Question

In cotton spinning, at the ring frame, the shore hardness of front top roller is normally

• A. Higher than that of back roller
• B. Higher than that of middle roller
• C. Lesser than that of back roller
• D. Equal to that of back roller

Hint:

In a ring frame drafting system, the front top roller is generally softer than the back and middle top rollers. This is to ensure good fiber grip and drafting.

Answer 1

The Correct Option is C

Step 1: Ring Frame Drafting System: The ring frame uses a drafting system (typically a 3-over-3 or 4-over-4 roller system) to attenuate the roving (reduce its linear density) before twisting it into yarn. Each pair of rollers (top and bottom) runs at a progressively higher speed.
Step 2: Top Roller Hardness: The top rollers are typically covered with a softer, synthetic rubber material (cots). The bottom rollers are usually made of steel. The hardness of the top roller covering is measured using a Shore durometer scale.
Step 3: Hardness and Function: Front Top Roller: The front top roller needs to be softer (lower Shore hardness) to grip the fibers effectively and provide good drafting. Typical Shore hardness values are in the range of 60-85 Shore A. Middle and Back Top Rollers: The middle and back top rollers are usually harder than the front top roller. They help control the fiber flow but don't need the same level of grip. Their shore hardness will be higher than that of front roller. So, the hardness of front roller is lesser than the back roller.