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Table screen printing process

 Table screen printing process

The table screen printing method is widely used to print various types of fabric. Fabric is printed on the table that is why this method is called table printing. Flat screens are used in method therefore it is also called the table screen printing technique.

Advantages of table screen printing:

1- This fabric printing technique is a cost-effective technique. 

2- The design repeat size is bigger than any other fabric printing technique. 

3- The wastage of colours and fabric is very low. 

4- The edges sharpness of the design results is excellent. 

5-Minimum order quantity is very short. 

6- We can even print one meter of fabric sample in table screen printing.

7- The printed fabric is dried by sun drying therefore drying cost is very low.

Disadvantages of table screen printing technique:

1- The number of colours in table screen printing is limited.

2 - Almost 6 - 7 colours design can be printed by table screen printing.

3- The fitting accuracy of the colours in the printed fabric design gets low.

4- if continuous fabric or yardage is printed in the table screen printing, the repeat joining line may appear in the fabric.

5- It is labor intensive printing technique.

6- approximately, 30 - 35 meters of fabric can be printed on the table screen printing at a time on one table. 

7- The depth of the printed colour may slightly vary due to manual striping.

8 -  This printing technique has width limitations as well.

9- Productivity is low.

Table screen printing process:

The whole printing process gets completed in the below steps:

1- Screen preparation

2- Table preparation and setting

3- Fabric mounting upon the table

4-Colour preparation  and matching

5- Fabric printing

5- Fabric drying

6- Fabric curing 

7- Fabric checking and touching

8- Fabric folding and packing

Screen preparation:

Screen preparation is a very critical task in the table screen printing process. this task is performed by a well-trained person. The screen preparation takes place in the below steps.

• The printer receives either printed fabric samples or artwork.
• If he receives a printed fabric sample, the artwork is developed by the printer.
• Now, the tracing of the each colour is prepared.
• The tracing is prepared upon the transparant plastic sheet having good flexibility and strength.
• The area having colour is painted with black colour in each tracing paper.
• The blank area is left unpainted in the tracing paper.
• Now, blank screens are prepared.
• Very fine and perforated polyester fabric is is mounted on the round pipes square or rectangular iron frame securely and tightly.
• One blank screen is prepared for each colour.
• Now all these screens are coated with photo emulsion and dried well under sunlight.
• Now, these photo emulsion coated screens are exposed to high intensity light as per tracing.
• The tracing is placed over exposing table then the photo emulsion coated screen is placed over the tracing. Now, the photo emulsion coated screen is covered by plan metal or plywood sheet.
• The exposing table light is switched on now for definite time.
• Thanks the photo emulsion coated screen exposes with high intensity light. The light falls on those areas of screen directly where the blank area of the tracing allows to pass light. The areas exposed with High intensity light gets hardened. 
• Now, these screens are washed in weather by high pressure water supply. The the hardened areas of photo emulsion in the screen remain fixed in the screen but unexposed areas of photo emulsion with light get washed out and the photo emulsion is removed. 
• Now, each screen is checked. If required, touching of photo emulsion is done on damaged areas.
• Thus, the all screens get ready for use.

Printing table preparation and setting:

• Two types of printing tables are used in table screen printing.
• Cushioned (bed type) table is used in some printing unit while adhesive bonded tables are used in the other Printing units.
• In the cushioned (bed type) printing table, few layes of fabric are spread out over the printing surface of the table.
• In the adhesive bonded table, the top surface of the printing table is covered with good quality non woven bonded cloth made of synthetic fibres.
• A layer of adhesive is coated upon the top surface of this table.
• In case of adhesive coated table, it is washed thoroughly before start printing.
• The screen positioning elements are fixed as per design properly. 

Fabric mounting upon the printing table:

• Now the fabric is mounted upon the printing table.
• In case of cushioned (bed type) printing table, the fabric is fixed with the help of steel pins. 
• The steel pins hold the fabric at the both selvedge.
• In case of adhesive coated printing table, the fabric gets stup upon the printing surface due to adhesive coating upon the surface.
• The fabric is mounted straight.
• The wrinkle free fabric mounting is assured.
• The fabric is mounted tightly in the both directions.
• The side margin in the table is kept as per fixation of screen positioning elements.
• Thus, the fabric gets ready for Printing.

