Thanks for your thoughts Geert. I have created empty voids by subtraction in CAD, but never by placing an STL inside another.
What I'm referring to is actually very similar to the support blocker function. Although I don't know if the support blockers are made up of STL files.. Those can be partially interfering a support and/or the printed model. Any portion that interferes the model is ignored, but the interfered support is effectively cut away.
I can tell you that I've done the practice in question in the past few months. I just don't remember the exact steps. It is an unintended function in Cura. I'm not sure which versions. To me it worked without qualification like a boolean subtract in CAD. Given that, I think it could fairly easily be added as an intended function.
The project at hand is a hand held topographical map of a ski area. My primary model was extracted as grey scale from a topographic map. This PNG file was imported into CURA like a lithophane with the model thickness relative to grey scale. This makes a model that is an accurate topo model, but it has sharp corners. Not a friendly shape for carrying in your pocket. I don't know a way to easily apply chamfers and radii to an existing STL model. What I can do easily, is model a subtract solid in Solidworks and export that to STL. In this case, the subtraction STL is shaped like a picture frame with an contoured inside edge. The shape cuts the exterior of the map with large radii. A cylinder was placed in the subtract model to create a lanyard hole in the map.
Edited by mastory
add picture
Recommended Posts
geert_2 560
As far as I understood, slicers don't do boolean math on the STL-files. They rather "count walls", sort of. The first wall it encounters, it switches material on. The second wall = material off. Third wall = material on, fourth wall = off, etc... So any objects totally enclosed by another, will automatically be subtracted and become hollow upon slicing and printing. (But correct me if I am wrong on this.)
At least, this is how I make hollow watermarks. In the beginning, I made complex subtract-operations in DesignSpark Mechanical on my CAD models, to get these hollows. But this made subsequent editing difficult, because these hollows are hard to reach. Now I don't: I just move the watermark logo and text inside the main model, without subtracting. So they are "solid blocks inside of other solid blocks". Upon exporting to STL, it makes triangles of those watermark-surfaces. An STL-file just consists of surface-triangles, as far as I understood. No colors, no materials, no solid/hollow-definitions, no dimensions; just triangles... And these triangles are then automatically sliced and printed correctly, using the "wall-count" method.
Not sure how it would/should handle models that partially overlap each other, if it should do the exact same, or throw an error?
A few examples of watermarks done in this way. Most of the watermark text is 3.5mm high, character-legs are 0.5mm wide, and they are sitting 0.5...1mm below the surface. Obviously, this requires transparent or translucid filament.
Link to post
Share on other sites