Objective: Inspect, stress-test, and finish your completed signature project so it meets a sellable, professional standard.
A finished seam is not the same as a finished product. Testing means deliberately pushing your item the way a real customer will: tug seams, open and close zippers twenty times, fill a bag to capacity, pull on straps, and flex fabric at stress points like corners and pocket openings. On the MC6650, weak spots usually come from un-backstitched seam ends, skipped bar-tacks at stress points, or tension that was slightly off. Fix them by re-securing: use the machine's lock-stitch button to tie off, or run a short zig-zag/bar-tack (narrow width, near-zero length) at handle bases, pocket corners, and zipper ends. Polishing is the visual layer that separates homemade from handmade-for-sale. It has four reliable moves: (1) clip every thread tail flush, including bobbin-side tails you can't see at a glance; (2) press every seam with steam, setting the stitch and sharpening edges and corners; (3) check topstitching for even distance from the edge, using the MC6650's seam guide or an edge-joining foot if it wandered; (4) finish raw internal edges so they won't fray in the wash, using an overcast stitch or a clean bound/French seam. Finally, run a quick quality-control checklist and write down what you changed, so your next unit is reproducible and consistent across orders.
Example: You made a zip pouch. Testing: you open/close the zipper rapidly 20 times and tug the pull hard; the zipper end lifts and threatens to pop. Fix: you drop the feed-dog-friendly bar-tack setting (zig-zag, width 4.0, length 0.4) and sew a 6mm bar-tack across each zipper end. Polishing: you clip four stray thread tails, steam-press the pouch flat pushing the seam allowances open, and notice your topstitch wandered to 4mm then 6mm from the edge. You re-sew a clean line at a consistent 3mm using the edge guide. The pouch now opens smoothly, lies flat, and has crisp even stitching.
Try it: Take your completed signature project and run this sequence: (1) Stress-test every functional part (seams, straps, closures, pockets) at least 15 repetitions or firm tugs, noting any weak point. (2) Reinforce each weak point with a backstitch lock or bar-tack on the MC6650. (3) Clip all thread tails flush on both sides. (4) Steam-press every seam and corner. (5) Inspect topstitching distance and re-sew any line that varies by more than 2mm. (6) Complete a 5-item QC checklist (seams secure / threads clipped / pressed / topstitch even / raw edges finished) and write one sentence per fix you made.