Converting webs of pressure-sensitive adhesives (PSAs) presents a variety of challenges. The inherent sticky properties of adhesives can be problematic throughout the slitting and rewinding process. Starting at the unwind, adhesives create noise and tension spikes when coming off idler and pull rolls at the master roll. As they move through the web flow, adhesives can stick to equipment, build up on slitting blades and ooze during rewinding if not handled carefully. In addition, converting adhesives often requires adding or removing liners, collecting unlined trim, and adapting machinery to specific customer needs.
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In order to effectively work with PSAs and produce high-quality finished rolls, specialized equipment is essential. Converting machinery can integrate features such as sound enclosures, non-stick roll coverings, traversing trim winders, blade wicking, tension isolation zones and precise control systems. The web flow can also be designed to minimize contact with exposed adhesives and properly position functions such as liner winding. Choosing the right solution depends on the nature of the web, the type of adhesive, the aggressiveness of the adhesive and the specifications of the finished product.
The special nature of pressure-sensitive slitting is evident at the unwind. Master rolls of adhesives are often misshapen or have special shaft requirements. In addition, sharp tension variations and high-decibel noise levels can occur when unwinding. As a result, unwinds for PSAs require features such as sound enclosures, peel-off rolls, infeed drive sections, wrinkle removal rolls and special chucks.
Sound enclosures are often necessary when unwinding film packaging tapes. Think of the tearing sound made by a consumer roll of film tape when used to wrap a package. That sound is multiplied when unwinding a 50- to 60-in. web of film tape at high speed. The decibels generated require the entire unwind to be located in a soundproof enclosure. These enclosures have special design features, such as slotted sliding doors to allow the loading of master rolls and removal of finished cores. They also require a small exit slot for the web to leave the enclosure.
Master rolls of PSAs are frequently out-of-round or egg shaped. The degree to which this occurs is a function of several factors, including the viscosity of the adhesive used, the web thickness, the temperature, core diameter and buildup ratio, and how long the roll may have been in inventory. Mitigating this problem is the focus of a number of steps and strategies from the moment the base material is coated with an adhesive.
Unwind features such as peel-off rolls, infeed drive sections and wrinkle removal rolls can help prepare the web for slitting. Peel-off rolls help even out the release of the adhesive across a web. Infeed drive sections maintain consistent tension output footage to the slitting zone, and wrinkle removal rolls smooth out any remaining tension-generated wrinkles prior to reaching the slitting or rewinding sections of the machine.
Pressure-sensitive unwinds may also need special chucks. Master rolls of PSAs are often wound on large diameter shafts, or &#;cans,&#; with ends requiring special chucks or adaptors. Large manufacturers frequently standardize their shafts from the coating through converting departments; winders on the coaters and unwinds on slitters must accommodate the same shaft ends. Master rolls may also be transported and stored on special racks. When this is the case, slitter unwinds must be made to lift out of these racks. This can involve a design specific to the customer&#;s racking system.
Many pressure-sensitive materials are wound with a liner that must be removed prior to slitting and rewinding. Liner removal can be done at the unwind. In this case, simple driven winders, located behind the unwind, wind up the liner as the material is pulled off the master roll.
More commonly, liner winders are found in the web path between unwind and rewind. Locating the best position for these winders is an important step. They must be accessible for unloading and at a good point for peel-off from the adhesive web. Additional idlers are often necessary to obtain the correct web path to and from these units. After the release liners are removed and wound into rolls, they may be reused in the coating process.
Some materials require that a liner be placed on the web after unwinding. It is not uncommon for a pressure-sensitive slitter to have both a liner unwind and liner winder. A material may require one type of liner during the coating process and another type of liner when being wound as a finished product.
Proper positioning of these liner unwinds is again key. Special web path design is necessary to ensure the liner is introduced in the correct position and at the correct point in the web conveyance. The liner unwind must also be located for easy and safe access for loading and unloading.
Processing unlinered or open-faced webs requires particular attention to the types and coverings of rolls coming into contact with the exposed adhesive. Web path design for exposed adhesives begins with a goal of minimizing the number of rolls contacted by the adhesive. Where adhesives must contact rolls, a number of solutions can be used to keep the adhesive from sticking to or transferring to the rolls. These include special non-stick roll surface coatings; some plasma coatings and tapes are effective. A contacted roll will occasionally be dimpled or grooved to lessen surface contact with the adhesive. The best solution for a particular product or family of products is a matter to be researched carefully. The right combination of web path and roll surfaces is critical to achieve the proper alignment and tension during web conveyance in order to avoid damage to the product.