Colour preparation and colour matching:

• The colours paste is prepared in the colour kitchen.
• Each colour is prepared separately and as per colour recipes.
• A band of fabric in each colour is printed in each colour till proper matching achieved.
• Now, our colours pastes get ready for use.

Fabric printing:

• Each colour is printed one by one.
• Lightest colour is printed first.
• The darkest colour is printed at the last.
• Printing starts from one end of the fabric and finishes at the other end of the fabric.
• The screen is placed over the fabric and is aligned with the help of screen positioning element.
• Now, the colours paste is dropped at the one side of screen.
• The colour paste is wiped out from one to other side of the screen. The colour paste penetrated through the fine holes of the screen and gets stuck upon the fabric.
• Now, other colours are also printed in the same way.

Fabric drying:

• If the steam heated table is used, the the fabric gets dried after my some time and it was s taken out from the printing table.
• In case of cold table printed fabric is left for drying by natural moisture evaporation.
• Ceiling fans air helps to accelerate the speed of drying there.
• After some time, the fabric is taken out from the table and is hung upon strings tied in the walls of the shed for further drying.

Fabric curing:

• This printed fabric does not show proper colour fastness.
• This fabric is passed through a heating chamber where hot air blows.
• The polymerization process takes place and the colour fastness gets improved.

Fabric checking and touching:

• Now the fabric is checked for any printing defect.
• If any unprinted area appears after printing, the colour is painted by touching brush or pen .

Fabric folding and packing:

• Now, the fabric length is measured and rolling if the fabric is carried out.
• The rolled fabric is packed in the polythene sheet and then in hussian cloth .
• Thus printing fabric gets ready for dispatch.

Siro spinning system, objective, properties of siro spun yarn, advantages and disadvantages of siro spun yarn

 Objectives of Siro spinning:

· The main objective of the Siro spinning is to achieve a weavable worsted yarn by capturing strand twist during twist insertion on the ring-spinning frame.

· To reduce the cost of production in the spinning stage up to half by increasing production per spindle by roughly two times.

· To eliminate the yarn doubling process cost.

 

What is Siro spun yarn?

· Siro spun yarn is a virtual - two-fold yarn in which the two components are untwisted strands rather than twisted singles yarns.

· It builds on the concept of self-twist spinning up to some extent.

· In elf-twist spinning, two drafted strands have cyclic false twist inserted by a set of oscillating rollers.

· One strand is made to follow a longer path so that when the two strands are brought together their twist is out of phase.

· In trying to untwist, the two strands twist about each other, capturing oscillating twist in each strand.

· Production rate 200 meters /minute is possible and the yarns could be used for knitting.

· However, to be weavable the yarn had to undergo a real twisting in a separate twisting step (ring doubling or two-for-one twisting process) as with normal two-fold yarn production.

Concept of Siro spinning:

· The initial steps were taken at CSIRO in the mid-1970s (Plate and Lappage, 1980).

· Two strands were fed side-by-side through the drafting system.

· These strands were passed through a further pair of rollers after leaving the front rollers.

· This pair of rollers was intermittently blocked the twist from propagating up to the nip line.

· The two strands were brought together by the twist to form a large, long spinning triangle (the ‘vee’).

· The twist-blocking rollers caused the twist running into the two strand arms to increase and decrease.

· This intermittent twist becomes trapped in the yarn below the convergence point, which is held fixed by a guide, as alternating twist of the strands relative to the rotating point of contact (i.e. the mean folding twist).

· The alternating twist enables surface fibers to be trapped between the two strands.

· Plate and Lappage (1980) showed that the amount of trapping is proportional only to the alternating strand twist and is independent of the two-fold twist.

· An alternative method by Lappage (1973) achieved a similar result by vertically oscillating the convergence guide without the twist-blocking rollers.

· Even though twist is observed in the strands during Siro spun spinning, if it is constant then none of it is trapped in the yarn.

· Real (net) twist cannot be introduced, only alternating twist.

Yarn model of Plate and Lappage for real two fold and virtual two fold yarn

· This is illustrated in the model of below Fig.  (following Plate and Lappage, 1982) in which the two singles strands are represented by long rubber cylinders.

