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Saturday, March 21, 2015

Common defects in Blowroom laps

With the evolution of the new concept of “Zero defects”, there is growing concern in the mills to control defects at every stage of manufacture. Lap defects can in the long run result in yarn defects, thus ultimately reducing the sale value of yarn. It is in this context that an understanding of the types of lap defects, their causes and remedies assumes importance.

Blowroom

The types of lap defects commonly encountered and their likely causes are as follows:

Ragged Lap selvedges
Causes
  • Waste accumulation at the sides of the grid bars, cages or calender rollers, obstructing smooth flow of material.
  • Torn leather linings of cages.
  • Rough spot at the sides of the feed plate delivering the material to the calender rollers.
  • Improper setting of selvedge guides.

Lap licking
Causes
  • Use of too much soft waste in the mixing.
  • Too high fan speed.
  • Excessive beating.
  • Insufficiently weight calender rollers.
  • Too much weight on lap racks.
  • Either cotton is damp or departmental humidity is high.
  • Sticky nature of the material and type of spin finish in the case of polyester.
Remedies
  • Use of roving ends to act as layer separators.
  • Incorporation of lap filters.
  • Blanking off of one of the cages.
  • Use of antistatic spray while processing synthetics.
  • Reduction of full lap weight.

Conical laps
Causes
  • Improper functioning of pedals on one side to pedals being choked with dirt.
  • Air entering at one side from under the grid bars of the beater.
  • Defective beater blades at one side.
  • Uneven suction at the cages leading to deposition of more material on one side than on the other.
  • Lap spindle racks not exerting even pressure across the lap width.

Dirty laps
Causes
  • Blunt grid bars or grid bars not properly set i.e. set either too close or at incorrect angle.
  • Grid bar interspaces choked up.
  • Excessive fan speed leading to ineffective cleaning.
  • Blunt and slow running beaters.
  • Beater set too far from feed roller or pedals.
  • Trash boxes overfull, or air current in trash box region causing retrieval of trash.

Thick and thin places in lap or patchy laps
Causes
  • Insufficient suction at the cages.
  • Damaged cages i.e. damages wire meshing or worn-out flannel or leather linings.
  • Insufficient opening of cotton lumps at the preceding machines.
  • Improper removal of air from the cotton stack at the overflow box or reserve hopper feed box leading to the formation of air pockets.

Holes in lap
Causes
  • Damages cages.
  • Too high tension draft between shell roller and calender roller.

Soft laps
Causes
  • Inadequate pressure at calender roller and lap rack.
  • Too low tension draft between shell roller and calender roller.
  • Worn out brake linings on brake pulley.

Stringiness of cotton tufts in lap
Causes
  • Feeding of damp cotton.
  • Cotton being over-beaten either due to high beater speed, choking of beater chamber or use too many beating points in the line.
  • Excessive rolling action of material in machines like the step cleaner.

Lap splitting
Causes
  • Cotton being blown equally on both the cages.
Remedies
  • Increase calender roller pressure.
  • Partially blank off one of the cages.

Disturbed tufts in laps
Causes
  • Excessive speed of fluted lap rollers.
  • Lap may be so large and bulky that it touches the plain calender rollers when it is getting built-up.
  • Disturbance to tufts of the outer layer also occurs during storage and transportation.

Sunday, March 15, 2015

Some essential Check points in Blowroom

Given below are some checkpoints which will guide the technicians about some common deficiencies in the blow room and the corrective action to be taken in such cases with regard to quality control, maintenance or work practices.

Blowroom

Mixing room
  • Check whether blend consistency is maintained, i.e. at any point of time, the amount of cotton of each variety that is fed should conform to the mixing proportion desired. Very often supervisors only check up that the required total number of bales is consumed in the shift, but it is more important to see that the proportions of bales of each variety taken for feeding compares with the set proportion.
  • The level of stock in the different bales taken for feeding should be about the same at any point of time.
  • Visually check whether the setting between the inclined spiked lattice and evener roller is uniform along the width of the machine. Some idea about this can be had by comparing the amount of cotton dropping off from the extreme ends of the inclined spiked lattice.
  • Ensure that the soft waste added to the mixing is free from oily and dirty sweepings, and the roving ends and bonda are well opened.

