Sunday, February 9, 2020

PROCESS PARAMETERS OF DRAW FRAME PROCESS



PROCESS PARAMETERS IN DRAW FRAME:

 The spinner has the last and final chance to improve the quality of yarn. It is the last process that helps to minimise the yarn irregularities. The unevenness present in the sliver gets passed into the yarn after the draw frame process. The best draw frame process practice makes a very big difference in the evenness and other yarn irregularities. The performance of the draw frame process depends upon the parameters selected in the process. The selection of the correct process results in the form of improved performance of the draw frame machine.

The main factors affecting the performance of the draw frame machine are given below:

•The fibre length of the raw material used.

The total draft to be used in the draw frame.

The fibre fineness of the raw material to be used.

•The number of doublings to be used in the draw frame machine.

The type of drafting system to be used in the draw frame machine.

The weight per unit length of sliver to be fed to the draw frame machine.

•The number of the draw frame passages.

the delivery speed of the draw frame machine.

•The break draft in the draw frame machine.

The type of auto leveller used in the draw frame.    
The setting of auto leveller.

common setting parameters of draw frame process:

The common setting parameters to be used in the draw frame process are given below:

The fibre length of fibre gets affected due to
the presence of hooked fibres in the sliver to be
processed.

• The hooked fibres present in the sliver affect the drafting efficiency of a draw frame machine.

• A draft of 7.5 is used to achieve better performance in both breaker and finisher draw frame.

 • A draft of 7.0 may also be used in the breaker. A draft of 7.5 to 8.0 is applied for combed material in a single passage draw frame.

• A draft of 8.0 is used in breaker and finisher to process synthetic material having a staple length of 44 – 51 mm.

The number of doublings to be used in the draw frame process is decided according to the linear density of the carded sliver to be processed and the total draft to be used.

• Today’s draw frame has the capability to process the sliver having a linear density of 36 – 40 grams per metre efficiently without making compromises with quality.

• Since these synthetic fibres possess high resistance to drafting so that a linear density of fewer than 38 grams per metre is used in the draw frame process.

Plus 8 – 12 mm break draft setting is used for longest cotton fibres processing in 3 over 3 or 4 over 3 drafting system both.

The value of break draft ranges between and 1.26. This value varies between   1.42 to1.6 for synthetic fibre processing.

The shore hardness of the rubber coating of the top roller is kept approximately 80 degrees or more to achieve a very high delivery speed of the draw frame.

The buffing of rubber coating of top rollers is done after every 30 days to achieve consistent yarn quality.

Coiler is selected according to the material to be processed. Bigger coiler tubes size is used for the processing of synthetic fibres. This bigger coiler size helps to prevent coiler choking and kinks in the slivers due to coiling in the can.

the diameter of the coil depends upon the coiler speed. There is a need to observe the clearance between the sliver and can after changing the coiler speed. If clearance increases more than 5 mm, then the turntable position is adjusted to maintain the required clearance between coils outer and cane inner.

The pressure bar setting is always combined with the front roller setting. If the pressure bar depth is high. Creel height is kept as low as possible for high depth pressure bar in the processing of combed cotton especially.

The setting of the sliver monitor is done precisely. The open-loop auto leveller acts immediately to stop the machine in case of linear density variation in sliver.  Whenever there is a problem with sliver weight, this will stop the machine. The calibration of the auto leveller is carried out from time to time to assure proper working of it.

The mechanical draft is selected accurately in a draw frame equipped with an auto leveller. The draw frame operates with auto leveller in switched-off position during calculating mechanical draft. The linear density of the sliver is analysed if found correct then the mechanical draft is correct. In case of variation in linear density of sliver gears are need to change as per required weight per unit length of sliver without an auto leveller

Intensity of levelling and timing of correction are two important parameters in auto levellers.

The value of mechanical draft varies in the same amount of percentage according to the percentage of variation is fed sliver. Higher feed variation needs a higher correction length.

Improper setting of the timing of correction of auto leveller results in the form of unevenness percentage in the delivered sliver.

Today’s auto leveller is capable to correct the overall 25% feed variation in the sliver. In other words, it has the capability to correct the variation of 12% plus and minus side both.

Please click on the below video link to watch the full topic in Hindi:




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