The Heart and Adjustment Knob of Circular Knitting Machines

The Heart and Adjustment Knob of Circular Knitting Machines

We often say the “heart” of a circular knitting machine. In China, the word “heart” is used more commonly because the main part of the machine looks like the human heart—the power organ of blood circulation. Coincidentally, this system is also located at the center of the machine.

When explaining to foreign customers, this situation may happen: If you say, “The heart of the circular knitting machine is very important,” a foreign engineer might ask, “Do you mean the main motor? The cylinder? The cam?”

“Do you mean the main motor?” — This is a common mistake. But the heart is not the power system that provides electricity. It is the knitting system or knitting mechanism. “the main motor” means the power motor.

“The cylinder? The cam?” — Not complete. Sometimes people even say the “cylinder-cam system” represents the heart. Because the heart mainly refers to the knitting system, and the cylinder and cams are the most core executing parts of this system.

Often, once it is clearly explained, the problem is easy to solve.

A circular knitting machine is essentially a frame supporting a knitting center. This knitting center does the main knitting work. Other parts only assist, including power supply, yarn feeding device feeding yarn into the knitting center, fabric take-down during knitting, dust removal, etc. This main knitting center is what we usually call the “heart.”

1. What is the “heart” of a circular knitting machine?

In knitting industry terms, the “heart” of a circular knitting machine usually refers to its “knitting mechanism” ，which specifically includes:

Cylinder (or Dial): The rotating part that holds the needles;

Needles: The core components that complete the loop formation;

Cams (also called Triangles): Metal blocks that control the needle movement path (up, down, loop formation);

Sinkers: Assist in holding, knocking-in, and knock-over;

Cam Carrier (also called Saddle): The frame that fixes and supports the cams.

Why is it called the “heart”? Because the entire loop formation process—clearing, yarn feeding, knocking-in, closing, knock-over—is all completed here. It directly determines fabric structure, quality, and efficiency, just like the human heart drives blood circulation.

2. What is the “adjustment knob”?

“Adjustment knob” is the common Chinese circular knitting machine industry name for the knit cam height adjustment knob (also called the stitch depth adjustment knob). In English, it is often called:

Stitch Depth Adjuster

Knit Cam Height Adjuster

Loop Length Regulator

It is usually a precision knob with scale marks, installed on the cam carrier, used to finely adjust the height position of the cams, thus controlling: the needle knock-down depth (i.e., stitch depth—the depth to which the needle descends during loop formation. Throughout the knitting cycle, the needle undergoes a significant downward stroke; the magnitude of this descent is controlled by adjusting the height of the knit cam, and this adjustment is precisely performed using the adjustment knob); and finally affecting loop length, which in turn determines fabric GSM, density (CPI/WPI), and hand feel.

For example, a 0.5-turn counterclockwise adjustment of the knob—typically increasing the dial setting from 6.0 to 6.5 on standard machines and thereby increasing stitch depth—may decrease fabric GSM by 8–12 g/m².

Since counterclockwise rotation loosens the knob and decreases GSM, clockwise rotation tightens it and increases GSM. Remember the mnemonic: “Loose–loose–low, tight–tight–high,” where “low” and “high” refer to fabric weight (GSM). The second “loose” and “tight” refer to stitch depth.

Clockwise tightening and counterclockwise loosening refer to the common configuration of approximately 90% of adjustment knobs on the market; the remaining 10% may be reversed.

Relationship between the two:

The adjustment knob is a key adjusting part of the “heart” (knitting mechanism), belonging to a subsystem. By adjusting cam position, the adjustment knob directly affects the most core action in the “heart”—the geometric parameters of the loop formation process. Experienced workers often say: “Adjust the adjustment knob well, and you bring the heart to life.”

Analogy with the human body:

Needles + cam system = heart — the core that performs loop formation, determines fabric structure and quality, and is the “life center” of knitting logic.

Main motor = muscles — provides power for the whole machine to run, driving the cylinder to rotate at high speed.

Inverter/servo control system = nervous system — precisely controls speed, start/stop, and coordination of all parts, enabling smart response and stable operation.

Yarn feeding system = lungs — continuously and steadily feeds yarn into the knitting zone, like breathing to maintain the “lifeline” of production.

Take-down and winding system = blood circulation — smoothly pulls out and winds the knitted fabric, keeping tension balanced and ensuring smooth “metabolism.”

Frame + bearing system = skeleton — supports the whole machine structure, ensuring high-precision alignment and long-term running stability.

One-sentence summary of the workflow: Skeleton supports — muscles drive — nerves command — lungs supply yarn — heart knits fabric — blood carries away the finished product.

Skeleton supports: The frame fixes the machine to the ground. It must be stable and ensure high-precision alignment.

Muscles drive: The main motor is powered, drives the main shaft, and rotates the cylinder (+ dial).

Nerves command: The inverter and servo system precisely control everything.

Lungs supply yarn: The yarn feeding system feeds yarn. Yarn passes through tensioners and yarn guides into the knitting zone.

