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Thursday, January 15, 2015

Faults found in Speed/Simplex/Roving frame with causes and remedies

We can find different faults in the speed/roving/simplex frame. They are described below -

Ratching
It is defined as undesired stretching of the roving to make it finer and it produces a high count variation.
Causes: Larger lifter wheel, or winding wheel, or ratchet wheel, or starting with half layer.
Remedies: This defect can be cured by using a correct smaller lifter wheel, winding wheel and ratchet wheel or rack wheel. At the start of a new doff the bobbin rail should be taken up or down to start with a full layer instead of a half layer which will produce uneven tension during winding the next layer on the bare bobbin.
Unequal tappers
This defect will occur if the pocker rack is not perfectly level when the pressure eye is at the middle of the lift. To equalize the tappers, mark the exact centre of the barrel portion of a bobbin and place the bobbin and a flyer in their working position. Mark the top rail until this is in the centre of the pressure eye and then level the two bars and the rack pocker by spiraled level. Reset the adjusting screws in the pocker bracket so that they operate the motion catches correctly at the top and bottom of the lift.
Stretched roving
Stretching is due to the difference in surface speed between the bobbin and the pressure eye being greater than the surface speed of the front roller. It occurs throughout the build, reduces the bobbin speed by using a smaller bottom cone drum change wheel.
     If stretching gets progressively worse in the bobbin build up, building motion ratchet wheel to be with fewer number of teeth or the spur wheel change building motion to be adjusted to give the same effect. This will make the cone drum belt along the cone drums at a higher rate and thus gives a greater reduction in bobbin speed as the package diameter increases.
     Too small a lifter change wheel can cause this defect through adjusting coils tending to ride on one another. This wheel is to be made larger.
     An accumulation of waste in the legs of the flyers will lead to stretching the individual spindles. In this case the roving will be slack between the front rollers and the affected flyers.
Sloughing
Causes:
-         Sloughing at the bobbin ends may be due to reversing bevels which are badly worn or too shallowly meshed.
-         Motion catches with worn ends.
-         Insufficient taper on the bobbins.
-         Balance weights not fitted correctly or touching the floor.
-         Hesitation at the change over either the building motion or the reversing mechanism resulting from dirt, tightness or incorrect setting.
Remedies:
-         The worn bevels should be replaced.
-         Correct shape of the motion catches.
-         Correct tapper of bobbins.
-         Proper setting of the related parts.
Incorrect tapper
This defect can be rectified by changing the tapper wheel. Reduce number of teeth in the tapper wheel reduces the tapper and vice-versa.
Ridgy bobbins
Faulty movement of the top rail results in ridgy bobbins at the bobbin ends.
Causes:
-         Tight or badly worn lifter shaft bearings.
-         Dirt on the top rail sides.
-         Worn revering bevels.
-         Slack lifter shaft pinions.
-         If the balance weight touch the floor when the rail is at the top of its lift.
-         Foul the chain pulleys at the bottom of the lift.
Remedies:
-         Faulty bearing should be removed.
-         The top rail should be cleaned.
-         Worn bevel should be removed.
-         Lift shaft pinion should be properly secured.
-         Correct setting of the balance weight.
Soft bobbin
Causes:
-         Too quick reducing of the bobbin speed as the package builds up in bobbin leading frame.
-         Too high speed of top rail, giving excessive spacing of the coils.
-         Individual soft bobbin may be due to: Incorrect threading of the roving round the flyer tap. Insufficient number of turn of the roving round the pressure arm. Lifting bobbin wheel. Removal of the long length of thick or single roving.
Remedies:
-         Large ratchet wheel or same effect with spur wheel change building motion.
-         A smaller top lifter change wheel.
-         Correct threading adjustment and piecing up.
