Secondary wire breaks

Hello, we run copper wire on single, tandem and multiwire machines with inline annealers. we have a problem with minor wire breaks that seem to occur somewhere in the annealer compartment, but as the machine slows to a stop, we get secondary breaks in the drawbox itself. this is usually at mid string, with the wire having a burned appearance (as if annealed) with the break being tensile. sometimes even if it isnt broken already, the wire will be so soft that it stretches and breaks during restring.

we would like to eliminate this problem if possible, or at least understand why it is happenning.

thank you

Hi there,

I am afraid that your question is far too general and philosophic to answer specifically.

All I can tell you is that if a short length of copper wire is very soft inside the drawing machine, it has been annealed by frictional heat between the the wire and the capstan (Slippage with inadequate lubricant between the surfaces but not to be confused with the designed slip in a drawing machine which you can learn about here - See www.stewart-hay.com/pshslip.htm ).

Drawing machines are inexact in the way they operate and are set up. (The number of wraps on the capstans, the angle of the wire into the dies and so on.) Generally, a satisfactory running condition is found once and that becomes the standard for that machine in that factory.

Likewise, the surface of annealer bands must be smooth because by design, the surface speed of each band is slightly faster than the wire speed. That means the wire slips on each band.

Generally, the annealer is mechanically tied to the drawing machine so that the annealer properly tracks the drawing machine during start up, run and shut down. The take up is a separate machine but it is normally dancer controlled and is a slave to the rest of the line. The power for annealing shuts off before the wire line speed becomes so slow that the wire burns off and thus when the line stops, the annealer is strung with hard wire.

I know this does not precisely answer your query but it will give you insight into the operation of these machines when it comes to the occasional wire break during the shutdown of the machine.

You might want to discuss the problem with your foreman and have your process engineers revisit the machine in an attempt to reduce the wire breakage on shutdown.

Sincerely,

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

It is certainly because of more annealing during slowdown. As Mr. Peter said annealer shoud shuts off after slow down. This will avoid overheating during slowdown, but you need to remove some wire from top as it is hard wire. If you still face this problem, I suggest you to check annealer belts. Slipage in annealer belts can cause this problem.