The basic reasons for lapping in the case of processing synthetic fibre is
· End breaks
· Pneumafil suction
· rubber cots type
· fibre fineness
· Oil content(electrostatic charges)
· department temprature and humidity
· Almost all the lappings orginate after an end
break. If a mill has an abnormally high lapping problem
the first thing to do is to control the end breaks,
the first thing to do is to control the end breaks,
- after doffing
- during speed change
- during the maximum speed
by optimising the process paramters.
· It is obvious that fine fibres will have a
stronger tendency to follow the profile of the roller.
Therefore lapping tendency will be more.
Therefore lapping tendency will be more.
· If the fibre is fine, the number of fibres in
the cross section will be more, therefore lapping frequency
will be more.
will be more.
· If the pressure applied on the roller is
more, then lapping tendancy will be more. Hence fine
and longer fibres will have more tendency for lapping because of high top roller pressure required to
overcome the drafting resistance.
and longer fibres will have more tendency for lapping because of high top roller pressure required to
overcome the drafting resistance.
· If the pneumafil suction is less, the lapping
tendency will be more both on top and bottom roller.
But the pneumafil suction depends on the fan diamater, fan type, fan speed, duct design, length of the
machine, profile of the suction tube etc. If any one of the above can be modified and the suction can
be improved, it is better to do that to reduce the lapping.
But the pneumafil suction depends on the fan diamater, fan type, fan speed, duct design, length of the
machine, profile of the suction tube etc. If any one of the above can be modified and the suction can
be improved, it is better to do that to reduce the lapping.
· The closer the setting between the suction
nozzle and the bottom roller, the higher the suction
efficiency and lower the lapping propensity.
efficiency and lower the lapping propensity.
· Higher roving twist will reduce the lapping
tendency to some extent. Therefore it is better to
have a slightly higher roving twist, provided there is no problem in ringframe drafting, when
the lapping tendency is more
have a slightly higher roving twist, provided there is no problem in ringframe drafting, when
the lapping tendency is more
· With Softer rubber cots lapping tendency will
be more due to more surface contact.
· The most minute pores, pinholes in the rubber
cots or impurities in the cots can cause lapping. Therefore the
quality of buffing and the cots treatment after buffing is very important. Acid treatment is good
for synthetic fibres and Berkolising is good for cotton.
quality of buffing and the cots treatment after buffing is very important. Acid treatment is good
for synthetic fibres and Berkolising is good for cotton.
· Electrostatic charges are troublesome especially
where relatively large amount of fibre are
being processed in a loose state e.g drawframe, card etc.Lapping tendency on the top roll increases
with increasing relative humidity. The frequently held opinion is that processing performace remains
stable at a steady absolute relative humidity, i.e. at a constant moisture content per Kg of dry air.
being processed in a loose state e.g drawframe, card etc.Lapping tendency on the top roll increases
with increasing relative humidity. The frequently held opinion is that processing performace remains
stable at a steady absolute relative humidity, i.e. at a constant moisture content per Kg of dry air.