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WrineX 17th September 2010 06:32 PM

Femm ?? i dont get it what did i do wrong
well i tried a simulation with femm

magnet N40 from femmas material size 40x10x10 all mm
steel frame 200x10x10 just to see what happens pure iron selected as material.

magnet direction i used 90 degrees but i dont know if this is right with other values things got even more wicked.

well question is why is the flux not at all in the air gap it remains in the iron fully. and i dont get the flux rating from the legenda on the right. look way to hig or am i wrong here.

for the mid piece i slected air, also around the whole procjet i made a rectangular and stated the material whas air.

i used this this from el posted somewhere on the forum

A short description:
File New - magnetic or electrostatic problem
Problem - define units, planar/radial
Grid Set Grid - define grid size (units per dot)
Grid Snap to Grid - defined points are aligned with grid dots
set points (with mouse)
select line icon
define lines by selecting two points
Properties Material Library
select materials by drag and drop to the right side
strange green icon is the material marker
set markers with mouse (better with deactivating snap to grid)
select marker with right mouse button
press blank on the keyboard
dialog opens, let femm choose mesh size is only recommended for air, 0.5mm is good for usual audio devices (you have to draw a frame around everything and label the inside with air)
File Save
yellow botton is for creating mesh, the wheel for calculation and the glasses for viewing
in the viewer press the colour icon and select "show density plot" to get everything nice and colourful
with the line icon you can draw a line and display a graph of the flux density over its length (typically define extra points in the editor before calculation)
press the blue graph icon for showing the graph
exporting pictures is done with Copy Paste

if anybody can help that would be great, cant find any tutorial step by step to desigh ribbing motors

WrineX 17th September 2010 06:41 PM

1 Attachment(s)
have to upload the image ofcourse :)

WrineX 17th September 2010 06:42 PM

1 Attachment(s)
whoops not cropped

båndsei 17th September 2010 07:20 PM

You have to make the magnet direction 0 or 180 degrees in that simm.The arrows must be in the same direction R-L or L-R.
But its not the ideal simm .You should make as a crossektion seen from the end.

WrineX 17th September 2010 07:48 PM

0 or 180 will try that and post result, by the way i only fill in 4 magnets instead of the whole bar. you know why the flux results look so strange ? and crosssection i only saw pictures like this so you can see what the output is over the whole setup. what crossbars do etc. or am i wrong here ?

WrineX 17th September 2010 08:00 PM

ok when i change magnet direction to 0 this is what happens, this ooks like strange.

by the way maybe i have to clear the folowing we look at the fron of the ribbon motor with metal bar that forms soem sort of frame and in there the 4 blocks are the 4 magnets i drawed, i did not enter all of them yet because i wanted to see if it worked.

tinitus 17th September 2010 08:01 PM

if your magnets and iron have the same measures, 10 x 10, then why do they look different in drawing

did you remember to mark N/S pole orientation correctly

WrineX 17th September 2010 08:01 PM

1 Attachment(s)
ok im getting anoyed by myself for forgetting to attach pictures

WrineX 17th September 2010 08:02 PM


Originally Posted by tinitus (
if your magnets and iron have the same measures, 10 x 10, then why do they look different in drawing

did you remember to mark N/S pole orientation correctly

whoops you are right, they should be 4 mm, i screw up there , gone change it quick.

also where can you assign poles??

båndsei 17th September 2010 08:16 PM

The arrows shows N/S direktion.And you are right about the problem with wieving the crossbars influence.But i can be done.But maybe the way you do it might be right too. I did not see that depth could be set too.

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