Optimization of cut path for cutting regular hexagons

Dear Sir or Madam,

I am running LIGHTBURN version 0.9.09 on MacOS 10.15.3 (Catalina).

I want to cut small hexagonal tiles from acrylic sheet with the shortest cut time possible. All the shapes are touching and no material is wasted between shapes. I want all the edges cut exactly once with no unnecessary laser movements.

I experimented with various ways to create the design, and I experimented with various optimization settings and checked the cut path with preview. After a lot of work (about two days) I never got close to what I was looking for.

I decided to compare the cut path I was getting for hexagons to what I would get if I was just cutting simple squares.

SQUARES
If I were cutting out squares from a sheet of acrylic I would make all the vertical cuts first and then I would make all the horizontal cuts. The first vertical cut would start at the top, cutting downward and next vertical would start at the bottom, cutting upward. This avoids traversing the entire height of the work between cuts. Similarly the horizontal cuts would alternate cutting right and left.

Each square would have each edge cut exactly once and there would be no unnecessary travel to get to the start of the next cut.

I create a 4 x 4 grid of squares using the grid tool and used preview to take a look at the cutting path for various optimization setting. None of them produced a cutting path similar to what I had in mind.

HEXAGONS
I would like to see the hexagons cut path be similar to the square cut path described above. Vertical cuts would be continuous zig-zag type lines and horizontal lines would be interrupted straight lines.

QUESTION:
Is there any way to get the type of cutting path I’m looking for?

By the way I watched the tutorial video on the Cut Planner and it is excellent.

Cheers,
Martin

The most likely reason your squares test didn’t do what you want is that LightBurn won’t break up a shape unless you do it. If you create two arrays of lines (one horizontal and one vertical) it should do pretty much exactly what you want, but if you create squares, it will cut each square completely before moving onto the next one. Hexes are the same.

You can come close to the result you want by doing this:

  • Create the hexagons, and make sure they’re truly overlapped by using the snap tools
  • Select all of them, then Arrange > Break Apart to split them into lines
  • Edit > Delete duplicate shapes (removes the shared lines)
  • The select the vertical zig-zags and use the Auto-Join tool to make them a single shape, like this:

The path planner should do a good job with it after that.

2 Likes

Dear Oz,

Thank you for your response, it was very helpful and I learned a lot and I have a couple of more questions.

Here’s what I did and what happened when I followed your instructions:

You can come close to the result you want by doing this:
(1) Create the hexagons, and make sure they’re truly overlapped by using the snap tools

I’m glad you mentioned the snap tools. It actually took me a while to figure this out.
Previously I had been positioning the hexagons precisely using the xPos and yPos and computing the location of the vertices with simple trigonometry by hand. Of course this is quite tedious. Using the snap tools is MUCH easier. However, it took me a while to figure out how the snap tools work. I saw the “Snap to Objects” and “Snap to Grid” settings on the Preferences page. I experimented for a while and for a long time it seemed like it didn’t work. Eventually, I realized that snapping to another object only works for a vertex or line if you grab the object by that vertex or that line. Whew!

I noticed the mouse cursor changes depending on context. (A) small circle within horizontal line,
like --o-- to grab the object by the line (B) small circle within a plus symbol, to grab the object by a vertex and (C.) small circle within an X symbol. This one I’m not sure about.

QUESTION:
What is the function of the circle within an X symbol?

QUESTION:
Can you point to this in the documentation?

(2) Select all of them, then Arrange > Break Apart to split them into lines
This worked great.

(3) Edit > Delete duplicate shapes (removes the shared lines)
This worked great.

(4) Then select the vertical zig-zags and use the Auto-Join tool to make them a single shape, like this:
This worked, I was able to join the selected line segments and create a single shape.
When I ran the preview simulation it did a better job at following the zig-zags but it still jumped around a lot. It was also not possible to JOIN the horizontal line segments into a single shape. I figure that’s because shapes must be contiguous. So I tried to GROUP them together instead. The result was actually not very good. I did select Order By Group in the Optimization Settings. It still jumped around a lot and did not result in a nice orderly traversal of the hexagon grid.

I see that you didn’t promise it would be perfect, but that it would “come close” to the result I want.
I guess vector optimization is a hard problem and my grid-of-regular-hexagons is a special case.
Thank you. I have been enjoying exploring LightBurn.

Cheers,
Martin

This one is the object center. The best description is here: https://github.com/LightBurnSoftware/Documentation/blob/master/Toolbars.md#selection-snapping, though even that is a bit lacking. I need to reorganize the documentation a bunch and try to make it simpler to find things, and pull a few parts of it into the present. :slight_smile:

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