The correct selection and maintenance of ring and traveller is essential in deciding the productivity and quality of the process as well as product, says R Senthil Kumar.
Rings and travellers are the dominant elements in the ring spinning process. Rings and travellers play a crucial role in the twisting process. The correct selection of ring and traveller influences the productivity as well as quality of the process.
Traveller selection influences the end-breakage rate. It is very important for the technologist to understand this and act on them to optimise the yarn production and quality. This article gives insight and broad outlook on various aspects of rings and travellers used in normal and compact spinning process.
Characteristics of a good ring
A good ring in operation should have:
- Best quality raw material
- Good, but not too high, surface smoothness
- An even surface
- Exact roundness
- Good, even surface hardness, higher than that of the traveller
- Should have been run in as per ring manufacturers requirement
- Long operating life
- Correct relationship between ring and bobbin tube diameters
- Perfectly horizontal position
- It should be exactly centred relative to the spindle.
The life of spinning rings depends on the following factors:
- Type of fibre processed
- Yarn count (traveller weight)
- Spindle speed
- Traveller running time
- General conditions (centring of rings, etc).
With high traveller wear (burnt travellers) the ring lifetime is reduced. On conventional rings, micro welding is damaging the running track and reduces the ring life dramatically. A worn-out ring surface influences the yarn quality, specially the yarn hairiness.
During the spinning process there is always a high load on the ring running track. The traveller´s centrifugal force (Fc) depends on the traveller weight (m), the ring radius (r) and the traveller linear speed (v). The centrifugal force is calculated with the following formula:
FC = (m x v2) / rRing This leads to very high values, compared to the relatively small weight of a traveller. The centrifugal force can reach a load, which is up to 8000 times the traveller weight.
These high loads create heat and leads stress to the ring surface. In order to prevent premature wear on the running track when working under extremely high loads or heavy conditions, it is recommended to use a ring treatment with very high wear resistance.
Load on ring and traveller
The lifetime of rings and travellers depends on two main parameters:
Raw material processed (lubrication potential) and
The mechanical and thermal load on ring and travel- ler (speed, ring diameter, traveller weight).
The centrifugal force increases in square in proportion to the traveller speed. The traveller temperature in the contact area of traveller-ring increases in cube in proportion to traveller speed.
In ring spinning, the energy to drive the twisting mechanism is derived from the bobbin, but the level of twist is controlled by the traveller. Each revolution of the traveller inserts one turn of twist into the yarn.
The mass of the traveller has to be balanced against the yarn linear density, and the so-called ´traveller weight´ is an important factor in determining the yarn tension.
The yarn tension, in turn, is an important factor in determining balloon size as well as the end-breakage rate. The bobbin rotates faster than the traveller an