common questions
Our staff are often asked particular technical questions by Agents and customers. Here are some of the most common. Please click on a question, if it is relevant to you.
If you have any technical questions which are not addressed in this section, then please contact us for detailed advice. Alternatively, place the question on the (contact board) which we examine daily.
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Can splicers be fitted with portable air bottles instead of air lines?
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Can another gas - say carbon dioxide - be used to splice yarns?
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1. What is the difference between a splice and a knt - why is a splice superior? Top
· The yarns in a knot cross over one another. The crossed yarns act as crude knives, and tend to cut each other. The result is that knots are not particularly strong, usually no better than 60% of that of the whole yarn.
· A good splice is a tightly-bound structure; its strength comes from the intermingling of individual fibres. This form is inherently stronger; the breaking strength of a splice commonly exceeds 90%.
· Also, a good splice appears much lower and smoother than a knot, and the splice passes more freely through the elements of textile machines. The splice is usually less visible than a knot in the finished fabric.
· Overall, splices reduce waste, in processing and in the finished fabric. As a consequence, although a typical splice takes somewhat longer to make than a corresponding knot, the downstream benefits of processability and quality enhance the overall efficiency.
2. How consistent is the strength of a splice? Top
The strength of a splice depends on a number of factors. These include the properties of the yarn itself, such as:
· whether the yarn is continuous filament or staple
· the material of the yarn - wool, nylon, aramid etc.
the splicer parameters such as:
· splicing chamber design
· air pressure
· blast time
As to consistency, it may fairly be said that continuous filament yarns, by their very nature, tend to be more consistent in their performance than natural materials such as wool.
The air in a splicing chamber is highly-turbulent. Because turbulence is a random process, it might be thought that the quality of the splice itself is certain to be variable. This is not true; splices are in fact quite consistent.
The turbulence is very intense, and it is on a micro-scale. So, although splices differ in fine detail, they are much the same on a macro-scale. Of course there is a statistical variation of splice strength. But this variation is usually less than that of the typical knot.
In 2008, the company completed a big programme of detailed research on the optimization of splicer performance. Much of the output from this work has been published in appropriate technical journals, including the Journal of the Textile Institute (UK) and the Textile Research Journal (USA).
3. Is it possible to splice highly-twisted yarns? Top
YES, but there are some comments. To intermingle the fibres of any yarns, it is necessary to separate their fibres; if the yarns are very highly twisted, they tend to remain tightly packed; then, splicing is very difficult.
Until recently, there were two possible solutions:
· One approach was to make a standard "cross-over" or "ends-opposed" splice, by applying reverse-twist to each yarn with a mechanical device, to open the structure. This approach works very well, but it requires the use of complex splicers.
· A simpler approach was to de-twist the yarns with air, using splicing chambers with a special asymmetric cross-section to spin the bundle and open up the yarns. This approach works only if both yarns enter the chamber from the same side, so that they are both de-twisted. The result is rather a crude splice, ( "ends-together" ) but one which is OK for non-critical uses. Chambers of this form were in production far about twenty years. They suffered from a disadvantage that, although they could handle twisted yarns satisfactorily, their dimensions and characteristics needed to be matched to the twist direction and physical size of the yarns.
This company has succeeded in dispensing with the asymmetric chambers. A new and patented form of splicing chamber used in the Models 100, 101 , 102 , and 103 makes ends-together splices in a huge range of yarns, using a single cross-section for all sizes, and for both S and Z twist.
4. Is it possible to splice intermingled yarns? Top
It depends on the type of intermingling, and its degree. Splicing itself is an intermingling process. If the yarns are so consolidated that their fibres cannot be separated, then splicing will not be possible.
Some yarns are processed in order to maximise the amount of filament intermingling and disruption. The "Taslan" process is a good example. We cannot splice these yarns.
Some yarns (such as bulked polypropylene) are passed through an intermingling jet, to introduce some cohesion to the yarn bundle. Such yarns have only small zones of regular intermingling. As long as the intermingled zones are not placed in the splicing chamber, it is usually possible to make a splice.
