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TOPIC: Magnet Wire Failing In PinHole Test

Re: Magnet Wire Failing In PinHole Test 5 years 9 months ago #267

You asked and I don't think I responded:
"Though just a small question there – Is it safe to run Copper and Aluminum wire on the same enameling machine? I know for wire drawing different set up is required. But what about the Enameling Machines ??"

the answer is yes and no. Typically people that have machines that run both aluminum and copper have a way of separating the first pass from the second and subsequent passes. This includes the enamel supply and return. Aluminum being soft is very easy to create dust and aluminum fines. If you do not separate the first pass what happens is the aluminum dust gets in the enamel and it appears to be a metalflake coating. The aluminum particals destroy your electrical properties and the wire fails. When you separate the first pass, the enamel with aluminum fines drains back to the tank and is filtered out. This problem is generally isolated to die ovens and the wire passing through a bath and sized by dies.
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Re: Magnet Wire Failing In PinHole Test 5 years 9 months ago #268

Dear Richard and Peter,

Back with updates.

The issue hasn't been fully resolved yet and still we are finding pin holes (salt water continuity test) and the issue has been tied to processing at the time of high humidity conditions.

Also the issue has surfaced with some other manufacturers which got me thinking as to what could be common between all the players.

My guess is that this problem is occurring because of presence of micro copper dust particles that stubbornly stick to the copper conductor and are not dislodged despite multiple wipes, pre-annealer, quenching bath and a hot air heater-blower.

We have installed a centrifuge for filtration of wire drawing lubricant and that has helped in filtering out dust ( which is mainly in form of paste probably due to mixing with the lubricant).

I am also of the opinion that the current domestic manufacturer of ETP copper rod is now generating a higher level of dust that before due to some change in their processes though I cannot quantify same. In any case it is outside my control.

My questions are :

1. How effective is a centrifuge filtration system versus a paper band filter ?
2. Can I install air wipes at the exit of the wire drawing machine. Will it help in dislodging the copper dust?

I am already in the process of installing a pre cleaning bath before the wires enter the pre annealer.

Your views and inputs as usual will be highly appreciated,

Thanks and regards,

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Re: Magnet Wire Failing In PinHole Test 5 years 9 months ago #269

CoolBlue: If other manufacturers are having a similar problem, I would look at what was common to both and that might be the insulating varnish supplier.

Over the years I used a variety of methods to clean bare wire before the pre-annealer. Which one used depends upon the size of the wire. One way is a piece of braided rope, cotton or other natural fiber and tie one end to a frame and then open the braid enough for the bare wire to get wrapped in the braid. You have to change the rope when it gets dirty. We have also made brackets that we can adjust pressure and then used 2 sanitary napkins with the wire passing between the pair. Other machines for finer wire, etc we used factory supplied wipes.

I really don't think that copper fines are causing the pin holes. Look under a microscope. Are you seeing copper flakes?

If you treat it like I have said for aluminum, separate the first pass so that any copper fines will be isolated to that section of the applicator.

Making good magnet wire can be challenging but I am certain that in these posting and others about magnet wire we have provided the answer. You just have to go to work and solve the problem. I would start with the enamel or varnish.

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Re: Magnet Wire Failing In PinHole Test 5 years 9 months ago #270

Boockmann GmbH manufactures the exact machine (Helicord) that Spectre07 mentions which wraps a cleaning thread around the wire as it runs and pulls it through. Their website is

Erik Macs
VP North American Machinery Sales
Fine International Corporation
148 Oak Street
Natick, MA 01760 USA
508-315-8200 fax: 615-658-1988
This email address is being protected from spambots. You need JavaScript enabled to view it.
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Re: Magnet Wire Failing In PinHole Test 5 years 9 months ago #271

Dear Spectre,

Thanks for the input. I have looked at the common factors and found.

The other companies are not necessarily using the same insulating enamels. In fact we have found the problem on wire processed on different machines and using different enamels as well.

Why I am zeroing in on the copper dust is that despite all the various cleaning devices just before the wire enters the oven we have installed felt pads and have found that even on these there is copper dust.

