AFRICASIAEURO.COM TEXTILE MACHINES KNOWLEDGEBASE
ABOUT SPINNING APRONS :
In practical usage, spinning aprons will need to be scoured after a prolonged time of use. During drafting, spinning aprons will remove seed coat fragments in microform from 0.1 microns to much larger ones.
This is essential as seedcoatfragments cause disturbances during the spinning process, as well as create yarn quality problems. Whilst not being a cleaning element in spinning process per se, spinning aprons fulfill an important function within the spinning process.
By and large a fiber guiding device, spinning aprons also will have an important influence on yarn evenness.
In synthetic - and man made fiber usage, spinning aprons will require more cleaning ( scouring ) due to use of anti slip and fiber to fiber friction, fiber to metal friction, and antistatic oleofins used by fiber manufacturers. These agents are applied on man made or synthetic fibers in 0.01 % of fiber weight processed.
SPINNING AGENTS form deposits within a short time of operation, and are required to be removed by scouring with hyrocarbons such as TCE, DCE or IPA. Alcohols will effectively remove deposits from the apron surface. ( toxicity and environmental risks are to be taken seriously, disposal must be in accordance with environmental laws.)
(WARNING USE WITH CAUTION: 1 drop of the chemicals can contaminate thousands of gallons of water. A suitable Activated carbon filter should be applied to remove any residual liquids. Protective gear such as facemasks and gloves must be used during scouring for effective protection.)
Unless such deposits are removed, fiber guidance and flow will be hindered and in case a new lot is processed will cause disruption in spinning due to different agents used. As a result also yarn quality parameters will suffer.
It is therefore a requisite to scour spinning aprons regularily as part of a preventive maintenance plan.
In three shift operations this should take place at least once every 3-4 weeks or 125 hours.
C) Cotton Fiber white fly honeydew contamination and its correlation towards neps and Fiber preparation
Cotton fiber is frequently found to be contaminated 'Honey dew' secretion created by white flies. These are normally found on African species more due to conditions under which Cotton there is grown. African Cotton is almost all grown non-irrigated and in vast areas in savanna stretched regions. These areas have a large number of white flies which love cotton buds. Their secretion contains a sticky substance called 'Honey dew'.
Nothing is more disturbing to the Spinning personnel than 'Honey dew'. Fibers stick together, they are difficult to open and clean, as well as tend to be easily damaged during the mechanical process in blowroom, and carding. Mechanical forces will break fibers and create more neps as a result, as well as fiber fly in the spinning process.
'Honey dew' can have serious effects on yarn quality and spinning mill operation. A thorough check is required by the purchaser to make sure that 'Honey dew' contamination is controlled. You do not want to end up with a lot being contaminated. In most cases the buyer leaves technical personnel with little choices. A well planned blending with other varieties should be kept a regular standard and must be rigorously checked.
B) Fiber immaturity in Cotton and its correlation towards nepsEvery 'spinner' knows the implications of immature fibers in cotton. In practical terms immature fiber content is noticed in several processes and stages.
First, a nep count is taken right at the bale - preferably from as many bales as possible - in at least every tenth bale and 4 corners. Before bales are put on opening line. High variations can be observed. Bales must be seggregated and classified , then sorted before adding to the processing batch.
Nep count must be followed through to final stage with correcting measuries applied to each process if necessary.
Depending on origin, staple, nep content, final count, spinning process, method, a more careful approach can so be achieved. The spinning process can be better controlled this way.
This method of seggregation can safe the mill substantial costs in terms of : reducing ends down, less imperfections, better quality ( elongation, tenacity ) and evenness values, as well as less creation of non - and - recyclable fiber waste.
The benefits of applied careful measures can not be underestimated, and will run into thousands of USDollars for each batch processed in this manner.
Todays modern testing instruments such as AFIS can assist you greatly, an HVI is a must. Still many mills do not invest in these instruments, and prefer the older methods like Pressley, Micronaire.
Constraints are put by mill owners with insufficient or no knowledge of the spinning process and their attempt to 'save money' in order to enhance their own gains.
Failed Project 1-
Cont. : ' The main factor however was overlooked. Machines were transported without adequate support of draft assembly (brackets).
