How to Choose the Right Cams for Circular Knitting Machine

In the context of circular knitting machines, the cam plays a critical role in controlling the movement and operation of needles and sinkers, which directly affects the quality and style of the knitted fabric. Here's an in-depth look at the key aspects to consider when selecting a cam for a circular knitting machine:

1. Trigonometric Curve Matching

The design of the cam’s trigonometric curve is essential because it determines the motion profile of the needles and sinkers, influencing the type and quality of knitted fabric produced.

Fabric Requirements: Different fabrics require distinct motion profiles. For instance, fine fabrics might need gentle curves for smooth needle movements, while thicker fabrics might require steeper angles to handle the yarn effectively.

Style and Emphasis: Designers often aim for specific fabric characteristics such as elasticity, texture, or pattern. The cam curve should align with these goals to ensure the desired outcome in the final product. The exact trigonometric profile will vary based on the intended fabric properties and machine capabilities.

2. Material and Heat Treatment

The material composition and heat treatment of the cam are crucial for its performance and longevity, especially given the high-speed and high-friction conditions it operates under.

Material Selection: GB Cr12MoV is commonly used due to its excellent hardenability, wear resistance, and minimal distortion during quenching. This steel is an alloy tool steel with good performance characteristics for high-stress applications like cams.

Heat Treatment: Proper quenching is critical. The target hardness for cams is typically HRC 63.5 ± 1. This hardness range ensures that the cam is tough enough to resist wear and deformation while still being able to absorb the impact stresses encountered during operation. Overly hard cams can become brittle and prone to cracking, while softer cams may wear out too quickly.

3. Surface Roughness

The surface finish of the cam is directly related to its operational efficiency and lifespan. The smoother the surface, the better it will perform in a high-speed environment with minimal wear and friction.

Roughness (Ra): The surface roughness of the cam should generally be lower than 0.8 µm. A low roughness value minimizes friction and wear between the cam and the needle butts or sinkers.

Impact of Poor Roughness:

High roughness can lead to several issues, including:

Needle Butt Wear: Excessive roughness can cause accelerated wear on the needle butts, leading to frequent replacements and potential machine downtime.

Needle Hitting: Rough cam surfaces can cause the needles to move erratically, resulting in knitting defects.

Cam Seat Overheating: Increased friction due to rough surfaces can generate excess heat, potentially leading to cam deformation and further operational problems.

Conclusion

Selecting the right cam for a circular knitting machine involves careful consideration of the trigonometric curve to match fabric requirements, choosing appropriate materials and heat treatment processes to ensure durability and performance, and achieving a precise surface finish to minimize friction and wear. Each of these factors plays a critical role in ensuring the efficient operation of the machine and the quality of the knitted fabric. Ensuring that these aspects are optimally aligned will help in producing high-quality fabrics and maintaining the longevity of the machine components.