Nothing is more frustrating than sitting down to sew a project only to find your fabric bunching as the machine hums along. Most of the time, bunching problems can be solved by making adjustments to the tension, thread or pressure of your machine.
Thread tension is the most common cause of bunching. Using a scrap of your material, adjust the tension dial up and down, testing as you go, to find the correct tension for the fabric.
The amount of pressure the presser foot puts on the fabric can also cause bunching. Using the small screw on the back of the foot shank, adjust the foot a tad higher.
The small teeth under the presser foot can also cause bunching if they are too high. Check your sewing machine manual for instructions on lowering the feed height.
Sometimes bunching is caused by a malfunction in the route the thread takes to the needle. Remove both the spool and the bobbin and re-thread both.
Pulling the fabric too tightly or quickly as you guide it can also cause bunching. Keep your fingers light and rather than pushing or pulling the fabric, guide it along as you sew.