Process Control in Draw frame

Process Control in Draw frame

 



Draw Frame

  Draw Frame is a machine for combining and drawing slivers of a textile fiber (as of hemp for rope manufacture or cotton for spinning).Draw Frame  is the operation by which slivers are blended, doubled and leveled. In short staple spinning the term is only applied to the process at a draw frame.

In drawing slivers are elongated when passing through a group of pair rollers, each pair is moving faster than previous one.

Actions Involved in Draw Frame

Drafting: It is the process of increasing length per unit weight of sliver. It is mainly due to peripheral speed of the rollers.

Doubling: The process of combing two or more carded sliver into a single form is called doubling. In draw frame m/c generally six slivers are fed to convert into one i.e. six doubling.

Drawing: In the cotton industry the term is applied exclusively to processing on the draw frame, where the operation is one of doubling and drafting. Drawing= Drafting + Doubling.

Diagram of draw frame

Tasks of Draw frame

1. Equalizing
2. Parallelizing
3. Blending
4. Dust removal

Equalizing: One of the main tasks of draw frame is improving evenness over short, medium and especially long terms. Carded slivers are fed to the draw frame have degree on unevenness that cannot be tolerated in practice and slivers from the comber contain the “infamous” piecing. It is obscured by draw frame.

Equalizing is always performed by a first process, namely doubling and can optionally also be performed by a second process, namely auto leveling. The draft and the doubling have the same value and lie in the range of 6 to 8.

Parallelizing: To obtain an optional value for strength in the yarn characteristics, the fibers must be arranged parallel in the fiber strand. The draw frame has the tasks of creating this parallel arrangement. It fulfills the task by way of the draft, since every drafting step leads to straightening the fibers.
 Blending : In addition to the equalizing effect, doubling also provides a degree of compensation of raw material variation by blending. Their results are exploited in particular way in the production of blended yarns comprising cotton or synthetic blends. At the draw frame metering of the individual components can be carried out very simply be selection of the number of slivers entering the machines.

Dust Removal: Dust is steadily becoming a greater problem both in processing and for the personnel involved. It is therefore important to remove dust to the greatest practical extent at every possible point within the overall process.

Dust removal can only be carried out to a significant when there are high levels of fiber. Since a large function the smallest particles adhere relatively strong to the fibers. High performance draw frame is equipped with appropriate suction removal systems; more than 80% of the incoming dust is extracted.

Actions involved in Draw Frame

Drafting: It is the process of increasing length per unit weight of sliver. It is mainly due to peripheral speed of the rollers.

Doubling: The process of combing two or more carded sliver into a single form is called doubling. In draw frame m/c generally six slivers are fed to convert into one i.e. six doubling.

Drawing: In the cotton industry the term is applied exclusively to processing on the draw frame, where the operation is one of doubling and drafting. Drawing= Drafting + Doubling.

Operating Devices

·        Creel (Sliver Feed)

·        The drafting Arrangement

·        Suction systems for the drafting arrangement

·        Coiling

·        Can charger

Creel

The creel must be designed so that:-

·        False Drafts are avoided.

·        The machine stops upon accordance of the sliver break.

·        Sliver breaks can be dealt with easily, comfortably and safely.

In this purpose it is necessary to provide a rotable roller or roller pair above each can. A guiding device for leading the rollers into the drafting arrangement is also required.

Requirements of drafting arrangement

The drafting arrangement is the heart of the draw frame. Drafting arrangement exerts most decisive influences on sliver quality. The requirements placed on the drafting arrangements are mentioned bellow:-

1.      Simple, uncomplicated construction.

2.      Stable design with smooth running roller. IT means rollers should be centric and smooth running.

3.      A mode of operation giving a high quality product at even high running speeds.

4.      High Degree of flexibility, suitability for all raw materials.

5.      Optimal control over the movement of the fibers during the drafting operation.

6.      High precision in both of operation and adjustment.

7.      Rapid and simple adjustability of roller spacing and draft levels.

8.      Ease of maintenance of cleanings.

9.      Optimal ergonomic design.

Factors dependent upon the fiber materials

1.      Mass of the fibers in the strand cross section.

2.      Degree of order of the fiber.

3.      Shape of cross section of the fiber strand.

4.      Compactness of the fiber strand.

5.      Length of fiber.

6.       Adhesion between the fiber depends upon:-             

·        Surface structure

·        Crimp

·        Lubrication

·        Compression of the strand.

