Is it really the bobbin thread that is globbing? Check closely. Usually it is the upper thread accumulating under the fabric.
If it is in fact the bobbin thread, then the bobbin case is not threaded correctly, the bobbin case tension needs adjustment, or it is broken and needs replacement. There are web sites and YouTube videos that show how to adjust the bobbin case tension.
QUICK FIXES: Remove all the thread from the machine. Clean the area around the feed dogs and bobbin area. Oil as instructed in the owner's manual using ONLY fresh, good quality sewing machine oil (only 1-2 drops each spot). Install a brand new needle insuring it is installed correctly. Avoid using fuzzy, old, or bargain bin thread. Rethread: Be sure you raise the presser foot BEFORE threading the upper thread so it will seat properly in the tension disk--and check to make sure you are threading the machine correctly. Check that the upper tension is set properly (the factory standard is usually the halfway point between the high & low number on the selection). Test on a scrap of the fabric you wish to sew. Adjust the upper tension--either tighten to pull the upper thread toward the top of the fabric, or loosen to pull more upper thread down.
Here are some web sites that may help.
Sewing Machine Thread Bunching Up Here Why sewing machine birdnesting https://answers.yahoo.com/question/index?qid=20100303212248AAnRUQA 8 Tips to Fix Birdnesting in Embroidery Birds nest under the fabric big loops of thread top side looks good... http://www.marthastewart.com/1085057/common-sewing-machine-repair-tips
and here's another Hint that may be helpful:
https://www.youtube.com/watch?v=KDERq4I7l-Q
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This just started for me, can't seem to fix it. Machine worked like a dream before. Now the bottom thread gets all bunched up and never comes up.
I have the same problem, the thread got all caught up and pulled my fabric into the feeder thing and I managed to pull it out and I've cleaned the dust out and can see that the bobbin thing isn't moving like it should.
it worked previously but after I took it out to make more bobbin it wouldn't re thread. I have manually threaded it from the front to back and back to front but the thread comes out as soon as I begin sewing
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