Improving roll forming productivity of roofing components
Developments and options in equipment, processes
Roll forming of roofing components for the pre-engineered building and component industries presents unique challenges for manufacturers. Tighter profile tolerances, wider product ranges, and compressed lead times present production challenges for producers running older equipment or those contemplating a move into this market. Some developments in equipment and processes that are important to producing secondary structural members include quick-change roll form tooling systems and tooling that can improve the productivity of roofing components- Cee's, Zee's, Eave Struts, Channel, and Base Angle.
|Photo courtesy of Follansbee Steel, Follansbee, W.V., and the Metal Roofing Alliance.|
The metal roofing industry has undergone dramatic changes in recent years. Builders expect better-quality parts, quicker lead-times, and lower prices. Prepainted material has mostly replaced postpainting of purlins, and galvanized material is being used more often, especially in coastal environments and agribusiness applications. High-strength steel is being increasingly specified. Punching requirements and product ranges have increased.
Roll forming roofing components for the pre-engineered building and component industries presents unique challenges for fabricators. Tighter profile tolerances, wider product ranges, and compressed lead-times are production challenges for producers running older equipment or those contemplating a move into this market.
Equipment manufacturers have responded with systems that are more flexible, produce a wider range of products, are more productive, and cost less. Of emerging importance are the equipment and processes required to produce secondary structural members.
The first step in improving roll formed roof framing components starts is coil handling equipment. Keeping the production line fed always has been a process that has a major impact on line productivity, and it is even more important today with the introduction of high-speed punching systems and quick-change roll formers. Reduced lead-times and just-in-time (JIT) manufacturing philosophies have increased the number of daily coil changes, in some cases by tenfold.
Running a complete coil is no longer the norm. Many producers are running a few parts and then switching to another coil, because they are increasingly producing complete buildings to order rather than rolling components to stock.
Many types of coil handling systems are available to help manage the process and improve productivity in this area. Coil storage racks, rotating turnstiles, and coil cars help production personnel stage coils into and away from the production areas. Coil management software is available to help streamline the flow of orders into manageable units that help the operator balance flexibility and productivity; knowing which coil is going to be run next (and the available length of that coil) is just as important as changing coils quickly.
Double-arm uncoilers with powered hold-down rolls allow the operator to prepare the new coil for production while the line is running and secure the partially used coil for offline rebanding, increasing line uptime. Automatic and semiautomatic feed-up systems with band breakers and nose benders reduce the time required to get a new coil into production.
An integrated coil handling system with all of these features in an engineered package that offers excellent, high-speed performance and faster line throughput to increase productivity in a process that often is overlooked or viewed as a secondary consideration to overall line speed.
It takes less than one minute to change from one profile to another—such as from a C to a Z profile, as shown—on a 14-pass semiautomatic purlin roll former. This handle rotates a knuckle that changes the flange-forming roll position. In photo 1, the flange-forming roll is in the upposition. In photos 2 and 3, the roll is vertical and being turned up toward the flange-forming down position. In photo 4 the roll is in theflange-forming downposition. If this outboard flange-forming roll is in the down formingposition on all seven flange-forming passes, the roll former is set to form a Z-shaped purlin. If it is in the up formingposition, it is set to form a C-shaped purlin.
Punching and Cutoff
Assume a company has a product mix of many different proprietary and custom punch patterns and requires a high level of flexibility to service a diverse customer base. For this company, traditional lap presses may not be flexible enough, and mechanical presses may be too noisy, costly and time-consuming to maintain, and require a massive foundation.
An option for this company might be a modular hydraulic punching system. These systems are available in a variety of configurations:
Highly flexible production. These systems use as few punches as possible and rely on multiple hits and intermediate servo movements to produce a complex part. Highly flexible systems are best-suited to lower-volume component manufacturers that cannot pre-define their punch patterns, offer a wide product range, and need the ability to put any hole anywhere on a part.
High production. These systems use many fixed punches and do not require die movements to produce parts with a given range of hole sizes and punch patterns. These systems are best suited to high-volume pre-engineered building (PEB) manufacturers that have some measure of control over their punch patterns and value high production speeds over flexibility.