7.      Evenness of distribution of fiber length.

8.      Twists present in the fiber strands.

Factors depending upon the drafting arrangement

1    1.  Diameter of the rollers.

          2. Hardness of the top rollers.

3       3. Pressure exerted by the top rollers.

4       4.  Surface characteristics of the top rollers.

5         5. Fluting the bottom rollers.

6        6. Type and form of fiber guiding devices, such as pressure rods, pin bars, aprons, condenser etc.

7        7. Clamping distance.

8      8.  Level of the draft.

** Both input and output of draw frame is sliver, then what is done in draw frame?

Answer:  From a purely commercial point of view draw frame is of little significance. But its influence on quality and evenness is greater. The carded sliver contains fibers which are oriented in various directions and they are crimped, hooked or curled. They entangled with one another and their height per unit length is high. They are irregular and contain some impurities. So they need a process for eliminating these errors.

In cotton spinning line raw frame is the definitive compensation point for eliminating errors. This draw frame:-

·        Straighten the fibers in sliver.

·        Make the fibers more or less parallel.

·        Reduce the weight per unit length of sliver.

·        Remove dust from sliver.

·        Make very perfect blending of fibers.

So, the carded sliver is actually made perfect in quality and evenness of draw frame.

Elements of drafting arrangements

Bottom roller: Bottom rollers are made of steel and are mounted in roller strands or in frames by means of needle or ball bearings. They are positively driven from main gear transmission.

On order to improve their ability to carry the fibers along, they are formed with flutes of one of the following types.

·       Axial flutes

·       Spiral flutes

·       Knurled flutes

Top roller: The top rollers are not positively driven; they are mounted by the means of ball bearings. These top rollers are made of steel and they are covered with thick coating of synthetic rubber. An important matter avoid this coating is its hardness. Soft rubbers coating can grip the fiber strand more perfectly than that of hard one, but soft coating of rubber wear out more quickly.

Hardness of rubber coating on top rollers in specified in terms of degree shore.

Soft coating -> 60-70 degree shore

Medium coating -> 70-90 degree shore

Absorb coating-> Above 90 degree shore

3 over 3 drafting Arrangement

                 

This is probably the most widely used form of drafting arrangement which was first developed by Platt in 1960. The drafting arrangement runs more smoothly with longer rollers. This is applied especially to the front rollers. For a given circumferential speed larger rollers can be operated at lower speed of revolution.

Roller slip

For pressure variation on top rollers gripping of fiber becomes irregular and due to this variation occurs in the draft of sliver. Due to roller slippage in front zone drafting becomes less. Roller slop also occurs if thick slivers are passed through drafting arrangement, because the bulky material cannot be drawn foreword by the rollers with exactitude. Though, more or less 3% roller slip in considerable.

Auto leveler

Without auto leveler we do not correct errors but avoid them. Auto leveler may be off 3 types.

1. Short term auto leveling system (for lengths of product from 10-12 cm)

2. Medium term auto leveling system (for length above 3m)

3. Long term Auto leveling system (for length above 20m)

Whatever be the system, the design of an auto leveler falls into two groups.

1. Open loop auto leveler

2. Closed loop auto leveler

Open loop auto leveler

In open loop auto leveler sliver weight is measured from input material. Here the measurement of sliver irregularity is expressed in terms of voltage and is compared with a desired value (DV). The resulting error signal is amplified (A) and after a suitable time delay (TD) its signal is used to vary the speed of variable speed device (S). A tachogenerator (TG) ensures that the variable speed device accurately follows the signal.

