DC Motor Magnet Adhesive 1

[Sparky2003]

I am currently using a DC motor and the vendor has informed me that they will be changing the adhesive to bond the magnets to DC motor shell. I want to generate a Validation plan for this change. Anyone have suggestions on applicable tests. I was thing along lines of Life testing in operation, Vibration. Any other suggestion would be greatly appreciated.
Thanks.

 

[ScottyUK]

Thermal cycling, perhaps?

 

[Lakey]

I would also suggest vibration and shock testing.

Best regards,

 

[jbartos]

Suggestion: Where adhesives are applied, the life-expectancy or life-cycle is often questioned.

 

[UKpete]

Before it gets to the testing stage, you might want to satisfy yourself that the process spec. is satisfactory, e.g. preparation of surfaces, method of application - the sort of instructions designed to ensure consistency. Ensuring correct physical positioning of magnets, although that won't be affected by an adhesive change.

 

[jbartos]

Suggestion: Experiment with the new adhesive on some old similar motor.

 

[mrquiet]

Hello,

We have bonded magnets to steel shells and flux rings for 20+ years and have seen the total gamut of failures. From my experience, surface preparation is essential. I have seen absolutely 'clean' shells have two stage epoxy bonded magnets literally fall out from their own weight.

We 'drop test' a significant lot (30 pcs) to validate a new run of material and check for good squeeze, cure, and adhesion and also continuously monitor the bonding stations (6 per shift) as the adhesion process can be easily affected by environmental conditions. We have vibration tested product in the past at resonance for 30 hrs, but felt that the drop test was sufficient as the bond is typically very stable.

We also will validate the material with a salt chamber test to ensure that there are no voids between the shell & magnet interface.

Hope this helps.

 

[UKpete]

mrquiet, what is a salt chamber test?

 

[jbartos]

Suggestion: The chemical composition of the adhesive to be effective in gluing is essential. I tried several adhesives to glue two plastics and none of them worked. I have not found right one yet. Also, I search for any suitable site on the Internet, and I have not found one.

 

[UKpete]

jb, have you considered either:
2-part acrylic
cyanoacrylate

eg see "plastic bonding LTS june 2003.pub"

https://www.permabond.com/

(go to FAQs then search on "plastic&quot

 

[UKpete]

oh, and Happy Christmas jb, and the same to any other Christmas-celebrating Eng-Tippers.

 

[jbartos]

Thank you. Merry Christmas!

 

[nbucska]

UKPETE
SALT water spray to test sea water endurance-- usually warm.

<nbucska@pcperipherals.com>

 

[Udayd]

You could try a &quot;push-off&quot; test. Using an Angstrom machine or similar, you can base line your existing adhesive on a statistically significant sample lot. You will be able to quantify the force required to push off a magnet. Do the same thing for the new adhesive. This will give you a good comparison between the relative strengths of the two adhesives. Your normal surface preparation methods, processes all can be evaluated by this test. This was the best method we found for assessing adhesive strengths. All the work we did was for smaller motors 3&quot; dia max.

Hope this helps.
Cheers and a Happy New Year to all!

 

[ScottyUK]

Hi Udayd,

I haven't come across an 'Angstrom machine' - could this be an 'Instron' machine used for stress testing of materials? Not my area of expertise, but I remember the materials labs at BAe were full of these units.

http://www.instron.com/index.asp

 

[jbartos]

Suggestion: Visit

http://www.satcon.com/pdf/47000rpm.pdf

for more info including an option to the adhesive approach.

 

[UKpete]

The Satcon application described in jbartos' link is for rotor mounted magnets. This is a much more complex issue than stator mounting.

 

[Udayd]

Hi ScottyUK,

I stand corrected. I realized my spelling error after I posted my reply but did not correct it.

Cheers..

 

[jbartos]

Comment on UKPete posting. I agree. Thanks. I did not mean to make things more difficult than they actually are.