Flyback SMPS transformer winding manufacturing document

[treez]

Hello,
Our transformer winding company have told us that they will simply wind all turns the same way round the bobbin, from the "starting pin" that we specify, to the "terminating pin" that we specify.

This is not what I am used to.

Other winders that I have worked with will wind the turn whichever way round the bobbin that results in the correct phasing of the coil with respect to other coils. -We provided a diagram showing which pins were to be "dots".

Has anyone ever heard of this practice of "winding all turns the same way round the bobbin"....even when such a practice is not actually requested by our winding specification, and when so doing does not result in the correct phasing of the coils?

 

[BradtheRad]

Speculating wildly here (having no experience with this)...

Is it possible the company was once obliging to all customers? But they recently had a mishap with some customer, and he came back saying 'These transformers you did for me? They have a winding going in the wrong direction. Someone ignored the dots.'

So they had to unwind and rewind 500 transformers?

And now they have a new policy: 'same direction, no exceptions'?

 

[D.A.(Tony)Stewart]

If you could find a video of how large scale multi unit coil winders work at high speed , you might understand why they don't want to reverse winding direction.

Their request makes sense to me.

 

[Orson Cart]

Yes, for high speed, high volume manufacturing, reversing the direction of the bobbin is a big no-no.

Even for low-med volume hand wound, the incidence of "getting it wrong" goes up quite a bit with a reversal, better to swap the start and finish pins unless you can find a manufacturer who will tolerate your winding oddities

 

[treez]

Thanks, though this spec doesn't say anything about winding all turns in the same direction...

Pages 18-20 shows a transformer spec (offline flyback)
https://ac-dc.power.com/sites/default/files/PDFFiles/der243.pdf

The thing is you have to turn the bobbin round to wind the secondary after winding the primary, so you are saying you have to consider the machine rotation and conform to that with the starting and finishing pins of all coils?