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  • Coil winder: reciprocating linear spool feed for variable pitch on takeup bobbin

    Discussion in 'The main mechanical design forum' started by tomcatonnet99, Aug 20, 2014.

    1. tomcatonnet99

      tomcatonnet99 Member

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      I'm trying to make my own automatic coil winding machine.

      the problem I'm facing is that of even coil winds ( for a given diameter of magnet wire )

      whats the best setup for a variable pitch reciprocal linear feed to the takeup coil.. ( purely mechanical solution requried)

      thanks
       
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    3. tomcatonnet99

      tomcatonnet99 Member

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      further to the above:

      I'm thinking of a cam(pin) on the motor shaft which also bears the takeup bobbin.
      the pin cam I envisage turning a gear (A) one tooth for every turn of the bobbin, this gear to be meshed to another gear (B)
      A:B = 1:2
      if e.g I use 1mm diameter magnet wire for the coil and the coil being 10mm long ( i.e 10 turns per layer)

      I am now clueless as to whether I could use a scotch yolk (for the linear reciprocating action ) to control the guide that feeds wire to the bobbin from the stock spool.

      Also this is where I need tech advice:

      If I use gears A & B would I need something like a 100 pin teeth on A and 200 on B ?? ( so for every teeth turn on A, B moves half that ) ; that really makes it unworkable for me to fabricate such gears...

      how best should I get the yolk to move 1mm for every turn on the bobbin, upto 10mm in one direction and then 10mm in reverse direction (1mm at a time)??

      Also is there something I could do to give it a variable pitch ability whereby I don't need these gears for different diameter wires??
       
    4. Lochnagar

      Lochnagar Well-Known Member

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      Winches require the capability to take on different diameters of cable (i.e. different pitches), and to ensure it is spooled onto the drum properly. So to do this, they use what is called a levelwind bar, and a pawl. The levelwind bar allows for continuous spooling, and there is a dwell area at both ends that holds the pawl momentarily at each side of the drum, but it also causes the pawl to change direction too, by leading it onto the scroll going in the opposite direction.

      To deal with different diameters of cable, the pawl needs to traverse at different speeds, and to do this, the levelwind bar is driven at different rotational speeds by using different sprockets, with different numbers of teeth.

      Hope this helps.

      Scroll down to the bottom of this page to see the levelwind bar and pawl.

      http://www.alibaba.com/product-detail/Level-Winder-Shaft_326929018.html
       
    5. tomcatonnet99

      tomcatonnet99 Member

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      I'm sorry looking at the link below didn't give me any idea of how it works... besides for me to craft one such at home may be a bit difficult.


       
    6. tomcatonnet99

      tomcatonnet99 Member

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      coil is for actuator and needs even a square winding

      Further to the above I don't think a level bar & pawl will do an even and square winding for this application
       
    7. Lochnagar

      Lochnagar Well-Known Member

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      If you have a look at the video links below - you will see how the levelwind works, spooling wire onto a winch. The chain drive is on the left hand side - and is guarded - but it synchronizes the speed of the drum to the levelwind. As I said before if you want to change the diameter of the cable you are spooling onto the drum (a different pitch), then you just change the sprocket size to do this. It is a very common system on winches - and almost all the large winches I have come across - have this system. You say you can't make a levelwind at home - which I would accept - but you can get them machined at a machine shop.

      The only other system I have come across on industrial winches - is a variable speed motor - driving a standard lead screw - but that requires some sensors and electronics - which you said you didn't want.

      Hope this helps.

      https://www.youtube.com/watch?v=mjWDIU8TmEE
      https://www.youtube.com/watch?v=8gjTZyQIOJQ
       
    8. tomcatonnet99

      tomcatonnet99 Member

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      Appreciate your help, but for my application of the coil which is for use in a micro actuator and hence needs to be wound evenly and square as it needs to generate well defined magnetic poles at its either ends ( unlike a winch which though wrapped pretty evenly doesn't allow for the cable to be square in relation to the spool.. ( the levelwind bar tends to criss-cross across the width of the spool ( take up )

      cheers


       
      Last edited: Aug 22, 2014
    9. Lochnagar

      Lochnagar Well-Known Member

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      It would be good if you could post some pictures of the problem you have - so that everyone can see what the problem is. However, if you think about things - you are never going to get the wire 100% parallel to the ends - since the wire when spooled on the drum must have a pitch equal to the wire diameter, otherwise it will not spool. If the diameter of the drum is quite big and the wire diameter is small - then the angle will be close to zero degrees - but never zero degrees.

      Although I sense you don't like the levelwind bar - it will spool it accurately - and yes you could do 1mm wire by merely adjusting the gearing between the drum and the levelwind bar. So you do not need a 1mm pitch on the levelwind bar - it can be much coarser than that.

      As far as crane winches are concerned - they don't normally have any spooling device - because the length of the crane boom is so long - the so called fleet angle is therefore so small - it self spools. See article on self spooling below - and the definition of fleet angle.

      Hope this helps.

      http://www.bridon.com/usa/x/downloads/usatechnical/fleet angle.pdf
       
      Last edited: Aug 22, 2014
    10. tomcatonnet99

      tomcatonnet99 Member

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      Lochnagar, thanks so much for your help, truly appreciate; I guess I'll have to consider using a levelwindbar; the only reason I'm averse to it is I'd have to build one as my application requires only a 10mm or may be 5mm coil length to be wound and I don't think I'd find a levelwind bar small enough like about 4inches or less ? I'd really have to make one... Are you able to take a look at this
      io1JL1U7kUs (rotary to linear reciprocal)

      How do I calculate the driven gear such that it makes the levelwindbar turn according to the pitch of the wire in use...
       
    11. Lochnagar

      Lochnagar Well-Known Member

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      O.K. The coils you are trying to produce are quite a bit shorter than I had initially envisaged - so the levelwind would not be the best way of doing this - because what you have got is tiny - to say the least. (However, you have maybe learnt something about winches and spooling that maybe of some use for some other project).:)

      So just looking back through your postings - you say you want to make this at home - which makes me think that you are only wanting to manufacture a small quantity?? If my assumption is correct - then if the wire diameter is 1mm - and the length of the coil is between 5 and 10mm - that means only 5 to 10 turns - which is begging the question of why not spool it manually??

      Whatever way you do this - you will need to have back tension on the wire supply - in order to keep it tight on the bar onto which you are spooling it. (When you are spooling a winch for the first time - putting new cable on the winch - you need to put back tension on the cable reel - which is normally done hydraulically - and the back tension is varied as each layer of cable goes on - so that the top layer does not cut into the layer below. In your case you will not need anything so elaborate).

      I have had a look at the video link you posted - but that is giving you a fraction of one linear translation for one rotational turn - whereas you need you need one full linear translation (10mm) for 10 rotational turns. However, more to the point - you would not make that piece of equipment with the "normal" tools you would have in a "normal" garage??

      It would be good to have some more feedback on this.
       

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