Carding Process recommendations
Process recommendations
The performance of the card is dictated by the quality and condition of the supplied material, the condition of the carding elements, the production rate and most importantly the setting of the components.
The settings have to be optimized by observing the running performance as well as by testing the sliver quality.
The procedures for setting the components of the card and suggested starting points are included in the machine manual.
In some cases there may have been tests previously conducted and they should be used as a reference. The following points are presented for a better understanding of some of the carding principles.
Matt weight and condition
• The best matt weight is when the carding draft is in the optimal range. For most fibers a carding draft of 95 to 125 is targeted.
• It is important that the matt should be consistent from side to side. Lengthwise variation can be corrected by the levelling system but irregularities across the matt cannot be accommodated. Holes or thin places in the matt are problematic because the fibers are not fully controlled at the feeding zone.
• Matt tension should not be too low with buckled matt feed. Nor should it be so high as to pull thin places. Tensions available from1.19 to1.37.
• A test for buckling is to remove tufts of fiber from the matt as it is being fed and see if the matt tends to lift with the tufts. If it does lift, increase the tension.
• A more consistent matt is produced when the chute feeding system is running at a high production ratio. It should be running for more than 90 percent of the time for best results.
• The material should be well opened with no compacted or entangled material.
Feed plate setting
The adjustment of the feed plate (feed trough) is normally made according to the fiber staple length. The recommendation from the manual can be used as an approximate guideline:
Adjustment of Feed Trough Determination of nipping point “D” / carding point.
Care should be taken to see that fibers are not being over controlled at the feeding point. If the longest fibers are being broken, the feed plate setting should be opened up.
Licker-in and cylinder speeds ranges by fiber types
The following table shows the C 51 Hi•Per•Card typical speed ranges for man-made fibers, cotton and trashy cotton. This information should be used in conjunction with the charts below referring to production rates.
|
|
Licker-in |
Cylinder |
|
speed |
Speed |
|
|
(rpm) |
(rpm) |
|
|
Synthetics and Blends |
900 to 1300 |
300 to 450 |
|
Cotton |
1610 to 2160 |
450 to 600 |
|
Trashy Cotton |
1000 to 2000 |
300 to 600 |
The following chart shows the suggested cylinder speeds for cotton and man-made fibers at different production rates on the C 51 Hi•Per•Card,
Cylinder Speeds rpm
Information regarding the C 51 card is included in the machine manual.
Care should be taken to be sure that the action of the licker-in is not too aggressive. The staple length and the short fiber content of the matt and the sliver should be compared.
If the SFC of the sliver is two-percentage points greater than in the matt then fiber damage is occurring and the licker-in speed and the feed plate setting should be checked.
Basic settings around the cylinder
The standard values for settings around the cylinder are included in the machine manual. A typical example from the C 51 manual is shown below. Doffer / Cylinder Settings for Cotton and Blends Cold Machine In the constant effort to maximize nep and trash removal there is a tendency for the customer to request closer settings of the flats, segments and doffer relative to the cylinder. Great care has to be given to very close settings, with attention being given to:
• Setting when the card is warm or cold,
• Cylinder speed, if the speed is increased the warm running settings become closer,
• The condition of the clothing on the flats, cylinder and doffer. It may be prudent to “dress the clothing before closing up on the settings.
• If flats are changed or new clothing installed it is necessary to dress the flats before adjusting to tight settings.
• After re-clothing the card, it should be “run –in” before going to high speed and close settings.
Doffer
The following chart is taken from the C 51 Hi•Per•Card manual and shows the basic cold machine settings of the doffer to the cylinder for a production range of 50 to 90 kg/hr.
Delivery section
A schematic arrangement of the components of the delivery section is shown below. The relative speeds of the various rolls are adjustable by changing the appropriate draft gears. Visual checks of the web condition are the normal way to judge the set-up.
Drafts in the delivery section
Key:
7 Doffer 12 Bottom delivery roll 13 Cross apron 9 Detatiching roll 11 Upper delivery roll 14 Stepped roll 10 Transfer roll
Alterations to the change gears influence the draft ranges.
|
Change of gear |
Gear to be adapted |
|
W 1 |
W 3 |
|
W 4 |
W 2 |
In general the tension drafts in the delivery section have to be increased with higher delivery speeds to obtain a smooth transition from the doffer web to the sliver. Details of the drafts between components are included in the machine manual.