5. Is it possible to splice P.O.Y. (Partially Oriented Yarn)? Top
POY cannot be spliced as if it were a normal, fully-drawn yarn. Splicing works best when the fibres in the bundle resist extension. POY filaments, which are not fully drawn, resist extension hardly at all. The resulting splice is very weak.
Partially oriented yarn can be spliced using special purpose splicers which have been developed to perform the task consistently.
However, POY can be spliced on standard splicers such as the Model 1-11 if some careful procedures are adopted by the user. The yarn can be spliced successfully if care is taken to extend it - usually by hand - to the fully-drawn state. The operator must be able to apply the correct amount of extension consistently from splice to splice. It follows that the operator must play a large part in achieving an acceptable splicing performance; thus sound training is vital.
6. Can mono-filaments be spliced? Top
Never by pneumatic splicing. For pneumatic splicing, filaments or fibres must be separated and intermingled. If there is not a substantial number of filaments, there is nothing to separate; nothing to mix; nothing to intermingle.
Some synthetic monofilaments can be spliced by other techniques - wrapper splicers, gluing, heat-welding, for example.
7. Can fibrillated tapes be spliced? Top
Some can, but most cannot. A fair amount of work has been done in this area. It appears that a splice can be made, if the splicer is persuaded to do two things at once:
· smash the tape so that it separates into its crude filaments
· splice the filaments.
This is not easy, and can only be done on tapes which are very thin compared to their width. Thin tapes can be split into a large number of strips which behave a bit like continuous filaments. The strips do not splice well, but some kind of splice will form if there are enough of them.
So we have succeeded in splicing wide, thin tapes. Best results are obtained using splicers which are NOT fitted with automatic cutters, such as the Model 110. Then, the splicer can be moved back and forth along the line of the yarn making a longer but stronger joint.
In general, however, it is not a promising area.
8. Can really big yarns be spliced? What is the absolute upper limit of count? Top
As yarns become heavier, issues of scaling arise. A typical conventional splicer has cutting knives set about 30 mm apart, so that this represents the standard splice length. Clearly, a 30 mm splice in a 100 tex yarn is proportionately longer than a 30 mm splice in a 1000 tex yarn. Eventually, a yarn may need a splice of say 200 mm to produce an acceptable splice geometry; so the scaling issues here become a problem, since it is impossible to make an ergonomically acceptable splicer with knives say 200 mm apart.
As yarns become heavier, issues of cutting performance arise. As mentioned above, a typical conventional splicer has cutting knives, and these trim the yarns cleanly so that the resulting splice is neat. Eventually, even the best knives will be unable to trim the ends if the yarn exceeds a certain size.
Therefore, in defining the upper limit of count, we need to be a little careful in defining splicing. Splicers can be used to make joints in two ways:
· Splicing in a single chamber including automatic cutting. Maximum count typically 1000 tex, 10,000 dtex. All our ends-opposed splicers such as the Model 1-11 meet this standard.
· Splicing in a single chamber without automatic cutting, but with hand-trimming. Maximum count typically 10,000 tex, 100,000 dtex. The Models 110, 113, and 114 are the products best suited to this application.
Extremely large assemblies can be spliced, if the user is prepared to set up a number of splicing chambers in parallel. It may be feasible to place large numbers of yarns into large numbers of chambers; if the air-flow to each chamber is sufficient, then there is no particular upper limit to yarn count.
We have managed to splice tows of about 500,000 tex using such multiple splicers. Devices of this form are very inconvenient to use, but may solve a particular problem for the customer. Obviously, these splicers are specially built for individual customers. Refer to the Design and Build section, where issues of bespoke design are addressed.
9. How important is the air pressure? Top
Pneumatic splicing is frequently treated as a "poor relation" within a textile factory; large textile machines will be well supplied with good clean air as routine. Splicing, since it uses little in the way of volume, is often regarded as of minor importance, being tagged onto the end of a long and busy air system. The result is often a wet and variable supply, and erratic splicing performance. This approach is short-sighted, since splicing, if consistent, can contribute greatly to the overall efficiency of a plant.
The absolute value of air pressure required will vary from fibre to fibre.
· A strong synthetic fibre such as nylon or polyester will typically need a pressure of between 5 and 7 bar.
· In contrast, a brittle fibre such as fine glass may be best spliced at 2 or 3 bar.
