CHAPTER 6.0 ROVING

Chapter 6.0: Roving

Roving Overview

  • Roving also known as:

    • Speedframe

    • Flyframe

  • Products include:

    • Roving Strand

    • Rover

Important Parts of the Roving Machine

  • Components include:

    • Drafting Rollers:

      • Can turn faster than roving frames.

    • Spindle

    • Flyer

    • Bobbin

    • Presser Arm

Need for the Roving Process

Importance of Roving

  • Why Roving?

    • Thickness of Slivers: 20,000 to 40,000 individual fibers versus 100 fibers in yarn.

    • Draft ratio required can range from 200-400 times.

Drafting Limitations

  • Current Roller Drafting Arrangement:

    • Limits drafting to about 40.

    • Roving allows drafting step by step with drafts ranging from 5 to 22.

Process Characteristics

Condition of Drawn Slivers

  • Issues with Slivers:

    • Hairy, creating fly issues.

    • No twist, leading to low strength.

Storage Challenges

  • Cans of drawn slivers take excessive space at the ring spinning creel.

    • E.g., 1000 spindles require 1000 cans.

Functions of the Speedframe

Main Objectives

  1. Drafting:

    • Reduce thickness of drawn slivers to achieve required fineness.

  2. Twisting:

    • Insert minimal twist for strength.

  3. Laying:

    • Wrap strands in parallel layers on the bobbin.

  4. Winding:

    • Wind strand onto bobbin at controlled speed.

  5. Building:

    • Control length of each layer with bobbin rail movement.

Roving Machine Operation

Principle of Operation

  • Input:

    • Drawn slivers from cans fed into roller drafting arrangement.

    • Drafted strands emerge from delivery roller and into flyer.

Drafting and Twisting

  • Twist Insertion:

    • Minimal twist added via rotation of the flyer during drafting.

  • Flyer speed higher than bobbin speed ensures winding.

Parts and Functions

The Flyer

  • Purpose:

    • Imparts twist and guides strand to bobbin.

    • Made from steel or light alloy; can rotate up to 1600 rpm.

The Presser Arm

  • Function:

    • Guides the roving strand, wraps it around 2-3 times for tension control.

Drafting System in Speedframe

Drafting System Types

  • Main types used:

    • 3/3 and 4/4 drafting systems.

    • 4/4 for higher draft applications (better fiber control).

Aprons and Fiber Control

  • Aprons made of leather or synthetic rubber, about 1mm thick.

  • Essential for guiding and controlling fibers during drafting.

Condensers in Drafting

  • Purpose is to bring fibers together to prevent spreading.

  • Spreading can cause:

    • Uneven roving strands.

    • High fly liberation.

Pressure Systems

  • Pressure applied by:

    • Spring weighting (common)

    • Pneumatic weighting.

  • Ranges from 100-300 Newtons per roller.

Twisting in Roving

Need for Twist

  • To give strength for:

    • Transportation and unwinding.

    • Enduring high drafting forces during processes.

Principle of Twist Insertion

  • Twist inserted between flyer and delivery roller, coiling fibers together.

  • Flyer speed and delivery speed dictate twist per unit length.

Importance of Managing Twist Level

High Twist Effects

  • Higher strand breakages lead to production losses.

Low Twist Effects

  • False drafts and breaks during winding and unwinding lead to increased fly liberation.

Winding Process

Speed Management

  • Flyer speed is constant; bobbin speeds must be adjusted as diameter increases.

Types of Winding

  • Flyer Leading:

    • Flyer speed higher than bobbin.

  • Bobbin Leading:

    • Bobbin speed higher, more common in modern machines.

The Building Motion

Functions of Building

  • Adjusts bobbin rail to accommodate increasing bobbin diameter.

  • Ensures tapered ends on the bobbin.