Hello, Dave Richards. SU, SVG, Gcode, etc.

Bill Arnold

1974
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Thomasville, GA
As our resident guru on all things related to SketchUp, I (we) have a few things to run by you. All of it is related to preparing drawings for a CNC machine.

A couple of us are building CNC machines from kits by Inventables. They have a software package that allows for small items to fit their basic size machine. For those of us who use SketchUp with some regularity, it would be great if there were a path from an SU drawing to the gcode necessary to drive a CNC machine.

One path is upgrading to SU Pro so one can use the SVG export, then use a CAM program to generate the gcode. At $600, that's a pricey way to get what we need.

Another route I found was SketchUcam from Phatboyz. I did a single-face drawing, provided the appropriate input and got a gcode file, but there were other problems that caused me to have to delete SUcam. There were issues with it changing the appearance of drawing elements that were related to the handling of "Styles". I could work around that, but the bigger issue was irregular, but routine BugSplats that I didn't have before SUcam was installed. As promising as SUcam looked, I had to delete it from all of my PCs to have stable SU2015.

I guess the real question for you is: Can you help us? Is there a pathway from SU to gcode that we haven't found yet?

Thanks!
 
I'm not dave, but I've got some mileage down this road.

First - you don't need SketchUp Pro. There are plugins that you can get for free that will export to DXF or STL. They work just fine.

Second - you do need a CAM app - the PhlatScript thing (SketchUCAM, i think it's called now?) is there - it's available. It's pretty hinky, though. I don't like using it. I use vCarvePro. They recently put out an update that will let it import Sketchup files directly which saves a good deal of time and you no longer need the plugin (so there's two ways to avoid buying Pro!) :p

Lastly - There are things about the way SketchUp draws stuff that you will have to keep in mind. One big one, and this may be more the fault of he plugins I use, is that the exported vectors are made up of segments instead of arcs and curves. That can be a little troublesome like circles that aren't made up of enough segments get cut out with facets and aren't smooth curves.

The other thing is more about 3D abilities. Sketchup is NOT a 3D CAD program - it's handy for visualizing, and it produces very nice looking models but underneath, the number of polygons and segments it uses aren't necessarily visible in the Sketchup view as easily to see how they'll cut. Also, Sketchup simply can't handle millions of polygons as well as true 3D CAD apps like Rhino or the like. For really complex 3D shapes - super organic 3D curves and such - a true 3D CAD (or something like Aspire) would be better suited for the task.


It is helpful for a lot of things - It's a cheap way to get into it. And for 2D cutting, it's really a great way to go as long as you keep your segment counts up on your curves.
 
the odd thing is dave, of the files that i had created in sketchup for my state cribbage boards, 40 worked nicely with sketchucam, the other 10 tried to create a new face, and made all of the created passes disappear. i redrew one of them, and it worked just fine. my question is, is why some did that, while the others, created at the same time, the same way didn't?
 
Dan, I'm thinking that's a question for the Sketchcam people. It could be a number of things. Maybe something as simple as reversed faces in the model.
 
Thanks, Jason and Dave.

A test I tried with SketchUcam was fairly simple, but failed terribly. I drew a 2D model of a zci for my table saw. I carefully set the 0,0 point on my CNC and started the job. The first thing that happened was the machine moved way off the 0,0 mark and started cutting in the air. When it moved back to my MDF board, it started cutting the side of the zci. When it got to the half-circle for the end of the zci, it began doing what Jason described - jogging back and forth as it cut many tiny segments. I could go into additional detail, but I've already deleted SUcam from my PCs.

As far as the handling of arcs is concerned, another test I did was using Easel. One of the drawing elements is a spiral, so I had it run that and it did so in a continuous arc.

Anyway, I'm looking at other options besides trying to do a SketchUp route.
 
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Bill, out of curiosity, where in the SketchUp model space was your drawing relative to the model origin? As for cutting arcs and other curves, you could draw them with shorter segments in SketchUp and that would improve the precision of the cut. If you were using SU Pro, you could export the drawing as a CAD file and convert the curves or you could draw the curves in LayOut and get nice smooth curves without line segments. then export DXF from LayOut.
 
Dave, I originated the drawing at the zero point of the SU axes, flat in the red, green plane with the long side along red. When finished with the drawing details, I set up the work space as described in SUcam, giving it the bottom left coordinate 0,0 and upper right as 15,4.5. I then moved the drawing off the edges of the work space as instructed in SUcam so it was fully contained within the work space.
 
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