Does anyone here use SketchUp with Shop Bot CNC router?


#1

I would like to be able to use the 3D models I create in SketchUp to cut parts with the Shop Bot. For this, I need 2D views in vector format, and I need them to be the correct size.

Thanks.
-Don


#2

i will be curious about this aswell. we are buying a jcut cnc and will need some help to set it up


#3

I have not but I am sure someone will chime in that has done it. I always revert to AutoCAD when doing things like this. Sketchup’s inability to make true circles and the lack of doing tangents from various size circles blows it for me. Not saying it cant be done, but its just way too much work.


#4

Hi guys,
I work at a uk garden furniture manufacturers and design and program wooden garden furniture.
I used 2d cad exclusively for years which works fine of course.
Then I discovered Sketchup which just blew me away at what I could now achieve, but I held off using it in my design process- because an arc is not an arc! If I simply exported dxf straight from sketchup I would have jagged curves. Not nice!
Time went on and the need for 3D turned into me using sketchup to design and showcase new products to customers.
Getting the profiles/toolpaths out of the model for machining is a bugger but it can be done using 2d cad to clean the sketchup curves into true arcs(I have an obsession for detail!)The less arcs the simpler basically.
Anyhow without rambling further here’s roughly what I do:
1-Select desired profile from model
2-copy and paste to new clean file
3-place flat on origin and delete any faces(set view to top and camera mode to parallel projection)save file.
4-export as dxf
5-open in cad and redraw the line arcs as true arcs, save file.
While this seems a lot of messing it works for me and gets the accurate result I want. It’s often easier than programming by hand put it that way. I can also use the cad file to build the vacuum jig to hold the piece down.
Seems daunting at first but it allows me to use sketchup to design and aid cnc manufacture at the same time. If budget allows there are simpler option out there but I love sketchup at the moment!

Hope this helps! :man_shrugging:Get back with any questions

Ian


#5

I haven’t tried it myself, but I read on this forum that if you use the 3D export to dwg, (Pro version of SU only) you get true circles - even if the SU file is only in one plane.

Might be worth trying…


#6

yes that is correct! I tried a basic extruded curve and exported it as 3d dwg, then imported it straight back in. The line arcs are still there but have true arc segments around them. Simply delete the inner original line arcs and voila you have a true arc!
Although the arc is still segmented,: I would recommend drawing the arc with fewer segments in the first instance to lower the lines of code in the program :grinning:


#7

Glad that it seems to produce something potentially helpful. What happens if you view the exported DWG file in an AutoDesk viewer of some sort that reads the DWG files natively?

However, be aware that if you edit any of the arcs or circles in SU - for example, by drawing an edge with the Line tool to intersect a segment - so that they lose their ‘arc’ or ‘circle’ property in SU, they will still, I expect, export as line segments.


#8

so I clean It up and I have a true and full arc now like this:

but when I export as 2d dxf for machining and open in draftsight _the arc is returned to an arc of lines as original as shown by lots of blue points Hmm…


#9

I think it can be done though, I’ll keep tinkering
Thanks for the tips though @john_mcclenahan


#10

From what I remember, the 2D to DWG export in SU keeps line segments. But you can export a 2D SU drawing using 3D export, so it should provide true arcs and circles in the exported file.


#11

SketchUp’s circles and arcs are a half-step toward the sort of parametric representation used by some other surface and solid modelers. Those modelers capture the nature of an object as a collection of parameter values. They don’t have any static, concrete rendering of the object, they plug the parameters into formulas to calculate and display the details of the object when and as needed.

In contrast, SketchUp’s geometry engine works exclusively in terms of straight finite edges and planar faces bounded by edges. This representation is fundamental to SketchUp. The edges and faces are all that participate in SketchUp’s geometry engine. There is no way to cause SketchUp’s geometry engine to use a real circle, arc, or any other true smooth curve or surface. If you think you got a true circle by round trip export-import to 3D dwg, you are being fooled by a SU circle with a lot of edges.

The “half-step” is that when you create a circle or circular arc, in addition to the geometry representation as a sequence of edges SketchUp captures the mathematical parameters of that circle/arc as metadata associated with the edges. But, the metadata has no effect on geometry operations in SketchUp. For example, intersections with other edges and faces are generated using the segmented representation of the circle, ignoring the metadata.

However, the metadata is used in certain non-geometry operations. For example, the Entity Info window displays the original radius and lets you edit it. But when you do, the geometry is immediately replaced by a new series of edges approximating a circle of the new radius. The inference engine in recent versions of SU uses the metadata to provide a snap point at the center of the circle. And, as observed in this topic, the 3D dwg/dxf exporter notices the metadata and exports a parametric representation of the circle instead of the segmented representation.

Despite how ideal it might sound, export of true circles is not all a bed of roses. For example, in SketchUp the intersection of a circle with another entity is generated based on the series of edges. If the intersection lands anywhere but on the end of an edge, it does not sit on the ideal circle. So, when the model is exported to 3D dwg, you may find gaps between the exported circle and other lines that were supposed to touch it. These flaws can be just as big a problem when using the export for CNC as the original segmented representation.

In contrast, the 2D graphic exporters were conceived as a sort of “smart screen shot” facility. That is, they are captures of the as-displayed presentation in the SketchUp view. And, since the as-displayed view always corresponds to the edge and face geometry, so does the 2D export. All that differs between export formats is the representation used. For example, a vector representation will avoid the “jaggies” that are inevitable in pixel-raster representations. In principle a 2D exporter could look at the circle metadata and export true circles if the destination supports them, but the existing ones do not.


#12

Yes it was how I did it, I exported as 2d after Imported it again.(won’t work!)

I don’t know about other threads but I have done it! :sunglasses:

Basically as machinists we are trying to achieve a true cad arc with start,center,through,end points and one continuous curve. Sketchup doesn’t work this way of course but its a pain in the rear when you have to convert sketchup arcs to true cad arcs!

HOW I DID IT:
Drew some ideas in sketchup like something that would be cut on a cnc, flat to plane with no faces, the arcs have only 6 segments to highlight them, one of the arcs (right) is tangent.I then exported this as a 3d dxf.(do not import back in as I did)

Then opened up the dxf in draftsight and check it out, true arcs all round! This is exactly what I need to achieve, as you can see the arcs have only start,end,through,center points. This should import to cnc very well I hope. :thumbsup:

ADDED LATER!
Then imported into xilog cnc software and it still has the arcs see image below

Also check the code for the pgm below, XL2P is a LINE, XAR is an ARC. I have all the arcs showing as XAR commands meaning they have also been imported in machine code as true arcs.

Thanks guys, gotta say this will save me and others many an hour of frustration!

Ian


True Arcs and Circle geometries - not just a series of straight lines