The ONLY time I've used plastic bobbins successfully is with the New Home Memorycraft (now Janome) I bought in the early 1990s. My daughter has it now; I can't even remember the model#. When I went to get some more bobbins for her as a gift, the dealeer told me that they always use the plastic ones for the Janomes. I use only Bernina metal ones now in my Bernie 1031.
Jan in VA