Circular vs Trunk Knitting: Setup and Output Differences

How Circular Knitting Works

A circular knitting machine operates around a fixed ring of needles, typically mounted in a circular bed that remains stationary. The yarns enter from a feed system positioned at the top of the machine, and the needles draw loops of yarn onto the fabric. As the machine cycles, these loops interlock to form a tube of fabric that moves upward in a continuous loop. The machine does not cut the fabric during the knit. The tube grows until the operator stops the machine, then the fabric is taken off as a roll or a cut piece.

The main parts are the needle ring, the fabric accumulation channel, the yarn feeders, and the take-up carriage. The needle count determines the machine width and fabric gauge. A small machine may have a few hundred needles, while a large machine can have thousands. The more needles, the wider the tube and the higher the speed. The spacing between the needles, or gauge, dictates the density of the knit. A higher gauge creates a finer, tighter fabric, while a lower gauge produces a heavier, looser knit.

Because the fabric moves in a closed loop, the machine can run for hours without stopping. The operator monitors yarn tension, needle movement, and fabric alignment. If a needle breaks, the machine may stop automatically to prevent a run. This automatic stop is a critical safety feature, as a broken needle can snag the yarn and pull the entire fabric through the machine.

The take-up carriage, often called the fabric lift, moves the fabric tube up and down the machine. This movement ensures that the fabric does not pile up or stretch unevenly. The tension of the fabric is controlled by the take-up system and the weight of the fabric itself. The operator adjusts the take-up speed to match the needle cycling rate.

How Trunk Knitting Works

A trunk knitting machine lays fabric in straight rows. The needles are arranged in a line or a shallow curve, and the machine moves the fabric across the bed. Yarn feeds over the needles, and the fabric is formed as a flat or slightly curved sheet. The machine stops at a set length, and the fabric is cut or folded.

The trunk machine uses a cutting blade or a manual cut at the end of each length. The fabric may be accumulated on a table or a conveyor before cutting. The setup is more open than a circular machine. The operator has access to the full width of the fabric, which helps with inspection and quality checks.

The main parts are the needle row, the yarn feeders, the accumulation table, the cutting mechanism, and the take-up system. The machine width determines the fabric width. The speed is set by the yarn feed and the needle movement.

Trunk knitting machines often use a reciprocating carriage that moves back and forth over the needle bed. This carriage carries the yarn feeders and the fabric take-up system. The needles in the bed rise and fall to form the loops, similar to the circular machine, but the fabric is laid out flat rather than forming a tube.

The cutting mechanism is a key feature of trunk machines. It can be a rotary blade, a straight blade, or a manual scissors. The blade cuts the fabric at a precise length, ensuring that each piece is the same size. The operator sets the cut length on the machine’s control panel, and the machine stops automatically when the length is reached.

Setup Differences

Circular machines take up less floor space. The machine footprint is roughly the diameter of the needle ring plus the take-up area. The operator works around the ring. Yarn feeds are arranged around the top of the machine, and the fabric tube comes out through a channel.

Trunk machines take more floor space. The footprint includes the needle row, the accumulation table, and the cutting area. The operator works in front of the machine. Yarn feeds are arranged along the top, and the fabric moves across the table before cutting.

The setup also differs in how yarn is fed. Circular machines feed yarns from spools or cones into the feeders around the ring. Trunk machines feed yarns from spools or cones into the feeders along the needle row. Both systems need tension control, but the path and the number of feed points differ.

Circular machines often use a circular yarn holder or a cone rack that surrounds the machine. The yarns are fed into the feeders through a series of guides that maintain tension. The number of yarn feeders is usually equal to the number of yarns used in the fabric. For example, a two-color fabric requires two feeders per needle.

Trunk machines use a linear yarn holder or a cone rack positioned above the needle row. The yarns are fed into the feeders through guides that span the width of the machine. The number of feeders is determined by the number of yarns and the pattern of the fabric. A simple single-color fabric requires one feeder, while a complex multi-color pattern may require many feeders.

Option	Best for	Limitations
Circular knitting machine	High-speed tubular fabric, hosiery, body garments	Cannot produce straight-cut fabric without secondary cutting; tube width limits fabric width
Trunk knitting machine	Straight-cut fabric, panels, garments needing cut edges	Lower speed than circular; cutting stops reduce output per hour
Large circular machine	Wide tubular fabric, high-volume production	Higher capital cost; more complex setup; larger floor space than small circular
Small trunk machine	Limited fabric widths, short runs, prototype work	Lower output; less suitable for high-volume straight fabric

Output Differences

Circular machines produce fabric in a continuous tube. The output is measured in meters per hour. The speed depends on the needle count, yarn weight, and machine speed. A large circular machine can produce many meters of fabric in an hour. The fabric is tubular, so the width is set by the needle ring.