Now the problem is that once we have established that the copper wire is carrying the dust at that stage, oven the felt wipes are not enough to stop them because once they have made their space between the two layers of felt , further cleaning stops.

I know it is an intriguing problem, as between the three companies there is at least a century of enameling experience and still there has been no understanding of the probable cause.

Till now I have listed the things I know for sure as under :
1. The problem is latent IE it is not evident at the time of manufacture.

2. It is most probably not due to insulating enamel or the enameling process (some of the wires that fail have been processed on enameling machines have catalytic systems)

3.Apart from salt water continuity of covering defects, the problem does not manifest itself in any other low reading, IE the BDV (Breakdown Voltage) values, peel, adhesion, cut through heat shock etc are all found way above minimum required levels.

4. The drawn copper surface is very bright and shiny to the naked eye and under 10 x magnification is reasonably good and without any major indentations or marks

5. There is visual evidence of higher than usual generation of copper dust.

6. The problem is more acute during rainy season.
Awaiting your inputs,

Kind regards,
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Re: Magnet Wire Failing In PinHole Test 5 years 9 months ago #272

Dear Ranjan,

This note is not meant to be critical but rather a means of getting to the resolution of your technical issue.
1) If you are really sure that your issue is indeed a unquantified "higher than normal" amount of copper dust somehow attached to the surface of the copper wire, you had better go back to first principles of the drawing process itself because all of your mechanical surface cleaning devices at your ovens are not getting to the root cause of the problem. Further, blowing hot air on the surface of the wire is nothing more than a way to blow copper dust and other contaminants into the air and this could contaminate the outer surface of the just applied enamel before the wire enters the ovens.

2) Regardless of whether you have installed a centrifuge for the filtration of wire drawing lubricant or not, the reality is that essentially all copper wire has to some degree or another a thin film of dried drawing lubricant on it and that there will be copper fines embedded in that film. Thus copper fines can always be found by using a wipe of hard white felt or some other form of clean wire wipe at the next downstream operation. (A weighted down, very hard white felt is commonly used to prevent felt fibers from being carried along with the wire.)

3) The copper dust on the wipe is always mixed with the dried drawing lubricant film in the form of a copper paste and there can be more or less dust on the wire by virtue of the health of your drawing fluid itself. This is something that I have experienced first hand at a very large data cable plant that really should have known better. In that case, and even with a new lubricant charge, the emulsifier in the drawing fluid had begun to break down and that lead to much more copper dust on the surface of the wire. The solution was to dump the whole system and start again but this time properly.

4) The whole game is therefore to minimize the amount of copper wire surface contamination to an acceptable level for your downstream process.

I have spent a fair amount of time in your country and my first suspicion is that your drawing fluids may not be as well managed as they should be.

5) The water for your drawing fluid is often trucked to a plant from a well somewhere in the region if not on site, so the start is to exclusively use deionized water as a base for your drawing fluids. Moreover the tanks must be completely cleaned out from the previous lubricant charge before creating and using a new drawing fluid.

6) After mixing up the new lubricant, there must be proper and tight management of your drawing fluid which means pH control, temperature control, % fat concentration monitoring, detergency, tramp oil contamination monitoring and so on. Long term data and graphical information should be available on your computer local area network for all to see and be aware of.

7) At the electric annealer, use deionized water with no lubricant in it. Moreover the air going to the air wipe should be clean and dry meaning desiccant drying medium and then high quality filtration at the annealer.

8) We cannot comment on the phenomenon of more problems during the rainy season because we do not know if you are referring to the perceived degree of copper dust on the surface of the conductor before enameling or the wire failure rate after enameling. In any event, don't use air wipes to blow copper dust off the surface of the wire.

9) Finally we recommend that you purchase WAI's "Nonferrous Wire Handbook, Vol. 3" from just as soon as you are able and use this 704 page handbook as your company's definitive reference book for drawing and drawing lubricant problems and issues.
We cannot solve your problem any more than that from the other side of the world because we cannot see what you see and it is very easy for you to overlook something which you might think is normal but we might see as critical if we were there. So, just as Spectre07 already said, "You just have to go to work and solve the problem."

Best regards
Peter J. Stewart-Hay
Stewart-Hay Associates
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