An Overview of Doffer in Carding Machine
Dept. of Textile Technology
Sarvajanik College of Engineering & Technology, Surat, India
What is Doffer?
Doffer is a revolving cylinder, or a vibrating bar, with teeth, in a carding machine, which doffs, or strips off, the fiber from the cards. The doffer is a small cylinder made and clothed like the main cylinder. Metallic clothing is used for the doffer. The function of the doffer is to collect the cotton from the cylinder in a uniform fleece, which is delicately removed to form the card web.
The doffer has a diameter of 686 mm, which is the large component next to the cylinder in the carding machine (as seen in Figure). Its surface speed is several times lower than the cylinder (10–20 times slower). The primary functions of the doffer are to collect cotton from the cylinder as a uniform sheet and to carry this to the calender roller section. The wire clothing of the doffer is arranged so that it will work point against with that of the cylinder.
Objects of Doffer:
The main object of the doffer is to take off the fibers that lie more or less evenly distributed between the cylinder wires, and to condense them so that they constitute a coherent web.
Types of Doffer:
There are two types of doffer in carding.
- Single doffer
- Double doffer
Specification of Doffer:
- DIAMETER: 27’’dia
- SPEED: 45rpm/minute
- WIRE POINT PER INCH: 300-400
- SURFACE SPEED ratio: 53.3
- DIRECTION: CLOCKWISE
The doffer strips the fibers from the cylinder. The rate of transfer is called the transfer ratio. The transfer needs to be optimized to reduce the re-circulation on the cylinder to a minimum. The specification of the doffer wire, together with the card settings will define the correct operation of the transfer of the fibers from doffer to cylinder.
Doffer Wire Maintenance:
Doffer is still working with a concept of Land formation. A normal grinding machine will be good for doffer grinding. All the wire points should be touched by the grinding stone. A slow and gradual grinding with the grind-out concept will give the best results. Harsh grindings will result in burr formation on the land. This will increase the number of hooks in the fiber; thereby the effective length of the fiber from this card will be reduced.
Flat tops grinding is very important. Every time a flat top is ground, yarn quality is improved. It is better to use a grinding machine with the emery fillet. Frequent flat tops grinding will result in less neps and the yarn quality will be consistent.
Some mills increase the life of the flat tops compared to cylinder wire. But it is better to change flat tops and cylinder wire together for better and consistent yarn quality.
It is a good practice to check the individual card quality before changing the wire
Uses and Characteristics of Doffer:
Suitable for carding of 1.5D-20D*38-65mm artificial fiber. Single cylinder high-speed carding and double-doffer outputting has high production capacities. Cotton stripping has been used stripper bar, the cotton feeding roller is controlled by frequency conversion.
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Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.