Blending/mixing - Objects and their effects on yarn quality
Explain the importance of blending different varieties of cotton (or) why mixing is done in Blow Room (or) what are the reasons for mixing different cotton in spinning mill. What are the objects of mixing (or) Briefly explain the necessity of mixing (or) What are the advantages of mixing of fibres in Blow Room Mixing is the process of intermingling of various varieties of cotton, to prepare the raw material for the spinning process.
It is not possible or economical to depend upon a single variety of cotton to produce a particular yarn throughout the year. So. different available varieties are selected and mixed in a suitable proportion so as to get uniform Quality product throughout the year. Object of mixing process are
To improve Processing Performance of Spinning:
Department
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Defects
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Remedial precautionary steps to be taken in mixing
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Carding
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The level and
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Can be controlled by maintaining
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variation of
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the mixing compositions as
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neps and waste
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Constant as possible.
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comber
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Fluctuation in noil%
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Can be reduced by eliminating
High short fibre content In mixing to control variation, in fibre length distribution of blend.
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Fly frame
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fly
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Fly frame
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Twist variation in roving
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Can be controlled by mixing cotton on the basis of closer fiber length and micronaire fibre length and micronaire reading tolerances cotton on the basis of .closer
fibre length and micronaire
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By closely controlling fibre length and micronaire reading of blends, twist variation in yarn is: kept minimum, resulting in better control over yarn strength and end breakage levels.
Uniformity of sliver and roving is dependent mainly^ on fibre properties and machinery adjustments.
Mixing influence the processing performance of spinning through control of yarn count variation, twist variation, end breaks, yarn properties, machinery adjustments.
To achieve uniform quality of Products:
There is wide variation in fibre properties from cotton to cotton. Even the same variety of cotton indicates' variation from fibre to fibre. So, to achieve uniform quality of product, different varieties of cottons are mixed in a suitable proportion in order to (average out the inherent variation exist in each variety of cotton.
To reduce and control the cost of production:
Mixing Influence the price of final product through control of fibre cost, fibre quality, Blend composition.
Availability, inventorying, ware housing, purchasing program & inherent fibre property variations.
To meet functional end use requirement:
Blending influences (I) physical properties such as tensile
& tear strength, elasticity, abrasion resistance (durabi1ity), wrinkle resistance, etc., (ii) Aesthetic properties such as
appearance, cover, surface, colour, luster, drape etc., and (iii) subjective properties such as comfort, hand and touch, softness, loftiness, fullness etc.,
1. Where ultimate strength is required,
cottons of high fibre strength are used to get strong yarn and fabric.
2. where aesthetic properties are required, cottons of low-nep potentials are used in blend.
3. where subjective properties (comfort, softness, fullness, etc., are required:
long and fine fibres are used in blend in combination with spl. fabric finishing treatments.
To regain the moisturecontent.
cotton is a hygroscopic material. The compressed bale of cotton losses some moisture during compression. So, cotton must be opened and stored sufficiently to regain its moisture content.
Fibre properties to be considered for blending: Fibre, length:
I. Variation in staple length between cotton in mixing should not be exceeding 1.5 mm.
ii. Variation in fibre length will affect every stage of process from blow room to spinning,
iii. At every stage, the control of material depends upon fibre length.
iv. Fluctuations of noil percentage in comber and fly in fly
Frame can be reduced by eliminating short fibre content in mixing.
Fibre fineness and fibre strength:
1. Variation in fineness between cotton in mixing should not
exceed 0.3 (up to 40s, & 0.2 for above 40s.
ii. Variation in fibre strength (g/tex-3mm gauge) between cotton
in mixing should not exceed 2 (up to 40s s* 3 for above 40s.
iii. Fibre fineness and strength affect the yarn strength directly.
iv. Twist variation and CSP variation in yarn can be controlled
by mixing cotton on the basis of closer fibre length and Micronaire reading. tolerance.
by mixing cotton on the basis of closer fibre length and Micronaire reading. tolerance.
Where ultimate strength is required.
Cotton of high fibre strength are" used to get strong yarn and fabric.
Fibre Maturity:
Maturity percentage of different cottons should be considered before mixing, because it will enable the smooth processing.
