Objective: Combine corners, curves, and bulk management into one controlled sewing pass so you can produce saleable items with crisp, professional edges.
Real products rarely are straight lines. A placemat, pouch, or tote panel forces you to change direction at corners, follow curves, and sew through multiple layers at once. Three MC6650 features make this manageable. First, the needle up/down button (set it to 'down') locks the needle in the fabric so you can lift the presser foot and pivot without the fabric shifting. For an outside corner, stitch to one seam-allowance width from the edge, stop with needle down, lift the foot, rotate the fabric 90 degrees, lower the foot, and continue. For an inside (notched) corner, clip into the corner nearly to the stitch line first so the fabric can open and lie flat as you pivot. Second, use the knee lift (the free-hand system lever at the front right) to raise the foot without taking your hands off the fabric, which keeps curves smooth because you can nudge the fabric continuously. Third, when crossing thick intersections such as where a binding overlaps, reduce speed with the slider, and if the foot rides up on the step, use the black 'button' on the left of the foot or place a folded scrap (hump jumper) under the back of the foot to keep it level. Lower stitch speed and a slightly longer stitch length (around 3.0) handle bulk better than tiny stitches, which bunch. Adjust presser foot pressure lower for thick quilted layers so feed dogs aren't fighting a jammed foot. Go slowly and let the needle-down pivots do the precision work.
Try it: Cut two 8"x8" fabric squares and one 8"x8" piece of batting; layer them (right sides out) to simulate a quilted placemat. Set the MC6650 to straight stitch, length 3.0, needle-down, speed slider to about half. Topstitch 1/4" from the edge all the way around: at each corner, stop with needle down 1/4" from both edges, lift the foot with the knee lift, pivot 90 degrees, lower, and continue. On one side, create an inside notch by cutting a small V into the edge, then pivot through it after clipping to the stitch line. If the foot rides up over the thick corner, pause and level it with a folded scrap before continuing. Inspect that all four corners are square and the stitch line stays a consistent 1/4".