Opening and Cleaning
  • Magnets installed in the line should be checked for their effectiveness and condition. If too much accumulation of metallic substances is found, their cleaning frequency may have to be improved as there is risk of a part of the metallic substances being carried forward with the cotton.
  • Check the condition of the grid bars at all beating points. Grid bars should be smooth and clean and should not be choked or bent.
  • Check beater blades for sharpness and freedom from burrs and damages.
  • Check the condition of the lap fringe. This will throw light on whether the setting between the beater and feed roller is correct, whether the grip on the lap sheet is proper and also whether the opening of the material at the earlier stages is adequate.
  • Inspect the trash chamber to check the richness of waste and also to observe whether the trash box is getting overfull. If the latter is observed, there is danger of trash getting recombined with the lint and the schedule for waste removal will have to be accelerated. If excessive lint loss is observed, a detailed quality control study will have to be undertaken to look into the cases and remedies.
  • Check condensers for the condition of the screens. Screens that has become dented, or with bent or broken wires, collect and deliver stock unevenly, resulting in high lap variation at the scutcher.
  • Ensure that the pedal levers do not meet with any obstruction during working, as this is not only affects the pedal weighting, but also the feed regulation. A safe clearance should be maintained between the tail end of the pedal and the cross bar when the material is in process and in no case should the pedals rest on the cross bar.
  • Check whether the level of material in the hopper reserve box is as per the prescribed level. Also check at what level the signals for starting and stopping the supply are given. Under normal conditions, these should not vary widely. If the two levels are found to differ widely, a detailed check up of the swing door mechanism, the working of the solenoids and micro-switches will have to be undertaken.

Scutcher end
  • Through the glass panel or side window, check the level of material in the reserve box. If the level is not found to conform to the standard marked level, prompt corrective measures are to be taken.
  • Open the cone drum box and check the position of the belt. The belt should operate in the central region most of the time.
  • The width of the belt fork should conform to the width of the cone drum belt.
  • Check for loose links in the pedal regulating motion and ensure that the pedal lever is properly weighted; otherwise transmission of motion from the pedals to the cone drum belt will not be faithful.
  • Worn-out leather linings in cages lead to excessive loss of good fibres in the gutter fly. Careful check should therefore be kept to prevent such a condition.
  • In case lap filters being used, care should be taken to see that they are set properly.
  • Check the leather lining of the brake. Worn-out leather linings lead to laps of improper build.
  • The load on the calender rollers is transferred to the calender roller shaft through the calender roller bearings. Consequently, worn-out bearings need prompt replacement.
  • Unroll a couple of doffed laps for a short distance to see whether the lap is properly made. The sheet should be able to unroll cleanly without splitting and at the same time the sheet should be of uniform thickness without holes and other defects.
  • Check selvedges of lap for thin, ragged edges. Any obstruction in the passage of material interferes with even flow and shows up as irregularities in the edges of the lap.
  • Where lap guards are used, care should be taken to see that they do not rest on the lap as this can lead to imperfections in the lap build and also disturbance to fibre tufts in the lap.
  • The flutes of shell rollers should not be too rough or have burrs.
  • Ensure that the lap width is about 5 cm less than the card width. Carelessness in this respect gives rise to imperfect selvedges of the web and also improper carding of the edges of the lap.
Thus, if the technicians make it a point to inspect the above-mentioned checkpoints during their round in the department, they can bring about significant improvement in the line in course of time. It is expected that it will normally take the supervisor about an hour to complete the supervision of one line. No fixed schedule for frequency of inspection of the blowroom line can be given, as this will depend upon a variety of factors, but it is recommended that such inspections be carried out once in a fortnight or once in a month.

Monday, October 20, 2014

Observation of AOO2D Automatic Bale Plucker

Bale Plucker application | Main specification | Description | Machine adjustment | Precautions


Application
          This machine being in the initial stage treatment of raw materials in the blow rooms is suitable for cotton, cotton type man-made fibres. The pluck-beater travels around and lowers intermittently to pluck the fibres in succession. Drawn by fan, these fibres are delivered to the nest machine through the conveying for treatment.
Main specification
·        Dia. Of out round frame – 4760 mm.
·        Inner round frame (rotary type) – 1300 mm dia.
·        Carriage frame –
Length: 2640 mm.
Width: 800 mm.
Height: 1425 mm.
·        Speed of the carriage – 1.7~2.3 rpm.
·        Pluck beater –
Dia: 385 mm.
Speed: 740rpm.
Blade: Zigzag type.
·        Blade arrangement –
First group: 9 teeth.
Second group: 12 teeth.
Third group: 15 teeth.
·        Working length – 1618 mm.
·        Position of the beater blades end above the ground – max~1110 mm and min~ 30mm.
·        Stepwise lowering of beater – 3-6 mm each time (Adjustable).
Description
          This machine is composed of inner round frame, carriage frame, beater frame, beater, centrifugal switch, telescopic pipe, outer round frame, slip ring and rail.
          The carriage is connected to the outer frame and supported at the centre on a central shaft. With two rollers wheels at the bottom of the carriages outer frame, the carriage can revolve clock wise on the circular rail.