Advantages:

1. Accurate regularity maintaining is possible.

2. Piecing which arises from combing can be partly eliminated by open loop system.

3. Suitable for control the variation of short to medium wavelength.

Disadvantages:

1. If the measuring be sensor is improper, it is not possible to control the regularity.

Closed loop Auto leveler:

In closed loop auto leveler system sliver weight is measuring (M) from the output material and the resulting signal is integrated (I). Then the signal is compared with the desired level. After amplification (A), the variable speed devices (S) vary the speed of the drafting rollers. Because of the absence of any averaging device this would cause irregularities in output.

Advantages:

1. Suitable for compensating errors of long wave length.

2. It can be used in error raw frame.

3. A part of faults can be eliminated by it in first passage.

Disadvantages:

1. It cannot eliminate piecing as finely as open loop auto leveling system.

2. It is very costly.

After going through closed loop auto leveling system the sliver needs a second passage for eliminating other faults. 

Correction Length

                                   

   

If there is a sudden deviation from the set volume as the material passes through, a corresponding signal is sent to a regulating device to correct the fault. Owing to the mass inertia of the system, compensation cannot be effected suddenly, but must be carried out by gradual adjustment. A certain time (the correction time:  I ) elapses before the sliver delivered has returned to the set volume. During this time, faulty sliver is still being produced, although the deviation is being steadily reduced. The total length that departs from the set value is referred to as the correction length (I). In closed-loop systems, the correction length is further increased by the dead time. In this case it depends upon the dead time (II) and the correction time (III). The correction length depends upon the system and the speed of operation, and therefore varies considerably.
The term “correction length” is used to describe the efficiency of a leveling device. However, this term is used in different ways and sometimes also incorrectly. The current interpretation is: “The correction length is the length of the product which would be produced when leveling a rectangular deviation of the product.“ The length therefore refers to an amplitude of the fault of 1%. The term “correction length” is therefore a theoretical value, since in practice rectangular faults do not occur. As they cannot be checked in the spinning mill, the quality of the delivered sliver is usually taken as the standard of comparison, and sliver evenness can be determined by any evenness tester.

Necessities of Auto stop motion

Stop motion is a device which provided to ensure in the machine are stopped immediately if: –

1. The sliver run out from the creeled can.

2. Sliver brakes in the creel.

3. Lap up on drafting roller.

4. If sliver is chocked in the sliver collecting plate and funnel.

5. If sliver is chocked in between trumpet and calando roller.

6. If delivery can is filled with sliver.

If stop motion system is absent then the following defects may arise:-

1. Considerable damage may cause to machine.

2. The output sliver may be thick or thin.

3. Lapping up of drafting or calendar roller.

4. Irregular drafting.

5. Excess of full can.

6. Too much waste produce.

7. The yarn strength or roving strength may vary from place to place.

8. Any operator must have to attend the machine full time to stop it at any fault.

Effects of Draft and doubling on sliver quality

We know that due to drawing and drafting the irregularity of sliver increase but due to doubling irregularity decreases.

Let us assume,

Cγm = Coefficient of variation of mass.

D =draft

Now,

Cγm α d

=>Cγm = k.d, where “k” is a constant for particle fiber.

Technical specifications of draw frame is as below :

Delivery speed [m/min]	up to 1 100
Production per delivery [kg/h]	up to 400
Deliveries per machine	1 or 2
Doublings	4 to 8
Draft	up to 12
Delivery hank [ktex]	1.25 to 7
Waste [%]	0.1 to 1

The advantages of high-performance leveling drawframes

 

In the spinning mill:

• reducing count variations;
• fewer short-term mass variations in the yarn (CV %);
• improving the coefficient of variation of yarn strength (CV % cN/tex);
• fewer yarn imperfections (IPI and Classimat);
• improving the efficiency of roving frame and spinning machine by reducing the ends down rates;
• fewer cuts on the winding machine.

