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Removing rubbery potting compound

S

Sam Goldwasser

Jan 1, 1970
0
N_Cook said:
Can you make a pilot hole with a thin steel rod, chisel ground at the end.
Then pass through it one of those carbide covered wire saw , garotte type
things, or even a coping saw blade, kept under tension. Would some scratch
damage matter? If so then perhaps spaced , glued-on, guard rings along the
blade

That's sort of what I've been doing, and have been contemplating making
a tool that is more matched to the job than the strips of aluminum and
other random items I've been using.

I'm coming to believe that any chemical approach will take to long, not
to mention the mess and health issues.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
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S

Sam Goldwasser

Jan 1, 1970
0
Rich Webb said:
Maybe one of the oscillating-face tools, like the Fein MultiMaster?
http://www.fein.de/fein-multimaster/us/en/main/

There are flexible blades that might do the trick. Won't work (very
well) to de-pot an SMT-stuffed PCB but might get you a long way towards
getting the stuff off of the tube.
<http://www.fein.de/fein-multimaster/us/en/products/accessories_scraping.php>

Could be. The only real problem is getting the tube out. Once it's out,
getting the stuff off of it and the cylinder it was in is no problem,
the adhesion is not very strong, just enough that you can't push the
tube out without likely smashing it.


Thanks!

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
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M

Michael Anton

Jan 1, 1970
0
Sam Goldwasser said:
This type is usually dark gray and soft - about the consistency of a
pencil
eraser, maybe a bit tougher. It can be removed laboriously with knives,
picks, and elbow grease. But the question is whether there is some easier
way to do this that would leave the underlying components undamaged.
This stuff is used in a variety of places including PCBs and laser
tube assemblies. Both of these are of interest to me. Modest heat
has no effect including immersing in boiling water - it's not hot-melt
glue.

Thanks!

If it is silicone based, you might try Varsol. It causes one part silicone
to swell and get even more rubbery, so maybe it will behave similiarly
on that stuff. It tends to be easier to remove in this state.

Mike
 
J

James Sweet

Jan 1, 1970
0
That might work for the PCBs, though what will it do to the components?

However, what I really need to remove it from are special HeNe laser tube
assemblies. Not the common laser heads, but ones where the tube is totally
surrounded by the stuff as well as in front and back. So, the tube will
still be stuck inside surrounded by brittle hard stuff. :)

Thanks for thinking about it!

That sounds like a real pain. If you can use a long drill to drill a
tunnel parallel to the tube, you might be able to saw around the tube
with some piano wire.
 
N

N_Cook

Jan 1, 1970
0
Could be. The only real problem is getting the tube out. Once it's out,
getting the stuff off of it and the cylinder it was in is no problem,
the adhesion is not very strong, just enough that you can't push the
tube out without likely smashing it.


Thanks!

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
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| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
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In that case would mounting a vacuum chamber around the outside give enough
force for air pressure to shift it. Or compressed air around it with
appropriate seal? With some nearby soft physical restraint of course for if
it does move.
 
J

JW

Jan 1, 1970
0
The PCB was just an example. But where this is needed is to remove
the stuff surrounding a glass laser tube - about 6 inches in length
and a space of 2 or 3 mm between the tube and the cylinder it's in.
Both the cylinder and tube need to come out undamaged.

How about using a thin blade from a coping saw? Once you manage to slip it
all the way through the length of the cylinder it should work fairly well.
I don't think it'd damage the glass either.
 
S

Sam Goldwasser

Jan 1, 1970
0
Lostgallifreyan said:
So do it the way a capacitor is removed from the PFN for the SSY-1. Use a
fast cutting disk, or slow hacksaw, to cut the outer cylinder parallel to
axis, peel it back enough to remove the innards, then peel the gunk off the
internal cylinder (cap, or laser in this case).

That's what someone else did, but the important part is really the cylinder.
I'd like to get the tube out intact as well, but the solution of last
resort is to simply smash the tubes. Yes, I know, that's going to upset
the gods of dead lasers, but we'll see how the alternatives work out! :)

Thanks!

--
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Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
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| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

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S

Sam Goldwasser

Jan 1, 1970
0
JW said:
How about using a thin blade from a coping saw? Once you manage to slip it
all the way through the length of the cylinder it should work fairly well.
I don't think it'd damage the glass either.

Yeah, that's been my thinking as well. I don't like chemicals and anything
that would get through several inches of the close-fitting cylinder would
almost certainly be rather ansty.

Whether a coping saw blade is optimal I don't know, but something that
can be forced through and then fastened at both ends with enough "teeth"
to be able to eat away at the rubber.

Thanks!

--
sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
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W

William Sommerwerck

Jan 1, 1970
0
Even hard epoxy is no real matter when it comes to reverse engineering
if you are willing to destroy the thing you are analyzing. I've found
that it's quite brittle stuff, and applying pressure in the right places
with a bench vise will usually cause it to crumble. Some components will
get broken in the process but they can usually still be identified.

Please note the adverb in my original post.
 
R

root

Jan 1, 1970
0
Sam Goldwasser said:
Whether a coping saw blade is optimal I don't know, but something that
can be forced through and then fastened at both ends with enough "teeth"
to be able to eat away at the rubber.

Thanks!

I've lost track of how long the laser tube is. If you can thread
dental floss along the length of the tube you can saw the tube
out with the floss.
 
N

N_Cook

Jan 1, 1970
0
JW said:
How about using a thin blade from a coping saw? Once you manage to slip it
all the way through the length of the cylinder it should work fairly well.
I don't think it'd damage the glass either.

My coping saw blades are only 6 inches long, I doubt they come any longer as
only intended for small light work.

After drilling a pilot hole I would try one of these sort of wire saws
http://www.ecamo.co.uk/product/webtex-commando-survival-wire-saw/265.html
fed through and then bodge fixed in a 12 inch hacksaw frame for rigidity.

Or straightened out bit of heater element wire
 
S

Samuel M. Goldwasser

Jan 1, 1970
0
root said:
I've lost track of how long the laser tube is. If you can thread
dental floss along the length of the tube you can saw the tube
out with the floss.

Interesting thought. At least that's something I have. :)

I have a feeling it is going to be something along those lines.

Thanks!

--
sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
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| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.
 
J

James Sweet

Jan 1, 1970
0
N_Cook said:
My coping saw blades are only 6 inches long, I doubt they come any longer as
only intended for small light work.

After drilling a pilot hole I would try one of these sort of wire saws
http://www.ecamo.co.uk/product/webtex-commando-survival-wire-saw/265.html
fed through and then bodge fixed in a 12 inch hacksaw frame for rigidity.

Or straightened out bit of heater element wire

Or a guitar string, the rough coily type.
 
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