CNC relief carving question

Still learning SM350. Working on CNC right now. For the most part, it seems intuitive, but I have one that I can’t resolve. Maybe I’m not using the right search terms so any links to previous posts will be appreciated.

When playing with a black an white stl file (as opposed to grey scale), I’m getting ‘tapered’ walls. As the relief carving steps down it also steps away from the previous carved path and doesn’t go down in a vertical carve. This results in a ‘V’ shaped carving. Is there a way to carve a vertical wall that I’m missing?

A 4mm deep carving has about a 45 degree slope on the walls.

Using the 3.175mm Flat End Mill, Double Flute bit with 0.5 mm step down, 1.2 mm step over in Luban. Working in wood and trying to do some inlay work. Creating the stl in Sketchup, in 3D. I realize I could use a vector path, but for me stl is quicker and easier. The post-process simulation looks good (no obvious tapering) but I can see the tapering in the workspace preview.

Is this a limitation in Luban, an artifact in Sketchup stl export, or I’m overlooking something?


It’s a limitation in Luban, for most any CNC work, you’ll want to get acquainted with a real CAM software package like Fusion360. I made a guide on multi-pass relief carves with this method if you’re interested.

For what it sounds like you’re doing when you say your stl files are b&w you’d be better off creating vector files for the basic design and then using Fusion 360 to create/extrude the object and for the toolpaths.
For more organic/curved shapes and engraving @Skreelink 's guide is really good.

For what it sounds like you’re doing, which I think is closer to doing logos, you probably want to check out this thread:


I’m new to all of this but having fun learning. I downloaded (SVG/STL ect) files but when I put it in Lunban to set it all up and get a G-code I run into issues. Not major but frustrating. For example; when you get to “Preview type” the Toolpath looks great. Click on “Simulation” and you now can see an edge line that cant be seen otherwise…That secret squirrel line is picked up and carved :frowning: , I don’t know how to stop that. Can anyone help?