· What is certain, however, is that once the optimum pressure for a given fibre has been established, it should be kept as consistent as possible. Variable pressure IS bad.
10. What are the rules of design for the air-line supply to a splicer? Top
The importance of the quality of the air supply has been touched upon in Question 9. In that section, it was explained that the pressure at the splicer should be as consistent as possible when the splicer is working.
How can that aim be achieved?
Adequate static air pressure in the supply line is not sufficient to ensure adequate performance. When working, the splicer uses a lot of air (typically 3litres/sec). Even when static pressure appears to be suitable, pipe friction may be high, so that the air is not replenished, and pressure drops. Then splicing performance deteriorates. So the air supply should have as little resistance and pipe-friction as possible.
Main feed-pipes should be fairly large (maybe 25 mm). Flexible hose feeding the splicer should not be small-bore, and not too long. Six metres of flexible hose between air main and splicer represents a good compromise between the requirement for a long reach and the need to minimise pipe losses. A large creel, for example, will be best served if it is provided with a number of air supply connectors of the quick-release type, so that the splicer may be carried from place to place and simply plugged in.
In special circumstances, if it is impossible to maintain a good supply of air, it may be necessary to provide a small reservoir of perhaps 5 litres capacity, near to the splicer. The reservoir will assure adequate air supply to the splicer while it is being used. The reservoir pressure will fall a little during splicing, but it will be replenished once the splicer is switched off.
11. Is there a lower limit to air pressure for splicing? Top
It is sometimes desirable to have a splicer which will operate at a low pressure. Some yarns, such as glass and carbon fibre, disintegrate when exposed to a high-pressure blast. Then splices are best made at around 3 bar.
Clearly, at extremely low pressures, the mechanical process of intermingling will no longer occur, and a splice will not be made.
In practice, a lower limit is sometimes set, not by splice quality, but by mechanical factors:
· Some splicers have a design limitation. Their structure is such that at low pressure they "lock-up" and cease to function.
· Other splicers are much less sensitive to pressure variations. Several GTW Developments models will function mechanically down to about 1.5 bar. These include the 101, 102, 103, and the 1-11.
· Please note that though these splicers will operate mechanically perfectly well at very low pressures, the adequacy of the splicing performance must be verified by experiment. With very fragile yarns such as glass and carbon, it may be necessary to make a trade-off between decreasing the air pressure and increasing the blast duration.
12. How noisy is a splicer? Top
Splicers aren't quiet, because they deliver turbulent air at up to 3 or 4 litres/sec, at perhaps 7 bar pressure.
Typical maximum noise levels vary from 80 db to 98 db, depending on the splicing chamber. Some chambers are quieter than others, simply because they have a smaller blast-hole, and allow less air to escape.
Our noisiest splicer, with the biggest blast hole in our range, generates a noise spectrum as shown in the table below:
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63
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125
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250
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16000
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47
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52
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57
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63
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74
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89
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92
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93
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95
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In practice, splicers are barely noticeable in a textile mill. This is because the other mill machinery tends to be very noisy, and the sound of the splicer is lost in the general noise. Also, the blast only lasts for about one second.
Nevertheless, in compliance with UK health and safety regulations, we recommend that ear defenders (to local standards equivalent to British Standard 6344 Part 1) be worn.
13. What should be the quality of the air supply; should it be dry and filtered? Top
Under normal circumstances, splicers should be supplied with clean, dry air. For most applications, provision should be made for modest standards of filters and water traps. Dirty air should NEVER be supplied. It is certain to give a poor-quality splice, and over a prolonged period is likely to damage the splicer itself.
Under special circumstances, however, and with appropriate designs of splicer, it may be appropriate to supply moist air, in order to splice yarns which splice more efficiently when damp. Such a step should be taken only after consultation with the supplier, however, as special rust-proof splicer components may be needed.
14. Can splicers be fitted with portable air bottles instead of air lines? Top
In certain very special circumstances, it may be expedient to run a splicer by using air supplied from an air cylinder. This may be seen as having some advantages - notably that a complex and expensive plumbing system need not be installed all round the factory.
However, bottle-driven splicers are very rare, because of the profound disadvantages:
· to ensure an adequate pressure, a heavy-duty bottle is required; such bottles are usually heavyweight, as well as heavy duty.
