1. When picking, see if the machine head is bright, whether there is paint stripping and bumping, whether the plating layer of the needle board, push plate, panel, upper wheel, etc. is intact; whether the platen is straight, whether the paint is cracked or partially discolored; Whether the frame is broken, lacquered or twisted; whether the upper shaft and needle bar clearance meet the standard requirements.
Second, remove the belt, the board presses the presser foot, gently rotates the upper wheel, whether it runs freely, whether the needle moves up and down in the middle of the needle plate hole.
3. Whether the machine sound is soft when turning.
4. When trying to step on or sew, first test the seam with two layers of thin cloth to check whether the stitches are flat and even. Then use the original test seam to see if the length of the stitch can reach 3.6mm, there is a phenomenon that the seamless material does not go or the sound is not normal.
5. More specific tests should be attended by the sewing machine maintenance and security workers.