Trunk machines produce fabric in lengths. The output is measured in meters per hour or pieces per hour. The speed is lower because the machine stops to cut. The width is set by the needle row. The output is straight fabric, which is useful for garments that need a defined cut edge.

The difference in output is not only speed. It is also fabric shape. Circular fabric is a tube. Trunk fabric is a sheet. The garment design determines which shape is useful. Hosiery and body garments often use circular fabric. Some outerwear and panels use trunk fabric.

Circular machines have a high throughput because they run continuously. The fabric is produced without interruption, so the operator can focus on monitoring the machine rather than handling the fabric. The output is measured in meters of fabric per hour, and the speed can be adjusted to match the yarn type and the fabric weight.

Trunk machines have a lower throughput because they stop to cut the fabric. The cutting process takes time, and the fabric must be accumulated on the table before cutting. The output is measured in meters or pieces per hour, and the speed is affected by the cut length and the frequency of cuts.

When to Pick Circular Knitting

Pick a circular knitting machine when the garment or fabric is tubular. Hosiery, tights, socks, body garments, and some knitwear use circular fabric. The machine runs continuously, so the output is high. The setup is compact, and the operator can monitor the ring from multiple points.

Circular knitting is also useful for high-volume production. If the plant needs to produce a large quantity of tubular fabric, a circular machine is the better choice. The machine can run for long periods without stopping. The operator focuses on yarn tension, needle health, and fabric alignment.

The main limitation is fabric width. The tube width is set by the needle ring. If the garment needs a wider fabric, the machine must be larger or the fabric must be cut and sewn. Circular fabric does not have a natural cut edge, so the fabric must be cut for some garments.

Circular knitting is the standard for hosiery production. The tube of fabric is cut and sewn to make socks, tights, and stockings. The width of the tube is determined by the number of needles, and the length of the tube is determined by the time the machine runs. The operator stops the machine when the tube reaches the desired length, and the fabric is cut and finished.

For body garments such as shirts and tanks, circular knitting is also common. The fabric is produced as a tube and then cut and sewn into the garment shape. The tube width must be wide enough to cover the body, and the length must be long enough to cut the front and back panels.

When to Pick Trunk Knitting

Pick a trunk knitting machine when the garment or fabric is straight-cut. Panels, outerwear, some knitwear, and garments that need a defined cut edge use trunk fabric. The machine stops to cut, so the output is lower. The setup is open, and the operator has access to the full fabric width.

Trunk knitting is useful for short runs and prototype work. If the plant needs to produce a small quantity of straight fabric, a trunk machine is the better choice. The operator can inspect the fabric more easily and adjust the cut length.

The main limitation is speed. The cutting stops reduce the output per hour. If the plant needs high-volume straight fabric, a trunk machine may not be efficient. The operator must manage the accumulation table and the cutting mechanism.

Trunk knitting is often used for panels that are sewn into garments. For example, a sweater may have trunk-knitted front and back panels that are sewn together. The fabric is produced in straight pieces, and the edges are finished with a seam. The trunk machine allows the operator to control the width and length of each piece, which is useful for garments that require precise dimensions.

Trunk knitting is also used for outerwear such as jackets and coats. The fabric is produced in straight pieces, and the pieces are cut and sewn into the garment shape. The trunk machine provides the operator with easy access to the fabric, which helps with quality control and inspection.

How to Choose for Your Facility

Look at the garment design first. If the garment is tubular, choose circular. If the garment is straight-cut, choose trunk. Look at the order size. If the orders are large, choose a machine that can run continuously. If the orders are small, choose a machine that can stop and cut quickly.

Look at the floor space. Circular machines are more compact. Trunk machines need more space for the accumulation table and the cutting area. Look at the yarn feed. Circular machines feed yarns around the ring. Trunk machines feed yarns along the needle row. Both need tension control and yarn monitoring.

Look at the operator experience. Circular machines require the operator to monitor the ring and the tube. Trunk machines require the operator to monitor the fabric width and the cut length. Both types need training. The choice should match the plant’s production model and the operator’s skills.

The choice of machine also depends on the type of yarn used. Circular machines can handle many yarns, from fine hosiery yarns to heavier garment yarns. Trunk machines are also versatile, but they may have limitations with very heavy yarns due to the open setup.

The maintenance requirements differ between the two types. Circular machines have a more complex needle ring, which requires regular cleaning and lubrication. Trunk machines have a simpler needle row, but the cutting mechanism needs regular inspection and blade replacement.

The operator’s role is different in each case. In circular knitting, the operator focuses on the continuous flow of fabric and the health of the needle ring. In trunk knitting, the operator focuses on the accumulation of fabric and the precision of the cut. Both roles require attention to detail and a good understanding of the machine’s operation.