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Old 16th Feb 2021, 1:50 pm   #4
Join Date: May 2005
Location: Adelaide, South Australia
Posts: 265
Default Re: DIY Transformer Bobbin

Slots are for the connections to the windings and the ribs between slots are for stiffening most of it is only around 1.75 - 2.0mm thick so I assumed it would need stiffening, the rib running across the width is for stiffening and also to increase surface contact area for the adhesive. Winding a transformer the old way with just a tube and margins you need to take a lot more care, I was making bobbins cut from fibreglass sheet I had left over from making turret boards, 6 pieces are needed 4 for the tube and the two end cheeks - they all lock together like a child's toy, it works quite well, but you need to be quite precise with the cuts - within 0.5mm or so otherwise the bobbin won't hold itself together, so it can be time consuming, marking it out cutting it and finally file a bit and trial fit - too tight? file some more etc.

I held off buying a 3D printer for a long time - I didn't think it would get much use but since buying I've found many things I can make/fabricate. Mounting the bobbin on the winder has always been a PIA, they are all different sized rectangles, I have always used a piece of wood cut to just the right size for a tight fit into the bobbin and drilled a hole through the middle, once again you need to be reasonably precise, if you get the hole slightly off, the bobbin may wobble - makes it hard to wind right up to the edge of the bobbin cheek. It is not real clear but if you look at the first photo top right, next to the bell end is a small square 3D printed piece with a hole through the middle, I printed two they fit precisely into the bobbin tube - hole is perfectly central, a groove across the hole takes a driving dog that is fitted on the spindle.
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