· to ensure an adequate service life for the contents of the supply cylinder, the bottle will need to be large, unless splicer use is very infrequent. This requirement adds to the problem of bottle size and weight.
· regulators will be needed; on occasion, users have connected splicers direct to bottles, with the result that splicers were operating outside their design limits, creating a distinct health and safety hazard. Moreover, when operated under these conditions, the free expansion of the bottled gas has led to some marked Joule-Kelvin cooling, which has frozen the splicer.
Overall, if a special situation can be found where a positive case for a bottled supply can be made, and the operating conditions optimised, there is no reason why a bottled supply should not be used. The usual solution in these circumstances is a trolley of sack-truck form, which bears the weight of the bottle. The whole assembly is then wheeled to where it is needed, and after use is parked up awaiting the next call for the splicer.
15. Can another gas - say carbon dioxide - be used to splice yarns? Top
This enquiry is closely relayed to Question 14. Except in very special circumstances, in unusual environments, gases other than air are available only in bottled form, and are therefore subject to the same strictures as those which apply to Question 14.
However, there are some circumstances in which other gases might be considered. For example:
· There is some evidence that the density of heavy gases such as CO2 can enhance splicing performance in some cases.
· Under some circumstances, a fibre of special chemical make-up may react with air, so that it is kept in a closed environment. Then other gases must be used.
It must be understood that these applications are extremely rare, because for most of its history the pneumatic yarn splicer has been used in relatively low-tech environments. Demanding applications may become more common with the development of exotic new fibres.
16. Are special air supplies needed to splice extra-tough yarns such as aramids? Top
In general, special fibres such as aramids do not need special air supplies. They may be very tough, but in many respects relating to splicing, they behave like any other synthetic.
Strength of fibre does not imply a corresponding need for additional brutality in the air supply.
Despite that assertion, it must be said that many people are under the impression that aramid splices are weak in comparison to their counterparts in commoner fibres - nylon or polyester for instance. We believe that this perception is largely due to a long-established convention of measurement. It is normal to quantify the strength of a splice, not by its absolute breaking load, but by the ratio of the braking load of the splice to the breaking load of the virgin yarn. (this practice probably has its origins from the introduction of splices on the 1970s, when it was common to compare favourably the strength of splices to the strength of knots, by using such percentages)
How does this convention lead to bad results for aramid? A splice is essentially a structure which holds together through friction - a multiplicity of interminglings fives a multiplicity of points of friction. All other things being equal - a reasonable first approximation for fibres of the same geometry - the friction in the cluster of an aramid splice and that in a similar nylon splice will be broadly similar. Therefore, as a first approximation, an aramid splice will have the same absolute strength as a nylon splice. But the aramid virgin yarn has a much greater breaking strength than the nylon. So, measured in the conventional manner, the aramid splice strength will be proportionately weaker than the nylon one.
17. Why are knives needed on most splicers? Top
New splicer users can sometimes be perplexed when when mention is made of knives, which are routinely fitted to the majority of splicers. The new users cannot immediately understand why cutters are needed on tools whose sole function is to create an intermingled joint.
The reason is quite simple. For the operator to use the splicer, he must place the two ends of yarn which are to be joined into the working part of the splicer. In principle, it is perfectly possible to position yarns of exactly the correct length into the splicing chamber, but the precision required of such an act would place great demands on the operator, who may have to make many hundreds of splices during a working shift. If the quality and consistency of the splice were to depend on such precision of placement, the result would be poor splices and stressed operators.
Instead, knives are fitted. With knives fitted, it is only necessary for the user to grasp a good length of yarn, and to place it in the splicer; length here is not an issue. As part of the splicing process, both yarn ends are automatically trimmed to exactly the right length, and consistency is assured.
18. Why are some splicers NOT fitted with knives? Top
Some attention was paid in Question 17 to the matter of fitting cutters to splicers. Having justified the presence of cutters in that answer, it is necessary to address the reasons why splicers are sometimes not fitted with knives.