Single and double
Single may be due to –
-         Slubs in the material being fed may prevent in passing through the back guide and results in the formation of single.
-         By piecing the full bobbins to the wrong end when creeling.
-         By lapping due to rough places or oil on the roller.
Doubles may be due to –
-         Broken end at the front lasting into an adjustment end and being carried forward with it.
-         Long piecing with creeling.
Any single or double in the previous process may also cause this effect.
Remedies:
Care must be taken for the above reasons of single and double so that they might not occur.
Cut roving
Causes:
-         Too close setting between two lines of drafting rollers.
-         A strained bottom roller.
-         Broken teeth in the draft gearing.
-         Roller gearing set too deeply in mesh.
-         Badly worn cap bar slides.
-         Loose sections of bottom rollers.
-         Badly pieced roller coverings.
Remedies:
We should maintain the proper settings of the machine parts.
Slubs
Causes:
-         Waste from the creel or clearers passing forward with the materials.
-         Loose fly accumulating on top of the creel bobbins and being incorporated into the roving.
-         Waste gathered in the top and hollow legs of the flyers.
-         Infrequent or insufficient cleaning of any port that comes into contact with the material being processed.
-         A broken end at the front, lasting into an adjacent end, can also produce this defect.
Remedies:
Actions should be taken accordingly.
Snapping
Snapping is a severe form of stretching and usually means that the roving being subjected to excessive tension due to too high a bobbin speed in relation to the spindle speeds. The roving generally breaks at each pressure eyes.
Causes and remedies:
-         If snapping occurs at an intermediate stage in the bobbin build, it will probably be caused by interference to the moment of the cone drum belt. This can be recognized by the fact that the lift is not being reduced. Check for the waste on the long rack and ensure that the long rack bowls revolve freely and that the rack pinion is firmly secured to the upright shaft.
-         If snapping occurs at the end of the build, it indicates that the ratchet wheel is too large. Thus giving insufficient movement to the cone drum belt or that the gear train in the spur wheel type building motion is producing the same effect. This has a cumulative action, stretching progressively increasing as the bobbin build up until finally occurs.
-         Too tight cone drum belt can produce this fault.
Dirt or oil strained roving
Causes:
-         Excessive oiling of rollers, spindles or bobbin driving wheels may be the main cause of this fault.
-         Cracked or broken bobbins, use of dirt boxes for transporting roving and oil on the top rail or clearer can also be lead to stained roving.
Remedies:
Correct oiling, cleaning etc.
Slack ends
Slack ends may always be caused by slack winding, a slipping cone drum belt, binding top rail slides, long collars clogged with waste and dirt, or too many turns of the roving round the pressure arm.
Incorrect twisting
Poor twist cause breakage prior to spinning and excess twist cause not to unwind during spinning in the break draft zone of the ring frame.
Excessive ends down
Causes:
-         Cut drawing.
-         Bobbin jumping.
-         Broken teeth in head stock.
-         Improper humidity.
-         Loose coupling of spindle pinions on spindle shaft.
-         Cone drums belt slipping.
-         Traverse motion not properly set.
-         Wrapping round bottom and top roller.
-         Hollow, rough and worn out gearing.
-         Slubs in roving.
-         Cut roving.
-         Improper pressure on the top roller.
-         Waste accumulating in the pressure eye.
-         Very badly keeping the under and top clearers.
Remedies:
Steps should be taken accordingly.
Irregular roving
Causes:
-         Irregular sliver feed to the machine.
-         Roller lapping.
-         Groove in the top roller.
-         Incorrect distribution of draft in the drafting zone.
-         Tension draft.
-         Incorrect weighting of the top roller.
-         Incorrect roller setting.
-         Single instead or double when used.
-         Lack of proper maintenance, oiling, and cleaning.