· One of the untwisted cylinders has a black line along its length Fig. (a), representing a surface fiber. 

· If real twist is inserted then the surface fiber traces a helical path Fig. (b). 

· Every turn of singles twist leads to a trapping point of the fiber after two-folding Fig. (c). 

· If the strand twist remains constant then there is no real (alternating) twist of the strands relative to each other. A fiber that starts on the surface always remains on the surface Fig. (d). 

· This is the basic reason why ordinary singles yarns (or Siro spun yarns at small strand spacing) are not weavable. 

· In such yarns there is a small amount of fibers migration, due to varying spinning tensions and movement of the delivery positions of fibers, but overall many surface fibers are poorly trapped and will be easily rubbed up along the yarn during weaving. 

· Constant strand twist above the convergence point just leads to fibers maintaining their relative positions in the two strand yarn; removal of the two-fold twist will leave two untwisted strands. 

· When two strands are held at both ends insertion of real twist is not possible and only varying twist can enable trapping.

Schematic diagram of two fold Siro spinning system with break out device:

The changes needed to the ring spinning frame to produce Siro spun yarns are as below:

1- A double roving creel (for twice the number of roving packages)

2- A double set of roving guides.

3-A wider middle (apron) roller recess, modified front zone condensers (if used).

4- The break-out device. 

· The yarn count per spindle is doubled and the amount of twist inserted is usually the same as would be inserted in the two-folding operation (a metric twist factor of 120 to 130) which is similar in turns per meter to that put in the singles yarn. 

· The recommendation is still to have the same total number of fibers in the yarn cross-section as the equivalent two-fold yarn (e.g. for wool, at least 2 ¥ 35 = 70, given the accepted spinning limit of 35 fibers in the yarn). 

· This twist level and number of fibers are needed to ensure good spinning performance by avoiding drafting of the strand arms. 

· Studies (Plate and Feehan, 1983; Plate, 1983a) have shown that the optimum strand spacing is a balance between improved abrasion properties and poorer evenness and spinning performance. 

· It was found that yarn abrasion resistance increases linearly with strand spacing, hairiness drops rapidly at first, then slowly, and yarn evenness, tenacity and elongation improve at first, then plateau and later decrease. 

· The standard strand-spacing of 14 mm has been adopted for worsted spinning (Plate, 1983a).

Properties of Siro spun yarn:        

· Siro spun yarns have higher tenacity and elongation.

· Siro spun yarn has lower hairiness.

· On average Siro spun yarn have marginally poorer evenness, possibly due to correlations between the drafting of strands through the same drafting zone and due to occasional strand-arm drafting.

· Siro spun yarns are not quite as abrasion resistant as the equivalent two-fold and more likely to fail on the loom under extreme conditions, such as in the selvedge.

· Siro spun yarns have more thin places than two-fold yarns produced from the same material and observed that extreme thin places are associated with higher spinning tension.

· It is much better to think of Siro spun as a singles yarn with improved binding of the surface fibers.

· As singles, Siro spun yarns are leaner than the equivalent two-fold yarns.

Disadvantages of Siro spun yarn:

· One drawback is that winding and clearing are carried out on the final yarn rather than the singles.

· The joins (splices) must survive weaving unaided by a good (un spliced) yarn. The performance of splices in weaving is so critical that Siro spun could not gain wide commercial adoption until improved wool splicing (the Thermo splicer™) was available.

· This is a potential cause of more visible streakiness in plain-weave piece dyed fabrics where the uniform colour and simple pattern provide the least hiding of the yarn irregularity that is always present.

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Siro spinning system, objective, properties of siro spun yarn, advantages and disadvantages of siro spun yarn

विभिन्न प्रकार के कॉम्पैक्ट स्पिनिंग सिस्टम्स, कॉम्पैक्ट स्पिनिंग के उद्देश्य, लाभ और सीमाएं (Objectives of compact spinning system, different types of compact spinning systems advantages and limitations)

 कॉम्पैक्ट स्पिनिंग  प्रणाली (कॉम्पैक्ट स्पिनिंग सिस्टम):

रिंग स्पिनिंग प्रक्रिया में कॉम्पैक्ट स्पिनिंग तकनीक की आवश्यकता क्यों होती है?

