Ultrasonic basket - mesh size?

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Hi

I bought a basket that clips onto the side of my ultrasonic cleaner. It appears to completely block the ultrasonic action - a piece of foil left in the basket comes out unscathed, whereas the same foil outside the basket is holed in a few seconds. I estimate the wires that the basket's made from are 0.7mm apart.

If I have the right calculation, (assuming the speed of sound in water at 20C is 1480m/s, frequency is 35KHz) the wavelength is ~4mm. Does this sound right? And if so, what mesh size is optimal for allowing the waves through?

Thanks
John

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84 views and no one has mentioned that my calculation of the wavelength is out by an order of magnitude? Tsk, you lot are slipping...

John

[Lightages]

I do not have anything to say from experience but a quick search found this relevant information:
http://www.ctgclean.com/tech-blog/2011/11/reader-question-baskets-for-ultrasonic-cleaning/

[DanielS]

Acoustic waves are quite similar to RF and in RF, mesh spacing tighter than your wavelength will considerably attenuate it unless the mesh is very thin.

I have not checked your wavelength calculation but assuming it is correct, you would be looking for a mesh size over 10mm.

Ideally, you want the most coarse mesh you can get that will still hold the smallest pieces you want to put in it to have the least obstruction possible.

[MrsR]

I have repaired a few Dental Units and they usually have a plane Alloy tray as the sound waves are transferred  by the container into the parts being cleaned.

HOPE THIS HELPS
 

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Thanks for the responses. Interesting that although sound is transmitted in liquids as longitudinal compression waves, the spacing between the wires at right angles to the direction of propagation should make a difference. Someone must have done some fascinating research into this...

John

[David Hess]

Thanks for the responses. Interesting that although sound is transmitted in liquids as longitudinal compression waves, the spacing between the wires at right angles to the direction of propagation should make a difference. Someone must have done some fascinating research into this...

I do not think it is that surprising.  The relatively stiff wires or surface still cause reflections leading to constructive and destructive interference.  Unsecured joints in mesh lead to further loss through friction.  As pointed out in the linked article, thin metal surfaces have relatively low loss and the same applies to thin mesh with wide holes.

I suspect some type of thin perforated hard sheet metal would be best like nickel or stainless steel.  I have seen cleaning baskets made from something similar to screen door material but I doubt that would hold up in an ultrasonic cleaning tank.

I have used stainless steel mesh like you find in kitchen strainers but I doubt it is ideal and induces high loss.