In the subsequent process stages:

• reduction of ends down rates in weaving preparation and weaving;
• even appearance of the finished cloth;
• reducing the cost for claims by eliminating a remarkable number of faults.

   

  Autoleveler Draw Frame RSB-D 50 and Draw Frame SB-D 50 – A new dimension in productivity, quality and easy operation  

  

   

   

  The new single-head draw frame generation from Rieter offers an unprecedented level of productivity with the highest quality standards. The patented drive concept ECOrized uses 25% less belt, saves up to 1 000 EUR per year on energy costs and now allows higher delivery speeds, for example for polyester and combed cotton. The unique SLIVERprofessional expert system is integrated on the easy-to-use touchscreen. Assortment changeover times are significantly reduced. Superb scanning precision and highest autoleveling dynamics ensure outstanding sliver evenness. A patented sliver coiling sensor guarantees precise coiling from the very first centimeter.

  

  Economy

  • The draw frame is designed for highest productivity of up to 1 200 m/min delivery speed. Depending on the fiber material, the speed can be increased by up to 33%.
  • The substantially shortened drive train with energy-efficient motors saves up to 1 000 euros in energy costs per year on each RSB draw frame. This is also reflected in a significantly quieter machine.
  • The patented sliver guide upstream of the drafting system guarantees centric sliver guidance with high productivity and sliver quality at all times.

  

  Quality

  • Superb scanning precision and highest autoleveling dynamics ensure outstanding sliver evenness – from the first to the last centimeter.
  • Superior Classimat values in the yarn are achieved due to efficient drafting system extraction with lifting cleaning lips and the frequency-controlled drive.
  • The new coiler CLEANcoil-PES extends the cleaning cycle on critical PES fibers by at least 100%. The CLEANtube option ensures clean sliver coiling when processing cotton.

  

  Flexibility

  • Convenient setting of the delivery speed, coiler speed, suction intensity and draft (RSB only) is made on the touchscreen via frequency-controlled drives.
  • High visibility LEDs indicate the condition of the draw frame and simplify the work for the operator. A colored touchscreen facilitates intuitive operation.
  • The SLIVERprofessional expert system is integrated in the machine. The direct adoption of setting recommendations allows a rapid assortment changeover with best sliver quality.

 TRUTZSCHLER Draw Frame

         

The right draw frame for every application

The Trützschler draw frame types are as diverse as their applications. The one thing all Trützschler draw frames have in common is a drafting system concept with optimized drives and pneumatically loaded top rolls, which are of great technological importance. Colour touch screens allow for simple and secure operation and maintenance by the user.
It is the task of the Trützschler draw frames to optimize the sliver after carding and before spinning. There is a matching machine type for every application: The autoleveller Draw Frame TD 8 is ideal for high productions up to 1,000 m/min. The TD 8-600 (600 m/min) was designed for combing mills. Due to their low energy consumption, breaker Draw Frame TD 7 without levelling and the newly developed TWIN Draw Frame TD 9T operate particularly economical. The advantages of the Integrated Draw Frame IDF 2 are low space requirement and a high level of efficiency.

The new breaker Draw Frame TD 9T

The Trützschler Draw Frame TD 9T is a twin draw frame with focus on reduced space requirement and efficient production. If required, it is also available as single TD 9 version. Thus, each even and uneven number of drafting heads is implemented.  

The reliable breaker Draw Frame TD 7

If the operational organisation does not permit the use of large cans, the reliable Trützschler breaker Draw Frame TD 7 is employed. Featuring a large can magazine, it is ideal for a space saving solution for cans with 500 or 600 mm diameter.

The successful autoleveller Draw Frame TD 8

The best autoleveller draw frame of all times convinces with consistently good sliver quality and excellent running behaviour. This draw frame is characterised by simple, intuitive operation and sophisticated optimization tools.

The special autoleveller Draw Frame TD 8-600 for combing

This version of the TD 8 was developed for use post combing. Optimization of the control algorithms to the typical application range of 450 – 550 m/min improves sliver quality. Selecting drives for a delivery speed of maximum 600 m/min reduces power consumption.

