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Francesco Gatti speech on 2007 May European Silk Forum
Author:  admin     PublishDate:  2007-05-11      Hit:  5963
Francesco Gatti's speech
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Electronic control of raw silk, silk yarns and spun silk yarns
Recent advancement in raw silk defects classification
(Francesco Gatti, Stazione Sperimentale per la Seta – Tessile di Como S.p.A. consortile)

At the International Silk Forum held in Hangzhou last October, surprisingly the Chinese presented a draft of an electronic method of silk measurement and its related classification and grading, which was greatly contested by European and Indian participants.
Actually, it is based on the use of two instruments, an evenness tester (Uster Tester 3) and a fault testers (Keisokki), to determine respectively silk evenness and defects.
Fortunately, the presence of European and Indian delegates allowed to disprove that it is sufficient to utilize only one instrument (Classifault by Keisokki placed on a winder), equipped with an evenness sensor (CV) and optical and capacitive sensors, in order to count and classify defects.
This last instrumental configuration allows to save considerably (of about 50%) the instruments cost and it needs only one sampling, rather than two.
Our position was shown on the occasion of further meetings with EEC Authorities in order to put pressure on China during trade bilateral meetings.
Other differences between the European and the Chinese proposal regarded the use of optical sensors and not only the capacitive ones, as it is actually treated all raw silk yarns.
Other different operating details regard the yarn collection system (high precision brushless motors and twin drum device), test speed, defects (IPM and thick/thin) parameters setting, etc.

Essentially, the draft of the Chinese method proposed a situation which was at least 3 or 4 years old and which suffered of the fact that in the Chinese standardization group were present some Representatives of Universities, who were promoter of the evenness measure (CV) with an evenness tester and who had a poor knowledge of the Classifault system installed at CIQ in Hangzhou.
From the Chinese part it was also proposed a draft of a method of classification divided in six classes based on the new electronic measurement, as a replacement for Seriplane, while it uses the parameters, already defined in the previous/traditional method (GB/T 1798-2001), complementary to the one of electronic classification, for other characteristics (breaking resistance and elongation, winding breaking, cohesion, etc.).
What above refers only on raw silk, while there hasn’t been any proposal concerning twisted yarns (organzines, weft, etc.).
After the International Silk Forum we met Keisokki technical managers, and discussed with them many technical details, which are not completely clear or they shuld be developed.
On his part, Keisokki is now preparing a new instrument (which is called Classifault Model CFT TRI CHORD Flex), that already utilizes both optical and capacitive sensors, as well as CV (actually capacitive) sensor, all of them managed by a single electronic control unit.
Defects measurement capacity is further increased with 25 classes for nep and slub, 15 classes for thick places and 15 classes for thin places.
This new instrument utilizes Windows® XP as its operative software, it is equipped with new optical sensors (tri cord flex), also provided with a sensor for coloured yarn places and, therefore, potentially able to measure the black places, sometimes present on raw silk yarn.
The CV sensor and the new software will be even able to calculate the CV5m, as the Chinese requested (besides the CV% and the CV50m, formerly measured).
The new instrument is optimized to test raw silk, but it should potentially work even for twisted silk yarn and for yarn made in any other fibres, at least up to a certain count.
Deliveries should begin at the end of this spring and two new instruments should be installed in China at CIQ in Hangzhou and IDEA Co. Ltd.

Parallely to the instrument improvement, with these new facilities definitive data will be collected in order to carry out studies and the development of a new grading system of raw silk based on such measures.
On the data collected last year n more than a hundred of raw silk lots, explorative statistical studies were carried out.

One of the results obtained carrying out the Factor Analysis of the following 8 characteristics:
Characteristics Classes of defects
small slub c A2+B2+A1+B1+C1
big slub c C2+D2+E2+D1+E1+A4+B4+C4+E4+A3+B3+C3+E3
big thick c F1+G1+H1+Z1+S1 (+35%)
big thin c K1+L1+M1+N1 (-35%)
optical small slub A2+B2+A1+B1+C1
optical big slub C2+D2+E2+D1+E1+A4+B4+C4+E4+A3+B3+C3+E3
optical big thick F1+G1+H1+Z1+S1 (+35%)
optical big thin K1+L1+M1+N1 (-35%)

is that only 2 independent factors are extracted and they account for most of the variability of the 8 characteristics.
Surprisingly the 1st Factor accounts mainly of the optical defects while the 2nd Factor accounts mainly the capacitive defects.

This first statistical analysis confirms that for raw silk is necessary to measure both this types of defects, with proper and adequate sensors.

Source: European Silk Forum
 
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