Another unique characteristic of converting adhesive webs (exposed or linered) is the conveyance of web trim. Non-adhesive edge trim is commonly vacuumed away with a vacuum trim removal system. Such systems are problematic with adhesives, as the strands can stick to the inside of trim tubes. Over the years, attempted solutions have included coating trim tubes with nonstick materials or soap solutions. These methods are never foolproof and can be expensive and messy.
Trim winders are a popular solution. These are individual winders, often traversing types, packaged into the machine as closely as possible to the point where the trim is slit. They only need be changed occasionally, depending on the width of the trim taken, and are easily loaded and unloaded by hand. Again, good machine design is necessary to accommodate these winders at the optimal point in the web flow.
The slitting section of a pressure-sensitive slitter rewinder also requires special attention. First, the correct type of slitting method must be selected. Choosing between shear (scissor), score (crush) or razor slitting is usually a function of two factors: the base web material and the minimum slit width.
Score is the most common slitting method for PSAs. The advantages are many: score knife holders are less expensive than shear tooling and are easily adjusted for various slit widths. They can be grouped close together (usually about half an inch apart) for narrow slitting. Today, most are pneumatically loaded, and pressures are easily adjusted for different materials. Score systems can also be equipped with intelligent manifolds that allow individual knives to be turned on and off in a programmable logic controller as part of a job recipe. This allows an operator to change slit patterns quickly while maintaining accuracy.
Another advantage to the score method is its effect on the web edge. For many materials, the scoring of the web between the blade and the anvil roll can serve to seal the edge, inhibiting the flow of viscous adhesives out from the edge. Shear and razor slitting also have their place in the pressure-sensitive world. Razor is used for many film tapes, and shear is common in labelstock work.
Adhesive buildup on knives&#;whether score, shear or razor&#;can be a problem and is most easily managed by score slitting. A common solution is the wicking of the blade. In this practice, a piece of felt is positioned against the blade. The felt is supplied with a mineral spirit or other material to lubricate the blade and prevent adhesive buildup. Without wicking, adhesives can build up and form small balls that can eventually drop off onto the web and cause quality problems in the finished rolls.
Certain challenges can occur on wind-up as well. Of the three basic winding methods&#;surface winding, center-surface winding or pure center winding&#;the latter two are dominant in pressure-sensitive converting. They provide the ability to wind in minimum gap, fixed gap or lay-on control modes.
When winding, web tension built into the roll is critical. Too little tension on linered products can create loose rolls that can easily telescope. Too much tension on either linered or open faced (self-wound) products can squeeze the adhesive, causing it to ooze out at the roll edges.
Pressure-sensitive finished rolls are wound most frequently on duplex winders, since separating the rolls on alternating winding shafts is the only 100% foolproof method of preventing some materials from sticking together during the winding or discharge process. Duplex winding, however, has a basic disadvantage over common shaft winding. With a single-shaft winder, it is simpler and less time consuming to load and position cores, web the machine, and unload finished rolls. While duplex winding will remain the dominant choice for most pressure-sensitive work, it should be noted that more work today is possible on common shaft winders. This is primarily due to advances in web tension control, shaft technology and web spreading techniques.
Whether certain work can be wound on one shaft or two depends on factors such as minimum slit width, web thickness, finished roll diameter and the aggressiveness of the adhesive. When single-shaft winding is possible, the results are reduced downtime between sets and operator simplicity.
Despite the intrinsic complexity of handling PSAs, these materials can be converted successfully. From the unwind through the rewind, converting machinery must integrate features to address challenges like noise, tension and adhesive transfer. The web flow must be designed to create as short a web path as possible and to minimize the number of rolls contacted.
Optimal slitter rewinder performance and finished roll quality can be achieved with good web flow design, along with specialized features for handling adhesives. It is important to identify product families, finished roll parameters, and job size (number of sets/bars) in order to identify the best possible machine configuration and style.
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Tape is known for providing high storage capacity and good security for protecting stored data. Thus, the tape is widely used and can be used to back up data.
A tape cartridge has a thin strip with a magnetic coating on one side and is used as a traditional method to store data and use the data to perform various tasks such as analysis, archiving, etc.
Large amounts of data can be copied from hard disk to tape so that data can be retrieved in case of an emergency.
Some people prefer to backup data through an online service by using cloud services but using tape for backup storage has its own advantages and disadvantage.
Data in the tape are accessed in a sequential kind of storage. This way data in the tape is accessed in a prearranged and methodical sequence which data can&#;t be skipped while reading.
Many big organizations also use tape storage. Users can choose to have a full backup or incremental backup.
Full backup helps the user to restore their workload without any essential data loss but it is very time-consuming.
