1. Introduction

 If different grade of same fibres are kept together, then it is called mixing. When different fibres of same or different grades are kept together, then it is called blending.

2. Points considered during Mixing and Blending
  • Similarity in fibre length
  • Strength of fibre
  • Similarity in color of fibre
  • Maturity of fibre
  • Similarity of fibre
  • Atmosphere in fineness of fibre
  • Skilled labour
  • Well equipped m/c to be used 

3. Object of Mixing/Blending
  1. Reduction of the cost of the final product through blend composition by mixing high quality fibre with low quality fibres.
  2. Blending influences the processing performance of the carding through control of nep level variation ,waste level variation and roving twist level variation.
  3. Control end breakages, includes processing performance.
  4. Blending influences the behaviour of dyeing and finishing through control of shrinkage variation variation, dyeing defects etc.
  5. It also influence tensile, tear strength, elasticity, abrasion resistance etc.
  6. It influence to increase lustre, appearance, cover, colour etc.
  7. It increases comfort, fabric touch, softness etc.

4. Various types of mixing

1)Volume Mixing-Here, volumetric mixing is performed. Cotton fibres of different quality falls in to the mixing bin and the bins are filled in different volume by pneumatic air. Thus mixing is done.
2)Weight mixing-In weight mixing, different quality cotton fibres are weighted at first and then they are mixed in different weight(gm).     
3)Hand stack mixing-This method is an old type of mixing. Normally used to produce higher count yarn. This mixing is done entirely with the help of hand.
4)Bin Mixing-In bin mixing, cotton flocks are transferred from the bale opener in to pipe line. The pipe dia is 10 inch & it passes over the bins, fibre flocks are delivered in to the bins from delivery boxes of the pipe placed in the pipe.
5)Lap Mixing-In lap mixing, double scutcher is used. One is breaker scutcher and another one is finisher scutcher. Different grade & different quality laps are produced in the breaker scutcher. Four lap stands are placed before the finisher scutcher. There mixing can be done different ratio like 1/3,1/1,3/1,1/1/2,2/1/1 or 1/1/1/1 etc. This method is still used successfully.
6)Automatic mixing-In this method cotton fibres are mixed automatically by different automated machines without breaking bales manually. Here, no. of bales are placed both side of the machine longitudinally. The machine moves in traversing motion & extract the fibre from the bales in to the duct for mixing. Example-Unimix of Reiter.
7)Card mixing-This mixing is sometimes used in high production carding, Where two laps are fed and mixed together.
8)Sliver mixing-In this mixing, different carded slivers are used in a particular ration by doubling to mix the fibres in draw frame.
9)Mixing by hopper-In this method, at first cotton fibres are passed in to bale breaker from where the fibres falls on a lattice. A series of lattice take the cotton fibres of different quality in to the mixing bins through a cross lattice.

5. Blending/Mixing Machine (Zone 3)
A. The Multiple Mixer

This is very simple mixture that gives very long term blend. The machine is composed of several(6-8) chambers. The fibre material is pneumatically fed from the top. All chambers are successively and simultaneously filled and the material is removed from the bottom through a single common duct.

B. The Unimix

The unimix is a combination of blending and cleaning machine and both of these two operations are carried out within the single machine.
The machine is divided in to three sections

  • Storage section
  • Intermediate chamber
  • Delivery section

The fibres are pneumatically fed in to six individual chambers of the machine. The fibres coming out of each of the six chambers are taken on a common lattice or a conveyor belt that takes the material to an intermediate chamber with the help of an inclined or upright lattice. From here, the material passes through a delivery section to the next machine with the help of pneumatic suction. In the delivery section a cleaning roller is used which does the course cleaning of the fibres as they are being delivered.