Wednesday, January 14, 2015

What are the Change places in Speed frame and their effect in changing?

Different changes take place in the speed/roving/simplex frame and affects in yarn count. Now we are discussing about it –

Draft change pinion (D. C. P): A large wheel reduces the draft and so gives a coarser hank (where the D. C. P is a driven one).
Draft constant change pinion: The larger the draft constant change wheel, the greater the draft constant.
Twist change pinion (T. C. P): A large wheel reduces the turns per inch (T. P. I) by increasing the both front roller delivery and the bobbin speed without affecting the spindle speed.
Twist constant change wheel (T. C. C. W): The larger the twist constant change wheel, the greater the twist constant.
Lifter change wheel (L. C. W): A large top lifter change wheel speeds up the lifter shaft without affecting the bobbin speed and thus increase the spacing of the coils. This wheel determines the number of coils/inch on the bobbin.
Bottom cone drum change wheel: This wheel is changed to obtain correct winding on the empty bobbin. A large wheel gives tighter winding. The winding wheel determines the initial bobbin speed.
Spur wheel change building motion: This can be used instead of ratchet wheel. With the spur wheel change building motion a finer hank requires either a large wheel in the top position or a smaller wheel in the bottom position.
Ratchet wheel: The finer the hank, the greater the number of teeth in the ratchet wheel. The ratchet wheel controls the bobbin speed after the initial speed of the bobbin.
Tapper change pinion: A large pinion gives more tapper to the bobbin.
Spindle speed change wheel: The larger the spindle speed change wheel, the slower the spindle speed.
 

Roller setting in Speed/Simplex/Roving frame

Roller setting is a very important task in the spinning department. Incorrect settings lead to creation of various problems and hampers spinning conditions. The speed of the leading roller is always greater than the preceding roller. Incorrect setting leads to the variation of weight/unit lengths. If the setting between two pairs of drafting roller is closer, than that required, the leading end of the fibres will caught by the front pair of roller and back end by the preceding pair of rollers, results in fibres breakage. The broken fibre is naturally shorten in length & create drafting wave irregularity in the material and frequently ends down in speed frame & ring frame. Closer setting produces slubs in roving, yarn, roller laps, and gum between the drafting rollers. On the other hand wider setting produce irregular motion of fibres mostly short fibres which is a cause of irregularity. Too wider setting also fails to bring the fibres in parallel and regular arrangement so, produce roving yarn of poor strength and appearance.
     To obtain efficient drafting, immediately the tailing end of a fibre is released by one pair of roller, its leading end should ideally be gripped and accelerated by the succeeding faster pair of rollers obviously, this is not possible if the roller setting is greater than the fibre length.
In roller setting the following factors must be kept in mind –
Length of the fibre:
The space between two pair of rollers must be slightly greater than the average length (modal length) of the fibre under processing.
Bulk of the materials:
 As the bulk increase the distance between the drafting roller increase and vice-versa. Otherwise the top rollers will strip and introduce irregularities.
Frictional properties:
If the frictional properties of fibre are higher for the same staple length and bulk, the roller setting need to be increased. For irregular fibre length the best setting is a compromise between the longest and shortest fibre.
     The setting becomes progressively closer in passing from the sluber through the intermediate to the roving frame. In a 3 – line roller system, the setting between the back and middle pair of rollers is not important in the view of the small draft applied at this stage. This setting is usually about 1(5/8)th inch for the short staple and 2 inch for the long staple. On the other hand, magnitude of the setting between the middle and front roller is important. At the sluber, the setting is about 1/8 th inch to 3/16 th inch in excess of the effective length of the fibre; at the intermediate frame 1/32 th inch less than that at the sluber and at the rover 1/32 th inch less than that at the intermediate frame. On the two zone simplex, the setting used for the two zones are about the back zone and the same as those on any intermediate at the front zone.

Tuesday, January 13, 2015

Importance and amount of Roller weighting | Advantages of Spring weighting

The roller weightings generally applied to the top rollers by weight hung below the roller beam are about 20 lbs for a double boss front roller, 14 lbs for middle roller and 10 lbs for back roller, the middle and back rollers may be suddle weighted (spring weighted) and in this case the applied weight is about 20 lbs. Heavier weightings are helpful to deal with the occasional thick ends and piecing in the creeled material to make even material.
Top roller weighting are very important in all the cases where the roller drafting are employed due to –
Over weighting contributes in the:
-         Production of roller – Jam between the drafting rollers.
-         Excessive ends down.
-         Production of weaker fibres.
On the other hand under weighting produces:
-         Irregular material (sliver, roving and yarn).
-         Insufficient parallelization of the fibres.
-         Insufficient straightening of the fibres.
-         Slubs in the material.
-         Waves in the sliver.
The advantages of spring weighting and top arm over dead weighting are as follows:
-         The roller beam is feed from the multiplicity of weight wires and hook and is therefore easier to keep the machine clear.
-         The top rollers are positioned more exactly over the corresponding bottom rollers.
-         The top rollers are held by top arms and can be swung out of the way easily.
-         The pressure applied is independent of the roller setting.
-         The weighting is commonly even greater with synthetic rubber covering top roller than that in the old method of weighting in order to avoid from stoppages by bad drafting.

