Objective: Apply the seam, stitch, and finishing standards that paying customers and retailers expect, and configure the Janome MC6650 to produce them consistently.
When you move from hobby sewing to selling, your work is judged against conventions buyers quietly assume. The most important is seam allowance: home sewing patterns in the US standardize on 5/8 inch (1.5 cm) for garments, while bags, quilts, and craft goods commonly use 1/4 inch or 1/2 inch. Pick the convention your product category uses and stay consistent across every piece, because inconsistency shows as puckered or uneven seams. Stitch length matters too: 2.5 mm is the accepted default for general construction, 3.0-3.5 mm for topstitching and heavier fabric, and shorter (1.5-2.0 mm) for curves and stress points. Every seam should be secured; customers return items whose seams unravel, so backstitch or use a lock stitch at the start and end of each line. Raw edges inside a product are a visible quality signal: retailers expect finished edges, achieved by zigzag, a three-step zigzag, pinking, French seams, or serged-look overcast stitches. Topstitching should be straight and evenly offset (commonly 1/8 or 1/4 inch from the edge). On the MC6650 these standards map to concrete settings: the needle-plate etched guide lines mark 1/4, 3/8, 5/8 inch for consistent allowances; the machine lets you set stitch length numerically so you can lock in 2.5 mm; the auto lock-stitch/reverse button secures seam ends; and built-in overcasting stitches with the overcast foot finish edges cleanly. Meeting these conventions is what lets a customer trust a handmade item at a premium price.
Example: You are making zippered pouches to sell. Convention for bags is a 1/2 inch seam allowance and a 3.0 mm topstitch. On the MC6650 you select straight stitch, set stitch length to 2.5 mm for construction seams, and align the fabric edge to the 1/2 inch guide line on the needle plate. You press the lock/reverse button at the start and end of each seam so nothing unravels. You then finish the interior raw edges with the overcast stitch and overcast foot. For the visible topstitching around the zipper, you switch stitch length to 3.0 mm and guide the presser foot edge along the zipper tape for an even 1/4 inch line. The result looks and holds up like a retail product.
Try it: Take two fabric scraps and sew one test seam to meet selling standards on your MC6650: set stitch length to 2.5 mm, align the edge to the 1/2 inch needle-plate guide, lock-stitch at both ends, then overcast the raw edges. On a second pair, add a topstitch at 3.0 mm an even 1/4 inch from the folded edge. Compare the two seams and note which settings gave the straightest, most consistent, retail-ready result.