By Cassandra Balentine
Welding is a popular finishing technique for wide format graphics production. An alternative to sewing, welding is ideal for finishing applications composed of materials like vinyl and fabric. Welded graphics provide durability and limited material waste. It supports numerous finishing functions including hemming, pole pockets, and pocket sign fabrication.
Carl Hoffman, director of sales and marketing, Royal Sovereign, Inc., points out that welding offers advantages over alternative methods. As opposed to sewing for example, welding eliminates visible stitches. Further, common banner tapes can fail in extreme hot or cold conditions.
Types of welding include high frequency (HF), hot air, and impulse—each have a place in the graphic arts. All three methods provide advantages and limitations so the investment in a welder should include several considerations.
Here we offer the pros and cons of popular welding techniques, as well as specific factors that may affect the decision in which method to invest in.
Above: Leister offers hot air welding equipment from handheld units to automatic crawlers and large stationary units for big shops.
HF or radio frequency (RF) welding is a popular welding method for wide format graphics production. This method uses energy from an electromagnetic field and pressure to bond two materials together.
When HF welding is used for finishing wide format graphics, Chase Pender, marketing manager, Supply55, Inc., points out that elimination of consumable costs, durability of the weld, the ability to process a range of materials, and high production output are associated benefits.
Eve Hawthorne, sales agent, Forsstrom, adds that HF welding can change and control the amount of energy needed to make a good weld/seam/bond. “The HF welding machine can change power settings and tooling quickly. This provides the ability to perform different sizes of welds according to the job requirements.”
According to Jeff Sponseller, EVP, Miller Weldmaster Corp., HF welding allows wide format users to align images on a step-by-step basis.
“HF should be used when the job requires straighter, stronger, and unwrinkled welds,” offers Hawthorne. “HF is the strongest method to bond two or more pieces of vinyl. It can bond two or more pieces at the same time. Other methods require additional work to add layers,” she comments.
“Superwide format fabric and banner images often require perimeter hems, which are difficult to produce without a HF welder,” notes Pender.
HF welding is appropriate for a variety of materials. Vinyl and vinyl mesh are common in the graphic arts market. Hawthorne says HF can bond to either of these materials.
“I’ve seen HF welding used for billboards and sometimes building wraps,” offers Sponseller.
However, there are limitations to HF welding, including the time it takes to create very large graphics. “It’s is essentially a ten second weld per hit,” states Sponseller.
Another possible downside is the initial implementation cost, says Pender.
Hot Air Welding
The method of hot air or hot wedge welding uses heat, speed, and pressure to join materials together. According to Miller Weldmaster’s website, the hot air welding process compresses and blows air across electrical heat elements to apply and inject that heat at the welding point.
Sponseller explains that there are two different types of machines that use hot air and/or hot wedge technology. One is a device similar to the concept of a sewing machine where digitally printed banners are finished, but in this case they are welded.
Further, hot air welding technology is used with machines when the material lays flat and it is locked into place with a vacuum. “This method is popular in scenarios where customers need to align images, finish large billboards, and very large building wraps. Hot air welding is used when the customer desires to limit the amount of material handling required for large boards,” says Sponseller.
Welding with hot air or wedge technology is fast and creates a durable bond. “Welds such as hems, pole pockets, and overlap can all be done on the same machine, which increases efficiencies for the operator. However, this process does require more space to handle materials and weld,” shares Ken Huber, manager, plastic welding products, Leister Technologies.
He adds that sign makers should utilize the strongest finishing method available in order to maximize banner life—heat welding hems and pockets. “This method creates a permanent molecular bond of the material, making the bond as strong as the material itself, especially for outdoor applications,”
Hot air welding is a fast way for finishing edges of a printed graphic, especially when compared to taping or sewing a banner. “Hot air welding is useful to reduce the amount of material handling required,” adds Sponseller.
“Hot air and hot wedge welding offer a wide weight range of substrates to weld. However, in the sign and billboard market, we predominately see digital textile, PVC or vinyl, and polyethylene and some of the 30 sheet billboards as substrate options,” shares Sponseller.
The most compatible material for welding with hot air and wedge are vinyl or thinner polyethylene for billboards, offers Huber.
Hoffman says vinyl banner materials from 13 to 18 oz. in weight work the best for hot air and wedge welding.
Hawthorne points out that a disadvantage of hot air and wedge welding is the amount of smoke created by the process. “I’ve been in a building when this process was used and you can see the haze in the room,” she comments.
Impulse welding is another consideration. This is a hot bar method of welding thermoplastics. According to Miller Weldmaster, in an impulse welding machine pressure is applied to the seam area with two impulse heating bars. Heat is created by pulsing energy through the heating element in the top and bottom bars for the duration of the weld. After a set weld time is completed, liquid is flushed through the impulse bars to allow a cool down cycle, helping eliminate wrinkles.
Advantages of impulse welding include elimination of consumable costs; durability of the welded product; a lower investment cost; and clean, strong, and professional seams, shares Pender.
