Motor torque calculation for Intermittent pull

[nitinp.gupta]

Hello,

I am working on selection of motor for intermittent wrapping steel strip on a reel, intermittent because system is equipped with a sensor which triggers motor after the strip reaches a certain level in the buffer box and then motor stops when the level of strip falls below another fixed level.

I think this calculation shall be based upon inertia of the reel. The system is symmetric, a reel weighing blank some 5kgs pulls the strip from a buffer box, the least diameter of reel being 300mm and fill it up to 800mm diameter. final weight somewhere around 60 KGs.

Additionally, to make appropriate tension to the reel an pneumatic tensioner is also provided which will act as resistance to the pull. and a gearbox (1:15) to be installed on the motor as well.

Please suggest how to do this calculation. key factors I think will be resistance of system (tensioner, bearing resistance etc.), inertia of the reel after it is filled to some level and start gaining weight.
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A separate (although linked to this system) question: operator also needs to turn this reel manually sometimes. In that case the resistance of the system should not be much that he can't turn the reel manually.

As far I could find, the most critical factor would be gearbox as while turning the reel, operator is actually applying torque at driven side of gearbox (worm type) which may need higher torque. please advice.

 

[Illmatic1]

For your first question, the calculation should take into account the total inertia of the reel, which increases as it is filled up with steel strip. You should also consider the amount of resistance that will be provided by the pneumatic tensioner, as well as any other resistances in the system such as bearing resistance and the torque required to turn the reel manually. You can use a torque calculation formula to estimate the torque required for manual operation, and then use this to determine the size of motor required to satisfy both manual and automated operations.For the second question, the most important factor would be the torque required to turn the reel manually. You should calculate the torque required to turn the reel by hand, and then use this to select an appropriate gearbox that can handle this torque. The gearbox should also be strong enough to handle the torque required for automated operation.