Fewmachines are as critical in a modern spinning mill as the roving frame.Building a solid and reliable roving frame is not easy. Yet, it is absolutelynecessary for the spinner as this machine can feed, depending on the countbeing produced, thousands of spindles at the spinning frames, says
Marzoli is the only Europeanmanufacturer of the full line of machines for spinning of short staple fibres.With over 150 roving frames sold every year worldwide, it is a reliable optionfor those looking for tried and tested technology. Its FT6E and FT7E representa state-of-the-art solution, yielding the best results for efficiency,reliability and quality.
Drivesystem
The spindles drive is a groupdrive where motion is transmitted through toothed belts. In traditionalmachines, spindles are moved by one motor which, through a long shaft,transmits motion to bevel gears which drive pulleys that drive belts whichultimately make spindles rotate. A group drive allows to simplify thistransmission system. The drive comprises several motors, each one driving alimited number of spindles. Each motor, through a pulley, drives toothed beltswhich transmit motion directly to the spindles. Shafts, gear boxes and bevelgears are eliminated.
Therefore,it is possible to:
- reduce maintenance costs sincefewer transmission components are needed and lubrication is no longer required
- reduce noise
- reduce vibrations since lowermechanical transmission entails lower wear of transmission components andtherefore lower vibrations. This enables the machine to work at higher speeds.
- increase transmission efficiencybecause the transmission system comprises only a pulley and toothed belts.There are no shafts and no bevel gears. This reduces energy consumption.
Draftingsystem
Marzoli roving frames canbe equipped with a 3-over-3 or 4-over-4 top-of-the-class drafting system. Thereare two options for the cylinder diameters. The standard solution has adiameter of 32mm; however, in case there is a high percentage of short fibresin the processed material, cylinders with a diameter of 27mm can be used toreduce the gauge between nipping points. This guarantees better control ofshort fibres during draft.
Marzoli drafting system can also
rely on highly efficient cleaners for both top rollers and bottom drafting
cylinders. For top rollers, there are two options: Rollers with rubber fins and
revolving felt belts. For the bottom cylinders, there are rubber scrapers.
These solutions guarantee that at every turn both top rollers and bottom
cylinders are always cleaned. This, along with the high quality of each and
every component, entails the perfect control of fibres during draft and top
quality of the roving.
False
twist area
As bobbins on modern roving frames
are arranged in two rows, rovings can have different angles at the delivery of
the drafting system and at the entrance of the flyers' top. It has been argued
that these different angles can entail differences in the spinning triangle at
draft delivery and different tensions of the rovings thereby causing an uneven
take up of twist and variations in roving count.
On Marzoli machines all rovings
lie parallel to one another, they have the same angle at the delivery of the
drafting system and at the flyers' entrance for both the front row and the back
row of bobbins.
Individual sensors ensure that
each roving break is properly detected and the machine securely stopped, even
in case of roving overlap around the cylinder/top roller. On the other hand, if
dust passes in front of the sensors, the machine would not stop. Individual
sensors also make suction redundant. This, with the IE3 motors and an overall
design meant to minimise energy consumption, allows to save up to 4 Kwh.
Roving tension is kept constant
within a pre-set range through sensors that constantly monitor roving's
fluctuations between the delivery of the drafting system and the flyer's top
and adjust the speed of the spindles accordingly. These sensors play an
important role in ensuring that there are no false drafts in the roving and
that roving breaks are kept to a minimum.
Winding
area
It is argued that to increase
productivity and lower investment costs, spindlage and dimension of bobbins
should be increased. This is only partially true. A higher number of spindles
per machine reduces the cost of the investment as the total required number of
spindles can be reached with fewer machines. From a unit cost (cost per
spindle) point of view, there is an economic advantage that stems from the
amortisation of the cost of the head and rear stocks on a higher number of
spindles per machine. However, the higher the number of spindles, the smaller
the benefit stemming from a further increase in machine's length. Machines
exceeding a certain number of spindles also entail higher costs for electronics
and drafting drive. Last but not the least, a higher number of spindles per
machine causes a reduction in efficiency.
The FT6E (110mm gauge)
can reach 224 spindles and produce bobbins of 16" x 6". The FT7E
(130mm gauge) has a spindlage up to 168 spindles and can produce packages of
16" x 7". These numbers represent the limit in terms of number of
spindles and dimensions of bobbins to maintain top efficiency standards. A
higher number of spindles per machine would not give an additional benefit to
the spinner as the decrease in machine efficiency would not be counter-balanced
by the reduction in the average cost per spindle.
The flyers installed on Marzoli's
roving frames are made of ultra-light alloy and are dynamically balanced so
that even when working at high speeds, vibrations are kept to a minimum.
Marzoli's roving frames can reach up to 1,500 rpm mechanically and the roving
can be wound on standard tubes, with a diameter of 53.5 mm, or on thinner
tubes, with a diameter of 48mm, to have a further slight increase in bobbin
capacity.
The creel
The creel is equipped with
hexagonal aluminum rollers to prevent false drafts, a very important aspect
especially when working with combed slivers. Optic sensors positioned between
the rollers ensure that in case of sliver break, the machine is immediately
stopped. Marzoli roving frames can be fed with cans with a diameter of up to
24" which allow to reduce machine stops and increase its efficiency.
Doffing
One of the crucial aspects on
modern roving frames is automation especially on doffing since doff is costly,
frequent, has an important negative influence on efficiency (especially on long
roving frames) and, done manually, can damage the roving bobbins.
Nowadays, there are several
options for automatic doffing. One of the simplest, most reliable and fastest,
automatic doffing systems is the one that Marzoli implemented, tested and
refined in the last 20 years. With this, in less than three minutes, full
bobbins are replaced with empty tubes and the machine is restarted. During the
new doffing cycle, full bobbins are forwarded to the transport system which
carries the packages to the spinning frames.
A semi-automatic doffing option of
the machine is available. With this version ergonomics has been substantially
improved if compared to standard manual-doffing machines. After bobbin
formation is completed, the bobbin rail lowers and tilts out for easy bobbin
collection. There is a parking rail in front of the bobbin rail with empty
tubes so that substitution of full bobbins with empty tubes is as easy as
possible.
With the release of the FT6E and
FT7E Marzoli offers also a third option: The roving frame with the
prearrangement for automatic doffing upgrade. During doffing, the bobbin rail
lowers and slides out horizontally, just like the fully-automatic model.
Besides permitting easy collection of full bobbins, this allows an easy and
cost-efficient upgrade of the machine to the fully-automatic version.
Energy
efficiency
To succeed in the highly
competitive and globalised sector, spinners must minimise production costs of
which energy consumption is an important component. Marzoli roving frames
represent an outstanding machine from the energy consumption point of view.
This machine is the only one that does not need suction. Thanks to individual
sensors installed as standard, any roving break can be promptly identified. No
suction is required to capture the broken roving and make it pass in front of
the photocell.
This, with the IE3 premium efficiency motors, the light weight components (e.g. the bobbin rail in aluminum) and overall design meant to minimise friction and transmission inefficiencies, entails energy saving of over 4 Kwh every hour of operation.
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