Automatic Bale Plucker

Thursday, October 16, 2014

Why ring spinning system is universal? | Technological points in Blow room | Influencing factors of cleaning

Why ring spinning system is universal? | The basic machines required for blow room line | State the influencing factors of cleaning | Technological points in Blow room | Cleaning point | Metal detector


Ring spinning system is a universal system
        The ring spinning system is the most widely used system due to significant advantages in comparison with the new spinning process.
         Ring spinning is the oldest of the present day spinning process. It is comparatively expensive than other spinning system because of its slower production speed and the additional processes (Roving and winding) required for producing ring spun yarns.
          By this system we can produce wide range of yarn count with better quality. Any type of fibre can be spun in ring spinning system. Ring spun yarn quality depends upon the quality of raw materials, preparatory process and finally ring spinning machine. Today’s machinery is quite developed for the production of better quality yarn and for the productivity.
          The fibres in the ring yarn are highly parallel and helical in nature and fibre arrangement is uniform along the thickness of the yarn. The high axial strength of the yarn is the result of unique self-locked structure.
         The yarns made from ring frame have fewer naps, slabs, trash and are mostly fine yarn. So, from above statement I assume that, ring spinning is the best and universal.

The basic machines required for blow room line
       a)     Opening m/c: To reduce tuft size.
       b)    Beaters: To open and clean.
       c)     Regulatory m/c: For uniformity of delivery material.
       d)    Mixing and blending m/c.
       e)     Dedusting unit: To separate the dust from the cotton.
       f)      Metal detector.
       g)     Heavy trash separator.
       h)    Air flow: For transporting the material from one m/c to another.

State the influencing factors of cleaning
       a)     The longer the dirt particles, the better they can be removed.
       b)    Opening should be followed immediately by cleaning if possible in the same m/c.
       c)     The higher the degree of opening, the higher the better of cleaning.
       d)    A very high cleaning effect is almost always purchased at the cost of a high fibre loss.
       e)     There should be slightly less cleaning in the blow room and slightly more in card.
       f)      Higher roller speed gives a better cleaning effect. But, also more stress on the fibre.
       g)     Cleaning is made more difficult if the impurities are distributed through a large quantity of material by mixing with clean cotton.
       h)    Damp stock cannot be cleaned as well as dry. 

The technological points in Blow room

Blow room
1.     Opening in blow room means opening into small flocks from compacted. Technological operation of opening defines the volume of the flick is increased while the amount of fibre remains constant. I.e. the specific density of the material reduces.
2.     The bigger the dirt particle, the better they can be removed.
3.     Since almost every blow room machine can fully open particles, as far as possible a lot of impurities will be eliminated at the start of the process. Opening should be followed immediately by cleaning and if possible in the same machine.
4.     The higher the degree of opening, the higher the degree of cleaning. A very high cleaning effect is almost always purchased at the cost of a high fibre loss. Higher roller speed gives a better cleaning effect but also more stress on the fibre.
5.     Cleaning is made more difficult if the impurities of dirty cotton are distributed through a larger quantity of material by mixing with clean cotton.
6.     The cleaning efficiency is mostly depending on the Trash%. It is also affected by the size of the particle and gumminess of cotton. Therefore cleaning efficiency may vary for different cottons with the same trash%.
7.     There is a new concept called cleaning resistance. Different cottons have different cleaning resistance due to their properties.
8.     If cotton is opened well in the opening process, cleaning becomes easier because opened cotton has more surface area, therefore cleaning is more efficient.
9.     If automatic bale opener is used, the tuft size should be as small as possible and the machine stoppage time should be reduced to the minimum level possible.
10.              If manual bale opener is used, the tuft size fed to the feed lattice must be as small as possible.
11.              Due to machine harvesting, cotton contains more and more impurities, which furthermore are shattered by strong ginning. Therefore cleaning is always an important basic operation.
12.              In cleaning, it is necessary to release the adhesion of the impurities to the fibres. The former is achieved mostly by picking of flocks; the latter is gained by leading the flocks over a grid.
13.              Using inclined spiked lattice for opening cotton in the initial stages is always a better way of opening the cotton with minimum damages. Of course the production is less with such type of machines. But one should bear in mind that if material is recycled more in the lattice, neps may increase.
14.              Conventional methods use more number of machines to open and clean natural fibre.
15.              Mechanical action on fibres causes some deterioration on yarn quality, particularly in terms of neps. Moreover it is true that the staple length of cotton can be significantly reduced.
16.              Intensive opening in the initial machine like bale breaker and blending machines means that shorter overall cleaning lies are adequate.
17.              In a beating operation, the flocks are subjected to a sudden strong blow. The inertia of the impurities accelerated to a high speed, is substantially greater than that of the opened flocks due to the low air resistance of the impurities. The latter are hurled against the grid bars into the waste box, while the flocks continue around the periphery of the rotating beater.
18.              By using a much shorter machine sequence, fibres with better elastic properties and improved spinnability can be produced.
19.              Air streams are often used in the latest modern machine sequence, to separate fibres from trash particles by buoyancy differences rather than beating the material against a series of grid bars.
20.              There are three types of feeding apparatus in the blowroom opening machines.
·        Two feed rollers (clamped)
·        Feed roller and a feed table
·        A feed roller and pedals
21.              Two feed roller arrangements gives the best forwarding motion, but unfortunately results in greatest clamping distance between the cylinders and the beating element.
22.              Feed roller and pedal arrangement gives secure clamping throughout the width and a small clamping distance, which is very critical for an opening machine.
23.              In a feed roller and table arrangement, the clamping distance can be made very small. This gives intensive opening, but clamping over the whole width is poor, because the roller presses only on the highest points of the web. Thin place in the web can be dragged out of the web as a clamp by the beaters.
24.              Stickiness in cotton affects the process very badly. Because of that production and quality is affected. Particles stick to metal surfaces, and it gets aggravated with heat and pressure. These deposits change the surface characteristics which directly affects the quality and running behavior.
25.              There are chemicals which can be sprayed to split up the sugar drops to achieve better result. But this system should use water solutions which are not recommended due to various reasons.
26.              It is better to control the environment inside the department when sticky cotton is used.
27.              The easiest way to process sticky cotton is to mix with better cotton and to process through two blending machines with 6 and 8 doublings and to install machines which will segregate heavier particles by buoyancy differences.

