Originally Posted by sentimentaljourney2974
Manufacturers strongly suggest to 'activate/magnetize your bobbin case' and never use plastic bobbins. Use metal bobbins only. If this is not done there will be bobbin issues eventually. My sewing machine repair person taught me this. Of course he may have cheated himself out of repair charges. One of my manuals states this as well. I learned this when plastic bobbins first came out and we were deciding which to use (metal or plastic). I know a metallurgist (metal engineer) and he said it makes perfect sense.
My old Pfaff only came with plastic bobbins. I had this problem also. I changed every tension I could with no improvement. Two repair shops and $200 later, still not fixed. One of the shops was the Pfaff dealer. I now have a Bernina. But even though I couldn't FMQ with the Pfaff, it still pieces like a dream with no pinning. I loved the IDF.