Problem with Elliptical parts when saved as a dxf

I am having some difficulty with any parts that are elliptical. For
example I have a piece of glass
in the shape of an oval and our glass cutting software uses a .dxf
file to cut the shape. When I
saw the part to an SW draing and then export it to a DXF, the ellipse
itself turns into a
bajillion line segments which cause havoc by creating a bajillion
lines of code in the
cutting software.

Has anyone else encountered this or found a way around it?

 

I think you will find this a common refrain about ACAD translations.
The bajillion lines is a poly line, and AUTODESK inovation that is
probably being abused just a bit here.

TOP

 

Just one dumb question: how do you expect te output code to
interpolate an ellipse, anyway? Does the machine have a
"Cut ellipse" command?

Worst case: create the ellipse in AutoCAD from it's major & minor axes
(or other parameters) in SW ..?

 

I don't suppose exporting it as IGES ... ?

 

Rule of thumb: Save output files in the oldest possible format.

R12 or R13 Autocad dxf-formats makes much less mess than if you save
them as R2000.

We had the same problems here with ellipses changing form if you save
them in the newer formats.
But also texts and hatchings seems to go wrong in teh newer versions.

To sum up, we save every dxf as a R12

 

To avoid the multi segment issue when saving a DXF you must use R13 or
later format. AutoCAD did not add support for true ellipses until
R13. Prior to that they were represented as polylines using many
straight line segments.

 

Nice info thanks, that will for sure become usefull to me later

But teh choice of version comes down to what you need the dxf for.
We use it for our CNC machines (Laser etc.), here the best results
have been from the R12 version.
It seems to me like you said that it turns the ellipse shape into
other (and more of course) line types. Which is suited for our CNC
machines, or in most cases actually a better choice (most our machines
are more than 5 years old so they dont support ellipse aswell).

But my message is still... use the oldest version that suit your needs.

 

If you want to use R12 to have line segments for CNC purposes, go to:
Tools|Options|Document Properties|Image Quality|Wireframe and high
quality HLR/HLV resolution|
Increase the quality to give the desired resolution of the line
segment resolution of your dxf splines and ellipses.

 

What version of SW are you using? I do not have that capability in
Sw2006.

 

I am running 07 but I am pretty sure you could do it with 06.

 

....or just trace the lines with a few 3-point arcs and delete the lines
afterwards.

An "ellipse" made of only six arcs will do fine for most practical
purposes. Hell, even an oval of 2 x 2 arcs would probably do
(unless, of course, a certified engineer has to okay the part)

<waves> Hi Cliff. <g>

 

This has been available for several versions. I remember using it
about 5 years ago when I had a similar issue with spline in dxfs.

 

They still probably want to break it up into little linear moves <g>.

<waves back> <G>.

 

I never noticed this before, but under "options" when you export as dxf or
dwg there is a box for spline export options, allowing you to choose to
export splines as splines or polylines. Does that have any effect on an
ellipse?

Jerry Steiger
Tripod Data Systems
"take the garbage out, dear"