the base model file that you created in Sketchup. You should now have the lithophane model and the base model on the build plate. To combine them you can do it one of two ways.

Merge Models

Hold [Shift] and select both models. Right click on one of them and choose 'Merge Models...' The merge models will merge the selected models together aligning them on the origin. Since we created the base model around the origin point and the origin of the lithophane was in the center this should work without issue. If things aren't lined up properly, press [Ctrl Z] to undo the merge and position both pieces manually using the next method.

Position manually

Positioning manually is pretty self explanatory. When you select one of the models, you will see green, red, and blue arrows. You can click on one of the arrows to drag it in that direction. Pan/orbit around the model to verify that you have the two models lined up properly. If you need to move both pieces to a different spot on the build plate and keep them aligned, just hold [Shift] and select both models and then right click on one and select 'Group models'.

Adjust your settings for the material and printer. I always use a 6mm brim just to minimize any warping. Once you've got all your settings dialed in, slice the model and save the gcode file and send it you your printer.

Step 6: Printing

In closing, here's a few others that I have made. These are really fun to make and everyone that sees them for the first time is in awe. They make really great gifts. If you don't have a 3d printer, there are plenty of printing services out there that you could send the 3d models to and have them printed. You may even have someone locally that would be willing to print them for a few bucks.

Good luck with making your own custom lithophane night lights. I'd love to see what you all make. And if you made it this far, thank you and please consider voting for this instructable.