When splicers have no knives, it is almost invariably associated with the business of making joints in very heavy yarns. The principle reason why heavy yarns pose problems for "normal" splicers is simply that the cutting capacity of any knife assembly has some sort of limit. When that limit is exceeded, the cutting performance becomes erratic, and when cutting is poor, splicing is poor.
Better in such circumstances to forget about the knives altogether, and to trim by hand, using scissors. this procedure makes for a more time-consuming splicing process, but at least it is consistent.
19. What is the significance of a blast timer? Should one always be fitted,or not? Top
Timers - units which control the duration of the air blast - are fitted to only a small proportion of our splicers.
Many of our products are used to make "ends-together" splices; for these, timers are not necessary, because splices normally emerge from the splicing chamber spontaneously. Timers are only needed when customers make "ends-opposed" splices; even then, not every user is convinced that they are necessary. Most customers operate perfectly satisfactorily without them. Timer splicers are obviously more complex in construction than the simpler models.
Customers seem to fit timers for one or more of the following reasons:
· They have evidence that, in their application, consistent time leads to consistent splice quality.
· They have been unable to train their operators to splice consistently; then automatic timing makes up for poor operator practice.
· Their yarn is fragile, and must not be subjected to a long blast.
The user must balance cost and complexity against a measure of improved performance, when making a purchasing decision. Our latest product offer an opportunity for the purchaser to change his mind after purchase. the Model 1-11 range of splicers are made as modules. If a user opts for a splicer which is NOT fitted with a timer, it is a minor matter for him to change tack in the light of experience; al that he needs to do is to purchase a timer module, and fit it to the standard splicer.
20. Why might it be necessary to change splicing chambers? Top
On old-style splicers, whether they are being used to make "ends-opposed" or "ends-together" splices, the splicing chamber fitted was never universal in its application. It was always necessary to offer a wide range of splicing chambers, to give satisfactory results on a wide range of yarns. Changing chambers is inconvenient. It has however been a feature of all pneumatic splicers; it has always been a characteristic of the product. In general, it has been the count, or tex, of the yarn which basically controls the choice of splicing chamber. But it is a fairly complicated subject, and chamber choice has always been the most difficult topic to learn when coming to terms with splicers.
Some completely new thinking, and new technology, has allowed us to design new splicers, such as the Models 100, 101, 102, 103, and the 1-11 family, which make splices in a completely new way, so that changing chambers is now very rarely necessary, across an enormous range of counts.
21. Are new-technology splicers purely hand-held, or are there mounting systems? Top
The new style splicers, such as the 103 and the 1-11 series, have been designed with flexibility of use as a priority. They have been designed as modular structures, so that they can be used hand-held, fixed, or as rail-mounted systems, without any re-machining.
In addition to the design modules, hanging kits exist, so that nominally hand-held splicers can hung as quasi-fixed splicers, or nominally fixed splicers can be hung then removed and used as quasi-hand-held splicers.
22. What technical support does our company offer to customers? Top
Through long experience, we are aware that customers may need support when making purchasing decisions, or when inexperienced in servicing matters. Support is available in a number of forms - for example:
· site visits by our representative at customer's premises
· site visits by customers at our premises
· splicing trials conducted at our premises, with or without the presence of the customer
· technical advice, by communication with us via telephone, fax, or e-mail
· technical advice, by the use of product-specific material resident on this web site
· supply of relevant literature
In the case of support within the UK, site visits will be made more-or-less on demand, so that a joint understanding of the local situation can be reached, and an agreed technical plan developed.
In the case of support for overseas markets, the first point of contact should be our local agent, if there is one in place. In most cases, local advice will be sufficient.
Occasionally, the nature of the enquiry will be sufficiently technical that input will be required from the UK office. In that situation, a three-way communication will be established between customer, agent, and the UK office, until a solution is reached.
In certain circumstances, our representatives will make a visit to the customer's site, to conduct a formal programme of training, involving off-line tuition in a lecture room or other neutral environment. This will be timed, if the customer wishes, to take place at a shift-change, so that two groups of operators can be taught simultaneously. There may be a small charge for this service - it depends on the times and distances involved.
We can lay on a formal course, for any reasonable number, and for any reasonable time, on our premises. Clearly, travelling and accommodation expenses will be the responsibility of the customer. In addition, there will be a charge for the instruction programme.