Carding synthetic fibers
Processing synthetic fibers on high-production cards requires “high performance fiber finish” to adequately lubricate the fiber and provide satisfactory antistatic properties. Heat is generated by the carding action and is transmitted to the card clothing. Overheated clothing encourages static charging of the fibers, making it difficult to detach the web.
Increasing the moisture content of the surrounding air by increasing the humidity can reduce electrostatic charging of the fibers. However this should not include increasing the room temperature. Try to keep the fibers from over heating.
When the synthetic fibers are well opened in the blowroom it is easier to process them at the card. With well-prepared fibers it is possible to operate the cards with wider flat settings, hence the friction forces and static charging are minimized.
The effectiveness of the fiber finish varies. In most cases it is at its best between two to three weeks after the date of manufacture, after which it deteriorates steadily. It is preferable to have the fiber delivered as needed and not to store bales for several months.
The rate of finish degradation varies from one supplier to another and in many instances from batch to batch from the same supplier. Consequently, changing from one batch to another should be phased in over several days.
Fiber crimp
The crimp of synthetic fibers affects the production rate of the card. Strong fiber crimp gives the card web better cohesion and web stability. To set a strong fiber crimp, the fiber producers use higher pressures and temperatures in the fiber production process. The additional heat treatment usually means a loss of fiber strength that is translated into a loss of yarn strength. Consequently, these high crimp fibers are not used in high strength applications such as sewing threads. To card low crimp fibers the production rates have to be reduced and sometimes the card web weight has to be increased.
Speeds and settings on the card
The following are general statements regarding cotton type fibers, i.e. fibers of 1.5 den and of staple length up to 11/2• (40 mm):
Licker-in speed, -
Cylinder speed, -
Flat settings, -
Clothing has to be specified for the particular needs.
For blends of cotton / synthetics, the type of card clothing can be closer to that of the cotton clothing, but it is still necessary to use a “combination” wire which can, if necessary be used for blends or 100% cotton.
he carding of longer synthetic fibers of coarser denier, (• 2.5 den x • 60 mm) associated with “wool – type” applications require that the card settings be opened up and speeds reduced.
In general, it can be said that if there are dust deposits in and around the card, the settings are too close and /or the speed is too high. The dust collected on the machine is primarily fragmented fiber polymer and is frequently wrongly referred to as fiber finish.
Air requirements
Air pressure
The compressed air requirements of the cards are:
Supply pressure: 7 to 8 bar
Working pressure: 6.0 bar,
Air consumption: Card 0.1 Nm³/h IGS-top 0.075 Nm³/h
Exhaust air / Suction
The suction to the cards depends upon the waste removal system and whether it is by local suction or by centralized suction, but the common localized requirements are
|
Suction for C 51 and C 51 Hi•Per•Card |
|
|
Exhaust air – volume |
3000 Nm³/h |
|
Partial vacuum at interface |
- 50 Pa for local or |
|
|
|
|
–1000 Pa for central suction |
|
|
Waste transport from the licker-in zone |
|
|
Volume of air |
0.5 m³/s |
|
Suction cycle (+/- 1 min) |
6 min (C 51) or 12 min (C 51 H•P•C) |
|
Suction duration |
6 seconds |
|
Waste transport from the carding zone |
|
|
Volume of air |
0.5 m³/s |
|
Suction cycle |
6 min, ( +/- 30 sec) |
|
Suction duration |
9 seconds |
Room conditions
The water content of the air in the card room should be sufficient to control static build up and maintain fiber strength, but not so high as to accentuate any sticky characteristics of the fibers.
It is also necessary for the air to be somewhat cooler when carding synthetic fibers. Increased heat can lead to fiber damage and deposits on the machine elements.
For some specific synthetic fibers special conditions are suggested by the fiber supplier and should be followed if possible.
The following are some guidelines:
|
Fiber |
Water content |
Temperature |
Humidity |
|
Cotton |
9 – 12 g/kg |
24 – 28 C |
46 – 54 % r.f. |
|
Polyester |
9 – 12 g/kg |
22 – 28 C |
48 – 60 % r.f. |
|
CO / PES |
9 – 12 g/kg |
22 – 28 C |
48 – 60 % r.f. |
|
Viscose |
9 – 12 g/kg |
22 – 28 C |
48 – 60 % r.f. |
|
Acrylic |
9 – 12 g/kg |
22 – 28 C |
48 – 60 % r.f. |
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