by John Baxter
The single most influential trend affecting the worldwide glass bending and tempering industry is the demand for increased economy of production. Simply put, users among both architectural and automotive glass segments of the industry want a more efficient process, less cost and better value. To meet these needs, companies such as ours, which produce glass bending and tempering systems, constantly analyze new designs and seek improvements in uptime, cycle time, initial investment and so on.
While all users want reduced costs of production, the architectural portion of the glass industry is also seeking new processing techniques for specific challenges.
Because of their energy efficiency, a range of reflective, or Low-E, glass products are increasingly in demand. But these innovations have created challenges for the industry. Traditional electric radiant heaters struggle to pass heat through the reflective surface, and many of the coatings partially or completely decompose at the processing temperature. Moreover, the throughput rate compared with standard clear float glass is dramatically reduced, typically by 50 percent or more, which renders the tempering process less economical.
Manufacturers of radiant heating systems introduced convection-assisted radiant heaters, which, although improving the quality and economy of coated glass processing, did not fully address the throughput shortcomings. In the early 1990s, our company commenced a project with the Gas Research Institute (GRI) of Chicago to develop a gas-fired forced convection heater (FCH), in which the principal heating mechanism is jets of heated air impinging on the glass surface. This permits heat to be transferred through the surface of the glass at a high rate irrespective of the applied coating (Figure 1).
The benefits of the gas-fired FCH system include:
In another trend of the last ten years, curved or bent glass has been specified more frequently for buildings and other specifications, creating more challenges for the industry. Glass bending and tempering systems capable of making bends in larger sheets either of cylindrical contour or combined cylindrical and flat contours have been adopted by some processors for use in buildings, storefronts, display cases, shower enclosures, furniture panels and appliance glass.
Our company, for example, produces three bending systems of different widths and capabilities that can be supplied with either the traditional radiation heater or the new FCH.
Trends in the automotive industry have also influenced designs from glass processors. Although the FCH design was initially directed at architectural uses, its benefits can also be utilized for automotive glass processing as well.
Coated glass is being specified more frequently for automotive applications. Our company has introduced a forced convection heater that can be supplied on new bending and tempering systems or be retrofitted to existing systems for automotive glass.
Other recent trends in the automotive sector include short glass part production runs, just-in-time delivery and reduction of part inventories. In certain facilities, part changeovers are required at least once a day and sometimes once a shift.
Automotive glass processors are under great pressure from automobile manufacturers to reduce glass prices. As a result, the glass processors are seeking systems that can achieve high productivity, low downtime, high yield and rapid part changeover at little or no tooling cost.
Machinery manufacturers have worked to devise such bending and tempering systems. Our cylindrical bending and tempering system, for example, does not require part-dedicated tooling and can be changed from one radius to another in only a few minutes. The CRB enhances uptime with its fast changeover abilities. The system is ideal for long and short original equipment manufacture glass runs and the typically very short automotive replacement glass runs.
Many backlites and fixed sidelites can not be produced on simple bending and tempering systems. Such complex shapes and precise design demands require part-dedicated tooling and, in the past, were often difficult to achieve satisfactorily. Our Deep Bend (DB4) press-bending system with its Quick Change System reduces part changeover time to less than 90 minutes, which results in more productive furnace time (Figure 2).
These technological advancements are examples of how the glass processing industry is continually engineering new answers for the challenges posed by glass users.
John Baxter is senior vice president, sales and marketing, for Glasstech, Inc. of Perrysburg, OH.
A number of manufacturers have released information about products that address the needs of fabricators. Machinery news and a sampling of some of the newest products follow.
Fleischle of Brackenheim, Germany, offers the screenprinting machine, SH, which features the printing stencil that moves horizontally towards the back. The machine also includes a loading conveyor that sits on the side of the machine and gear belts to transfer glass sheets. The conveyor is powered by an adjustable three-phase motor.
Breton S.p.A. of Castello di Godego, Italy, offers the Contourbreton NC 160 work center. According to the company, the work center is designed to ensure a high-production capacity and large flexibility, due to a wide gamut of possible geometries that allow processing on glass, marble and granite slabs and billets, without the intervention of a operator.
CTD Machines, Inc. of Los Angeles, CA, has introduced the Model D20R Single-Double Mitre Saw, which it says can make two independent 45-degree mitre cuts within seconds. According to the company, the saw can also cut wood, aluminum or vinyl sections up to 5-3/4 inches wide. Standard features of the saw include two one-horsepower, single-phase motors at 115 volts with a toggle switch, a 12-inch blade capacity, a rotating inner blade guard and adjustable outer finger guards.
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