March 11, 2011
If existing coil feeding equipment is functioning, but productivity needs a boost, stampers can achieve measurable gains in their production efficiency through various types of upgrades to their coil handling and feeding equipment, including servo drives, variable speed controls, and operator interfaces.
Competition among manufacturers for market share in the new global economy is fierce. Many manufacturers have seen their markets dwindle, with some of their customers disappearing from the landscape entirely. Given the intense competition, attaining the highest productivity possible from the shop floor is increasingly important.
With these challenges, installing new equipment is not always an option. So optimizing productivity often comes down to finding ways to maximize the use of existing resources.
Some conditions are clear clues that it is time to upgrade the coil line—either by refurbishing or replacing components or refurbishing or replacing the entire coil line. Excessive downtime, increased maintenance that affects overall productivity, and safety deterioration are indicators that the equipment needs upgrading.
Or it may be that existing equipment is functional, but that productivity needs a boost. In this case, various types of upgrades to coil handling and feeding equipment can help stampers achieve measurable gains in their production efficiencies.
First, replacing the controller is a relatively easy way to simplify setups and increase functionality (see Figure 1). Many new servo controllers are designed to be installed quickly into coil lines—sometimes even over a weekend.
Servo. Many servo feeds in operation today were installed when servo technology was new. While they were a great replacement to air and mechanical feeds, many were built on unsupported hardware and software platforms. The failure of a critical drive, motor, or motion controller can cause extended downtime.
Variable Speed. Many original straighteners and reels in coil feeding systems were designed with simple drive mechanisms. Today's variable-speed controls are programmable. This allows stampers to customize parameters to optimize uncoiler and straightener machine performance to provide the proper torque necessary for these operations.
Interfaces. Many roll feeds in operation today have outdated operator interfaces. These are often simple devices that offer only the basic setup functions of feed progression and speed percentage. This limits their effectiveness in today's stamping operations. With a modern upgrade, stampers gain many new features that reduce setup time, improve consistency, and raise productivity, such as storage recipes, operator prompts, servo feed diagnostics, multilingual programming, and direct downloading of press parameters.
Loop Control. Loop control upgrades can help improve accurate sensing of the loop position and precise feedback of the straightener or reel drive. These are crucial for effective operation of the coil feeding system. Original loop control systems are often simple on/off switches or potentiometers. Modernized loop controls—ultrasonic, photoeye, and laser—provide noncontact detection technology to meet higher-quality requirements. Loop height and response output signals are programmable to achieve optimal coil line performance for each job setup.
Other potential areas for press line optimization are the coil, feeder, and straightening equipment itself.
Line Speed. Output rates may be constrained by the straightener or reel line speed capability. Many progressive press lines were originally specified to run at a max-imum line speed of 40 to 60 feet per minute (FPM). Upgrades to the machine drive and reducer package can double coil rate speeds—up to 100 FPM.
Straightener Capacity. The increased use of higher-strength materials has created coil straightening problems for many stampers. Much of the existing equipment was designed to straighten only mild steels with low yield strengths. It is now common for yield strengths to exceed 60,000 PSI. Straighteners can be upgraded to meet this demand with new, high-performance drives and motors, improved reduction packages, and by adding a center backup assembly to prevent deflection of the straightening rolls (see Figure 2).
Coil Containment. Many stampers are being challenged to process not only higher-strength materials, but also a wider range of material thicknesses using their existing equipment. Upgrades to the threading drive system and the addition of hold-down arms, lower hold-up arms, and motorized end-wheels can help stampers process more thicknesses.
Load Direction Changes. Presses and auxiliary equipment often are shuffled around to make room for new presses or to improve the stamping process flow. The feed and loading direction of the coil can limit the flexibility and options for optimizing plant layout. Changing the loading direction of the coil reel or the controls position on the straightener and servo feed can give stampers the flexibility to improve plant layout.
Threading Safety. Although quick changeover is essential to pressroom productivity, it is not efficient or safe to allow operators to manually thread heavy-gauge or high-strength coil strip into a straightener or feeder. Existing coil feed lines can be upgraded with thread tables, peeler tables, debenders, and hands-free peeler/threader hold-downs to improve coil change efficiency and safety.
Motorized Line Functions. Motorizing key functions of the coil feed line can enhance setup speed and consistency. Machine axis such as passline height setting, edge guide adjustments, and straightener roll depth settings can be effectively motorized.
To companies that are not in a position to make a capital investment in new equipment, the decision to retrofit may be a favorable alternative. Refurbishing an old press to bring it up to new standards required for today's demand for quality, clearances, and control can result in significant savings over the cost of a new press.
However, extensive rebuilds often can take up to six months to complete. Field retrofits to existing lines can be performed in less time than those that require the system to be shipped to a service center. Field retrofits may include line speed increases, the addition of coil containment devices, loop control upgrades, and threading system improvements.
Thus, the decision to remanufacture or upgrade press equipment should be made only when the expected workload and part volume justify the cost to rebuild.
Each situation is unique regarding the decision to upgrade or purchase new equipment. It is important to evaluate all aspects of the stamping process, from the standpoint of mechanical, electrical, power train, line configuration, and line speed, to help arrive at the best solution. After analyzing the separate yet interrelated issues of time, cost of new versus retrofit, and potential productivity gains, each company will come to its own conclusion.
Obviously, sometimes new equipment—or a combination of new and upgrades—makes more sense than a retrofit. An analysis of the existing system, production requirements, and a cost comparison by a qualified coil line professional can help stampers determine the best approach.
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