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DXF Import Tricks & Tips (and questions) from a FEMM Newbie

To: "Femm@Yahoogroups. Com" <femm@xxxxxxxxxxxxxxx>
Subject: DXF Import Tricks & Tips (and questions) from a FEMM Newbie
From: "Jay D. Greener" <jdgreener@xxxxxxxxxxxxx>
Date: Thu, 10 May 2001 12:50:38 -0600
Importance: Normal
Hey Everybody,

I just recently started with FEMM and E-mag analysis in general; please
forgive any ignorance. I?ve encountered a few problems with importing a
.dxf and would like to share them for the new guys and ask for any insight
the more experienced users might be able to provide.

Problem Background:

I?m using SolidWorks2000 to generate an axisymmetric dxf model of a pot core
solenoid.

Findings:

1.	The .DXF seems to import in a random position w.r.t. the FEMM coordinate
system ? even drawing the model from 0,0 in Solidworks seems to result in
(random?) placement in FEMM. The model crashes upon analysis (perhaps
because of the undefined region of space between the model axis of symmetry
and FEMM?s r=0 axis?).
2.	The model scale may or may not import correctly, on occasion the import
scale is 1:1, I?ve also had models import at 2x.
3.	Hidden dis-jointed lines in the dxf model will result in unexpected
results: Occasionally the model won?t mesh, I?ve found that erasing all
lines (in FEMM), then re-drawing between the points fixes the problem.
4.	Be careful about ?point imports?. In one model two points were very,
very close together, appearing as 1, it allowed a small connection between
two regions that I thought were separated ? one defined as air, the other
defined as iron ? the model solved as if the total region were iron! It is
(apparently) possible to define 1 region with two different material
types.(?)


Questions:

1.	The FEMM manual specifically say?s ?AutoCAD? DXF? is SolidWorks DXF
different enough that my problems may be solved by using AutoCAD?
2.	Because I can ?move? the model in FEMM, the import location isn?t a big
deal, but the only way I can find the location of a point (to define
?translation coordinates?) is to ?hover? the mouse pointer over the point.
I?m worried that I?m getting some erroneous results by having a ?sliver? of
undefined space between my model axis of symmetry and FEMM?s r=0. (I?ve
seen flux densities of an erratic nature down the model centerline, wonder
if it?s because it?s not perfectly aligned at FEMM z=0)
3.	I?ve attached 3 .fem files. One contains an example pot-core solenoid
model (without an air region outside of the magnetic circuit), an example
problem from the Ansys guide (thanks Si Hang). One of my pot core models
without a region of air defined around the magnetic circuit and the same
model with the region of air. Why do I have to add the region of air to get
the flux lines to close in my model, but not in the model provided by Si
Hang?

Thank you for you time,

Jay D. Greener


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<div class=3DSection1>

<p class=3DMsoNormal><span class=3DEmailStyle15><font size=3D2 color=3Dblac=
k
face=3DArial><span style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font=
-family:
Arial'>Hey Everybody,<o:p></o:p></span></font></span></p>

<p class=3DMsoNormal><span class=3DEmailStyle15><font size=3D2 color=3Dblac=
k
face=3DArial><span style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font=
-family:
Arial'><![if !supportEmptyParas]>&nbsp;<![endif]><o:p></o:p></span></font><=
/span></p>

<p class=3DMsoNormal><span class=3DEmailStyle15><font size=3D2 color=3Dblac=
k
face=3DArial><span style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font=
-family:
Arial'>I just recently started with FEMM and E-mag analysis in general; ple=
ase
forgive any ignorance.<span style=3D"mso-spacerun: yes">&nbsp; </span>I&#82=
17;ve encountered
a few problems with importing a .dxf and would like to share them for the n=
ew
guys and ask for any insight the more experienced users might be able to
provide.<o:p></o:p></span></font></span></p>

<p class=3DMsoNormal><span class=3DEmailStyle15><font size=3D2 color=3Dblac=
k
face=3DArial><span style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font=
-family:
Arial'><![if !supportEmptyParas]>&nbsp;<![endif]><o:p></o:p></span></font><=
/span></p>

<p class=3DMsoNormal><span class=3DEmailStyle15><font size=3D2 color=3Dblac=
k
face=3DArial><span style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font=
-family:
Arial'>Problem Background:<o:p></o:p></span></font></span></p>

<p class=3DMsoNormal><span class=3DEmailStyle15><font size=3D2 color=3Dblac=
k
face=3DArial><span style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font=
-family:
Arial'><![if !supportEmptyParas]>&nbsp;<![endif]><o:p></o:p></span></font><=
/span></p>

