Problem in tandem line

Our tandem line has problem. If line running without plastic in die (only copper wire and extruder machines are stopped) line can run well. But when we close plastic valve, plastic flow to die to insulate copper wire after some minutes wire is broken. I checked everything but cannot find the reason of problem. Please help me to solve it

Hello there hoangaut and welcome to the Forums,

Unfortunately you are making this very difficult for us because you are not telling us very much information and we cannot see what you see.

- First we assume that you are discussing a tandem drawing insulating line for telephone wire or wire for data cable. If it is telephone wire, we assume the plastic insulation is polyethylene in one these configurations (solid, foam, foam-skin or skin-foam-skin.). If it is wire for data cable the insulation could be PVC or Tefzel.

- Second, if it is telephone wire, the wire size could be near 24 and 26 gage, say 0.4 mm and 0.5 mm, and if wire for data cable, it would be close to 24 gage or say 0.5 mm.

- Third, you have not told us the line speed you are talking about. (Tefzel say 7.66 meters/second with vacuum, PVC 20.5 meters/second, PE perhaps up to 37 meters per second).

- Fourth, you have not told us anything about the tooling. We presume you are using a new diamond nipple (tip) and that it has been changed to a new one so that you know that the diamond is not cracked or that the nipple is NOT partially plugged with copper dust and dirt.

- Fifth, you have not told us anything about the cleanliness of the wire coming out of the annealer. Is it very clean? Are you using a thin concentration of water soluble lubricant in the annealer? (We recommend clean, potable water.)

- Sixth, you have told us nothing about the history of the line. Has this machine been running successfully for years or is this a day one problem?

- Finally, we are not sure how the conductor is failing. Is it just a straight tension failure in the crosshead? Does it get slightly loose and burn off in the annealer? Or is it jammed in the tip (nipple) with copper dust and dirt?

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Now, saying all those things, if we assume:

- that this is 0.5 mm or smaller diameter copper,
- that the copper is very clean,
- that there is no lubricant in the annealer water,
- that this is not a day one problem,
- that the diamond nipple (tip) is new (absolutely clean) and in good shape (A properly orientated, uncracked diamond.),
- that the diameter of the diamond in your nipple (tip) has the proper clearance that you have used successfully for years,
- that the distance between the exit of the nipple (tip) and the die is the standard that you have been using successfully for years (fixed center cartridge of some sort that is in good shape and not damaged or worn.),
- that the wire is properly guided on center into the crosshead,
- that the insulated wire is exiting the crosshead horizontally and on center,
- that you haven't changed the design of the die (Angles and bearing length.)

Then at first look it would seem to have nothing to do with the crosshead and the insulation except for a one basic thing:

This is the tension on the wire begins to add at the exit of the last driven sheave (pulley) on the annealer. Thus every guide pulley, including those on say an induction preheater is adding tension (drag) to the wire. If for whatever the reason:

- there is more than normal tension going into the crosshead and,
- if the drag inside the nipple (tip) and the plastic fluid drag on the wire between the exit of the nipple and the exit of the die is right on the verge of breaking the conductor.

Then after a few minutes of running, perhaps the plastic cools a bit or the dust and dirt builds in the nipple a bit giving slightly more drag inside the crosshead and thus the wire breaks.

Everything counts in a high speed tandem drawing-insulating line and we suggest you carefully review your line. This is exactly why process documentation is so important if high volume production is to be consistently achieved.

This is all we can do with your limited information and being so far away.

Sincerely,

Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com

Many thanks for your reply. The web is very useful for helping people, It has made us all closer. Here is some information about my tandem line:

- Production : telephone wire with two layers foam - skin. 0,4 mm diameter copper

- Machine : Kobelco, normal working speed is 1600 mpm.

Last month, before stopped line, we changed the tip.

The tip was checked and we ran the line at 1600 mpm for 8 hours. Everything was good.

Some days ago, we restarted the line and met the problem. I checked everything, cleaned die and tip but didn't succeed.

With regard to with your ideas, I think the tension helper part of the preheater had a problem. I have a little experience with it so I can not check it is working properly.

Please help me with some information as how to check it.

Thanks

Hello Again,

First you need a hand held mechanical tension meter (Three wheel type) so that you can statistically build a tension profile of each wire type at various positions along the line at your standard operating speed. This confirms and standardizes your settings. This is most important between the annealer and entry to the extruder crosshead.

Contact Schmidt Control Instruments in Germany, www.tensionmeter.de/Ncontent/user/framel...modus=1&id_seite=101
They have a form to fill out for you to get the proper measuring model for your tandem drawing-insulating line. www.tensionmeter.de/Ncontent/user/framel...&id_seite=1132669151

Make sure you tell them about all the sizes of conductors and all the ODs of all the insulations you produce on this line along with the materials and line speeds.

Get their recommendation and buy the recommended instrument.

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An assist capstan to reduce tension in a telephone wire or data cable wire line is often a torque controlled non-positive device designed to have a surface speed slightly faster than the wire line speed and thus slip on the wire and reduce tension downstream of that capstan. (It can also be achieved with highly accurate speed controlled drives.) The capstan is usually a single wheel with a very smooth ceramic insert and the the bare conductor contacts somewhere between 270 and 330 degrees depending upon the manufacturer. The only way that you can truly tell if it is doing its job properly is to measure the conductor tension before and after the assist capstan at one particular setting. If you adjust the setting, you must take new readings.

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A tip can easily and quickly become plugged with a mixture of copper dust, residual lubricant and a small amount of dust and dirt. (I have seen dirty wire plug a tip in much less than 4 hours.) Thus conductor cleanliness is fundamental to achieving high volume production. The dirt packs very tightly into the tip before the diamond and the build-up can produce conductor drag without breakage. I have even seen the dirt behind the diamond make the diamond itself into a fulcrum and push the conductor off-center.

Diamond tips are not very easily cleaned. Many people try ultrasonics and solvents but there is no guarantee that the tip is actually clean and that the drag has been eliminated. Commonly they are just returned to the tooling supplier for evaluation, repair and or replacement. The diamond can also be cracked by impact with a foreign hard inclusion in in the wire.

Sincerely,

Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com