Web201.42d Center-Surface Winder – Gap Mode
***201.42d – Center-Surface Winder – Gap Mode
05 Slides Duration 04.56 v 15.08.03
201.42d.01 – Title Slide
Welcome to Web-Handling. My name is Dave Roisum. In this clip, we clarify two uses of the gap mode and how each would have a different torque strategy for the roller just upstream of the windup.
201.42d.02 – The Traditional Gap Mode
The purpose of a gap winder was covered in in great detail Web101. In short, it is to provide the most wrinkle resistant winding mode by using several tricks and tools. Of course, we have to give up the tightening benefits of a nip and may quite possibly be speed limited on wide smooth products such as most film grades.
However, in that class we often did not have time to explain what to do with a center-surface winder when it is put into gap mode as opposed to a pure gap winder. In other words, what do we do with the motor attached to the roller. You can’t, or at least shouldn’t, merely turn it off.
201.42d.03 – No Load Motor Torque
Recall from the drive section of Web101 the concept of no load motor torque. It is the torque required on the motor so that no tension change is seen on the web going over that point. The value of the torque the sum of motor and roller drag and other sources of friction, but most especially of the gearbox that is used as a speed reducer for the motor. All good drive engineers should know how to find out the amount of torque that is required to match web speed versus machine speed, but with no web present, and program that curve into the drive. That curve may need to be retuned occasionally, especially as the gearbox breaks in. When you take the nip off, that torque is what should be applied to the motor. If done correctly, the tension read by the load cells upstream would be very close to the tension going into the winding roll. If there were no torque applied to that roller, the large drag would cause a very large tension rise meaning that the roll was wound at a much higher, but unknown level of tension. To this we also add inertia compensation as was discussed in the web and winding schools.
201.42d.04 – The Super Loose Mode
In the two day web handling class we showed how the TNT’s can be adjusted so that the wound roll could be made anywhere in a range of tight to loose. In the two day Winding class of Web101 we described how the center-surface winder motor torque split can be adjusted so that the wound roll could be made anywhere in a range of extra tight to extra loose. In the last clip introduced thesuper loose mode, even more loose than a surface or centerwinder can obtain. However, we didn’t explain how to run the motor.
In this and all other modes, the winding roll motor is in load cell tension control. In this mode the roller motor will be run in torque, or better yet, tension difference mode. The distinction here is merely the properly display units as the motor cares not what you call its effort, so you might as well use proper web units of tension. The motor will be run at increasing levels of tension difference until the wound roll is loose enough or the web entering it is too loose. The confusing thing about this mode is that any changes in the upstream load cell tension settings will directly affect web and winding tightness in that span. This mode, however useful it may be, violates a best principle drive design guideline of not putting a motor, or any other large source of torque, between the load cell and the motor it talks too.
201.42d.05 – Questions?
Thank you so very much for watching this module in my plant practical video clips. If you have questions, you may want to replay this clip series. If the material still doesn’t make sense then perhaps my web or winding school might help give you the required background. Of course, I always welcome comments, suggestions and questions and try to respond within one day to each and every one.