Heart knits fabric: Needles and cams complete the knitting task. The cylinder rotates, cams control needle paths, needles form loops from yarn, sinkers assist in holding and knocking-in—this is the core knitting action.

Blood carries away finished product: The take-down and winding system pulls out and winds the fabric.

This process repeats continuously and runs efficiently. To ensure every step is accurate, stable, and correct, adjustments must be made according to the required product. Fabric quality is decided by the heart, not the main motor. The main motor only provides power. Only by properly adjusting the adjustment knob can the heart operate in accordance with the requirements pertaining to the adjustment knob and fulfill the functions that the knob is designed to control. Other requirements need other adjustments, such as:

Take-down roller force affects fabric density, GSM stability, and winding quality. It usually works with a winding device. The winding device is another system, responsible for rolling the long fabric into manageable rolls.

Cylinder speed is decided by the main motor + inverter or servo drive. The operator sets the target speed on the control panel, for example, 30 RPM (30 Revs Per Minute, i.e., 30 Revolutions Per Minute). The inverter adjusts output frequency, then controls motor speed. The main motor drives the main shaft via belt/direct drive, which decides cylinder rotation. Higher speed means higher output, but may cause more wear, greater yarn tension fluctuation, and easier yarn breakage. If speed is increased without adjusting take-down, the fabric will pile up, wrinkle, or even jam.

Fabric tension adjustment.

Tension source: Yarn tension.

Adjustment method: Adjust tensioners (Hysteresis Tensioner / Electronic Tensioner) on each feed.

Stage: Before loop formation, affects knocking-in stability.

Tension source: Take-down tension.

Adjustment method: Adjust take-down roller pressure or speed.

Stage: After loop formation, controls fabric pulling force.

Tension source: Winding tension.

Adjustment method: Set center winding torque or surface winding roller pressure.

Stage: Winding stage, affects roll edge neatness.

Tension source: Sinker force.

Adjustment method: Adjust sinker cam height.

Stage: During loop formation, assists in holding old loops.

The adjustment knob is just one main type of adjustment. It controls loop geometry (How loops are formed. Even though the needles and cams are already installed and fixed—thereby fixing certain physical parameters—the adjustment knob effectively controls fabric tightness (i.e., stitch length and GSM) by finely adjusting the vertical height of the knit cam to alter stitch depth. This is the core method by which circular knitting machines produce fabrics with different GSMs on the same machine model.)There may be other adjustments needed, collectively called other adjusters.

The scale range of the adjustment knob is not necessarily fixed from 0–10. Common ranges are 0–10 or 0–20, depending on machine brand, cam structure, and manufacturer design.

For example, when knitting 100% cotton 32S single jersey, if measured GSM is 195 g/m² but customer requires 180±5 g/m², change the original setting from 6.0 to 6.5. Loop length increases from about 2.8 mm to 3.0 mm, and GSM drops to 182 g/m².

Increasing the adjustment knob from 6.0 to 6.5 increases loop depth and loop length. With take-down tension unchanged: Course per inch (CPI) decreases; Wales per inch (WPI) decreases; Overall GSM (g/m²) decreases; Fabric hand feel becomes softer, elasticity slightly increases, and breathability improves.

The adjustment knob adjusts some data to control the system in one aspect. To achieve a specific function, it must be set to a specific value. The more complex the required function, the more practical the adjustment knob needs to be. There may even be smart adjustment knobs that enable automatic micro-adjustment within seconds. Traditional manual mechanical adjustment usually requires stopping the machine for large adjustments.

Real case example

Scenario: Knitting 32S cotton single jersey, GSM too high (195 g/m²), target around 180 g/m².

1. Stop machine or jog at low speed;

2. Use a 12mm wrench to loosen the lock nut;

3. Turn the adjustment knob counterclockwise by hand from scale 6.0 to 6.5;

4. Retighten the lock nut (feel "snug but not forced");

5. Start machine, knit 5 meters, check GSM, CPI, and fabric uniformity.

In short, the adjustment knob controls loop depth by adjusting cam height, directly determining loop length. With take-down tension, machine gauge, and yarn count unchanged, raising the adjustment knob lifts the cam, increases loop length, and reduces fabric GSM. But the adjustment knob generally cannot change machine gauge (must replace cylinder), yarn count (must change yarn), take-down tension (must adjust take-down roller), or cam angle (It refers to the cam track (or cam groove) profile) (must replace the whole cam).

As part of the heart, only with good quality can the product be good. Most modern products meet these conditions. But for a fairly complex large precision machine like a circular knitting machine, every part must meet standards. With workers being careful and thoughtful, the machine runs smoothly and produces satisfactory fabric. With continuous investment and deep understanding over time, skills keep improving, and the path becomes clearer.

Operating a circular knitting machine also requires years of accumulation to become skilled. The requirement for talent is not low, especially for young talent. Not everyone can fully handle it. Every industry has its requirements and complexity, and the circular knitting industry is no exception. Only those deep in the industry know the hard work and challenges. Future operation may become more computerized. While efficiency and accuracy increase, personal skill requirements may lower. In this transition period, doing well today is the only way to welcome the future smoothly.