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Old 1st May 2013, 02:49 AM   #21
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Originally Posted by Calvin View Post
Hi,

. The only thing I'm still missing ...... and that's the point You Gerald my friend, come into play, are transparent toroids

jauu
Calvin
One can use mirrors to hide non-transparent things like David Copperfield does.
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Old 1st May 2013, 06:02 AM   #22
golfnut is offline golfnut  New Zealand
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Originally Posted by alexberg View Post
I would not use laser on acrylic: it creates extreme stress at the edges and one have to anneal the whole thing and still you'll get the whole bunch of whisker kinda cracks. Proper router bit would yield any kind of edge you like.
I have used laser cut acrylic for all of the ribs, spacers and other structural members for my ESL, without any sign of any problems - so far at least.
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Old 1st May 2013, 06:05 AM   #23
Calvin is offline Calvin  Germany
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Hi,

nice Idea Alex, as always from You. ;-)
The idea only suffers from that I haven´t got the smart looks and mysterious aura of Mr. Copperfield, nor can I afford those beautiful assistances holding the mirrors.
The mirrors would rather crack in my faces presence. For me the speaker needs to do all of the trick alone *lol*

jauu
Calvin
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Old 1st May 2013, 03:36 PM   #24
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Originally Posted by golfnut View Post
I have used laser cut acrylic for all of the ribs, spacers and other structural members for my ESL, without any sign of any problems - so far at least.
It's from my own sad experience,
if you do not believe:
Having problem gluing laser-cut acrylic parts
or that
Problems Gluing Laser Cut Acrylic
Also it's fair to say that three main kinds of polymethylmethacrylate exist: emulsion solution and bulk(cast). They differ in the aspect in question.
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Old 1st May 2013, 03:49 PM   #25
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Originally Posted by alexberg View Post
It's from my own sad experience,
if you do not believe:
Having problem gluing laser-cut acrylic parts
or that
Problems Gluing Laser Cut Acrylic
Also it's fair to say that three main kinds of polymethylmethacrylate exist: emulsion solution and bulk(cast). They differ in the aspect in question.
In a previous prototype of a curved esl I used curved plexiglas spacers. I did not observe any problems upon solvent welding. However, the plexiglas did receive a high temperature treatment after the laser cutting which lowers internal tensions so that might explain something.
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Old 1st May 2013, 08:54 PM   #26
golfnut is offline golfnut  New Zealand
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Alexberg

Thanks very much for the links - most informative.

As I say, its not been my experience so far. The particular acrylic I used is sold under the brand name shinkolite, or something like that. It has tighter tolerances on the thickness of the material than the normal acrylic sheet. It is possible that it has also been annealed during manufacture to reduce intrernal stresses (does anyone know?). I also used a very low viscosity methacrylate glue to attach the acrylic to the PCBs - not much else worked. I may have fortunate in my choice of glue too.

I have had the experiences you describe with polycarbonate - machined edges on polycarbonate tear like tissue paper. If you try washing machined polycarbonate parts in an utrasonic bath they shatter into dozens of small bits - quite stunning actually.
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Old 2nd May 2013, 04:40 PM   #27
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Quote:
Originally Posted by golfnut View Post
I have had the experiences you describe with polycarbonate - machined edges on polycarbonate tear like tissue paper. If you try washing machined polycarbonate parts in an utrasonic bath they shatter into dozens of small bits - quite stunning actually.
Interesting...now where can I get my hands on an ultrasonic bath.

I had switched from acrylic to Lexan(polycarbonate) because it handled cutting and drilling without chipping or cracking much better than acrylic.
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Old 2nd May 2013, 04:51 PM   #28
Bazukaz is offline Bazukaz  Lithuania
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Quote:
Originally Posted by bolserst View Post
Interesting...now where can I get my hands on an ultrasonic bath.

I had switched from acrylic to Lexan(polycarbonate) because it handled cutting and drilling without chipping or cracking much better than acrylic.
Yeah I have too had serious problems with acrylic. It was almost unusable.
Some materials I have tried:

1) Polystyrene plexiglass.much better than acrylic, still develops cracks over time and pressure.
2) Axrylic plexiglass. Too brittle IMO.
3) Rigid PVC sheets. Good material and resists cracking, however high epsilon(~4)
4) Low density PVC. Much lower epsilon and resists cracking. Not as strong and may have worse tolerances
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Old 3rd May 2013, 06:08 AM   #29
golfnut is offline golfnut  New Zealand
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Bolserst: Most scientific supply places would have them I expect. There are plenty of the smaller ultrasonic cleaners at at amazon.
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Old 4th May 2013, 11:28 AM   #30
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DX and other Chinese bargain sites have them for 20-30$ but I have no experience with the m so I can't say anything about quality. These are small cleaners used for cleaning jewelry and small parts.
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