Surface Winder... I have searched first!

[HJTRBO]

Hi all,

I am rebuilding a circa 1970's twin surface winder for light gauge plastic film. The old motors were of the eddy current variety.
I have purchased load cells, AC motor and Weg CFW11 vector drive. I am going to use the drives inbuilt surface winder application as it looks after taper tension and has sub tension alarms etc. However I have one question with regards to the application.

(1.1kW 6 pole motors. 2 x Weg CFW11 vecter drives. 2 pairs of 2 x 25kg radial load cells. 150N desired web tension. 60m/min max line speed. Web width 1.5m. Gauge (calliper) 50 micron.)

I have traced through the program and it appears WEG's method is trim the master line speed reference with the output of the PID loop (PID out limits set to to -2 to 20%) (These are the default values). I have a concern that if I left the default values then if we had an upstream wrap around the winder would continue to wind at a speed of -2% of line speed. Obviously the web would snap.

Would I adjust the lower PID limit to -100%?
or, would I be better served using a window comparator looking at over tension to make coarse adjustments of the line speed reference?

The application inside the drive is written in ladder and is not OEM locked so if needed I have the power to program additional logic to alter the drives original application.

(By the way I am merely the plant sparky so no extreme terminology please.)

 

[Manglemender]

Are you sure this is a surface winder?

Surface winders usually have a driven drum - often PU coated onto which rewinding rolls are pressed without any centre drive. The amount of wound in tension is generally governed by the overspeed of the drum (0.2 - 0.3%) and the amount of force which is pressing the rewound roll onto the winding drum.

Centre winders work by means of a rewind motor that delivers torque to the centre of the rewinding roll. They may also have a contact or layon roller to squeeze out air but this wouldn't be driven on a centre winder.

A third hybrid variant exists called a Centre-Surface winder which, as the name implys, combines both methodologies and so has an over-driven winding drum and a rewind motor for centre torque.

You mentioned that the original machine has an eddy current type arrangement. Would that be an eddy current coupling connected to a motor or individual eddy current clutches (not powered) for rewinding rolls? The required controls are quite different.

You mention that you have load cells and that you want to use them for closed loop control. To acheive good tension control using load cells and a drive in speed control requires a high bandwidth; you may find it easier to give the drive an overspeed signal and control the torque limit - it will be more tollerant of disturbances. A 1% speed error is an infinite tension error but a 1% torque error will be a small tension error.

Just a few things to think about.

Nick

 

[HJTRBO]

This is a surface winder. The existing drums were driven by eddy current motors (All components inside one motor housing and a belt drive via a 1:10 gearbox to the winding drum). They had a 30V 10A variable DC supply adjusted via a panel mounted pot to adjust torque.
I know from past experience that I can wind very well in speed mode (as I rebuilt one last year using the same components I just purchased for this job) however I just wanted to be a little more in line with an OEM style of functionality. I'm sure many in house Sparky's here can relate to that way of thinking.
I need the PID trim to be kept narrow to ensure close control 99.8% of the time, however it's just the over tension when there is a line fault (eg wrap around upstream) that I want the drive to be able to also deal with without breaking the web.

 

[rdrast]

First of all, if you are trying to prevent a web break due to an upstream problem that results in the web coming to a sudden stop, give it up. Unless this is extremely tiny, there will be far too much inertia on the winding roll to stop it instantly.

Second is a question, you said this is a two drum surface winder, but aren't clear on the actual number of drive motors... Is each drum driven independently? If so, it is typical to run only the master drum in speed mode, and the slave drum as a torque follower, where the torque split varies as the diameter changes. For non-extensible webs I've used as much as 90/10 (Master/Slave) at start, and 10/90 (Master Slave) at the end. Extensible webs can run in a narrower range, like 35/55 or so depending on the material.

 

[HJTRBO]

The attached image is off the net but it is close to what I have.