Here at RepRapPro we love to hear about the prints and projects our customers are working on with their RepRap printers. We are pleased to be able to share some of the stories from our customers via our blog. The first comes from Peter Blacker who has been creating lithophanes on his Mendel.
Creating Lithophanes – Guest Blog
By Peter Blacker
I was fascinated when I first saw Amanda Ghassaei’s 3D printed lithophanes; A high tech nod to an art-form which is almost two centuries old. Amanda is lucky enough to have access to an Objet Connex500 3D printer, a serious bit of kit and costing $250K new. Here’s how I used my, slightly cheaper, RepRap Mendel to create my own lithophanes and found a new trick along the way.
Getting your image ready to convert into a lithophane: The processing script Amanda has written creates a pair of triangles for (almost) every pixel in the image. Since our RepRaps have either 0.3 or 0.5mm nozzles there’s no point using a full resolution image and creating an STL files with 10-20 million triangles. Your computer will probably run out a ram first anyway! I down-sampled my images so that each pixel is half the width of my extruder nozzle. This may feel like you’re brutalizing your pictures, but these lithophanes really don’t need any more resolution than that. The highest resolution image I’ve printed to date was 300×400 pixels! You can use Amanda’s own instructions to generate your lithophane STL files. I’ll describe here the settings you will need to get a good result on your own RepRap. There are four settings you will need to change in the processing script:
You will need to place the image file in the same folder as the processing script, and set the name variable to its file-name. Ignore the (in inches) comment on the other lines, STL files have no concept of units. So the units you use here are whatever your slicing tool thinks they are. MM is a pretty safe bet for most of us. Now set the width of your lithophane. The height with be inferred from the image files you are using. Now the interesting parts: Thickness defines the height of the solid base the image part of the lithophane will be built on. I used 0.25mm, but whatever your first layer height setting is will be perfect. The zDim defines the distance from the thinnest to the thickest parts of your lithophane. I used 2mm and printed this in 0.1mm layers giving 20 steps from black to white.
For starters you will need a solid infill. Lithophanes are all about transmitted light so there is no use having a fancy honeycomb pattern hiding in there. I used a linear infill at a 30 degree angle; this had the minimum visual impact on the image and helped a little bit to stop the print peeling off the bed. Now, you will want to set the first layer height to base thickness of your lithophane – 0.25mm in my case. Everything else you will want to print with 0.1mm layers or as thin as your printer can go. Now you can generate and slice your lithophane! I used slic3r V0.9.9. The first problem I ran into was crashing slic3r all the time. This was caused by it running out a physical ram. Unless your computer has a huge amount of ram you will probably run into the same problem. I fixed this by reducing the number of threads slic3r was using. If it still crashed using one thread I’d then start reducing the ‘resolution’ setting, first to half of my nozzle size, then equal to my nozzle size. These settings can be found in PrintSettings>Advanced>Other when you have slic3r in expert mode. Using this method I even succeeded in slicing my large 6×4 inch lithophanes. When I started printing lithophanes, the larger ones would tend to start peeling half way through. I have a big pile of curled up almostprints! I’ve now solved this completely by adding Kapton tape to my glass bed and making sure my bed temperature was correct. I am now printing in PLA at 55 degrees and have perfected the printing of the lithophanes as you can see below:
It did get me thinking though. There’s no reason these lithophanes have to be rectangular, I have found a simple trick that can be used to make lithophanes any shape you want. You will need to modify the image using a fairly good editing program such as GIMP or photoshop. Firstly add an extra blank layer on top of the image and paint solid white into the areas where you don’t want the lithophane printed.
Finally, do a levels adjustment on your image layer and raise the bottom end of the output range. If your lithophane is 2.25mm thick in total, you will want to set this to 227 (89%).
What you have just done is to artificially create the base layer in the jpeg image itself, along with zero height areas where you don’t want anything printed. So save your image as a jpeg and you are ready to go. Now you will need to change the ‘thickness’ setting in the processing script to zero and increase the‘zDim’ setting by 0.25 and you’re ready to go. The resulting STL files look a bit strange because large parts of them have no volume. I’ve found these all slice perfectly in slic3r.
Hey presto! You can now make lithophanes in any shape you want. This opens up a lot more possibilities especially for jewellery and decorations.
If you are doing something great with a RepRapPro 3D printer, why not get in touch? We may feature you in our blog!