पारंपरिक रिंग कताई प्रक्रिया में फाइबर्स  के माइग्रेशन  का मुख्य कारण यार्न के निर्माण के दौरान फाइबर्स  के बीच तनाव का अंतर होता है।

जब रिबन की तरह फाइबर बंडल  में ट्विस्ट डाला जाता है और यार्न का निर्माण होता है।

तब फाइबर बंडल के रिबन  के किनारों पर फाइबर्स  तनाव का  का सामना करते हैं और फाइबर्स के बंडल के बीच में फाइबर्स संपीडित होते  हैं जब तक कि अत्यधिक यार्न तनाव न हो।

तनाव को मुक्त करने के लिए, तनाव के अधीन फाइबर यार्न में अपने पथ की लंबाई को छोटा करने की कोशिश करते हैं, जबकि संपीड़न के तहत फाइबर इसे लंबा करने की कोशिश करते हैं।

इसके परिणामस्वरूप, फाइबर्स अपना संपूर्ण पेचदार पथ छोड़ देते हैं और धागे की परतों के बीच माइग्रेशन  करते हैं।

दूसरे शब्दों में, एक लंबे कताई त्रिकोण(स्पिनिंग ट्रायंगल ) के परिणामस्वरूप यार्न में  लंबे समय तक कमजोर बिंदु उत्पन्न होता है, और इस प्रकार रिंग फ्रेम में अधिक अंत टूटता  है।

हालांकि, एक लंबे त्रिकोण की वजह से फाइवर्स  यार्न में बेहतर ढंग से बंधे होते हैं।

कॉम्पैक्ट स्पिनिंग  के उद्देश्य:

कॉम्पैक्ट स्पिनिंग  का मुख्य उद्देश्य कताई त्रिकोण ( स्पिनिंग ट्रायंगल) को खत्म करना होता है क्योंकि फाइबर माइग्रेशन  की समस्या पारंपरिक रिंग स्पिनिंग  प्रक्रिया में बनने वाले कताई त्रिकोण(स्पिनिंग ट्रायंगल) के आकार से जुड़ी होती है।

स्पिनिंग त्रिकोण के लगभग उन्मूलन के कारण कॉम्पैक्ट स्पिनिंग  प्रणाली से लैस रिंग स्पिनिंग  में ट्विस्ट सम्मिलन के दौरान फाइवर्स  के बीच तनाव का अंतर काम  होता है।

इसलिए कॉम्पैक्ट यार्न में फाइबर माइग्रेशन पारंपरिक रिंग स्पन यार्न की तुलना में कम होने की उम्मीद की जा सकती है।

क्लेन ने एक स्टडी में पाया है कि एक छोटा कताई त्रिकोण एक छोटे कमजोर बिंदु का प्रतिनिधित्व करता है और इस प्रकार रिंग स्पिनिंग पोसेस के दौरान एन्ड ब्रेकेज रेट काम होता   है।

यदि कताई त्रिकोण बहुत छोटा है और किनारों पर तंतुओं का विक्षेपण बाइंडिंग-इन के दौरान बहुत तेज होना चाहिए।

· यह सभी तंतुओं के साथ संभव नहीं होता  है। इसलिए एक बहुत ही छोटे  कताई त्रिकोण के परिणामस्वरूप किनारे पर कुछ फाइबर यार्न में एकीकृत नहीं होते हैं, जिसके परिणामस्वरूप ढीले फाइबर या 'फ्लाई'  उत्पन्न होते हैं।

किनारे पर अन्य फाइबर केवल एक छोर पर बंधे हो सकते हैं, जिससे बालों का झड़ना हो सकता है।

कॉम्पैक्ट स्पिनिंग  एक चिकनी  और कम फ्लाई युक्त यार्न  पैदा करती है।

विभिन्न प्रकार के कॉम्पैक्ट स्पिनिंग  सिस्टम्स:

मुख्य रूप से तीन प्रकार के कॉम्पैक्ट स्पिनिंग  सिस्टम्स आज के समय में रिंग स्पिनिंग मशीन में प्रयोग किये जा रहे  हैं जिनका वर्णन नीचे किया गया है:

