How do you rotate geometry for an image in MeshCAM?

So, I’m using MeshCAM 6 (with the Nomad-Specific script), and run into an odd problem: if I import a JPG in order to try milling it out, it works perfectly, except for one small detail: the Rotate Geometry menu option is greyed out (along with Slice and Translate). This is not a problem when loading an STL, only JPGs (and, I assume, other “image” type files, though I haven’t tried them yet).

Now, I can (and have) rotated the image before importing it into MeshCAM, so this is far from a major problem. But I do wonder why this happens, and whether it’s normal or a sign that I’m doing something incorrectly.

As you have discovered, MeshCAM treats bitmaps differently than STL’s. You do need to do any rotating, cropping etc. before you import the bitmap into MeshCAM. Just a heads-up, even for B/W bitmaps MeshCAM machines the whole rectangular bitmap and “Don’t machine top of stock” and several other commands do not apply.


Is there a way to convert an image or bitmap to an stl file so you don’t run into those limitations?

FYI: I discovered that if you use an square/end mill in your finish pass the “Don’t machine top of stock” works!.

1 Like

ColdCoffee, thank you so much for that reply! I’ve never tried a bitmap using a flat-end mill for finishing but you are exactly right and taught me a new fact.

I made a generic 3-level PNG for input, scaled to X=3", Y=3", Z=.5", black is Z-

I ran parallel and pencil finishing and confirm your statement (waterline works too but would not machine along the top surface anyway…):

One quirk I found is that I had to set Max Depth to a little below the bottom surface of the stock to get MC to finish the lowest level.

Darren, after you load a bitmap into MeshCAM you can save it out as an STL, but the resultant STL does not behave the same as a native STL for some reason. This is even using a losless-compression format like PNG as the input which gives true level top surface where it is white (or black). There are also no true vertical surfaces. MeshCAM scales the height of the centerpoint of each pixel and draws triangular facets connecting the centerpoints. So the steepest wall you’ll see is one pixel wide, even where there is a sharp transition between gray levels.