Exporting 2d faces for CNC


I won’t be creating my own gcode generator or part-fitting. I’ll only add it if I can find a library that offer such functionality. I can wire it up, but I don’t want to dive into creating such thing myself.

Just got around to cut the bottom part of my Caverna tray:

Everything fit snuggly together. Proof of concept for SU 3D model to lasercutter complete! :smiley:

Though, the sheets for the top tray was bulging a bit more, so they didn’t cut cleanly through all the way. A fraction still left. And too much to be cleaning it up with a scalpel. So it’d back to the workshop tomorrow and do another cut. I’ll have to try some more settings and see if I can reduce the sooting along the edges which gets everywhere.

Also, I realised that when drawing the parts I should think of how it’s assembled. I had to do some dry runs before I found a way to maneuver all the interlocking pieces together.


ThomThom, I have found success in lowering my laser power output and slowing the movement down led to less blackening on plywood.
Sketchucam has figured out the gcode output nicely (although I don’t think they have lead-in, lead out lines option). So if you have created the ability to pull faces out of a model and nest them on the plan isometric view then it would be just another step using Sketchucam to export the gcode. I wouldn’t think you would need to reinvent that.
Do you have any more thoughts on the finger joint corner challenge?


Are you using the File>Export>2D Graphic to export your dxf files to create your gcode in an alternative software? I have had problems using the built-in dxf export feature because it exports everything in the window and not just the selected component or group. I have been using the Export To DXF plugin fairly successfully but it seems to fail on more complex drawing outputs. I am curious what you use?


I’ll try that. (I also read that someone turn down phasing/pulse - need to read up more on that.)

I found that I need to make adjustment to the top tray - and hence that it would be nice if the extension could rebuild the components it created previously. That way I wouldn’t have to reposition everything. But that would require some more work to set up link between the parts.

Not yet. As I was working on this last model I realized it was more complex than I first though. Need to ponder some on what solution gives a good flexibility vs ease of use.

Not in this case. The laser I got access to now is a Full Spectrum Muse, using RetinaEngrave2. It prefer PDF. Actually doesn’t look like it accept DXF (which I find very surprising.) So what I ended up doing in this case is importing the model into LayOut. One page per sheet. Then exporting as PDF. (Though I could have exported DXF if the laser accepted that.)
One annoying thing I ran into was that I wasn’t able to pick a page from the PDF. So I had to split it out to a PDF per sheet.

Though, in the past, for another laser I used the DXF export. But I’m not sure if I used the 2D exporter. I think I just drew everything in SU flat and used the 3D exporter.
I find SU to be rather nice to draw up for laser cutting, as it automatically merges lines. No overlapping lines which cause the laser to cut twice. Though some care must be made when handling circles and arcs.


I always use File>Export>3d Model, with the following options:

I tried different extensions for dxf export, but this is the best method I found. I think the extensions I tried had problems exporting arcs as line segments, but this way I get actual arcs.

Segments of a circle or arc

I did notice that using Export to DXF plugin that my ovals turn to circles. But usually it works very well. I tried your settings with success. However I am still getting everything on the visible screen, not the object selected only. Unfortunately that means I have to delete everything I don’t want to cut. Do you have this problem?
For the Laser I am also using an FSLaser, but the 4x8 table and MetalCut software so I have to import the dxf and then apply the cutting path and export directly to the machine in a proprietary control format. Strange that RetinaEngrave2 doesn’t import dxf.


Yeah, I always have to do some clean up, deleting all the extra geometry I don’t want when I import the parts into SigmaNest. Haven’t found a solution for that yet, but it doesn’t take me long to fix manually.


Copy >> Paste in Place in a new drawing is my approach…

you can do it piece by piece or pre-select all those you want…



If you’re getting line segments when you export, export as a 3D DWG or DXF file, and select only edges. If you’ve drawn arcs and circles in SketchUp (and haven’t stretched or scaled them) they’ll appear as proper arcs on the export. 3D export only though!

A common misconception with SketchUp is that it segments all arcs, which is true, but it also “remembers” what is an arc or a circle, when you do 3D export it actually exports the arc, not the segmented representation of that arc.

To check to see if something in SketchUp is a proper arc or circle, select the art or circle and open “entity info”. If it’s got a radius, it’s a proper arc or circle, if it doesn’t, you’ll get segments no matter how you export.


This might be a feature to suggest to SU development: To export only what is selected when exporting a dxf. Seems simple enough and would save a ton of clean up later on.


As it is, now, DXF export respects layer and visibility. If you have what you want exported in specific layers, all you have to do to clean up in cad is delete the extra layers.


Back home again. Just before I left for my trip I found that the grey card I had used simply created too much soot. I clouded the lens of the laser and make the cuts not go all the way through eventually.

The local maker shop had some 4mm plywood laying around, so I’ll be trying that. However, it required adjustments of the drawing. So I ended up adding a new feature to adjust the thickness of selected parts:

Again, it’s the tabs that creates the most work.


Finally got the drawing adjusted and new parts cut. Everything fit snuggly! :smiley: The pumpkin space was a wee bit small, need to carefully stack them to fit them all.

I’ll see if I can wrap up the tools I wrote for this project. The challenge of the tabs is something for a later time when I’ve got more time to ponder on a good solution.


Looks great!
I may have some formulas for you to help with the finger joint and corner layout. Someone is helping me with it but they are away on vacation this week.


Hello: Just a couple of dumb questions!
What power laser does it take to cut through that 1/4" plywood?
Does the cutting happen all in one step or do you have to process through a 2nd & 3rd time, especially with thicker mat’l?

If you’re short on ideas about tab cutting, sizing, etc. don’t they cut puzzles by laser? Maybe a look at their software would give you ideas. Plus, there are a LOT of cardboard boxes that have some amazing tab cuts on them.

This is really interesting to me as I have been reviewing desktop sized CNC routers.
Personally, I don’t see how you can come up with “extensions” so quickly, or at least the basics for one.

Veeery Interesting!!


The laser I used was a 40W Full Spectrum Muse. The cut was made in one pass with full power and 40% speed. I don’t think I’ve used lasers with less power, so I don’t know how thick they will cut. Best refer to the description per laser.

It more of a challenge on how to implement a a tab editing tool in SketchUp - allowing the tabs to be edited.

With this it’s rather trivial iteration of each face in the model. To extract the 2d versions of the 3d parts I just look for the faces on the ground plane of each selected instance. And for adjusting the height I just look for faces parallel to the ground plane and adjust the to the desired height.
Editing tabs on the other hand will be a bigger challenge. The solution is not obvious.


I have an excel sheet someone worked up for me that may help with the math for the finger joints. I am new to the forum so I am not sure how to pass that on to you. Can you advise the best way to get that to you?


Are you able to upload here?

Or you can PM me if you prefer that.


Ok, I pushed version 0.4.0 of Milling Tools to Extension Warehouse and SketchUcation: http://extensions.sketchup.com/en/content/milling-tools


sorry for the delay. Work pulled me into the other world…
I just tried to upload the file but it is xls so the uploader won’t allow it.
Maybe PM? please advise.