The Integrated Draw Frame IDF 2 for rotor spinning

For rotor spinning, especially when processing cotton and any type of waste and secondary raw materials, there is no better solution than direct coupling of the Integrated Draw Frame IDF 2 with the card. Yarn quality and economic efficiency outperform any conventional process.


 LMW Draw Frame

Draw Frame LDF3

 

 

Salient Features

• Deliver y speed of up to 1,100 mpm (mechanical)
• 4 Over 3 drafting arrangement with Pressure bar
• Duo – Digital auto levelling system

Change Gearless Drive

• Inver ter controlled main drive facilitates deliver y speed change from display
  • – Stepless increase in speed
  • – No change pulleys
• Ser vo motor drive to drafting
  • – Main Draft adjustment through display
  • – Elimination of main draft change pulleys

Quality

• Automatic suggestion of Autoleveller correction point based on Roller setting and Break draft
• Sliver monitor ensures the quality of output sliver
• Spectrogram for self diagnosis of mechanical faults

Drafting & Delivery Zone

• – Electronic sliver cutting
• – Auto piecing using Pneumatics
• – Top roller end bush with sealed bearings and Life time grease
• – Self-cleaning top roller strippers – Stripper is automatically lifted periodically

Suction System

• – Integrated suction system for drafting, console, and sliver feed at Scanning
• – Filter box with Wiper arrangement for easy maintenance

• Ergonomically designed four row creel for accommodating feed cans upto 40” dia.
• Replaceable stainless steel coiler for man-made fibres
• Deliver y Cans dia. 12” to 24” / Deliver y Can ht. 36”, 42”, 45” and 48”
• Adjoining platforms for space saving – optional layouts

Marzoli Draw frame

 

DF1 - DFR1

 

Speed	Up to 1,000 m/min
Feeding	Up to 8 doublings
Drafting system	3 over 3 + guiding roller
Delivery cans	18", 20", 24" and 40"

• Perfect fibers control in the drafting area
• High eveness of the output sliver
• Speed up to 1,000 m/min
• DFR1 with state-of-the.art open-loop autoleveling technology
• Positively driven creel to prevent false drafts
• Contact sensors and sliver control system before the T&G to ensure an immediate stop of the machine if a sliver breaks
• Toothed belts for power transmission to reduce energy consumption, noise and maintenance
• 3 over 3 drafting system with guiding roller
• Quality monitoring sensor located at the delivery calender
• Fast and reliable automatic can change
• Highly efficient suction system 
• Special design of the coiler to avoid dust and fibers accumulation inside the tube

• 

Technical Data:

Delivery heads	One
Raw material	cotton , man made fibers , blends
Delivery speed	Up to 1,000 m/min
Doublings	6 or 8
Draft	4 to 10
Can sizes	18" to 40" diameter

 

Drawing frame

On their way to become high-quality yarn, staple fibers must first be subjected to extensive processing. In this process, the drawing frame is a major quality driver, since all flaws that are preserved in the drawn fiber structure will also become visible in the yarn. Siemens offers a high-quality solution in order to meet the resulting challenges for the automation solution. SIMOTION and SINAMICS products support a sophisticated automation concept that provides many benefits for the machine. The drawing frame is located in the spinning process between the carding machine and the spinning machine. It serves to draw out and parallelize the fibers. Major components of the drawing frame include the feeding gate, the drawing equipment and the take-off cylinder.

Siemens Solution example for drawing frames

The automation serves to ensure the accurate speed synchronism of the four drives - especially during the start and stop of the machine and in case of power failure. The Motion Control system SIMOTION D and the drive system SINAMICS S offer a fully integrated automation solution from a single source.

Benefits

• Optimum production resultsthrough high-speed material thickness control (with closed-loop controlled system)
• Superior control dynamicswith differential gearbox, or
• Direct control using a highly dynamic servo motor

Products used:

•  SIMOTION D
•  Servo motor 1FK7
•  Distributed I/O module ET 200