सुसेन एलाइट कॉम्पैक्ट स्पिनिंग  सिस्टम्स:

· इस कॉम्पैक्ट स्पिनिंग  सिस्टम्स में एक अतिरिक्त 'ड्राफ्टिंग ज़ोन' लगाया जाता  है जो एक मानक थ्री-रोल रिंग स्पिनिंग मशीन पर लगाया जाता है।

इस ड्राफ्टिंग  जॉन में एक सक्शन  ट्यूब के ऊपर एक हवा-पारगम्य लैटिस   एप्रन का घूमता  हैं।

सक्शन ट्यूब के ऊपर एक  नकारात्मक दबाव होता  है और सक्शन तुबे में प्रत्येक स्पिनिंग  स्थिति के लिए फाइबर मूवमेंट  की दिशा में झुका हुआ एक स्लॉट होता है।

जब फाइबर्स सामने वाले रोलर निप लाइन को छोड़ते हैं, तो जालीदार एप्रन सक्शन स्लॉट के ओपनिंग्स  पर फाइबर्स का मार्गदर्शन करता है।

· सक्शन  वायु प्रवाह के कारण फाइबर्स किनारे की ओर बढ़ते हैं और संघनित होते हैं।

· सक्शन स्लॉट्स के ओपनिंग्स  का झुकाव रेशों के प्रवाह की दिशा में होता है।

ये सक्शन  स्लॉट झुकाव स्लॉट पर अपने परिवहन के दौरान फाइबर बैंड पर एक अनुप्रस्थ बल उत्पन्न करके संघनन में मदद करते हैं, जिससे फाइबर बैंड अपनी धुरी के चारों ओर घूमता है।

जाली एप्रन इससे जुड़े रेशों को डिलीवरी निप लाइन तक ले जाता है।

· डिलीवरी  (ड्रिवेन ) शीर्ष रोलर का व्यास फ्रंट बॉटम  (ड्राइविंग) रोलर के व्यास से थोड़ा बड़ा रखा जाता है।

डिलीवरी टॉप रोलर और फ्रंट बॉटम रोलर के बीच व्यास का अंतर संघनक प्रक्रिया के दौरान अनुदैर्ध्य दिशा में तनाव उत्पन्न करता है।

तनाव कर्व्ड फाइबर्स  को सीधा करना सुनिश्चित करता है, और इसलिए नकारात्मक दबाव के संघनक प्रभाव का समर्थन करता है।

रीटर  K44 'ComforSpin' कॉम्पैक्ट  स्पिनिंग सिस्टम:

इस प्रणाली में मुख्य ड्राफ्टिंग जोन के बाद ड्राफ्ट किए गए फाइबर रिबन को बाद में संघनित करने के लिए वायुगतिकीय बलों का उपयोग किया जाता है।

· वायुगतिकीय बलों के परिणामस्वरूप, कताई त्रिकोण बहुत  छोटा हो जाता है या लगभग समाप्त हो जाता है।

· रीटर  K44 ComforSpin कॉम्पैक्ट  स्पिनिंग सिस्टम में तीन-रोलर, डबल-एप्रन द्रफरिंग सिस्टम  शामिल होते हैं ।

· इस सिस्टम  के निकास क्षेत्र को फाइबर संघनन की होने देने   के लायक बनाया जाता  है।

निकास रोलर को एक छिद्रित ड्रम (1) से बदल दिया जाता है, जिसके भीतर एक स्थिर सक्शन यूनिट  होती है जो मशीन की केंद्रीय निष्कर्षण इकाई (2) से जुड़ी होती है।

ड्राफ्टिंग सिस्टम की एक्जिट निप लाइन द्वारा डिलीवर किए गए फाइबर ड्रम की परिधीय गति से चलते हुए छिद्रित ड्रम की सतह पर रखे जाते हैं।

इस तरह, कॉम्फोरस्पिन तकनीक मुख्य ड्राफ्टिंग जोन के बाद वायुगतिकीय समानांतरीकरण और फाइबर्स  के संघनन में मदद करती  है।

