Milton Florest understands welding -- not just how, but where and when to weld. He also knows about the drawbacks to welding. A mechanical engineer, Florest is president of Tooling Research Inc (TRI), a full-service machine shop in Walpole, MA. In recent years, his company has ventured into building signs, at times creating 3D architectural structures that resemble modernistic sculptures. In the process, he has learned the value of structural methacrylate adhesives as an alternative to welding.
"We are not a sign company," Florest is quick to point out, "nor are we architects." TRI primarily designs and builds custom mechanical, electrical, and pneumatic equipment and control systems, in addition to machining metal and plastic components. But word is spreading that Florest and his crew know how to turn a conceptual sketch into a sign or sculpture that is as durable as it is pleasing to the eye.
"Our role is to build structural integrity into the architect''s concept," Florest explains. Using 3D modeling software and a variety of materials, TRI has designed and fabricated a multitude of structures. For example, the company has built modern and colonial-style street signs, lampposts, and "tavern signs" that hang above shop entrances. Other creations include indoor and outdoor building directories (some featuring "you-are-here" maps), portable indoor displays for museum exhibits and hotel functions, plaques, and three-dimensional machined letters and logos.
Florest is always looking for ways to do things better. That is why, when he was hired to build a series of signs for a college campus in early 2002, Florest started looking into high-performance adhesives. Ordinarily, such signs are welded together, but this time he wanted to transcend the ordinary.
"The plans called for thin sheets of aluminum to be mounted on a structural framework," Florest recalls. "The completed panels had to be as light as possible because they had to be removable. From the start, I knew that welding would not be the best way to go on this project. When you weld something that thin, the weld has a pulling effect on the metal. You wind up with indentations on the outer surface -- not something the customer wants to see."
Florest had learned about sheet-metal distortions through experience. On previous similar jobs, he and his crew found creative ways to hide welds. When this wasn''t possible, it fell upon the finisher to fill in the low spots with body filler before painting the sign. The process was time consuming, and the end result was not up to TRI''s high standards.
"I knew there had to be a better way," Florest says. "But I wanted to be sure that whatever I used to bond the panels together would hold as effectively as a weld, not just against wind and weathering, but against vandals as well. I knew there had to be a solution, so I started investigating."
Shortly before work was to begin on the campus sign project, Florest spotted a magazine ad for Devcon Metal Welder™ Adhesive. He recognized the Devcon name because he had successfully used the manufacturer''s metal-filled putties in the past. He called the company in nearby Danvers, MA, and discussed his requirements with a Devcon application specialist. A Devcon representative visited his shop the next day, and Florest has used Devcon structural adhesives ever since.
The man who came knocking at TRI''s door was Jim Dunn, Devcon''s northeast regional sales manager. "I was very impressed," Florest recalls. "Jim not only demonstrated the application techniques for Devcon Metal Welder, but also explained the adhesive''s characteristics as he went along. He left some samples with us, and later we conducted our own experiments. We glued aluminum panels to steel, to plastic, and to an aluminum frame, simulating the assembly of different kinds of signs. In every test, we created a smooth, flat surface that required no finishing work because it had no deformities. I was amazed at the adhesion -- we pulled at those panels until the metal bent, but we could not break the bonds. Once I had proved the product''s ability to bond a variety of metals for myself, I knew that Metal Welder was exactly what we had been looking for."
Formulated specifically for bonding metal to other metals or to dissimilar substrates such as thermoplastics or composites, Metal Welder is a two-part, 10:1 methacrylate that requires no primers. Mixed as dispensed from handheld manual or pneumatic dispensers with static mixing nozzles, the adhesive has a working time of 5-6 minutes and attains functional cure in about one hour at room temperature. Tensile shear strength is 2450 psi, as tested on grit-blasted steel with a bond-line thickness of 0.020 in. Tensile elongation is 50-75%.
