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![]() Know Your Tools: Finishing with Efficiency
By Jeff Burton, Digital Printing Analyst, SGIA
The finishing tools used for large-format digital printing are as varied as the substrates on which one can print. But what equipment should you use to complete your finishing efficiently and effectively?
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From year to year, many companies change the products they make, or begin producing new product lines in niche areas that require new and different finishing methods. In some shops, the steps taken to finish products are done with inappropriate tools. Furthermore, many shops keep their laminators, cutters and other finishing tools too long and put off new purchases or upgrades, which negatively affects productivity and quality. This article examines tools used in the finishing marketplace and will address opportunities for better and more efficient production for the future.
Finishing Solutions for Banners and Textiles
Sewing Machines The feed movement on a consumer-grade sewing machine utilizes a set of toothed, metal walking plates that move under the material, pressing it up onto the machine’s presser foot. In contrast, a dual (or unison feed) commercial sewing machine is a better investment. Also known as “walking foot machines,” these units have a presser foot with its own set of gripping teeth that walks in unison with the bottom feed to facilitate double feeding of the material. The end result is a larger, more consistent stitch. These machines typically are used by upholsterers and people who need to sew heavy-grade industrial fabrics. The one-needle, unison-feed lockstitch is the most common type of industrial sewing machine in use. Double-needle, chain-stitch machines also are used. They use four thread spools that feed from the unit’s top and do not require the bottom bobbin thread to be changed. These are a better choice for companies producing large volumes of work without interruption. Given the many variations and options found on industrial machines, talking to a manufacturer may be the best way to narrow down the possibilities.
Sticky Alternatives to Stitching VHB tapes have enormous gripping power and are used when material stress is of concern, there is no access to a sewing machine or the project requires tape for the intended product life. Hem tapes also can be used in a one-sided application as a reinforcing material when inserting grommets. Vinyl that is not reinforced is a soft material in which grommets have a tendency of tearing out under stress. Using reinforced hem material, a high-strength plastic that has an adhesive on one side, solves this problem. It is applied to the banner’s back before grommeting.
Banner Welding
Hot Air or Hot Wedge Hot air rotary heat sealing is used to join thermoplastic industrial fabrics and films using precise heat, speed and pressure settings. Hot air temperatures for these units can range from 537.8oC (1,000oF) to as high as 732.2oC (1,350oF). On these systems, a heated wedge is positioned precisely at the weld point, providing the required heat. The fabric or film is then pulled across the heated wedge. There are strong advantages to both rotary welder types. Wedge welders can use less power than their hot air counterparts and do not have the noise associated with hot air blower systems. However, hot air systems can provide a better, more dependable bond. Also, for substrates that are not always produced perfectly, hot air systems seem better suited in dealing with these variations.
For grand-format RF welding, the seaming head is on a traversing rail that runs the length of a long, narrow table. Companies such as Zemat and Forsstrom High Frequency AB have units for seaming together billboards. Of all vinyl seaming technologies, RF units are the most expensive and consume the most energy. They are used from automobiles, swimming pools, tarpaulins and electronics to the food industry, and are widely used in material sealing and welding.
Grommeting Automated grommeting devices cut the hole, place it and set the grommet in under a second. Many of these units can handle grommets of varying sizes and set them through many difficult materials, such as Sintra and Durabond. When there is a need for the operator to place one or both parts of the fastener, varying degrees of semi-automation include a pneumatic or electric-powered press for closure.
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Cutting and Trimming Solutions
Normally, safety rulers are aluminum extrusions with painted inch markings or an applied ruler tape. Aluminum cutting edges eventually become uneven, as they are repeatedly cut into, and become “shaved” through repeated cutting or trimming. Some safety rulers come with stainless steel rods or sheets fastened to or embedded into the ruler. This greatly improves the effective life span of the ruler.
For synthetic or other fabrics, the use of a rotary cutter results in a cleaner cut, without pulling out threads or leaving behind a fuzzy edge. Even better than the rotary knife for use on heavy synthetics is the “hot knife.”
Environmental Controls
These air cleaners may be used with flexible piping — much like the vent hose on a clothes dryer — that connects directly to the exhaust ports found on many printers. Room scrubbers, which clean ambient air, capture fumes only after they have entered a room or space, not at the source. Shops that utilize higher solvent ink volumes or cleaning solvents that are more volatile may benefit from using potassium permanganate grids with activated charcoal to achieve higher VOC capture rates.
Dust Removal for Print Finishing Dirty machines, tables and dusty operators are the first priority for dust removal. Operators can use an air hose to de-dust themselves after using any saw in order to remove wood, plastic or metal particles from their hair and clothing. This should be done far away from the finishing area. To clean finished prints and substrates, Drytac offers a Dust Removal System (DRS) Roller in a 30.4-cm (12-inch) width. It comes with 50 tear-off adhesive sheets in a pad, which clean the dust and dirt from the roller. One must simply roll the print clean, clean the roller on the pad and roll and repeat as necessary.
Jeff Burton, Digital Printing Analyst for SGIA, has served with the Association since 1998. He provides solutions to digital printing production, computer and work-flow issues as well as digital equipment and vendor recommendations. Burton currently teaches Introduction to Digital Printing and Color Management at SGIA headquarters in Fairfax, Virginia. jburton@sgia.org This article appeared in the SGIA Journal, 1st Quarter 2009 Issue and is reprinted with permission. Copyright 2009 Specialty Graphic Imaging Association (www.sgia.org). All Rights Reserved.
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