Fabric moves through your sewing machine by the pinch and pull effect created by the combination of feed dogs and presser foot. It is like picking up a piece of paper between your thumb and finger. The pressure on the presser foot must be adequate to grab the top of the fabric while the feed dogs lift and pull from beneath. Many machines preset the presser foot pressure. If adjustment is needed it must be done by changing the position of the brackets on the presser bar assembly. However, some machines empower the user to increase or decrease the pressure by simply turning a knob. Above you see the adjustment knob. Turn it to the right to increase the pressure. Turn it to the left to decrease it.