Metal Welder offers labor-saving advantages over mechanical fasteners, as well as welding. It eliminates the time and labor required to drill or punch holes when using screws or rivets. And by eliminating the fasteners themselves, it allows for a more aesthetically pleasing appearance. Whether used to assemble a sign, an appliance, or even a vehicle, an adhesive distributes stresses across a much greater area (the entire length of the bond line) instead of concentrating them at rivets or screws. This not only produces a stronger bond, but also prevents the loosening and leaking that can occur when fastener holes expand due to vibration, flexing, or temperature cycling. When used to join dissimilar metals, the adhesive has yet another advantage over welding and fasteners: because the adhesive layer keeps the two metals from touching, it prevents corrosive electrolysis.
"Don''t get me wrong," Florest says. "My satisfaction with Metal Welder doesn''t mean that I''ll never weld anything again. Large signs and structures can be more complex than one might think, and we will always weld certain sections. Likewise, there are some signs in which the use of rivets or screws is part of the overall design. But the adhesive works particularly well on panels and thin sections where clean lines and surfaces are the ultimate goal."
TRI had been using Metal Welder for only a few months when Devcon introduced Metal Welder II, a new formulation with essentially the same attributes as Metal Welder but a longer working time (14-16 minutes). It didn''t take Florest long to switch to the new adhesive. "Putting together a big sign takes time, so it was the obvious way to go," he explains. "We sometimes have three or four people working at the same time -- one gluing, one holding, and one clamping -- to complete an assembly before the adhesive sets up. Every minute counts, so we appreciated the new adhesive''s extra working time."
Nowadays, Florest is more likely to choose Devcon''s Plastic Welder II, which has an 18-minute working time. Although Florest appreciates the extra time, it is not the main reason he likes this adhesive better. For optimum adhesion, both Metal Welder and Metal Welder II contain tiny glass beads designed to ensure a minimum gap of 0.030 in. between the surfaces to be bonded. With Plastic Welder II, the minimum gap is only 0.010 in.
"The gap is not always an issue," Florest says. "But we work within very precise tolerances, and for some of the more sophisticated signs we''ve been building lately, a 0.030 in. gap is too wide. That''s why we find ourselves using Plastic Welder II more often. I guess I''m turning into sort of an adhesive connoisseur. I''m learning how to choose the best adhesive for the job at hand."
Ideal for outdoor applications, Plastic Welder II is particularly resistant to weathering and ultraviolet light. In addition to standard plastics, it bonds nylon, nylon-containing alloys, modified polyesters, epoxy composites, metals, fiberglass, and wood. It is also 100% reactive and has very low VOC emissions. Mixed in a 1:1 ratio, Plastic Welder II achieves functional cure in two hours at room temperature. To maximize the adhesive''s durability on aluminum or stainless steel, the manufacturer recommends the use of a primer (Devcon Metal Prep 90).
Among Florest''s most recent creations are two 23 ft high, lighted, metal-skinned directories for the Massachusetts Institute of Technology (MIT), in Cambridge. These modernistic structures stand at the entrances to the university''s Technology Square, a grouping of offices and laboratories that draw on the faculty''s brainpower and investment capital for genetic engineering and other research.
"In the business, these are called sculptures," Florest says. "And sometimes I feel like a sculptor; I enjoy bringing substance to a vision. It''s rewarding to figure out how to build something that intricate, yet sturdy -- a first-class structure that''s going to last."
Florest is sold on Devcon adhesives; so much so that he constantly keeps an eye open for new uses for them. He notes, "When I discovered they were resistant to harsh chemicals, I immediately began looking for ways to use these adhesives in our line of chemical handling equipment."
When he encountered problems, Florest sought new tools to overcome them. He found several solutions in Devcon''s methacrylate adhesives. The versatility of these tough, user-friendly adhesives on a variety of materials has helped him grow the architectural segment of his business, a segment that continues to evolve. Armed with experience and several particularly useful new tools, Florest is looking forward to his next challenging project.