Topic: Harvesting elements from transducer

[W9GFO]

Hi all,

I've been reading a lot here the past couple days, lots of good info! I was quite disappointed reading about the lack of precise alignment of the piezo elements in the transducers that have been disassembled. Makes me want to get mine x-rayed.

It seems that it is a lot of trouble to get the element out of the housing. I am wondering if a CO₂ laser would make the job easier. The laser would burn away the epoxy while leaving the copper foil untouched.

If someone wants to donate one (non-working), I can give it a try.

Rich H

[Rüdiger]

Hi Rich

Interesting way, and thanks for the offer. Let's see first the results.

mvh
Rüdiger

[Rickard]

Hi Rich,
I have disassembled several transducers and found bad alignment of piezos inside most of them. This is not particularly critical if you plan to use the transducer as it is, but if you try with joining them to get a longer transducer with better resolution it could be critical. Do you plan for making a longer transducer?
Rickard

[W9GFO]

My thoughts were that using the laser may save a lot of trouble in removing the piezo elements from transducers so that a custom one could be made.

[Rickard]

Removing piezos is really difficult. The elements are brittle and can break easily. Since work prevents me from playing with sonar projects for a few weeks ahead I thought I could test a time consuming method - dissolve the transducers in acetone. This will likely remove everything from the elements, also the cork insulation and the copper shield, but that doesn't bother me. I have one question, will acetone affect the piezos themselves? I know they are not soluble in acetone, but perhaps acetone can penetrate into the ceramic and alter the piezo electric properties permanently?
 
Rickard

[W9GFO]

I know acetone works well for cleaning up uncured epoxy, I don't think it dissolves cured epoxy.

Methylene chloride is what is reported to work but I have not tried it.

The laser will vaporize the epoxy without causing any harm to the copper wrapped piezo. No mechanical stresses.

[abraquelebout]

hi,
i crash a ducer (hdsi) during a test there's 2 month, i cut it and take out the two array in two hours.
if you take out the pvc in few part of the ducer, there's a not hard resin inside, with a cuter you can cut it slowly and take out the array.
now i m whaiting for a second crashed hdsi ducer to take out the array an making a double array in 445 / 800 khz
ps : the resin inside not scotch the array, it's verry simple to take out

[Rickard]

Abra,
I thought it would take much longer than two hours per transducer! My own cutting in the double-ducer projects and Sea-Rover's precision machining method gave me the impression it would take much more than one hour per element.
 
I took a discarded piece from one of the SI transducers, which I used for a double-ducer, and put it in acetone overnight. The PVC housing dissolved rather quickly, but the soft epoxy-like resin fill was not affected at all. It seems as a mechanical method (or laser?) is quicker and better, although I hate to use such force so close to the long, slim and brittle elements.
 
Rickard

[abraquelebout]

  hi rickard,
arrays may be more resistant than whe thing
waiting for a next crashed ducer, two hour's to take out the array

[Rickard]

Interesting abra!
It looks as if one array consists of two piezos, is that correct?
 
About laser, wouldn't laser generate heat and therefore cause risk for high temperature? Piezo materials use to have a Curie temperature (the highest temp that must not be exceeded to avoid loss of the piezo electric properties) between 150 and 350 degrees Celsius.

Rickard

[abraquelebout]

yes two piezzo
i don't know if it's ok but sea rover have one piezzo in one element.
i must take out two piezzo again and build a 455 / 800 sonar. for depht a 200 khz at 6° in 1 kw must work....

[W9GFO]

Lasers generate very high temperatures - but only where it is vaporizing material. You can immediately handle a piece of acrylic that has been cut out. I doubt that the element would get hot at all, maybe luke warm at best.

Also, while cutting there is a strong blast of air directed at the cutting point. It's purpose is to help with the removal of the vaporized material and to limit the amount of heat that is transferred to the work piece.