Re: [femm] Re: Incorrect force direction

[Dave Squires <djsquires@xxxxxxxx>]

Steven,
I am evaluating Amperes right now. I have to say I think their
interface leaves a lot to be desired. It is a pain in the butt to enter
and define a problem. Geometry entry is not at all intuitive not to
mention boundary element definition. I told them already I don't
think the software is worth the $15,000 they are asking.
When did you evaluate and use it? It seems to me to be worth
about $2K-5K on the open market. I guess they don't have
any competition and charge the high price as a result.
Do you know of another 3D package that is worth the price charged?

My gut feel so far is not to buy IES Amperes.

Thanks,
Dave Squires

Steven Stretz wrote:

> Comparison is a very good idea however I have had such terrible luck with
> IES software I would not trust it any farther than I could throw the CD.
> Boundary elements are great for far field effects but historically their
> attempts at handling near fields, nonlinearities, induced currents, etc. has
> been at best questionable. I'll trust your judgement and hope the software
> has improved but be careful using it. I leased the software for a year and
> returned in after several months and asked for my money back, which I never
> received.
> ----- Original Message -----
> From: "Greg Watson" <gowatson@xxxxxxxxxxxxxxx>
> To: <femm@xxxxxxxxxxx>
> Sent: Wednesday, January 03, 2001 3:48 PM
> Subject: Re: [femm] Re: Incorrect force direction
>
> > ----- Original Message -----
> > From: "David Meeker" <dmeeker@xxxxxxxxxxxxxxxxx>
> > To: <femm@xxxxxxxxxxx>
> > Sent: Thursday, January 04, 2001 1:47 AM
> > Subject: Re: [femm] Re: Incorrect force direction
> >
> >
> > > Anyhow, I modelled your problem on Amperes by IES, which is a rather
> expensive
> > > commercial 3-D magnetostatic solver based on boundary elements, rather
> than
> > finite
> > > elements. This ought to give a good idea of how things would run in a
> real
> > 3-D test
> > > rig, assuming everything is carefully aligned. I arbitrarily made the
> machine
> > 1"
> > > deep in the "into the page" direction, for the purposes of making a 3-D
> > geometry. I
> > > chose a relatively fine density for the surface elements, and then set
> it to
> > > evaluate the forces on the magnet at a bunch of different axial
> positions.
> > What it
> > > predicts is that the centring force peaks when the front edge of the
> magnet is
> > just
> > > past the iron, with the centring force dropping to near zero when the
> magnet
> > is
> > > completely between the iron bars. femm predicts the same sort of
> behaviour,
> > except
> > > that femm predicts the peak force to be more like 15 Newton/inch, rather
> than
> > 9 N.
> > > The force from the 3-D geometry is smaller than in the 2-D model because
> some
> > of the
> > > magnet's flux leaks into the sides of the bars--this is an intrinsically
> 3-D
> > effect
> > > that can't be modelled by a 2-D solver.
> >
> > Hi David,
> >
> > Thanks for the effort.
> >
> > My concern was not that FEMM should report a large centring force but that
> a
> > program which I normally have found to be very realistic would report a
> > repulsive & not a centring force, no matter how fine the mesh or how much
> care I
> > took in making sure the geometry of the mesh and / or of the model didn't
> effect
> > the result.
> >
> > My duplication involved a round Neo, 4 on point right angle plastic guides
> hot
> > glued to the vertical faces of 2 right angle steel pieces (two guides per
> face,
> > 1 top, 1 bottom). Alignment isn't too critical. Although the plastic
> guides
> > aren't ideal, you can get a feel for the forces by the amount of effort
> needed
> > to roll the magnet back & forth between the guides.
> >
> > Greg
> >
> >
> >
> >