Monday, January 12, 2015

Changes to be made in a speed frame when a certain hank is made finer

Suppose, a certain hank is made on a machine and it is desired to change to a higher count. The same sliver or roving is used in the creel. The necessary changes are as follows –
Draft: This must be altered in order to make the delivery roving finer. The draft change pinion (D.C.P) will therefore be made smaller in order to drive the back roller more slowly.
Lifter change wheel: A smaller lifter change wheel slows down the lifter shaft without altering the bobbin speed and thus decreases the spacing of the coils.
Ratchet wheel or Spur wheel change building motion: The finer roving also requires that the ratchet wheel should be entangled (i.e. greater no. of teeth) in order that a lessened movement be given to the rack at each up & down lift. There will be more layer/inch of diameter for the finer than for the coarser roving, therefore each action of the lift must give a shorter traverse to the rack which moves the cone drum strap in short steps.
With the spur-wheel change build motion, a finer hank will require either a larger wheel in the top position or a smaller wheel in the bottom position.
Bottom cone-drum change or winding wheel: A smaller wheel (if it is driver one) will be required to correct winding on the bobbin as the front roller delivery will be less for the finer hank.
Twist change pinion: A finer roving requires more twist/inch into it than a coarser one. Twist wheel is changed for this purpose and by making it smaller, the speeds of the front roller is reduced but since the speed of the spindles is not altered, more twist will be put into the roving.   
From this change, it will be noticed that the speed of the cone drum is also changed, which is a necessary consequence of changing of the speed of the front roller to slow, the bobbins must have the same reduction in the speed in order to wind on the smaller amount of roving that is delivered to them.

Functions of Cone drum, Flyer, Bobbin Tapper and Differential motion

Cone drum
As each layer of roving is added to the bobbin in the speed frame, its diameter is increased. In flyer leading and bobbin leading frame, it is necessary to increase or decrease the bobbin rpm respectively to maintain a constant surface speed on the bobbin surface as each layer is added to its diameter so that the delivered roving can be wound on the bobbin always at a constant rate. For this purpose bobbin speed is increased or decreased by moving the belt on the cone drum. Top cone drum is driver and bottom cone drum is a driven one. Bobbin driving shaft is connected with bottom cone drum. In case of flyer leading or bobbin leading frame, the belt on the top cone drum is moved a short step from smaller to larger diameter or larger to smaller diameter to increase or decrease the bobbin rpm respectively.
Flyer
The functions of the flyer are as follows –
Twisting and winding: The roving delivered by the front roller is twisted by the flyer. The flyer being driven by the spindle is projected through the centre hole of the bobbin. As the strand of fibres held by the front roller at one end and the flyer is revolved with the strand round the bobbin at a different speed so, twisting and winding take place.
Building: It guides the roving through central hole of the flyer top and a eye at the flyer gives pressure to a specific place on the bobbin so that, successive coils are wound on the bobbin without lapping throughout the build of the bobbin package. The pressure of the flyer applies a certain amount of tension to the roving as to build a firm bobbin.  
Bobbin Tapper
The function of the bobbin tapper is to produce conical shape of the bobbin being built up at both ends. As the bobbin build up progressively its lift is shortened at each reversing of the bobbin rail.
Differential motion
Differential motion transmits motion from the bottom cone drum to the bobbin with increasing diameter of the bobbin with the regular change in speed with the instant movement of the belt on the cone drum. Thus the roving can be wound on the bobbin without stretching or slackness. This motion acts as a media to transmit the changing (increasing or decreasing for flyer leading or bobbin leading frame respectively) speed of the bottom cone drum to the bobbin in a steady manner with the changing of bobbin diameter and moment of belt on the cone drum.

