Determining the Draft Between Taker-In and Cylinder, Cylinder and Doffer, and Feed Roller and Doffer in a Carding Machine

In textile manufacturing, the draft is a critical factor that influences the quality of the final yarn or sliver produced by the carding machine. The draft refers to the ratio between the input and output fiber mass, determining how much the fibers are elongated or stretched during the carding process. It directly affects fiber alignment, evenness, and quality, which are essential for producing high-quality yarn.

The carding process involves several stages, each playing a significant role in fiber opening, cleaning, and alignment. The key stages include the interaction between the taker-in, cylinder, doffer, and feed roller, where different drafts are applied. This article focuses on determining the draft between the taker-in and cylinder, cylinder and doffer, and feed roller and doffer to better understand how each draft contributes to fiber processing.

 

What is Draft in Carding?

In the context of carding, draft refers to the ratio of the speed at which a component moves to the speed of the subsequent component. For example, if the feed roller moves faster than the cylinder, the fibers will be stretched between the two components, resulting in a draft. Proper control of draft ensures uniformity and consistency in the carded sliver, and it helps in fiber alignment, removal of impurities, and the prevention of fiber breakage.

 

1. Draft Between Taker-in and Cylinder

The taker-in is the first component in the carding process that interacts with the fibers after they enter the machine. It is responsible for picking up the fiber from the feed section and feeding it onto the cylinder. The cylinder, a large rotating drum covered with wire teeth, works in coordination with the taker-in to open up the fibers further and begin the carding process.

Determining the Draft Between Taker-in and Cylinder:

• Role of Taker-in: The taker-in is designed to remove fiber tufts from the feed roller and transport them to the cylinder, where further fiber separation and alignment will occur.
• Draft Formula: The draft between the taker-in and cylinder can be calculated using the following formula:

Draft between Taker-in and Cylinder=Speed of CylinderSpeed of Taker-in\text{Draft between Taker-in and Cylinder} = \frac{\text{Speed of Cylinder}}{\text{Speed of Taker-in}}Draft between Taker-in and Cylinder=Speed of Taker-inSpeed of Cylinder​

Typically, the cylinder moves at a higher speed compared to the taker-in, which helps elongate the fiber. The speed of the cylinder is controlled to ensure effective opening and carding of fibers, while the taker-in operates at a slower speed to gently guide fibers to the cylinder.

• Example: If the cylinder rotates at 1200 rpm (revolutions per minute) and the taker-in rotates at 600 rpm, the draft between the taker-in and cylinder is:

1200600=2\frac{1200}{600} = 26001200​=2

This means that the fibers are being elongated by a factor of 2 as they move from the taker-in to the cylinder.

Impact of Draft Between Taker-in and Cylinder:

• Improved Fiber Opening: The draft between the taker-in and cylinder helps in opening the fiber tufts and preventing them from tangling.
• Preliminary Cleaning: As the fibers are transferred to the cylinder, the draft also assists in the removal of coarse impurities like dust and dirt.
• Fiber Stretching: The draft stretches the fibers, preparing them for the next stages of carding.

 

2. Draft Between Cylinder and Doffer

After the fibers have been carded on the cylinder, they need to be transferred to the doffer, which is responsible for removing the carded fibers from the cylinder and forming them into a web. The draft between the cylinder and doffer is crucial as it determines the final fiber alignment and the quality of the web that will be delivered as sliver.

Determining the Draft Between Cylinder and Doffer:

• Role of Cylinder and Doffer: The cylinder’s primary function is to open, separate, and align the fibers. The doffer, located after the cylinder, gently removes the fiber web from the cylinder without disturbing its alignment. The doffer operates at a slower speed than the cylinder to avoid disrupting the formed web.
• Draft Formula: The draft between the cylinder and doffer can be calculated similarly to other drafts:

Draft between Cylinder and Doffer=Speed of CylinderSpeed of Doffer\text{Draft between Cylinder and Doffer} = \frac{\text{Speed of Cylinder}}{\text{Speed of Doffer}}Draft between Cylinder and Doffer=Speed of DofferSpeed of Cylinder​

Typically, the cylinder moves faster than the doffer to ensure that fibers are drawn off the cylinder without damaging their alignment. The exact speed ratio depends on the type of fibers being processed and the machine settings.

• Example: If the cylinder rotates at 1200 rpm and the doffer rotates at 300 rpm, the draft between the cylinder and doffer is:

1200300=4\frac{1200}{300} = 43001200​=4

This means the fibers are being elongated by a factor of 4 as they move from the cylinder to the doffer.

Impact of Draft Between Cylinder and Doffer:

• Smooth Web Formation: The draft between the cylinder and doffer ensures that the fibers are removed gently from the cylinder, forming a uniform web.
• Prevention of Fiber Breakage: A controlled draft ensures that the fibers are not over-stretched, which can lead to breakage and unevenness in the web.
• Quality Control: The right draft between the cylinder and doffer helps maintain the quality of the fiber alignment, ensuring that the sliver produced is consistent and of high quality.

 

3. Draft Between Feed Roller and Doffer

The draft between the feed roller and doffer determines the overall fiber flow through the carding machine. The feed roller is responsible for delivering the fibers into the taker-in, while the doffer removes the fiber web from the cylinder and forms the sliver.

Determining the Draft Between Feed Roller and Doffer:

• Role of Feed Roller and Doffer: The feed roller supplies the fibers to the carding machine, while the doffer removes the processed fibers from the cylinder. The draft between these components is essential to regulate the fiber input rate and ensure an even flow through the machine.
• Draft Formula: The draft between the feed roller and doffer can be calculated by considering the speeds of both components:

Draft between Feed Roller and Doffer=Speed of DofferSpeed of Feed Roller\text{Draft between Feed Roller and Doffer} = \frac{\text{Speed of Doffer}}{\text{Speed of Feed Roller}}Draft between Feed Roller and Doffer=Speed of Feed RollerSpeed of Doffer​

In most carding machines, the feed roller moves at a slower speed compared to the doffer. The feed roller’s speed controls the input of fibers, while the doffer’s speed influences the overall sliver production rate.

• Example: If the feed roller moves at 400 rpm and the doffer moves at 1000 rpm, the draft between the feed roller and doffer is:

1000400=2.5\frac{1000}{400} = 2.54001000​=2.5

This indicates that the fibers are stretched by a factor of 2.5 as they pass through the machine from the feed roller to the doffer.

Impact of Draft Between Feed Roller and Doffer:

• Fiber Consistency: The draft between the feed roller and doffer helps maintain a steady fiber input and ensures that the carding process occurs at a consistent rate, reducing the risk of sliver unevenness.
• Sliver Thickness: This draft influences the final thickness of the sliver by controlling how much fiber is drawn out from the cylinder to the doffer.
• Sliver Quality: By carefully controlling the draft between the feed roller and doffer, manufacturers can ensure that the sliver produced has minimal variations in fiber density and quality.

 

Conclusion

Draft is a critical factor in the carding process, directly influencing the fiber's alignment, quality, and evenness in the final sliver. The drafts between the taker-in and cylinder, cylinder and doffer, and feed roller and doffer all play distinct roles in fiber processing. By understanding and controlling these drafts, textile manufacturers can achieve optimal fiber opening, cleaning, and alignment, ensuring high-quality yarn production.

Each draft needs to be carefully calibrated to suit the type of fiber being processed and the desired final product. Operators must monitor the speed ratios between the different components and adjust settings to ensure smooth machine operation, consistent sliver formation, and minimal waste or fiber damage. By mastering these drafts, carding machine operators can enhance the efficiency of the entire spinning process, leading to better productivity and superior product quality.