The short answer is no. OpenSCAD performs a top-level union. Since your largest circle encompasses the smaller ones, you are always left with one big circle.

You can approximate it using a difference.  This creates nonintervention thin shells.

for (a=[1,5])
{
difference()
{
circle (r=a);
circle (r=a-0.1);
}
}

Sent from my iPhone

The application is creating gcode files for CNC and the overlapping circles
was just an example of my problem. If it's impossible, I'll need to
selectively display and create several SVGs of my design. Not the best
solution, but it works.

On Wed, Jul 26, 2017 at 4:45 PM Ezra Reynolds shadowwynd@gmail.com wrote:

On 2017-07-26 23:35, fred_dot_u wrote:

Usually, but [1, 5] will go through to the loop twice with a equal to
first 1 and then 5, which is useful at times.

On 07/26/2017 06:27 PM, rglissmann wrote:

Maybe it would be easier to make the concentric circles using Inkscape
to generate the SVG which can then be exported to OpenSCAD using the
library from Drew Newman https://www.thingiverse.com/thing:25036.

Generally spoken, OpenScad is not the right language to produce Gcode, as
Gcode is always target machine dependent. For simple stuff like circles try
http://www.intuwiz.com/circle.html and see what you get.

Well, if you know what you do, you indeed can use OpenSCAD to design "flat"
and "line-like" 3D objects, export them as STL and abuse a slicer tool to
generate Gcode from that. Say you want to have your 5 circles with 1 to 5 cm
radius then your code would be something like this:

after F6 and export as STL, you can use a slicer to do the dirty work. A
slicer uses a profile to adopt its code to the target machine. It outputs a
text file and you can use any editor to find what you are trying to find, if
you know what you are looking for. Of course you should study G-Code a bit,
but the sematics is quite simple and straight forward.

For the above code my  kisslicer http://www.kisslicer.com/  (which uses
the profile for my 3D Printer) produced the following circle code (find the
raw file attached):

The E Parameter is the Extrusion and the F parameter the speed. It depends
on your target machine, whether it just ignores it. Also you should add a G0
X122.18 Y118.94 and some other code to instruct your targetmachine to do
what you want it to do before and after each circle.

Here is the raw gcode file:  test.gcode
http://forum.openscad.org/file/n21949/test.gcode

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