· इस कॉम्पैक्ट स्पिनिंग सिस्टम  में कताई त्रिकोण को कम से कम कर दिया जाता  है।

कॉम्पैक्टिंग ज़ोन मशीन का दिल होता है जिसमें छिद्रित ड्रम, सक्शन इंसर्ट और एयर गाइड एलीमेंट होते हैं।

· सकारात्मक रूप से संचालित छिद्रित ड्रम कठोर होकर   रेशों के चिपकने के लिए प्रतिरोधी हो जाता है।

प्रत्येक ड्रम के अंदर की तरफ जरुरत के समय बदला जाने वाला और विशिष्ट आकर के स्लॉट वाला स्थिर सक्शन इन्सर्ट होता है।

· यह ड्रम मशीन के सक्शन सिस्टम से जुड़ा होता  है।

छिद्रित ड्रम में उत्पन्न निर्वात द्वारा निर्मित वायु धारा मुख्य डरफटिंग  के बाद फाइबर्स  को संघनित करती है।

ड्राफ्टिंग ज़ोन के बाद से स्पिनिंग  त्रिकोण तक निप लाइन से फाइबर को पूरी तरह से नियंत्रित किया जाता है।

एक अतिरिक्त निप रोलर ट्विस्ट  को संघनक क्षेत्र में फैलने से रोकता है।

संघनक क्षेत्र में संघनन दक्षता को विशेष रूप से डिज़ाइन किए गए और पेटेंट किए गए वायु गाइड एलीमेंट  द्वारा बढ़ाया जाता है।

Zinser AIR-COM-TEX 700® कॉम्पैक्ट स्पिनिंग सिस्टम:

यह प्रणाली कताई त्रिकोण को खत्म करने के आधार पर भी काम करती है।

· इस तकनीक में पारंपरिक तीन रोलर्स ड्राफ्टिंग सिस्टम  का उपयोग किया जाता है।

· फाइबर्स ड्राफ्टिंग सिस्टम  से निकलते हैं और एक छिद्रित बेल्ट की सतह पर सक्शन  के वजह से  संघनित हो जाते हैं।

· ट्विस्ट इंसर्शन से पहले संघनित फाइबर स्ट्रैंड की  चौड़ाई में काफी कमी आती  है।

ड्राफ्टिंग सिस्टम से निकलने वाले फाइबर्स  की चौड़ाई और यार्न के व्यास के बीच के अंतर में यह कमी प्रभावी रूप से स्पिनिंग  त्रिकोण को समाप्त कर देती है।

कॉम्पेक्टिंग ज़ोन को अतिरिक्त फीड की एडजस्टेबिलिटी द्वारा कच्चे माल के लिए अनुकूलित किया जा सकता है, क्योंकि दो फ्रंट सिलिंडर के बीच कॉम्पेक्टिंग ज़ोन छिद्रित एप्रन की कम गति से अधिकतम -4.0% के साथ प्रभावित हो सकता है। कॉटन कॉम्पैक्ट कताई प्रक्रिया के लिए तकनीकी दृष्टि से 0 से 4% अतिरिक्त फ़ीड की आवश्यकता होती है।

इस स्पेक्ट्रम के साथ मशीन को सबसे अधिक फाइबर पर सेट किया जा सकता है।

इसका व्यक्तिगत तंतुओं की स्थिति पर सकारात्मक प्रभाव पड़ता है, क्योंकि केवल बिना तनाव वाले और समानांतर तंतुओं को ही विक्षेपित और संकुचित किया जा सकता है।

कॉम्पैक्ट स्पिनिंग के लाभ:

हैरीनेस का कम स्तर।

·बढ़ी हुई स्ट्रेंथ  के धागों के  उत्पादन करने की क्षमता।

लौ ट्विस्ट लेवल  के साथ भी ब्रेक पर बेहतर बढ़ाव।

लो ट्विस्ट के कारण सॉफ्ट फील का होना ।

कॉम्पैक्ट स्पिनिंग  प्रक्रिया एक नई रिंग-यार्न संरचना का निर्माण करती है जो आदर्श स्टेपल फाइबर यार्न निर्माण के करीब होती है।

