Introduction Overlock machine is a special purpose machine used for finishing edges and sometimes for seaming. It falls under the class 500. Stitch types in this class are formed with one or more groups of threads and have a general characteristics that loops from atleast one group of threads pass around the edge of the material.
Machine Terminology: • Bed: working surface. • Differential feed • Differential feed regulator • Feed dog • Handwheel • Knives • Dummy needle • Head
Lower looper • Needle bar • Presser bar lifter • Presser foot • Presser foot lifter • SPM • Spreader • Stitch length regulator • Table • Thread finger or stitch tongue • Upper looper • Width selection knob.
Basic features: • Generally called a serger in home sewing. • Makes a class 500 that trims, stitch and overcast seams as they sew. • Upto 1,500 stitches per minute. • Stitch length vary from 0-5mm. • Used to sew wide variety of items- from placemats to draperies and even sportswear. • Stitch is very elastic and can stretch upto 300%.
Decorative effects can be achieved using special threads in loopers. • In some, upper knife can be rotated up to disengage the cutting action. • Stitch can be made using 2,3,4, or 5 threads, depending on the no. of needles and loopers. • Seams sewn with a combination of conventional and overlock stitching can be used in a variety of fabrics and garment styles.
Two thread overlock: Stitch type 503. One needle and one looper. Best for finishing seam edges and allowances. Has little effect on fabric drape, and rarely causes a pressing imprint. Frequently used for serging edges on men’s slacks, lightweight fabrics or when using heavier decorative threads . Selecting an overlock machine:
Looper • Used when stitching active wear, elastic and lace. Also hems can be sewn. • Unsuitable for seaming, because does not hold plies securely, causing seam grim when stressed. • Can be adjusted to sew a rolled edge.
Three thread overlock: • Stitch type 504, most common overedge stitch. • Also called basic serging stitch. • One needle and two loopers. • Stitch looks the same on both sides (good for reversibles). • It has excellent stretch and recovery. • Has narrow bight(3-5mm). Stitch type 504
Upper looper Lower looper • Used for finishing edges as a narrow, decorative, rolled edge on napkins and scarves. • Also for seaming budget garments. • Most useful for sewing knits, wovens (not in areas that receive stress). • Can be used as a stable seam finish on loosely constructed, ravel prone fabrics.
Upper looper Lower looper • Four thread overlock: • It will stitch a chain stitch or a safety stitch as it stitches and overcasts seams. • Two needles and two loopers. • Can be converted to both two and three thread overlock. • All 4 threads are necessary to sew a serged seam.
Four thread overlock with safety stitch: • Suitable for sewing both woven and knits. • Can be used in areas that receive stress. • Suitable for sewing blouses, shirts, skirts, dresses, pants, lingerie, actionwear, swimwear, and even sleepwear.
Four thread overlock and chainstitch: • The left needle and the lower looper form a 2-thread chain stitch. • Suitable when sewing woven fabrics, even in area of stress. • Stitch does not stretch therefore not used in knitted garment. • Used when sewing shirts, blouses, skirts, pants, sleepwear, draperies. • Used when fitting garments, since stitches are easily removed. • Used when a wider seam allowance is desirable for strength (upholstery).
Upper looper Right lower looper Five thread overlock: • A 2-thread chain stitch combined with a 3-thread overlock. • 2 needles and 3 loopers. • The left needle and lower looper form a 2-thread chain stitch. • The seam is very durable, particularly for wovens. • Can sew rolled edges with either 2-thread or 3-thread stitch. • A very wide seam width is created when the chain is serged with 2 or 3 thread stitch. Left lower looper
Difference between portable and commercial overedge machine: • Portable (home serger) used in small workrooms and classrooms, commercial used in industries. • Portable is less expensive, more versatile, smaller, and easily serviced. • Commercial one is faster (Upto 8,500spm) than portable(1,500spm)overedge. • Commercial is permanently mounted on table, whereas portable is set on top of the table. • Differential feed ratios on commercial overedge have a greater range. • Commercial one has a knee lift, while portable does not.
Adopting oil forcing revolving device: • The new design assures fully lubrication of the needle bar & prevent it from oil leaking problem .
Thread trimming & suction automatically by air- pressure system. (OPTIONAL ATTACHMENT)
The new type upper threading structure: New design of the upper looper mechanism provides easier threading operation .Besides, the looper inserts from the front, whichmakes the replacing work simple & easy.
Disadvantages of overedge machines: • Can’t be used to attach patch pockets or for top stitching as it would trim along the seam line thus destroying the fabric. • High thread users. • Seams stitched must be pressed to one side rather than being pressed open and flat.