Trash % in cotton:
seed bits, & other foreign matters, etc.,) present in the cotton.
Also trash % in the cotton indicates the blow room treatment
necessary to clean the cotton.
Selection of cotton
Cotton is selected by considering the following points.
i) Fibre length, fineness, strength influences yarn strength & spinning value.
ii) Short fibre content, fineness influences on Regularity of yarn.
iii) Maturity and fineness of cotton determine neps generation at different stages,
iv) Trash % in the cotton -indicate- no of beating points treatment necessary in blow room.
II. Fibre quality Index '(FQI) = lusm / f
Where
l u = product of 2.5 % span length in mm and uniformity
Ratio %(u) measured on digital fibrograph divided by ICC
s = Bundle fibre strength in g/tex at 3mm gauge
length. measured on stelometer.
m = maturity co-efficient determined by sodium hydroxide swelling technique,
f = fibre fineness or micronaire value (micro games/inch) FQI is a measure to assess the quality characteristic of the cotton required for spinning different counts with desired CSP values.
III. CSP ( Count Strength Product) = (310-count) √ FQI
IV. Maturity Co-efficient= (M + 0.6H + 0.4I)/100
V.
Where, M,H and I are % of mature. Half mature and immature fibre respectively (Determined by standard sodium hydroxide
swelling technique)
vi) Fibre propensity for imperfection = trash % x short fibre % divided by Micronaire value
It is a useful tool in the selection of cotton for minimizing . the imperfections in the yarn and it should be maintained below : 16.
Continue to write the article 1.12 - fibre properties -
consideration for the selection of cotton.
Selection of cotton
Cotton is selected by considering the following points.
i) Fibre length, fineness, strength influences yarn strength & spinning value.
ii) Short fibre content, fineness influences on Regularity of yarn.
iii) Maturity and fineness of cotton determine neps generation at different stages,
iv) Trash % in the cotton -indicate- no of beating points treatment necessary in blow room.
II. Fibre quality Index '(FQI) = lusm / f
Where
l u = product of 2.5 % span length in mm and uniformity
Ratio %(u) measured on digital fibrograph divided by ICC
s = Bundle fibre strength in g/tex at 3mm gauge
length. measured on stelometer.
m = maturity co-efficient determined by sodium hydroxide swelling technique,
f = fibre fineness or micronaire value (micro games/inch) FQI is a measure to assess the quality characteristic of the cotton required for spinning different counts with desired CSP values.
III. CSP ( Count Strength Product) = (310-count) √ FQI
IV. Maturity Co-efficient= (M + 0.6H + 0.4I)/100
V.
Where, M,H and I are % of mature. Half mature and immature fibre respectively (Determined by standard sodium hydroxide
swelling technique)
vi) Fibre propensity for imperfection = trash % x short fibre % divided by Micronaire value
It is a useful tool in the selection of cotton for minimizing . the imperfections in the yarn and it should be maintained below : 16.
Continue to write the article 1.12 - fibre properties -
consideration for the selection of cotton.
1-14 Methods
of Grading the Cotton;
Cotton is graded in the following manner:--- Possible to spinLow grade cotton (short stapled cotton) coarser counts-
below 40s
Medium counts-40s to 60s
Fibre property requirements to spin various counts of yarn.
10s
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20s
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40s
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60s
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80s
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Fibre length mean length mm
Effective length (mm)
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17
24
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20
28
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24
32
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27
34
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29
37
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Short fibre %
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16
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16
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18
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20
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22
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Micronaire value
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5.2
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4.4
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4
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3.7
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3.5
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Maturity fibre %
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60
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60
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60
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60
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60
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Bundle fibre strength (grams/tex)3mm gauge
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19
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21
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24
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27
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29
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Fibre property requirements to spin various counts of yarn.
Typical mixing for coarse, medium and fine counts:
Count Group Typical Mixing ,
6 to 12 Desi,Wagad, Jayadhar, Kalgin.
14 to 26 v777,Yl,virnar,J-34,Gaorani, Ak-235.
28 to 34 Digvijay, co2, 1007, Laxmi sankar 4(B)
36 to 44 sankar 4(a),MCU-5(B),HYBRID4,1007,LAXMI.
