[retailer]

I believe there are forum members that diy their own transformers from time to time, finding the lams can be an issue, one source is to reuse lams from a scrap transformer and if you do find a suitable sized lams then the lack of a bobbin can be another issue. Winding without a bobbin is do-able, I've done quite a few myself just for the experience but you do really need a coil winder with auto traverse. An acquaintance came to me the other day and wanted 2 matching PP output transformers - he had 2 sets of lams and bell ends but no bobbins, feeling lazy and not wanting to wind without a bobbin I thought of my 3D printer and came up with a bobbin fabricated from 3 pieces - a central square tube and two identical end cheeks. Design time was around 2-3 hrs and print time is around 4.5 hrs, once cleaned up some epoxy glue was used to fit the bits together, a perfect fit, once the glue had set I just needed to file away 2 sections of the central tube to allow the laminations to seat against the bobbin end cheek. I could have designed the central tube so eliminate this step but I wasn't sure how well the part would stick to the printer bed with only 2 small strips 1.5mm wide contacting the bed.
I used PLA which all I have at present it is not great as far as temp goes, around 55-60C being the limit, but we figured an output transformer shouldn't get that hot, the output transformers in my my workshop SE stereo amp get barely warm to the touch, I'll get some ABS which a better as far as temperature goes for any future transformer projects.