Thursday, January 8, 2015

Difference between Apron and Roller Drafting system

The differences between apron and roller drafting system are as follows –
 
Apron Drafting
Roller Drafting
Better control of short fibres movement
Poor or no control of short fibres movement
Better yarn quality with a given draft
Poor yarn quality for the same draft
Regularity of material is better
Regularity of material is poor
Less influenced by changes in staple length and length distribution.
More influenced by changes in staple length and length distribution.
Higher range of draft
Lower range of draft
Smoother, durable and reliable running.
Less smoother, durable and reliable running.
Lower end breakage rate and roller lapping.
Higher end breakage rate and roller lapping.
Automatic clearer increases yarn cleanliness.
No such clearer and thus poor yarn cleanliness.
Higher production.
Lower production.
Higher spindle speed.
Lower spindle speed.

Different drafting systems used in Speed/Simplex/Roving Frame | Describe a modern drafting system

What are the different drafting systems used in speed frame?
The following drafting systems are used in speed frame –
-         4 - over - 4, two zone drafting system.
-         Two-zone apron drafting, (4 - over 4), aprons are adjusted on 2nd top and bottom roller, better fibre control and higher drafting can be attained with this drafting system at the speed frame.
-         2 – over – 3 drafting system, this gives effective grip on the fibre, usually suitable for synthetic fibre, less slippage of fibres in this drafting system.
-         4 – over – 4 graduated roller drafting system.
-         3 – over – 3 drafting system.
-         Casablancas – 2 – zone system.
-         Casablancas U – 3 system.
-         Platt special 3 – line drafting system.
-         S.K.F PK 400 system.
-         Toyodas 3 – over – 3 two zone system.
-         Toyodas 4 – over – 4 three zone system.
-         Toyodas FL 2 (D type one zone system).

Describe a modern drafting system
Description of Casablancas two-zone drafting system
The Casablancas two-zone drafting system is widely used for cotton on speed frame. The back zone draft takes the place between two pairs of roller, after which follows a zone with practically no draft, in which a special condenser is placed to fold the fibre strand upon itself for consolidation prior to finally drafting it once again in the front zone.

Modern drafting system

The front zone is composed of the casablancas double apron unit followed by a congenital pair of front rollers. The draft in this zone about three times that in the back zone. Between the Casablancas bands and the front pair of rollers there is a second condenser, the “collector” which incorporates the stray fibres into the bulk to prevent the creation of excessive amount of fly. The Casablancas weighing arrangement consists of a saddle assembly, which receives weight through a single hook and lever.

Objects and Operations of Speed/Roving Frame

What are the Objects of Speed Frame?
The purposes or objects of speed frame are –
-         Attenuating of draw frame sliver to a suitable size for spinning.
-         To insert small amount of twist to form strand known as roving. The twist being adequate to held the fibre together.
-         To wind the twisted strand or roving on to an upright bobbin suitable for creeling at the next process.
The package so produced is tapered or conical at each end and made sufficient firm so that it can be transferred without damage to the roving and yet will unwind readily at the next machine.

What are the operations involved in Speed Frame?
The following operations are involved in speed frame –
-         Drafting: The draw frame sliver feed to the speed frame is reduced in size by the action of drawing and drafting. So that, the reduced size of the roving is within the drafting range of the ring frame.
-         Twisting: Spiraling the fibres around each other about the axis of the strand so to bind themselves together to impart sufficient strain, to enable it to build-up in the form of a suitable package, convenient to handle from one process to another. Here, the amount of twist used should be just sufficient to hold the fibres together but it should preclude drafting in the ring frame.
-         Laying out: To put the coils on the bobbin in regular arrangement so that, no over lapping or excess spacing between the coils can occur. The coils are laid side by side throughout the build of the bobbin. This operation is done by alternate reversing motion of the bobbin rail.
-         Winding: To put successive layers of roving on the bobbin at a proper rate of speed. The speed being governed by the building motion with the help of differential motion.
-         Building motion: Shortening of successive layers of roving to make conical ends of the package with the help of building mechanism.