50 to 6 MCU-5(A), Vara1axmi(B),Vishnu,sankar 4(A)
70 to 10c Varalaxmi(A),MCU-5(a),Sujata, CBS-156.
100 to 140 Varalaxmi (A), suvin
Comparision between mixing and blending
Blending means, in very unit cross section of the yarn, every fibre characteristic is found in the same proportion of different cotton as in the original blend.
Blending is based on the measurement of important fibre properties 1ike 1ength, fineness, strength, etc. and quantitatively proportioning and combining the compatible Properties under controlled condition.
Physical properties (fibre length, fineness, strength) of the resultant blend can be predicted, and are reproducible.
It is combining together in some what haphazard proportions of different cottons whose physical properties are only partially known, and the resultant mixture has average physical property characteristic which are not easily reproducible. Totally, blending is based on principles of measurement and proportion while mixing is not.
Blending bale opener or hopper bale breaker:
Number of bales of various varieties of cotton to be mixed will be arranged on either side of the creeper lattice.
8.The latest Mixing Bale opener with weight blending
From stripping roller, the cotton flocks are thrown into trunk, which guides them into the pair of feed roller which is spring loaded.The compressed sheet of cotton which are delivered from feed roller are heavily beat by saw toothed cylinder. This beating action divides the material ' into smallest flock. Saw toothed cylinder projects the flocks over the grid, where sand and heavy trash particles are extracted.
It is filled only to just below the photo cell situated in the adjacent hopper, then the closing flap of the second hopper * is opened by push button operation..
whilst the last hopper is being charged, material transport is switched on and material in the hoppers starts to drop.
Condensing funnel
Opening & mixing section :
VOLUME vs. WEIGHT
VOLUME BLENDING :
WEIGHT BLENDING :
Blending bale opener or hopper bale breaker:
Objects :
i) To mix the various varieties of cotton thoroughly
ii) To comb the cotton,
iii) To open un clean the cotton.
iv) To extract the iron particles from cotton. The constructional details of the machine are shown in fig.
Number of bales of various varieties of cotton to be mixed will be arranged on either side of the creeper lattice.
Stack Mixing:
According to the proportion, different varieties of cottons to be mixed are uniformly spread on the floor one over the other. This mixing is now allowed to stand/for a day to allow it expand, aerate and condition naturally. The cotton is then pulled manually, from top to bottom so that we can achieve uniform mixing, and is fed into the creeper lattice of the bale opener.
Creeper lattice will deliver the cotton on feed lattice. By the movement of feed lattice, the cotton is conveyed against the spiked upright lattice.
Swing door and limit switch for the feed control in hopper:
Swing door is used to control the feed in the main bin or maintain the constant level of cotton on feed lattice. This- is kept, so that it is always towards the upright lattice, if the cotton is gets accumulated inside the hopper then the door will come back by the pressure of the cotton that feeds and that comes in contact. Thus the swing door acts according to the amount of cotton” inside the hopper.
The shaft of the swing door is connected to a switch box with a cam on it i.e., on the stud / shaft and it is free on the stud. And on the other side of the shaft a lever with dead weight is fixed. : This is to keep the swing door always towards the upright lattice.
While the swing door is towards the upright lattice, the cam will press the micro switch and the make the creeper lattice to act. While the swing door is away from upright lattice, the cam will not press the. Micro switch, this will make the creeper lattice to stop the feed to the hopper.
According to the amount of cotton we require inside the hopper we can adjust the dead weight. By moving the dead weight away from the fulcrum, the swing door will gets more towards the upright lattice, and this makes the cam to press the micro switch and make the creeper lattice to feed more.The level of the cotton- inside the hopper should be always in 3/4 level at all time if not we will forced to run .the upright lattice at a high speed or forced to make more open or more gap between the evener roller and upright lattice (if the gap is made more then the opening of the cotton will be reduced)
Due to the spikes on the inclined lattice and direction of movement, lumps of cottons wil1 be carried upwards by the inclined lattice. Hard pressed layers of cottons are well combed by the spikes of the inclined lattice. Rapidly revolving spikes of the evener roller (or regulating roller) beats and open the cotton.
