Seamless Knitting Machine

Overview

A seamless knitting machine is a small-diameter circular weft knitter that knits a whole garment, or most of one, as a single tube with no side seams. The cylinder is sized to the body, roughly the circumference of the waist or chest, so the tube comes off the machine already the shape and size of an item of underwear, shapewear, a sports top or a pair of leggings. Because the panel is not cut and sewn at the sides, the garment has no seam to chafe, less waste, and a smooth body-mapped fabric where different zones can be knit tighter, looser or with elastic to support and shape. Only the toe or the top edge is closed afterward, so labor and seam bulk drop sharply compared with cut-and-sew.

The machine knits on a rotating Needle Cylinder worked by a fixed Cam Box, adds rib and welts with a Dial and Transfer, presents yarns through a Yarn Feed, draws the tube down with the Takedown and Dispenser, turns under the Drive and Rotation, and is run by Control Electronics.

The needle cylinder

The Needle Cylinder is a steel Cylinder Body milled with vertical grooves called tricks, one per wale. Each trick holds a stack: a Cylinder Needle latch needle at the top, a Cylinder Jack that transmits cam motion below it, and a Selector Jack at the bottom whose butts the selection actuators act on. A body-size cylinder carries around four hundred needles. As the cylinder turns, each needle stack passes the fixed cams in turn, so rotation is what drives loop formation. A Retaining Ring holds the stacks in their tricks against the centrifugal pull of high-speed rotation.

Cam box and selection

The garment is shaped by what the cams and selectors do to each needle as it passes. The fixed Cam Box carries a Cam Ring with several Cam Block stations, one per feed. At each station a Raising Cam lifts the needle to clear its latch and take new yarn, and a Stitch Cam, set by a small motor, fixes how deep the needle pulls and therefore the stitch density. Ahead of the cams a Selection Actuator presses each selector jack to set knit, tuck or miss for that needle at that feed. Because selection is electronic and per needle, the machine can place a tighter zone, a mesh panel or a pattern anywhere on the tube simply from the program.

Dial and transfer

Above the cylinder sits the Dial and Transfer, a Dial Body disc with radial tricks holding horizontal Dial Needle needles. Worked by Dial Cam cams in time with the cylinder, the dial needles make rib structures and a stable tubular welt at the start of the garment so the edge does not curl. A Transfer Jack can hand loops between dial and cylinder, which is how the machine makes welts and shaped openings rather than just a plain tube.

Yarn feed and elastic

Body mapping needs many yarns available at every feed. Each feed has a bank of Feed Finger solenoid changers that swing a chosen yarn into the needle path, so color, fiber and density can change course by course. A Storage Feeder buffers each yarn so feed tension stays even, and a Tension Unit smooths surges. The support and shaping that seamless garments are known for comes from a Elastic Feeder that meters bare or covered elastane positively into the waistband and compression zones. A Stop Motion guards every yarn against breaks.

Takedown, drive and control

Inside the cylinder a Takedown Roller pair, helped by a Suction Tube that starts the tube with airflow, draws the fabric down at controlled tension from the Takedown Motor. When the garment is finished a Garment Dispenser releases and collects it. The Drive and Rotation turns the cylinder with a Servo Motor through a Ring Gear and Helical Gear Pair timing to the dial, with a Rotation Encoder reporting angle so selection and feed stay synchronized. The Control Electronics runs the garment program on an Microcontroller with Bare PCB selection drivers, Servo Drive amplifiers, a Power Supply and the Operator Panel panel.

Products, variants and use

Seamless machines dominate intimate apparel, shapewear, leggings and base-layer sportswear, where a smooth seam-free body and zoned support sell the garment. The same circular weft principle, in a much smaller diameter, is the sock and hosiery machine, which adds a toe-closing step. Larger body-size machines make tops and dresses. Across all of them the gain is the same: shaping, density and support are knit in from the program, so a finished garment needs only a toe or top seam to close, which cuts both labor and the seams that a wearer would feel. The machine sits on a Machine Base with a Yarn Creel holding the body, pattern and elastic cones and a Cylinder Oiler keeping the head lubricated.