Weaving Resistance:
The Effect of Shed Balance:
They show a very significant effect of tension ratio in the two warp sheets on weaving resistance. It had earlier been reported by Bramma21 and Snowden8 that an unbalanced shed was helpful in achieving high setts. Jederan22 considered the effect on weaving resistance and, according to the English abstract of his Hungarian paper, found that "contrary to what is generally accepted" no reduction resulted. Mallah20 had reported that peak warp tension was reduced when the shed was unbalanced and both Yehia11 and Leung in their limited experiments, from which the present study has evolved, showed a significant reduction in beat up force when the shed was unbalanced. Yehia's work suggested that the effect was influenced by shed timing. Leung used a crude method of unbalancing that avoided Ito's "kinematic" effect and was incidentally independent of shed timing; he inserted a heavy roller like a lease rod in the warp so that each of the slacker and tighter sheets was always composed of the same threads. With the more normal arrangement, using a raised back rail to unbalance the shed, each yarn is alternately in the slack and tight sheet of the open shed; but when the shed is closed, i. e. crossing, it is by definition also balanced.So it would be expected that the timing of the shed relative to beat up would affect the weaving resistance.
The Effect of Shed Timing:
In view of what has already been said, it is not surprising to find contradicting statements about shed timing. Greenwood said the effect was so small that its significance must be doubted. Badve found a difference but not all his results show the effect consistently. Yehia's results suggested a "normal" timing gave least resistance. to a small extent. Theoretical studies suggested that it was not so much the effect of timing (and hence shed angle at beat up) on the actual beating up that mattered, but its effect in opposing slipping back. In industry it seems generally to be accepted that an early timing enables picks. to be beaten more closely. So a confused picture emerges and it is clear that a more detailed and more precisely defined range of settings should be used than the "late", "normal" and "early" often adopted.
Cloth Fell Distance and Beat-up Force:
Although cloth fell distance is not a basic or independent parameter (except when it is set at the start of a period of weaving) it is a visible feature that forms an important link in the relationships between other variables and so has received some attention. Badve set out to measure c. f. d. in order to test Greenwood's equations and pointed out that in developing the beat up force it is not the fell displacement in absolute terms that is related to beat up force, but the displacement relative to that which would occur due to shedding, back rail movements, etc., in the absence of beat up. When he had developed a means of measuring that relative movement, the modified c. f. d. or, as he termed it, the "interference" between reed and fell, was still often greater than seemed necessary for the force, even when true load/extension curves were used instead of constant moduli in the relationship. These results led him to suggest slipping back of picks might be responsible, so that the cloth fell was not clearly defined but was rather a region that was neither warp nor cloth. Greenwood found some evidence that c. f. d. was influenced by loom speed being slightly increased when the speed was reduced. That might be explained in the elastic moduli being slightly lower for slower rates of strain but it could also be an effect of fell movement rather than displacement by the reed.
When warp and weft are interlaced in a fabric then they oppose to each other due to static electricity or other factors. This opposition or resistance is called weaving resistance. Weaving resistance or its counterpart, beat up force, is at the center of the relationship between pickspacing, yarn properties and loom settings.
Factors Affecting Weaving Resistance:
In case of pick spacing requires a larger beat up force or, for a given spacing, a thicker weft requires a larger force. It is suggested that a discontinuous relationship between pick spacing and weaving resistance but that has not been confirmed by experiment - possibly because irregularities in yarn properties would smooth the discontinuities. Loom settings are also known to influence the relationship.
There are some factors which affecting weaving resistance are given below:
There seems to be general agreement that increasing warp tension increases weaving resistance. Theoretically increased tension increases inter yarn forces and hence the effect of friction. . However, the influence seems to be fairly small, both indicating a rise of about 10% in weaving resistance for a doubling of the basic or average tension.