Due to the close space between evener roller and inclined lattice and rotation of evener roller in opposite direction, unopened excess lumps of cottons are' thrown back into the bottom mixing bin. (on feed lattice)
Wiper roller (or clearer rol1er) effectively removes any cotton’s which are adhering to the evener roller.
Stripping’ roller strips the cotton from inclined lattice and projects it over grid bar system where sand and heavy trashes are extracted.
The cotton falls into an outlet funned are taken away pneumatically to the next machine through pneumatic pipes.
In the outlet funnel, permanent magnets are fitted to extract the iron particles from the cotton fibre for trouble-free' operation, particularly in Blow Room and carding.
How the production and degree of opening on a hopper bale breaker or blending bale opener or mixing bale opener can be altered?
A. Distance, between inclined lattice and evener roller will determine degree of opening and production of the machine. This setting can be adjusted sleeplessly by means of hand wheel so as to regulate the flow of material in accordance with the production.
Settings : 1/2 inch for fine and 1/4 inch for medium and coarser cotton, closed setting - gives less production and will make the tufts more opening and vice versa.
B. i) The speed of the spiked inclined lattice may be varied b means of an expanding pulley, according to the requirement production and degree of opening.
Comparision between hopper bale breaker and blending bale opener.
The blending Bale Opener has
1 Shorter, finer and more spikes on the inclined lattice as compared to hopper bale breaker.
ii) Evener cylinder also has more pins or spikes.
iii) Stripper has three rows of intersecting leather flaps and three rows of spikes, so that tufts delivered are smaller than hopper bale breaker.
8.The latest Mixing Bale opener with weight blending
technique
Object, passage of cotton & working procedure of Mixing bale opener is same as the hopper bale opener, but the difference is
The cotton falls into an outlet funnel are taken away Pneumatically to the next machine.
In addition to the cleaning through grid bar system an exhaust fan at the top of the machine will suck the dust, air and short fibres from inside of the machine through perforated sheet.
This pepper trash is taken by pneumatic pipe to the cellar (dust chamber).
AUTO MIXER
BEQ : Which method of mixing will- give uniform end .product why? how stack mixing principle is adopted in modern mixing m/c?
Auto mixer with bale opener unit will gives uniform end product.
Objects:
i) To double the different layers of material ,-. and achieve
uniform thorough blending of material.
uniform thorough blending of material.
ii) To comb the cotton.
iii) To open" and clean the cotton.
[Condenser collects * the cotton from the bale opener and delivers it on to the conveyor belt of the distributor! Conveyor belt of the distributor is traversing from one end of the machine to another (40ft.long) and being reversed at the end of the each traverse.
during its traverse, distributor uniformly spread the cotton, layer by layer in the upper mixing compartment.
When the required number of layers is reached in the upper bin, it is automatically opened and the layered stack now falls into the feed lattice of the bottom mixing bin.
The layered mass of cotton is then conveyed slowly towards an inclined spiked lattice, which will take the cotton from various layers.
Lumps of cotton will be carried upwards and hard pressed layers of cottons are well combed by the spikes of the inclined lattice.
Rapidly revolving spikes of the evener roller beats and open the cotton tufts.
Due to the close space between evener roller and inclined lattice and rotation of evener roller in a opposite direction^ unopened excess lumps of cotton are thrown back into the bottom.
Stripping roller strip" the cotton from inclined lattice and from here it is conveyed pneumatically to the opening and cleaning line of the machine through out let pipe.
OW /span> IT IS POSSIBLEif AUTO MIXER?
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stack mixing principle is adopted, uniform end product is achieved, more advantage over other mixing
Blending is partially achieved in the bale opener, but in Auto mixer, uniform blending is achieved by doubling the various subsequent layers of cotton with stack mixing principle.
In auto mixer, 40-60. layers (when the M/c. is equipped with upper trunk,) or 80 to 120 layers (in the case of. absence of upper trunk) of cottons are stacked horizontally and extended over aenlarged area (40ft long and 3 to 6 ft. height) and the subsequent layers of material is arranged one over the other because of this, doubling effect is achieved.