In the graphics market, Sponseller says impulse welding is used by customers welding awnings and digital graphics. “It’s not very prevalent in sign-only markets,” he adds.
“Impulse welding has a lower cost of entry and is well suited for smaller print shops looking to produce pole pockets for municipal light pole banners, pocket signs, and perimeter hems for garments,” says Pender.
Impulse welding joins a variety of fabrics, however it is typically most successful with thinner textiles, offers Sponseller.
Pender points out that one disadvantage of this technology is its limited range of materials to process.
Investing in a Welder
Welding is used as an alternative to sewing and taping. There are many benefits to this technology, but choosing the right method and equipment is a unique process for every shop.
Pender believes that a print provider should consider the type of work they are looking to complete. “For example, if a small print provider needs to make pole pockets, pocket signs, and perimeter hems in banners, then an impulse welder would work great. If someone is looking to fabricate tents, billboards, and larger projects, a different welding method would be more suitable,” he explains.
Huber says that the biggest factors in determining which welder a print shop should buy include materials printed, size, and volume.
Print providers should consider everything when making a decision to invest in a welding method and machine. “I think the quality of the weld process would be my number one concern. Followed by the ease of use of the equipment. Then, the support you receive from the manufacturer. Of course, we can’t forget cost,” suggests Hawthorne.
Hoffman recommends looking at the number of banners produced in a given day, as well as the size of the banners before selecting a welder. “Some welders are more suited for small to medium banners, such as ones seen hanging from the fence on the outfield of a little league baseball field to banners as large as billboards,” he offers.
Overall, it is essential to consider the total output required to get out the door to match customers’ demands. For example, if a provider has multiple, high-speed printers and yet has a slow means of finishing those products, then its bottleneck is with its finishing. “It is important to select a finishing solution that enables a print provider to match finishing close to or exceeding what their printers can output. Furthermore, a print provider will want to consider a quality-looking seam as to match the print quality that it is sending to its customers,” says Sponseller.
On the Market
Several welders are available to PSPs.
Forsstrom offers a range of HF welding machine models—each developed to suit different types of manufacturing. The company categorizes them as stationary and traveling. It recommends the TDW traveling welding machines and the TX stationary welding machines for welding digitally printed wide format output.
The TDW is a large traveling machine with customized table length and 785 millimeters of free space behind the electrode. The welding table is equipped with a large trough for material storage. With its fast machine movement, ability to pre-program welding cycles, and ability to switch the machine over to automatic welding, the TDW machine is suitable for large products with long, straight welds, such as tents, truck covers, and billboards, as well as large-scale production.
Forsstrom TX Automatic is a fully automatic, HF welding machine for continuous production. In addition to welding, the machine offers off-winding, indexing, and an optional up-winding unit. The TX Automatic has a production capacity of 200 to 300 meters per hour depending on end product. The TX Automatic produces items like keder and tubes in a continuous process.
Leister offers hot air welding equipment from handheld units to automatic crawlers and large stationary units for big shops. Its TRIAC heat guns are ideal for repairs and finishing work. Leister’s HEMTEK ST is an entry-level hem welder for small shops welding hems and pole pockets. The UNIPLAN 500 welds edge work as well as panels large banners together.
Miller Weldmaster provides a range of welders for the print maker, including the 112 model available in sizes from three to 50 meters for large and grand format printers. Additionally, its T3 and T300 models are both used to finish the edges of banners. A shop’s output and speed needs dictate if the T3—one finished banner every 90 seconds, or the T300—one finished banner every 40 seconds, is correct. Further, the company’s newest model, the Digitran, features a digital transit conveyor system. Sponseller says the Digitran is quickly growing in popularity to help its customers finish digital textiles and dye-sublimation (dye-sub) products in the sign industry.
“As we have several customers in the digital market considering dye-sub, we’ve had to adapt to accommodate digital textile,” shares Sponseller. “We frequently receive requests for silicone edge graphics (SEG) framing systems, which allows our customers to provide an even wider range of products to their customers. We developed an automated sewing machine that has a synchronized conveyor system. With this system, you can easily switch out the sewing machine and sync up your welder too. Thus, one system enables sewing, welding, or both.”
Royal Sovereign offers the RBW-1500S banner welder. According to Hoffman, it works well with wedge or sometimes referred to as heat plate technology. The RBW-1500S is a standalone unit designed to be positioned to the side of a production finishing worktable. The unit can be raised or lowered to accommodate the height of the table and features adjustable speed and heat temperature to optimize banner production. It is designed to weld the outer edges of a banner and to produce pole pockets up to six inches in depth.
Supply55 offers the BannerPRO Professional Banner Hemming System. It is an impulse welder that offers many capabilities including hemming for grommets, pole pockets, and pocket sign fabrication at a fraction of the cost of other hemming systems.
Welding is an effective way of finishing printed graphics. This method is used to hem banners, create pole pockets, and manufacture parts necessary for SEG. Print providers consider many important factors—including technology type—when searching for a welding solution.
Jun2020, Digital Output