Hybrid production. As the name suggests, these systems combine flexibility and high production speeds in one package. Using a combination of fixed die clusters for industry-standard punch patterns and a series of movable dies for special patterns and custom punching requirements, these systems can put a hole anywhere on the part and still maintain high levels of productivity. With die layouts optimized to specific requirements, the number of feeds and stops can be greatly reduced, increasing line throughput.
These systems offer the best balance of throughput and flexibility but require greater understanding of specific punching requirements during the design process to execute successfully.
Cutoff systems. Most of the high-volume, quick-change purlin systems on the market today are precut, as the postcut die changeover required for each shape and size would be cost-prohibitive and negate the quick-change capability. Systems are available with a programmable partial cut that allows suppliers to ship a string of short parts (previously these were sawed to length offline) that are snapped apart in the field, eliminating the added processing and handling costs, as well as field loss issues associated with these small parts.
Here the strip enters a fully automatic quick-change purling roll former with the tooling set in the Z profile.
Today's roofing component producers need the ability to change from C to Z to single- or double-slope-eave struts, in a variety of sizes and gauges, all within the confines of a single order.
Some new purlin production systems on the market today offer this flexibility with both automatic and semiautomatic changeover (see Figure 1). It is possible, for example, to change a roll former from rolling a 4-in. C-purlin to a 14-in. Z-purlin in about a minute, simply by pushing a button on the fully automatic machine or turning a hand wheel on the semiautomatic design.
Eave struts can be produced inline in either single- or double-slope configurations, eliminating an offline bending operation. Positive gauge changes can be manual or automatic, or in some cases accommodated with floating tooling.
By their very nature, these new roll former designs precluded using old tooling technology, and earlier systems that tried to adapt or automate these processes were less than successful in the marketplace. The typical quick-change purlin roll former today uses a combination of drive and idler rolls and has individual shape control features for ski, twist, dive, camber, and each of the individual forming corners.
At least one equipment manufacturer has eliminated air bending; with true angle-bisect forming technology, there are no hidden corners on any part.
It may sound basic, but a high-speed purlin production system requires a high-speed material handling system, and a system capable of producing a range of parts requires a material handling system that can handle the full product range.
Stacking systems available today range from simple stacking tables to state-of-the art, programmable robotic stackers. Software is available for automatic part marking, bundling, and batching of orders. Automated side discharge and inline conveyor systems speed the safe handling of finished stacks and bundled orders.
Keeping pace with the change in forming technology, line controls have evolved as well. Machine controls are available with open-architecture operating systems, enabling direct communication with a variety of production control systems. Many of these systems use off-the-shelf components for local serviceability.
Upload/download systems are available with real-time production management reporting. Standard software can decode the output from a building design program and automatically code the required punch patterns, allocating them for corresponding order production and storing them for future recall. Touchscreen operation now is common.
The Good News
The good news for purlin fabricators is that the manufacturing equipment to meet these production challenges is available today, and the price for these high-tech systems continues to decrease as market demand and design standardization by the equipment suppliers increase.
The fast changeover times achieved with quick-change, high-speed purlin production systems result in lower unit production costs and increased throughput. In addition, suppliers using these systems can respond quickly to local market demands, offer a wider range of products, provide custom sizes, and offer custom punching, to increase their market presence in the roofing component industry.
Both for entry-level producers just starting out or experienced high-volume fabricators running multishift operations, there have never been so many options available in quick-change purlin manufacturing systems.
|2006 Energy Tax Credits for Metal Roofing|
From now through Dec. 31, 2007, the U.S. government is awarding tax credit savings up to $500 to consumers of energy-conserving metal roofs. The Energy Policy Act of 2005 allows for a tax credit for homeowners who install qualified energy-efficient improvements to an existing home. The policy, in the case of roofing, defines improvement as a metal roof with appropriate pigmented coatings that meet the Energy Star-program requirements. As an Energy Star labeled metal roofing system has at least 65 percent solar reflectance for low-slope roofing and 25 percent solar reflectance for steep-slope roofing. The government-funded Tax Incentives Assistance Project (TIAP) has posted on its Web site the complete list of eligible measures for this tax credit that include pigmented metal roofs.
The FABRICATOR is North America's leading magazine for the metal forming and fabricating industry. The magazine delivers the news, technical articles, and case histories that enable fabricators to do their jobs more efficiently. The FABRICATOR has served the industry since 1971.