The stack thus formed is constantly being taken off in the vertical direction by the inclined lattice automatically so that in the delivered material there must be parts from at least 20 to 30 different layers and time spaced bundles. The auto mixer thus permits a controlled accumulation and thorough uniform blending of material.
Trutzschler's MULTI MIXER:
Achievements
Perfect and Homogeneous blend is achieved, ii) simultaneous mixing by doublings' over an extended period of time is achieved.'The cotton bales are opened and premixed by bale opener.
This blend is blown by the material transport fan and conveyed into the feed duct above the hopper.
The charging of the multimixer starts with the first hopper at the end of the feed duct.
It is filled only to just below the photo cell situated in the adjacent hopper, then the closing flap of the second hopper * is opened by push button operation..
Second hopper is charged” to a rather higher than the first. The charging level of the hopper rises uniformly up to the last hopper which is fully charged, when the last hopper is full theClosing flap shuts automatically and charging restarts with first hopper, as soon as the level second hopper has dropped below the Photo Electric cell.
whilst the last hopper is being charged, material transport is switched on and material in the hoppers starts to drop.
When the charging level rises, more and more of the holes in the perforated plate of the upper part of .hopper are blocked with material. This increases the pressure the conveyor air. Once a pre-selected pressure is reached, which corresponds to a particular charging level, an electronic switch closes the flap of this hopper and opens up the flap of the next hopper."
The base of each hopper is closed by a pair of deliver roller which transfers the material gradually and uniformly to an opening roller. The delivery rollers of the entire hopper are
two variable speed motor with control range up to 1 : 6 in this way it is possible to adjust the output of multimixer to the feed requirement of the subsequent machine.
Opening roller gently loosen the material into tufts and
deliver them into the blending channel from which they are sucked
by the subsequent condenser.
In this machine, an intensive, instantaneous perfect and homogeneous blending of minitufts (.005-.010 gram) together with simultaneous mixing by doubling over an extended period time is achieved.
Storage section:
It consists the material distributing duct into which the tufts are blown. Over a adjustable separating noses, a relevant turbulence is formed which creates a thorough instantaneous blending. Six vertical filling trunks of varying heights are arranged in the direction of flow of material.
Condensing funnel
This, brings about a 2-3 fold mechanical condensation of six layers of material. In this way, holding capacity of 350 kg is obtained. A conveyor belt together with conveying roller carry the material to the opening & mixing section.
Opening & mixing section :
This section directs the flow of material to the action of
two pairs of pressure roller each with an opening roller.
Owing to the different stretches to be traveled the
Constituent comprising the mixing, which have been fed
. simultaneously to the trunks, arrive at the delivery and sucked-
off by the subsequent machine.
. simultaneously to the trunks, arrive at the delivery and sucked-
off by the subsequent machine.
VOLUME vs. WEIGHT
BLENDING
Variation in density of material will affect Blending, so a study of volume and weight blending is essential to understand the correct blending.
VOLUME BLENDING :
In all blending equipment, the cotton is charged into hopper. It is assumed that the height of cotton in the hopper will be kept constant, resulting in constant volume, the" density of the cotton is constant and rate of feed is constant for all fibre component and for the over all mass of cotton.. But these assumptions are far from true in the ^actual working condition further the spiked aprons are not designed to maintain constant weight feeding from a cotton source of varying density and volume
WEIGHT BLENDING :
In weighing hopper feeder or in latest mixing bale opener (M.B.O) at last, the tuft leave the machine at delivery duct from where they fall into weighing pans.
The charge of the weighing pan is set on a weighing beam between 50 g and 1350 gram in one gram steps.
The weighing pans are first filled at the fast speed. Before the charge reaches the set weight, an electronic switch switches the material transport motor to slow speed.
When the full charge has been reached, another electronic switch trips the material transport motor off immediately and shuts the closing flap so that no further tufts can fall into weighing’ pans.
When the weighing pans of all the weighing hopper feeder or MBO ('3 or 4) of a tuft blender have been filled, the bottom traps of all the weighing pans are opened pneumatically at the same time. Thematerial falls on to the blending conveyor of the Tuft blender machine.
The filling of the weighting pans begins again immediately.
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