Draw Frame

Draw Frame is the machine where the slivers are doubled or combined, blended & mixed, leveled, and attenuated transiently through a series of pairs of rollers. In the drafting arrangement, each pair of rollers move faster than the prior one.

There are two types of draw frame

1.    Draw frame -1/Pre-comb drawing/Breaker draw frame

2.    Draw frame -2/Post-comb drawing/Finisher draw frame

The machine has multiple sets of rollers arranged in pairs, with the fiber sliver passing through each pair to stretch and elongate the fibers. The rollers are adjusted to provide the desired level of drafting, which determines the final thickness and evenness of the yarn.

In addition to doubling or combining slivers, the draw frame machine can also be used for other purposes, such as:

  1. Blending: The machine can be used to blend different types of fibers to create a uniform mixture for spinning.
  2. Leveling: The machine can level out the variation in the thickness and density of the fiber sliver, ensuring that the final yarn is even and consistent.
  3. Attenuation: The machine can attenuate the fiber sliver to reduce its thickness, making it suitable for spinning finer yarns.

Drawing= Drafting + Doubling

Doubling refers to the process of combining two or more strands of fiber, such as slivers, roving, or yarns, into a single strand. This can be done to improve the strength, consistency, or other properties of the resulting yarn. Doubling can involve more than two units, and the resulting strand is typically thicker than the individual units that were combined.

Drafting, on the other hand, refers to the process of reducing the thickness or linear density of the input material, such as lap, sliver, or roving, by stretching or elongating it through a series of rollers. This process can improve the evenness and quality of the resulting yarn, as well as control its thickness and strength.

Drawing, as you mentioned, involves both combining and attenuating the slivers simultaneously. This process is typically carried out in a draw frame machine, which uses a series of rollers to draft the fiber slivers and combine them into a single strand. Drawing can also involve blending different types of fibers to achieve specific properties in the resulting yarn.

It’s worth noting that doubling and drafting can be done separately, but combining them in the drawing process can help to achieve a more consistent and high-quality yarn.

Working principle of draw-frame:

  1. Feeding of Material: Four to eight card or draw frame sliver can (1) are fed underneath of creel frame. These slivers are then creel and fed to the drafting arrangement (3) through a feed roller pair (2), which is located above each, can (1) to enable the feeding in a controlled manner.
  2. Drafting of Material: The slivers then run through the drafting arrangement (3) where a range of draft of 4 to 12 as required is applied. Here straightening, parallelization, and attenuation operation take place.
  3. Sliver formation: leaving the drafting arrangement a package of fiber called web, lacking significant cohesion between fibers is produced. In this condition, the fibers do not form a transportable intermediate product in order to avoid the disintegration of the web. The intermediate transportable product sliver is produced by condensing the web immediately after leaving the drafting arrangement.
  4. Delivery of material: This sliver is then guided through a tube (4) via a passage (6) of the tube [coiler] gear into a can (7), in which it must be laid in clean coils with optimal utilization of the space in the can. To enable the can to take up as much material as possible, the sliver is compressed by passing it through calendaring rollers (or discs) or grooved discs (5).

Elements of Drafting Arrangement

The primary elements of the draw frame’s drafting arrangement are stated below-

1. Bottom roller

2. Top roller

3. Top roller pressure

1. Bottom Roller

Bottom rollers are made of steel driven from the main gear transmission. The bottom rollers are the following type:

a.   Axial flutes

b.   Spiral flutes

c.   Knurled flutes

2. Top Roller

Top rollers are not positively driven. They are driven with the surface contact of the bottom roller. Top rollers are coated with synthetic rubber. The hardness of the rubber should be adjusted carefully. Hardness is specified in terms of degree shore.

  • Soft                    60-70 shore
  • Medium            70-90 o shore
  • Hard                  above 90 o shore

3. Top Roller Pressure

To clamp the fibers, the top rollers must be forced at a high pressure towards the bottom rollers. The pressure can be generated by following means.

  • Dead weight (Now obsolete)
  • Spring loaded (The most usual form)
  • Hydraulic system (Rarely used)
  • Pneumatic system (Rieter)
  • Magnetic (Saco Lowell)

Types of Drafting Arrangements

  • Conventional 4-o-4 roller drafting system.
  • 3-0-4 roller drafting system.
  • 3-0-3 roller drafting system with pressure bars.
  • 4-0-3 roller drafting system with pressure bars.
  • 5-0-4 roller drafting system

Drafting Wave

When the sliver is passed through drawing rollers the short fibers causes a succession of an alternate thick and thin place due to the irregular movement. This thick and thin place gives a wave in the surface of sliver. This wave is called drafting wave.

The amount of drafting wave depends on:

  • The amount of draft.
  • The roller setting.
  • The doubling.
  • The bulk of the material
  • Degree of orientation
  • The character of fiber.

Effect of Doubling and Drafting On Sliver Irregularity

In the spinning preparation, correction of these variations is normally undertaken by equalizing or leveling or averaging effect through doubling at the draw frame. There is only a small possibility that all thin places, and separately, all thick places of slivers will coincide during doubling. Rather, they will tend to be distributed and hence to compensate each other.

1. What are the main differences between breaker draw frame and finisher draw frame?

The main difference between a brekaer draw frame (pre-comb draw frame)  and a finisher draw frame (post-comb draw frame) is- normally breaker draw does not possess the autoleveller device where as finisher draw holds it to reduce the mass variation of slivers. There are no other such differences between the draws.

2. Why autoleveller is used only in breaker draw frame but not in finisher draw frame?

Since autoleveller is a costly device and the finisher draw frame or post-comb draw frame is the last machine to improve the sliver quality hence yarn qaulity, that is why autoleveller is used only in finisher draw frame.

3. Why doubling and drafting is done altogether?

It has been observed that due to doubling the irregularities in sliver are reduced and mass variation is average out due to multiple number of slivers. On the other hand, drafting increases the irregularities in lengthwise throughout the end product. That is why to compensate these irregularities due to attenuating, drafting and doubling are done altogether

References:

  1. http://www.definetextile.com/2014/03/draw-frame.html
  2. http://www.rieter.com/en/textile/short-staple-yarn/fiber-preparation/c-60-card/
  3. http://www.indiantextilejournal.com/articles/FAdetails.asp?id=2010
  4. http://textileeducationtips.blogspot.com/2013/02/what-is-draw-frame-objects-of-draw.html

Leave a Reply

Your email address will not be published. Required fields are marked *