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from the Automation List department...
Torque mode or dancer mode?
Continuous process industries, DCS questions. topic
Posted by Anish Kumar on 30 October, 2007 - 1:32 am
I work in a cable factory. Here we have payoffs for paying off cable for each process. Payoffs are huge structures where a drum (bobbin) is hung and rotated so that cable can be unwound for the next process.
I have observed that for certain types of cables they use "torque mode" and for certain other types of cable they use "dancer mode" for paying off. Can anybody explain what's the difference between the two modes?


Posted by Brian Beal on 31 October, 2007 - 12:32 am
They work in different ways. Torque mode is typically just a constant drag on the drum. In other words, a fixed amount of torque is used to resist the turning of the drum. If the cable were disconnected from the drum, it would tend to wind the cable back onto the drum. The problem with this setup is that the torque setting to produce a certain tension changes as the diameter of the drum changes while it it payed off.

Dancer mode uses a sensor on the cable to essentially measure cable sag. Either torque or speed of the drum is automatically adjusted to keep that same tension.


Posted by markinnh on 31 October, 2007 - 12:35 am
Hello,

Dancer mode uses a "dancer" sheeve or set of sheeves that maintains tension on the wire with the use of an input regulated by a pot that moves when the sheeves go up and down... Torque mode usually employs the use of amperage on the capstan (or pulling) motor(s) to slow or speed up the take ups and payoffs. Are you using Fincor drives with the master control reference board?


Posted by Bill Schwarz on 31 October, 2007 - 12:29 am
They are different methods of cable tension control. Torque mode involves tension control by regulating payoff reel load current. Dancer mode would involve the use of a dancer roll mechanism, in which the physical position of a tensioning roller is regulated in order to control cable tension. Modern drive systems utilizing motor torque regulation typically provide better tension control than dancer systems. Maybe your newer process lines employ the torque method, and the older lines utilize dancer systems?

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