<p class=3DMsoNormal><span class=3DEmailStyle15><font size=3D2 color=3Dblac=
k
face=3DArial><span style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font=
-family:
Arial'>I&#8217;m using SolidWorks2000 to generate an axisymmetric dxf model=
of a pot
core solenoid.<o:p></o:p></span></font></span></p>

<p class=3DMsoNormal><span class=3DEmailStyle15><font size=3D2 color=3Dblac=
k
face=3DArial><span style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font=
-family:
Arial'><![if !supportEmptyParas]>&nbsp;<![endif]><o:p></o:p></span></font><=
/span></p>

<p class=3DMsoNormal><span class=3DEmailStyle15><font size=3D2 color=3Dblac=
k
face=3DArial><span style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font=
-family:
Arial'>Findings:<o:p></o:p></span></font></span></p>

<p class=3DMsoNormal><span class=3DEmailStyle15><font size=3D2 color=3Dblac=
k
face=3DArial><span style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font=
-family:
Arial'><![if !supportEmptyParas]>&nbsp;<![endif]><o:p></o:p></span></font><=
/span></p>

<ol style=3D'mso-margin-top-alt:0in' start=3D1 type=3D1>
<li class=3DMsoNormal style=3D'color:black;mso-list:l0 level1 lfo1;tab-sto=
ps:list .5in'><span
class=3DEmailStyle15><font size=3D2 color=3Dblack face=3DArial><span
style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font-family:Arial'=
>The
.DXF seems to import in a random position w.r.t. the FEMM coordinate
system &#8211; even drawing the model from 0,0 in Solidworks seems to =
result in (random?)
placement in FEMM. The model crashes upon analysis (perhaps because of=
the
undefined region of space between the model axis of symmetry and FEMM&=
#8217;s
r=3D0 axis?).<o:p></o:p></span></font></span></li>
<li class=3DMsoNormal style=3D'color:black;mso-list:l0 level1 lfo1;tab-sto=
ps:list .5in'><span
class=3DEmailStyle15><font size=3D2 color=3Dblack face=3DArial><span
style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font-family:Arial'=
>The
model scale may or may not import correctly, on occasion the import sc=
ale
is 1:1, I&#8217;ve also had models import at 2x.<o:p></o:p></span></fo=
nt></span></li>
<li class=3DMsoNormal style=3D'color:black;mso-list:l0 level1 lfo1;tab-sto=
ps:list .5in'><span
class=3DEmailStyle15><font size=3D2 color=3Dblack face=3DArial><span
style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font-family:Arial'=
>Hidden
dis-jointed lines in the dxf model will result in unexpected results:<=
span
style=3D"mso-spacerun: yes">&nbsp; </span>Occasionally the model won&#=
8217;t mesh,
I&#8217;ve found that erasing all lines (in FEMM), then re-drawing bet=
ween the
points fixes the problem.<o:p></o:p></span></font></span></li>
<li class=3DMsoNormal style=3D'color:black;mso-list:l0 level1 lfo1;tab-sto=
ps:list .5in'><span
class=3DEmailStyle15><font size=3D2 color=3Dblack face=3DArial><span
style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font-family:Arial'=
>Be
careful about &#8216;point imports&#8217;.<span style=3D"mso-spacerun:=
yes">&nbsp;
</span>In one model two points were very, very close together, appeari=
ng
as 1, it allowed a small connection between two regions that I thought
were separated &#8211; one defined as air, the other defined as iron &=
#8211; the model
solved as if the total region were iron!<span style=3D"mso-spacerun:
yes">&nbsp; </span>It is (apparently) possible to define 1 region with=
two
different material types.(?)<o:p></o:p></span></font></span></li>
</ol>

<p class=3DMsoNormal><span class=3DEmailStyle15><font size=3D2 color=3Dblac=
k
face=3DArial><span style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font=
-family:
Arial'><![if !supportEmptyParas]>&nbsp;<![endif]><o:p></o:p></span></font><=
/span></p>

<p class=3DMsoNormal><span class=3DEmailStyle15><font size=3D2 color=3Dblac=
k
face=3DArial><span style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font=
-family:
Arial'><![if !supportEmptyParas]>&nbsp;<![endif]><o:p></o:p></span></font><=
/span></p>

<p class=3DMsoNormal><span class=3DEmailStyle15><font size=3D2 color=3Dblac=
k
face=3DArial><span style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font=
-family:
Arial'>Questions:<o:p></o:p></span></font></span></p>