बेहतर फैब्रिक अपीयरेंस 

· बुनाई के चरण में बेहतर प्रदर्शन।

कच्चे माल का बेहतर उपयोग।

· उच्च वितरण दर प्राप्त की जा सकती है।

· डाउनस्ट्रीम प्रसंस्करण चरणों में लागत बचत।

कम एन्ड ब्रेकेज  की दर के कारण मशीन की दक्षता में सुधार करता है।

इसलिए समान ट्विस्ट  स्तर के साथ पारंपरिक रिंग स्पन यार्न के बराबर यार्न की ताकत बनाए रखते हुए कम गुणवत्ता वाले कपास का उपयोग करना संभव होता है।

कॉम्पैक्ट स्पिनिंग  की सीमाएं:

कॉम्पैक्ट स्पिनिंग  की एक सीमा यह भी होती  है कि पारंपरिक रिंग स्पिनिंग से कॉम्पैक्ट सिस्टम में पुनर्वास के लिए अधिक निवेश की आवश्यकता होती है।

महत्वपूर्ण बात यह है कि कम बालों के झड़ने के नकारात्मक प्रभाव के बारे में चिंताएं हैं।

· एक अध्ययन में बताया गया है कि बालों के कम होने से ट्रैवेलर्स  में बार-बार बदलाव आ सकता है, क्योंकि धागे के बॉडी  से निकलने वाले बाल ट्रैवेलर्स को चिकनाई और ठंडक प्रदान करते हैं और इस तरह ट्रैवेलर्स के पहनावे को कम करते हैं।

यह मुद्दा कॉम्पैक्ट रिंग स्पिनिंग प्रक्रिया के अर्थशास्त्र पर सवाल उठाता है।

एक अध्ययन से पता चलता है कि यह केवल लंबे (कोम्ब्ड) फाइवर्स  के लिए प्रभावी होती है (कैम्पेन, 2000)।

Objectives of compact spinning system, different types of compact spinning systems advantages and limitations

 

Compact spinning 

system:

 

Why does compact spinning technology require in the ring spinning process?

·  The main reason  of the fibres migration in the conventional ring spinning process is the tension difference between fibres during the yarn formation.

·   When the twist is inserted into the ribbon like fibres bundle and the yarn formation takes place. 

·The fibres at the edges of the fibres bundle face  with tension  and  the fibres in the middle of the fibres bundle are subjected to compression unless there is excessive yarn tension.

· To release the stress, fibres subjected to tension try to shorten their path length in the yarn while fibres under compression try to lengthen it.

· As a result of this, fibres leave their perfect helical path and migrate between layers of the yarn.

·   In the other words, a long spinning triangle results in a longer weak point, and thus more end breaks in the at ring frame.

·   However, with a long triangle, fibres are better bound into the yarn.

Objectives of compact spinning:

· The main objective of the compact spinning is to eliminate the spinning triangle because  the fibres migration problems is  associated with the size of the spinning triangle being formed in the conventional ring spinning process.

 

·The tension difference among fibres during twist insertion is small  in ring spinning equipped with compact spinning system due to the almost  elimination of the spinning triangle.

·Therefore fibre migration in compact yarns could be expected to be less than that in conventional ring spun yarns.

· Klein has found out that a short spinning triangle represents a short weak point and thus fewer end breaks.

·If the spinning triangle is too short and the deflection of the fibres on the edges has to be very sharp during the binding-in.

·       This is not possible with all fibres. Therefore a very short spinning triangle results in some fibres on the edge not to be integrated into the yarn, resulting in loose fibres or ‘fly’.

·  Other fibres on the edge might be bound-in at one end only, causing hairiness.

·Compact spinning produces a smoother yarn and less fly.

Different types of compact spinning devices:

There are mainly three kinds of compact spinning devices which are described as below:

Suessen EliTe compact spinning system:

·This system consists of an additional ‘drafting zone which is mounted on a standard three-roll ring spinning machine.

·An air-permeable lattice apron runs over a suction tube in this drafting zone .

·The suction tube is under negative pressure and there is a slot tilted in the direction of fibres movement for each spinning position.

·   When the fibres leave the front roller nip line, the lattice aprons guides the fibres over the openings of the suction slots. 

·The fibres move sideways and condense due to suction air flow.

·The openings of the suction slots get inclined to the direction of fibres flow.

