42 AWG/ 47 SWG copper magnet wire coil winding query

In preparation for the next time (if) I do another one, as many thousands of turns I don't fancy doing another one, to explore this anomaly.
I successfully wound my first 0.05mm wire guitar pickup rewind, but one curiosity- anyone know the reason?
This sort of rewind needs winding on a demountable former and transfering, as a hank of wire, into a trough. On demounting, there is a distinct banana shaped bowing to the hank Hank is about 65mm long , place onm a table and the ends are , equally, about 8mm off the table. Possible reasons , I can think of 1/ there must be a twist in the wire on the spool , despite pulling the wire off the supply spool tangentially rather than axially. 2/ some bias on left hand traverse versus RH traverse on the coilwinder machine. 3/ For this sort of very fine wire, instead of a final delivery pulley I use a tiny PTFE lump on a small bar. A hole in the PTFE squashed to form a sub-mm slot. Then a 15 foot run back to the spool (and a light felt slip clutch) to allow for any snatching. Because of room arrangement , to get a 15 foot run , the winder and so PTFE is set at an angle of 25 or 30 degrees rather than straight fore-aft. Perhaps that puts a set on the wire.
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wrote:

My totally uneducated guess (I am not a professional coil winder, I deal with 12-GA and 14-GA solid...) is that there are residual stresses on the wire from when it was wound onto the spool.
You might want to use a set of pulleys in series as a Straightener after the supply reel (and felt clutch) to gently work the stress out of the wire - you put five or seven pulleys in a sawtooth pattern so the centerlines of the groove are only a few degrees off a straight path, which makes the wire bend back and forth ever so slightly as it goes through them.
One set of pulleys for vertical, then a second set for horizontal. Then go through your PTFE slip block and onto the coil winder.
Oh, and is there any problem with putting a drop of varnish onto the finished coil in several spots while it's in thew winding bobbin, let it wick through and set, then remove it from the bobbin form?
Pick a resilient varnish that won't eat into the insulating varnish on the wires and cause shorted turns (ask the wire manufgacturer for suggestions, they probably have several...) and it'll be a solid form coil but it could be bent if you need to without going "Sproing!"
--<< Bruce >>--
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Unfortunately the UTS of such wire is about 5 ounces, before any work/age hardening or imperfections, so any more path resistance more than the minimum will cause a break. The felt slip clutch for back tension at about 2 ounces was too high, wide brroke after 1000 turns, and I had to reduce it to about 1 ounce. Not possible to dab varnish on before demounting. The former has to resonably match the profile of the trough which is intenal dimension about 60 x 3 mm , far from the normal circular form, and on top of that the cross section should be square, but for practical reasons its not possible to make the former square in section as the wire would catch on edges while winding. So it is necessary to allow the windings to move over one another to reform into the available space.
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wrote:

If you were going to do this a lot, you might have to build an unspooler to handle the wire - same thing they used on old computer mainframe tape drives, a vacuum stack to pull a slack loop off the reel and a motor drive with electronic feedback from a slack stack box to control the wire reel. The straightener would not be pulling straight off the reel, just from the slack box.
But that would be as you build a production machine to wind the coils in bulk, thousands a day. For one or two a year it would be nuts to spend that kind of money and wastye that kind of effort.
--<< Bruce >>--
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Bruce - do you remember what sort of sensor was used to provide the electronic feedback from the vacuum stack?
Hul

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On Thu, 13 Aug 2009 22:57:47 +0000 (UTC), snipped-for-privacy@kbrx.com wrote:

Never worked with one, but yes, I was just old enough to remember - they used a series of optical sensors to determine how much slack was in the box on either end of the tape drive. And a vacuum to suck the slack down into the stack box.
And memory tells me that they quickly found out that wan't the best design the first time someone tried to use a professional high power photo-flash unit to take a picture of a running mainframe's row of tape drives.
All the slack units freaked and locked up whern the photo flash fired, since depending how the light arrived they either thought there was no slack at all or way too much - or both at the same time...
Unfortunately the tape drive sections didn't shut off when the slack boxes did, and they promptly snapped and/or snarled all the tapes. Some got spewed all over the floor... Not pretty.
--<< Bruce >>--
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:On Thu, 13 Aug 2009 22:57:47 +0000 (UTC), snipped-for-privacy@kbrx.com wrote:
: :>> If you were going to do this a lot, you might have to build an :>> unspooler to handle the wire - same thing they used on old computer :>> mainframe tape drives, a vacuum stack to pull a slack loop off the :>> reel and a motor drive with electronic feedback from a slack stack box :>> to control the wire reel. The straightener would not be pulling :>> straight off the reel, just from the slack box. :> :>Bruce - do you remember what sort of sensor was used to provide the :>electronic feedback from the vacuum stack? : : Never worked with one, but yes, I was just old enough to remember - :they used a series of optical sensors to determine how much slack was :in the box on either end of the tape drive. And a vacuum to suck the :slack down into the stack box.
The only old tape drive I had a chance to examine closely had vacuum sensors at two levels at the back of the column plus a flow sensor in the vacuum line. Top sensor sees vacuum --> not enough tape in the column. Bottom sensor stops seeing vacuum --> too much tape in column. Excessive flow --> tape broken or not loaded. Pretty straightforward and reliable. Might not work as well with wire as it does with tape since the tape column is much, much wider than the gaps between the tape edges and the front and back walls.
--
Bob Nichols AT comcast.net I am "RNichols42"

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wrote:

I'd be suspicious that the wire leading into the guide at an angle compounded by an insufficient radius on the guide is the problem. You can get a proper guide from these folks at surprisingly low cost.
http://www.cosmos-na.com / http://www.cosmos-na.com/Coil-Winding-Nozzles-Tungsten-Carbide.html http://www.cosmos-na.com/Eyelet-Guides-Introduction.html
I've purchased guides for winding very fine tungsten wire several times from Cosmos, though I've never tried to buy just one or two pieces. The standard ceramic guides and eyelets should be less than $10 each. My last order was for several custom carbide guides -- I think those were less than $40.
--
Ned Simmons

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Ned Simmons wrote:

Making light bulbs, are you? <G> No, seriously, what were you making?
Bob
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A
to
Because
set
that
You have passed wire as thin as 42 AWG over , rather than just through , ceramic guides. ? I would have thought PTFE would be the only suitable material. Because the former is about 60mm in length, the wire has to emerge at varying angles, corresponding to that 60mm so perhaps about 70 degree variation.
-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net /
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wrote:

The wire in a standard 15W, 120V lamp is around .0008", which is smaller than 50 AWG. Though in that case the filament is wound from a "primary coil," where the .0008 wire is wound onto a larger steel core. In other words, the finished filament is a coiled coil. The smallest plain wire I can recall working with is around .005".
The problem I see with PTFE (besides the fact that it's a lousy wear material) is that it's difficult, if not impossible, to control the surface finish and radii at the inlet and outlet of a tiny hole because the PTFE is so soft. Too sharp a radius, or even a bump in the surface, will put a set in the wire.
It would be easy enough to see if your guide is a problem by comparing the straightness of a short piece of wire fresh off the spool with one that's been drawn thru the guide before winding onto the form.
--
Ned Simmons

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