Using incremental backup helps to save time and the user only every time backup is initial, only new data is backed up but it also slows down during system restore.
If there are is several data awaited to back up in different tape, then file restoration gets time-consuming. Also to look through several incremental backup files, it will take time to find and restore one particular file.
Although incremental backup is done for small backup only requiring a small section of tape. To save costs, tape drive backup software can be used in such a way that tape starts writing from the place where the previous session finished.
To avoid any mistakes, do follow the guidelines on the tape. Tape drives do notify their users if the tape drives can&#;t be used to backup data anymore. Although tapes have a lifetime of 30 years it is necessary to follow the guidelines to get the maximum years of benefit otherwise tapes can have damage if not used properly and since they will be holding huge amounts of data, it is necessary to maintain the tape so that data can be accessed anytime required.
Also, make sure to label the tapes to save time and prevent damages. Labels on tape will also prevent the mixing up of tape and thus reduce the chance of human error.
It is also better if regularly perform tests are run to ensure that the backup is still valid. It is also advised to perform a full backup at once every month.
Storage capacity &#; as mentioned earlier, tape provides a large storage capacity. Storage capacity is increasing in tape storage day by day and thus remains a very crucial IT infrastructure in a business. It helps in storing data, information, files, and software for smooth operation in a business. Hospitals, banks, large scale industries use tape storage to provide services to their customer, keep records of their customers and these data can also be used to give direction to the business where will be used as a source of information about the expectation of its users and how can the company improve.
Archiving and Back-up &#; tape was initially introduced to be used in archival storage. In archival storage, people can shift some data that they were not currently dealing with so that they can free up some working area.
Tapes can store in two ways, native storage, and compressed storage.
Tapes are good for backup as they copy exactly like the original which reduces the chances of error rates. Also, while retrieving data, it can&#;t be assured that the data will be retrieved as ditto but keeping it back up in tape storage ensures recovery of data the same as it was.
If the user doesn&#;t have access to the data because the data was hacked, the company or the user will still be able to provide uninterrupted services to its customers and can continue their work since tapes have high storage capacity and all of the data will be saved.
High security &#; data are part of a company and it needs to be protected. On a daily basis data, information is shared by the company. Company data can be leaked in any form and in any way. Firstly, tape storage comes with an authorization which means that particularly authorized personal can access have access data, and access is given by the security key. Secondly, the tape storage is not always connected to the server just when required.
Low cost &#; tapes storages have less cost per gigabyte which makes it an affordable option compared to disk or cloud backups. Also, tapes drives are capable to create data storage offline thus reducing the cost for support and maintenance.
Durable and reliable &#; tape storages are reliable for 30 years and also has fewer error rates. Therefore, with regular updates, tapes can be helpful for a very long period of time. Also, tapes have higher transfer rates.
Easily removable and portable &#; unlike other storage options, tapes are connected to the server when not in use which means that the tape storage can be removed when not in use. When a company receives an attack, the users can pull out the tape physically which will create an air gap. This way, quick action can be taken to prevent the loss of data. Since the tape storage can be physically removed, to transfer data in a tape, the tape can be physically transferred to the required destination without involving the risk of transferring the data, software through a server. Thus, saving energy and lowering risk.
Compatible &#; luckily, tape storages are compatible with their previous tape storage meaning it will be easier to transfer from the previous generation of tape to a new generation of tape.
Lengthy access speeds &#; Tape formats need the authorization to access data and the data can&#;t be accessed randomly. Restoring data from tape also consumes a large amount of time since it takes time to locate a particular file.
High Initial costs &#; installing any storage system requires installation investment. Thus, companies will need to purchase new media and pay operating costs for system management if the user is shifting from another storage type.
Limited Scalability &#; scalability depends on the capability of the tape system and it is necessary to have the system updates.
High Maintenance &#; since it is made of magnetic tape, it is necessary to keep the tapes in a clean environment so that the tapes do not attract any dust particles.
Lastly, it is an eco-friendly solution. Tapes sit idle when not in use but disk storages continue to rotate even when not in use. This implies that when tape storage is connected to an energy source, tape storage rotates only while performing a function but disks rotate even when not performing a function, thus consuming energy when not in use.
This step also increases the generation of heat around the disk storage leading to installing HVAC equipment which would consume energy.
Tapes also better block energy due to larger magnetic bits which are less affected due to heat. Tapes already produce less heat due to fewer rotations even being connected to a source of energy.
Also, not to forget that disk storage has a life span of 5 years but tape storage has a lifetime of 30 years. Thus, the user will not be required to change the storage drive or device frequently thus reducing e-waste in the environment and the user will need space to store them as well.
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