Toolpath creation on imported stl files

Hi all,

Before asking this question here, I’ve searched lots and lots of hours.
I have built up my experience with Shaper Origin, which is very user friendly, but of course starts with 2D drawing in stead of 3D drawing.

I’m having problems to create a toolpath (CNC carving) from imported stl files.

Just for testing I made a very simple object in Fusion 360 and Shapr3D:

A square block from 50x50x18mm with a round “hole” in it from 10mm deep.

In the STL preview it looks fine:

I use a 6mm flat end mill:

And the toolpath ends up looking like this:

A sort of cone shaped hole.

But for me the strangest thing: when I import (from my point of view) a much more complicated shape in the 4-axis environment, it all looks fine.

I also know I can draw this simple design in Luban itself. And that works fine with the same settings. But I haven’t bought this machine to make things I can do on a drill press :wink:

So now my questions:

  • Why do I have to set a target depth? Isn’t this information in the STL file?
  • Can some explain the odd shaped toolpath?
  • And even better: con someone tell where I can find the solution?

I know a workaround would be creating the toolpath in Fusion 360 (which I did and looks fine), but it can’t be the goal to buy a “beginner CNC machine” and having to learn (again from my point of view) a pretty complicated 3th party software.

I hope someone, and preferrably Snapmaker themselves, can help with this. Or am I the only one with this issue?

Thank you in advance,


My STL file:

basic test v1.stl (16.5 KB)

Welcome to Snap Maker forum Roy. I initially replied with what I thought would help before realizing you wanted CNC help and my reply was based on 3D filament printing. :frowning: Note to self: Wake up first :wink:

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If you import an stl file into 3 axis CNC Luban will default to relief carving, i.e. it will use the stl file as a depth map to create a picture rather than a whole object. An stl file describes a 3D object and in 3 axis CNC the best that can be achieved is 2.5D carving. You would need to use another file format to CNC the object you were testing with.

However, if you have a 4th axis stl files make sense and Luban can carve (mostly) 3D objects.

OK, I understand what you’re saying. Thank you for the explanation.
Any suggestions on which file format to use?
I tried OBJ, but Luban doesn’t recognize is when trying to import.

Unfortunately Fusion 360 is the answer.
Luban is the workaround.
It’s just not ready for primetime. Up until recently when you opened the CNC workspace a warning about it being in “alpha” stage popped up. Not sure it’s still not alpha and maybe just barely beta.

Meanwhile not giving up on trying :slight_smile:

I downloaded a (pretty complex) stl file of a carved owl on Thingiverse : Owl CNC High Detail by billywoodworks - Thingiverse

And I was very surprised this worked well. It took some time to generate the G-code, but the simulated preview looked fine.
So I’m happy to believe that Luban isn’t the best CAM software out there, but can someone explain why it can calculate a complex owl, but not a simple round hole in a board?

It actually does okay with reliefs. For some reason they concentrated on making that useable. (maybe whatever software they’re lifting they’re code from already did that well).

You can import an svg or png file and use that. Black is deepest, White is not cut. Grays are in between depending on the shade.


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Yes as sdj544 says, stl files default to using a carving toolpath and it uses the file as a depth map.

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Newbie, just about to try cnc. If using stl and black is depth, how do you control how deep the black goes?

Target depth.