·These suction slots inclination help to condensing by generating a transverse force on the fibres band during their transport over the slot, causing the fibre band to rotate around its own axis.

·The lattice apron carries the fibres attached to it up to the delivery nip line.

·The diameter of the delivery (driven) top roller is kept slightly bigger than the diameter of the front bottom (driving) roller.

·The difference of diameter between delivery top roller the front bottom roller generates a tension in the longitudinal direction during the condensing process.

·The tension ensures the straightening of curved fibres, and therefore supports the condensing effect of the negative pressure.

Rieter K44 ‘ComforSpin’ compact spinning system:

·The compact spinning concept illustrated in the figure  is the one represented by the Rieter ‘ComforSpin’ process.

·Aerodynamic forces are used to laterally condense the drafted fibres ribbon after the main drafting zone in this system.

·As a result of the aerodynamic forces, the spinning triangle becomes so small or  it gets  almost eliminated.

·The Rieter K44 ComforSpin machine consists of a three-roller, double-apron drafting system.

·The exit zone of this system is modified to allow fibre condensation. 

·The exit roller is replaced by a perforated drum (1), within which is a stationary suction unit that is connected to the machine’s central extraction unit (2). 

·The fibres delivered by the exit nip line of the drafting system are held on the surface of the perforated drum, moving at the drum’s peripheral speed.

·In this way, the ComforSpin technology allows aerodynamic parallelization and condensation of the fibres after the main draft.

·The spinning triangle is reduced to a minimum in this compact spinning system.

·The compacting zone is the heart of the machine which consists of the perforated drum, suction insert, and air guide element.

·The positively driven perforated drum gets hard-wearing and resistant to fibres clinging.

·There  is an exchangeable stationary suction insert with a specially shaped slot inside each drum.

·This drum gets connected to the suction system of the machine.

·The air current created by the vacuum generated in the perforated drum condenses the fibres after the main draft.

·The fibres are fully controlled all the way from the nip line after the drafting zone to the spinning triangle.

·An additional nip roller prevents the twist from being propagated into the condensing zone.

·       The compacting efficiency in the condensing zone is enhanced by a specially designed and patented air guide element.

Zinser AIR-COM-TEX 700® compact spinning system: 

·This system  also works on the basis of eliminating the spinning triangle.

·The conventional three cylinder drafting system is used in this technology.

·The fibres emerge from the drafting system and get condensed under suction onto the surface of a perforated belt.

·The condensed fibre strand undergoes a substantial reduction in width prior to twisting.

·This reduction in the difference between the width of the fibres emerging from the drafting system and the yarn diameter effectively eliminates the spinning triangle.

·The compacting zone can be adapted to the raw materials by the adjustability of the additional feed, because the compacting zone between the two front cylinders can be influenced by a lower speed of the perforated apron with maximum –4.0%. For the cotton compact spinning process, from 0 to 4% additional feed is required from a technological point of view.

· The machine can be optimally set to the most fibres with this spectrum .

·This has a positive influence on the position of the individual fibres, since only unstressed and parallelised fibres can be deflected and compacted.

Advantages of compact spinning:

·The reduced hairiness level.

·Ability to produce yarns of enhanced strength.

·Improved elongation at break even with lower twist levels.

·Softer feel due to low twist.

·The compact spinning process produces a new ring-yarn structure which is close to the idealized staple fibre yarn construction.

·Better fabric appearance

· Improved performance in weaving stage.   

·better utilization of the raw material.

· Higher delivery rates can be achieved.    

· Cost savings in the downstream processing stages.

· Improves machine efficiency due to low end breakages rate.

·It is therefore possible to use low quality cotton while maintaining yarn strength equal to that of conventional ring spun yarn with the same twist level.

Limitations of compact spinning:

·The only limitation of compact spinning is that the rehabilitation from conventional ring spinning to the compact system needs more investment.

·Importantly, there are concerns about the negative influence of the low hairiness.

·A study pointed out that the reduced hairiness might lead to more frequent traveler change, since hairs protruding from the yarn body provide lubrication and a cooling effect on the traveler and thus reduce traveler wear.

·This issue questions the economics of the compact ring spinning process.

·A study shows that it is effective only for longer (or combed) fibres (Kampen, 2000).

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