What kind of actuator/control?

[Alfninux]

Hi everyone,
I would like to realise simple mechanism in order to make smaller coils of optical fibre starting from a bigger coil.
The idea is to use two bearings in order to facilitate the rotation of the two coils. The problem is that I don't want to actuate only the little rising coil because it would stress too much the optical fibre. So basically, I would like to make the bigger coil rotate at a constant angular speed, so that the optical fibre unrolls at a constant rate, while to adjust the angular speed of the smaller coil in order to avoid either tensioning of the optical fibre or excess of uncoiled optical fibre. Therefore, I would like to control a DC motor placed in the small coil so that when the fiber is in tension (higher load torque) it decreases the angular speed to "wait" for the other motor rotating at a constant speed, while when the load torque is under a certain treshold, it increase the angular velocity until the fiber is again in tension.

I don't know if I've been clear.

Thank you

 

[jraef]

Classic “winder” application. But to implement it you need to decide if you want to do it with motors on each spool with the pay-out operating at a constant speed and the take-up operating at a constant torque, or have just one motor on the take-up with speed control some other form of continuous tension control such as mechanical braking or what’s called a “dancer loop” in the pay-out. There are companies that specialize in this and given that you are working with optical fiber that may be easily deformed, this may be beyond the skill set of a novice unless you can afford to accept a learning curve of trial and error.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[Compositepro]

This is a very common process:

https://www.google.com/search?client=firefox-b-1-d&q=tension+control+for+rewinding+fiber

Tension control is only one aspect. How do you want the spool to look? You can do a level wind or way wind, precision wind or random wind.

https://www.google.com/search?client=firefox-b-1-d&q=fiber+spool+winding+methods

 

[Alfninux]

I don't care too much about the winding method. From a spool of several Km I need to realise small spools of about 100/200 m with an axial lenght of the spool of around 10 mm.

The question is: if I use two motors (one at a constant speed to the big pay-out spool and the other one at a constant torque in the small one) by controlling the torque of the second one, is it possible to get what I want (and so a self regulating angular speed of the secondo motor) in a amatorial level? The sensitivity of the motor is enough to detect the presence of a tensioned fiber in order to avoid any strain?
And if yes, which kind of micro-controller is recommended for these kind of applications?
Thank you all for your time.

 

[waross]

For the unwinding motor on the large reel you may run at a set speed or you may opt to speed it up as the diameter reduces.
You can use the position of the dancer roll to control the speed of the takeup motor.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[crshears]

How much flexing can optical fibre take? Seems to me every sheave throughout, including those on the dancer, must be sized to maintain a comfortably greater radius than whatever the flexure limit is...

How often will you be replicating this?

Can the fibre be supplied by the manufacturer in the lengths you need? I'd be concerned about voiding the warranty in this type of roll-your-own application...

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[waross]

How much tension can the fiber withstand?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Alfninux]

Minimum bending radius 35mm. Regarding the maximum strenght, it could withstand enough to be rolled in the small spool with a single motor just by dragging it. The problem is that this affects some particular property of the fiber. That's why I would like to build a DIY machine able to unwind and wind the fiber autonomously without : 1) stretching too much the fiber, 2) uncoiled fiber from the big spool due to possible slow winding speed of the small spool