Factors Affecting Weaving Resistance:
In case of pick spacing requires a larger beat up force or, for a given spacing, a thicker weft requires a larger force. It is suggested that a discontinuous relationship between pick spacing and weaving resistance but that has not been confirmed by experiment - possibly because irregularities in yarn properties would smooth the discontinuities. Loom settings are also known to influence the relationship.
 |
| Weaving resistance |
- The effect of warp tension
- The effect of shed balance
- The effect of shed timing
- The effect of cloth fell distance and beat-up force
- The effect of weave
There seems to be general agreement that increasing warp tension increases weaving resistance. Theoretically increased tension increases inter yarn forces and hence the effect of friction. . However, the influence seems to be fairly small, both indicating a rise of about 10% in weaving resistance for a doubling of the basic or average tension.
The Effect of Shed Balance:
They show a very significant effect of tension ratio in the two warp sheets on weaving resistance. It had earlier been reported by Bramma21 and Snowden8 that an unbalanced shed was helpful in achieving high setts. Jederan22 considered the effect on weaving resistance and, according to the English abstract of his Hungarian paper, found that "contrary to what is generally accepted" no reduction resulted. Mallah20 had reported that peak warp tension was reduced when the shed was unbalanced and both Yehia11 and Leung in their limited experiments, from which the present study has evolved, showed a significant reduction in beat up force when the shed was unbalanced. Yehia's work suggested that the effect was influenced by shed timing. Leung used a crude method of unbalancing that avoided Ito's "kinematic" effect and was incidentally independent of shed timing; he inserted a heavy roller like a lease rod in the warp so that each of the slacker and tighter sheets was always composed of the same threads. With the more normal arrangement, using a raised back rail to unbalance the shed, each yarn is alternately in the slack and tight sheet of the open shed; but when the shed is closed, i. e. crossing, it is by definition also balanced.So it would be expected that the timing of the shed relative to beat up would affect the weaving resistance.
The Effect of Shed Timing:
In view of what has already been said, it is not surprising to find contradicting statements about shed timing. Greenwood said the effect was so small that its significance must be doubted. Badve found a difference but not all his results show the effect consistently. Yehia's results suggested a "normal" timing gave least resistance. to a small extent. Theoretical studies suggested that it was not so much the effect of timing (and hence shed angle at beat up) on the actual beating up that mattered, but its effect in opposing slipping back. In industry it seems generally to be accepted that an early timing enables picks. to be beaten more closely. So a confused picture emerges and it is clear that a more detailed and more precisely defined range of settings should be used than the "late", "normal" and "early" often adopted.
Cloth Fell Distance and Beat-up Force:
Although cloth fell distance is not a basic or independent parameter (except when it is set at the start of a period of weaving) it is a visible feature that forms an important link in the relationships between other variables and so has received some attention. Badve set out to measure c. f. d. in order to test Greenwood's equations and pointed out that in developing the beat up force it is not the fell displacement in absolute terms that is related to beat up force, but the displacement relative to that which would occur due to shedding, back rail movements, etc., in the absence of beat up. When he had developed a means of measuring that relative movement, the modified c. f. d. or, as he termed it, the "interference" between reed and fell, was still often greater than seemed necessary for the force, even when true load/extension curves were used instead of constant moduli in the relationship. These results led him to suggest slipping back of picks might be responsible, so that the cloth fell was not clearly defined but was rather a region that was neither warp nor cloth. Greenwood found some evidence that c. f. d. was influenced by loom speed being slightly increased when the speed was reduced. That might be explained in the elastic moduli being slightly lower for slower rates of strain but it could also be an effect of fell movement rather than displacement by the reed.
The Effect of Weave:
For given yarns it seems obvious that, just as maximum possible sett depends on the density of intersections in the weave, so weaving resistance would also depend on that density. Galuszinski, working on plain weave derivatives, claims to show a direct simple relationship between weaving resistance and setting formula. Chen Jui-lung had previously reported similar results but expressed in less precise terms.
For given yarns it seems obvious that, just as maximum possible sett depends on the density of intersections in the weave, so weaving resistance would also depend on that density. Galuszinski, working on plain weave derivatives, claims to show a direct simple relationship between weaving resistance and setting formula. Chen Jui-lung had previously reported similar results but expressed in less precise terms.
No comments:
Post a Comment