Diy AMT

[båndsei]

It might help for rigidity ,but my tape is 50mm wide.I have to tape 3 or 4 pices together.
I think my new tape is used for SMPS trafos.I is light yellow,and maybe used for some capacitors.It is self adhesive.

[SEdwards]

I'm a grad student at a technical university in Germany, but unfortunately I don't have friends in the nearby experimental departments. I see so many cables and old power supplies in the recycling bins near my building. I bet that they have all of the special tapes and films (since they make detector equipment). It's a bummer.

If you have time during your next measurements, would you be willing to do an experiment for me? I'm curious about the output when you only expose some of the diaphragm. It might be better behaved in the middle than at the ends.

[båndsei]

I will try to do that.I have seen it done on RAAl.
Will it improve distortion or frekvence?

Bernt.

[SEdwards]

I would expect there to be more distortion at the top and bottom (and sides) than elsewhere on the diaphragm, since we have boundary effects there. I think that it makes sense to discard some of that.

I bought some of what I'll need to try etching aluminium. Hopefully I'll have my own test diaphragms soon.

Another cool thing to try would be to have narrower pleats in the center, and wider at the sides.

[SEdwards]

I started playing around with diaphragm materials today, cutting and such.

I wanted to chemically etch aluminium foil from a capacitor but I couldn't find H202 in the house and so used electrolysis instead (with a DC power supply). That works but I got little islands of aluminium left in between traces. Still need to get a better mask for the diaphragm if I want to try that again (paint or nail vanish maybe).

Right now you're using alu tape sandwiched between the pieces of tape? You leave the paper on the alu?

[geraldfryjr]

You can use sodium hydroxide to etch aluminium.
Better known as lye or drain opener,Drano in granular form (caustic soda).
I have done this before but handle it very carefully with it as it is very very active and caustic.
Do not handle it with exposed skin and use protective gloves.

I had never tried electrolysis before can you explain the process?

jer

[SEdwards]

Sodium hydroxide shouldn't be too hard to find here, cool. What did you use for a mask? I imagine that it dissolves some things which work for PCB etching.

For electrolysis, you dissolve some salt in water. Then you attach the + of a DC power supply to the thing that you want to etch and the - to another piece of (preferably) the same metal. So I used some household foil on the -. The alu makes it's way from the etched piece and deposits on the cathode (which bubbles). I will compare the 2 ways and see which gives me cleaner edges.

I had an idea that it might be possible to fold the diaphragm first (pre etch) and then let it sit in both sides in a shallow etching solution.The tip of the pleats would be submerged but not where the traces are. You could mask the top and bottom strips and then snip for the serpentine pattern later.

This could, possibly, give better alignment of the traces and pleat folds. On the other hand, it might not.

[SEdwards]

Perhaps it is possible for us to compile the thicknesses of diaphragms used in commercial products.

ESS's diaphragm is apparently .0005" ~ 12 um in thickness. Do you guys know the specs for the others?

They mostly use kapton these days, it seems. Alu has a density of about 2.7 g/cc. Kapton and Mylar have about 1.4 g/cc. Weight-wise it would be best to reduce the amount of Alu thickness.

[båndsei]

I only use one layer of mylar selfahedsive and 20my incl.glue 8my.Alu 7my ,no paper.
I print the pattern on the alu/paper,cut slices,tape slices,place it on the tape,remowe paper and tape with water,add talcum to the exposed glue ,fold it and bake it at 175c. for 20 min. in a form made of heatsink from CPU.
The original diaphragm has 2 traces in series to increse powerhandling.I use only one 3-4mm.wide.
My idea was to use alu/mylar and print the pattern on it and etch the exposed alu.http://simaintl.com/store/aluminum_mylar_PET_tape.htmlAlu might be covered with some sort of paint.
It is difficult to find the right film.It is difficult to find alu/paper as well,outside Denmark.

Bernt.

[geraldfryjr]

On my last project I just used some transparent packaging tape.
Although the warm water tends to soften the backing glue.

It was for to etch holes in the aluminium duct tape for a micro ESL driver.
I posted the pictures of it sometime ago and it worked well.

Sometime at a later date I have been thinking about using a toner transfer method to a sheet of foil to see how well that would work.

The very first one I made I had used copper tape and ferric chloride masked with with some automotive pin striping tape.
But I never made a complete AMT due to the lack of building the magnet structure.

jer