bonding 1008 to grade 5 ferrite

[BrassMonkey4]

In loudspeakers how do they attatch the magnet slugs to the top plate and back plate?

I know its some kind of glue or epoxy but i don't understand how that effects the flux flow between the magnet and the steel?

What bonding agents are better for this purpose and why?

 

[MagMike]

The glue does not have any effect on the flux flow between the magnet and steel. It is there to keep the magnet in place, maybe help in dampening unwanted vibration.

Regarding your question about best bonding agent: Whichever has the right combination of strength and cost.

 

[MJR2]

Try a 'superglue' like LOCTITE 495-50 SUPERBONDER

 

[nbucska]

The surface of the ferrite magnet or of the plate is not
absolutelly plain - the glue occupies the inevitable
gaps -- i.e. no effect.

I was actually involved with loudspeaker manufacturing
if you have any other question.

<nbucska@pcperipherals DOT com> subj: eng-tips
read FAQ240-1032

 

[RHMagster]

Hi BrassMonkey4,

Loctite 330 is a good material. It comes in a kit form with the 330 adhesive and the 7387 activator. Always follow instructions but basically its:
Apply adhesive to ones side of the magnet and activator to the mating side of the steel plate. Place items together and wamo, your glued !!!

To answer the question about magnetics. If you were using a more dutious material, say NeFeB,
(designed with this material is evidence of a high flux density requirement in the air gap) I would say it would have an effect in that the air gap between the magnet surface and steel should be a small as possible. With that, you would want a very thin adhessive (remember, air gaps = resistance to flux , similar effect as resistance has to current in an electrical cicuit). As the speaker is built using a ferrite; being somewhat pourous on the surface; a thick, gap filling adhesive may be more adventageous to the application. Although, you should always try to minimize the airgaps when ever possible.

Another important attribute for glue used is temp handling capabilities ! This maynot be as important for ferrite units vs NeFeB assembly though.

RHmagster