<p class=3DMsoNormal><span class=3DEmailStyle15><font size=3D2 color=3Dblac=
k
face=3DArial><span style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font=
-family:
Arial'><![if !supportEmptyParas]>&nbsp;<![endif]><o:p></o:p></span></font><=
/span></p>

<ol style=3D'mso-margin-top-alt:0in' start=3D1 type=3D1>
<li class=3DMsoNormal style=3D'color:black;mso-list:l1 level1 lfo2;tab-sto=
ps:list .5in'><span
class=3DEmailStyle15><font size=3D2 color=3Dblack face=3DArial><span
style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font-family:Arial'=
>The
FEMM manual specifically say&#8217;s &#8220;AutoCAD&#8221; DXF&#8230; =
is SolidWorks DXF different enough
that my problems may be solved by using AutoCAD?<o:p></o:p></span></fo=
nt></span></li>
<li class=3DMsoNormal style=3D'color:black;mso-list:l1 level1 lfo2;tab-sto=
ps:list .5in'><span
class=3DEmailStyle15><font size=3D2 color=3Dblack face=3DArial><span
style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font-family:Arial'=
>Because
I can &#8220;move&#8221;<span style=3D"mso-spacerun: yes">&nbsp; </spa=
n>the model in
FEMM, the import location isn&#8217;t a big deal, but the only way I c=
an find
the location of a point (to define &#8216;translation coordinates&#821=
7;) is to &#8216;hover&#8217;
the mouse pointer over the point.<span style=3D"mso-spacerun: yes">&nb=
sp;
</span>I&#8217;m worried that I&#8217;m getting some erroneous results=
by having a &#8216;sliver&#8217;
of undefined space between my model axis of symmetry and FEMM&#8217;s =
r=3D0.<span
style=3D"mso-spacerun: yes">&nbsp; </span>(I&#8217;ve seen flux densit=
ies of an
erratic nature down the model centerline, wonder if it&#8217;s because=
it&#8217;s not
perfectly aligned at FEMM z=3D0)<o:p></o:p></span></font></span></li>
<li class=3DMsoNormal style=3D'color:black;mso-list:l1 level1 lfo2;tab-sto=
ps:list .5in'><span
class=3DEmailStyle15><font size=3D2 color=3Dblack face=3DArial><span
style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font-family:Arial'=
>I&#8217;ve attached
3 .fem files.<span style=3D"mso-spacerun: yes">&nbsp; </span>One conta=
ins an
example pot-core solenoid model (without an air region outside of the
magnetic circuit), an example problem from the Ansys guide (thanks Si
Hang).<span style=3D"mso-spacerun: yes">&nbsp; </span>One of my pot co=
re
models without a region of air defined around the magnetic circuit and=
the
same model with the region of air.<span style=3D"mso-spacerun: yes">&n=
bsp;
</span>Why do I have to add the region of air to get the flux lines to
close in my model, but not in the model provided by Si Hang?<span
style=3D"mso-spacerun: yes">&nbsp; </span><o:p></o:p></span></font></s=
pan></li>
</ol>

<p class=3DMsoNormal><span class=3DEmailStyle15><font size=3D2 color=3Dblac=
k
face=3DArial><span style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font=
-family:
Arial'><![if !supportEmptyParas]>&nbsp;<![endif]><o:p></o:p></span></font><=
/span></p>

<p class=3DMsoNormal><span class=3DEmailStyle15><font size=3D2 color=3Dblac=
k
face=3DArial><span style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font=
-family:
Arial'>Thank you for you time,<o:p></o:p></span></font></span></p>

<p class=3DMsoNormal><span class=3DEmailStyle15><font size=3D2 color=3Dblac=
k
face=3DArial><span style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font=
-family:
Arial'><![if !supportEmptyParas]>&nbsp;<![endif]><o:p></o:p></span></font><=
/span></p>

<p class=3DMsoNormal><span class=3DEmailStyle15><font size=3D2 color=3Dblac=
k
face=3DArial><span style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font=
-family:
Arial'>Jay D. Greener<o:p></o:p></span></font></span></p>

<p class=3DMsoNormal><span class=3DEmailStyle15><font size=3D2 color=3Dblac=
k
face=3DArial><span style=3D'font-size:10.0pt;mso-bidi-font-size:12.0pt;font=
-family:
Arial'><![if !supportEmptyParas]>&nbsp;<![endif]><o:p></o:p></span></font><=
/span></p>

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