In MVS 751 the draft assembly is made of 2 pre draft zone cylinders, 1 bridge, and 1 main draft cylinder, a four over four draft assembly. A negativ factor was the 8 mm steel support main side plates.
These plates give way when left unsupported during transport. The weight of the heavy draft cylinders will bend sideplates at the slightest knock if left unsecured. Thus the draft geometry will become distorted.
This exactly happened with the MVS 851. The blame must be put on both parties : Buyer ( without adequate knowledge and experience - and seller ( who did not provide original MURATA transport safety support brackets)
The machines are rendered useless, as one will not obtain correct drafting results, even after straightening, or attempt to do so. Plates can not be brought back to original dimension.
In spinning distortions of 0,01 mm are visible in CV and manifest themselves in form of periodic waves.
Therefore the whole project was a failure, right from the onset. When confronted with such problems one has to make a decision. For owners do not blame themselves, but always put the blame on their subordinates. (hover over pics to see full size)
During assembly the first step was salvaging what could be salvaged. Total distortion on either side of each section corresponded to from 1 inch to 1.5 inches in height.
Steel support frame plates had to be wrought back to original dimensions. Anything more than 0.01 mm was unacceptable.
This could only be achieved by means of a hydraulic jack with a minum of 5 KN hydraulic force. Without such device spinning results would be disastrous.
Operating at a max. delivery speed of 350 m/min, the MVS would create periodic faults resulting in poor - yarn tenacity, - CV %, - elongation, - count CV, imperfections in yarns.
The yarn can not be sold on the market, apart from horrible running scenarios on machine itself.
A true nightmare for a spinner. Knowing that no matter what you do the disaster has been created from the onset.
All these facts were communicated, yet totally ignored - mainly due to ignorance. The chain of command was left to incapable personnel chosen according to personal relationship.
Truthfully anyone confronted with this dilemma in fact nobody had the choice but to :
A) ask for complete replacement of both steel support plates - and create delays in start up, causing millions of loss.
B) apply hydraulic tools, fabricate templates with exact dimensions, shape distorted old plates ( enhanced by heating ) and consider loss of tensile strenght properties (extremely difficult).
Failed spinning project - (PART 3) Airjet Spinning MVS 851
In the third part we continue to elaborate on the chain of human mistakes that lead to the failure of the project.
Blowroom was adequate in machinery setup, with a opening / filter / condenser line sufficient for Rayon / Viscose blend. Carding machines were not of prime excellent quality, but would have sufficed in case of Rayon staple fiber 1.3 dtex - 38 mm S.D.
What did NOT suffice was the poor quality drawing frames which came into use from a previously failed attempt to spin airjet yarns.
Since there was only one drawing passage - and the applied drawframe had a four over four twin head delivery - without autolevelling - this was one of the greatest mistakes made by the mill owner.
If your blowroom - and carding preparatory stages are of medium quality, but your drawing is poor - any spinning - including all other methods (OE, Ring, and Airjet) will be a failure.
Without achieving a low CV 1m on drawframes, the spinning process is a total disaster.
Two passages of drawframes (Toyota) with double head delivery, a machine that has been previously used as a 1st ( and 2nd) passage alternately, spinning results are disastrous. In the absence of an evenness tester, setting of draft elements is impossible.
To add injury to insult, main bearings on MVS 851 came under increasing duress, operating at 350 m/1' - without being able to water level machine sections due to distorted and mangled draft assembly frames - continuous periodic variations occur as patterns in yarn structure. These distortions will result in yarn weakness and cause 'Tiger stripes' in all following process, plus cause low efficiency - and as a result poor yarn quality.
Managerial and technical personnel was unable to recognize any of these negative factors. It was a foreclosed disaster. The millowner decided to get the supplier (seller) of second hand machines involved to remedy the situation, who in turn only tried to cover up for the mistakes made after shipment.
The supplier went on to work on bearing seats (trying to grind bearing seats of draft assemblies !!! ) Such type of 'helpshift' work can only be condemned. The question must be asked of how it will be possible to grind bearing seats in order to achieve a uniform level with required tolerances of +/- 0.01 mm.
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