Cleaning point
          There are several machines are remains in blow room lines for various purposes. But, these machines which are involved especially for cleaning the fibres is called cleaning point. In other words, beaters are called cleaning point. The names of cleaning points are:
      a)     Step cleaner or, ultra cleaner.
      b)    Porcupine beater.
      c)     Kirschner beater.
      d)    Cotton cleaner.
      e)     R.N beater.
      f)      S.R.R.L beater.
      g)     Mono cylinder beater.
Metal detector
          Magnets are used in blow-room line to remove iron/ irony substance from the cotton. These magnets are called metal detector.

Friday, December 6, 2013

Definition, objects and process layout of Blow room

Blow room|Objects|Basic operations|Actions|Process layout of yarn manufacturing with a modern blow room line 
Blow room: The section where the supplied compressed cotton bale turns into a uniform lap of particular length by opening, cleaning, blending or, mixing is called blow room section. It is the first step of spinning. The section consist a number of different machines used in succession to open and clean the fibres.

Sequecce of blowroom machines in blow room line

Objects of blow room:
● Opening- Opening of compressed cotton bales and cotton bales are made into small tufts.
● Cleaning- To eliminate dust, dirt, broken leaf, seed particles, grass and other foreign impurities from the fibre.
● Blending/mixing- To produce a comparatively good quality cotton fibre by mixing different types of cotton together.
● Lap forming-
(a) To convert the opened and cleaned fibre into a sheet of particular width and uniform weight/unit length is called lap.
(b) To give a cylindrical shape to the pre determined lap by winding it in the lap pin and to make it suitable for the next process carding.

Basic operations involved in the blow room:
● Opening- Opening is the first operation in the blow room carried out to the stage of flocks in the blow room and to the stage of individual fibres in the cards.
● Cleaning- To remove the impurities, foreign materials and the raw materials as clean as possible.
● Dust removal- To remove the dusts which are completely enclosed in the flocks.
● Blending- To achieve the required quality of yarn by blending different kinds of cotton into a particular ratio.
●Even feed of the material- To produce a lap of uniform weight per unit length or, to process the maximum quality which is suitable for carding.

Actions of blow room:
          (a)   Action of opposite spike(Opening)
          (b)  Action of air current(Transport Cleaning) 
          (c)  Action of beater and grid bar(Cleaning and opening)
          (d) Action of regulating motion(Uniform output)

Process layout of yarn manufacturing system with a modern blow room line:
                                         Bale plucker
                                               
                                       Metal detector
                                                
                                          Uniclean
                                               
                                           Unimix
                                               
                                           Uniflex
                                               
                                        Vision shield
                                               
                                         Condenser
                                               
                                         Chute feed
                                               
                                           Carding
                                                
                                                                
                                                                              
          For carded yarn                                     For combed yarn
                                                                               
          Breaker drawing                                    Pre-comb drawing
                                                                                
          Finisher drawing                                    Lap former
                                                                                                    
          Simplex/Roving/Speed frame            Comber
                                                                                
          Ring frame                                              Post-comb drawing/Finisher drawing
                                                                                
         Auto coner                                          Simplex/Roving/Speed frame
                                                                                
          Heat setting                                              Ring frame
                                                                                 
          Packing                                                    Auto coner
                                                                                   
         Heat setting
       
     Packing