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The machine tool industry has worked diligently to continuously improve the performance of its products through the years. Turning machines are markedly more accurate and repeatable and provide increasingly faster spindle speeds. Many now use sophisticated, intelligent controls that help manage production schedules with more flexibility. And some OEMs have transformed their dedicated turning machines into multifunction machining centers that can also drill, bore, mill, grind and more.
A New Perspective
With all of this increased machining power and its potential for making products faster, better and at lower cost, it’s logical to assume that productivity will soar as soon as you install a new machine tool. In fact, maximizing productivity and cost savings requires machining parts in as few operations as possible to minimize the number of setups, machines and operators. Therefore, choosing the best turning machine for an operation is only the beginning. It’s equally important to address loading, guiding and supporting barstock; quickly and safely unloading machined parts; maximizing tool life; filtering and reclaiming coolant while efficiently removing chips; providing a safe, clean, oil-free work environment; and reducing material waste and downtime by enabling communications between the turning machine and the bar loading and unloading processes.
This view represents a fundamental shift in manufacturing’s perspective. While the turning machine or multifunction machining center is still the heart of the process, only by maximizing the effectiveness of the other components can the manufacturer realize the most efficiency and, therefore, the best return on investment.
The 12-Ft. Solution
The first consideration is how to efficiently load barstock into the turning machine or machining center. On the surface, this appears to be a simple issue. There are, however, a number of bar feeding factors that will affect machine tool performance. Among these: the range of barstock diameters being machined, the need for quick part program change-overs, part finish and dimensional tolerances, and production volume.
If a business centers around making small numbers of unique parts, it’s an option to pre-cut barstock into slugs and hand load them into a turning machine without the help of a bar feeding device. Depending on the nature of the parts you’re making, however, you may need additional support for the workpiece inside the lathe. A complex or very large diameter shaft, for instance, may require special chucks or a custom designed automatic workholding solution.
In almost any other situation, it’s not practical to manually load slugs into the machine tool, particularly when the goal is to cost-effectively produce large volumes of a few or even a large variety of parts. That’s when selecting the best bar feeding solution is critical.
Not that many years ago, machine operators manually loaded 12-ft. lengths of barstock into a turning machine and then steered clear of the work area as the largely exposed bar end whipped wildly around in a steel tube while the lathe chattered along at 3,000 rpm or less. The subsequent vibration was hard on the turning machine components and affected the accuracy of the cutting operation. Then, in 1974, Switzerland-based LNS patented and introduced the first revolution in barstock feeding. By enclosing the barstock in a bath of oil, the Hydrobar used hydrodynamic forces to center and support the barstock, thus smoothly feeding the bar into the turning machine and enabling the machine spindle to operate at higher speeds than previously possible, while significantly reducing vibration.
The hydrodynamic feature combined with the ability to store and automatically load multiple bars improved productivity, provided a safer working environment, reduced wear on the turning machine, enabled faster and more accurate cutting of 12-ft. barstock, enabled the use of constant cutting feeds, and made possible untended operation. After more than 35 years and countless refinements, including intuitive, user-friendly controls, the addition of servomotor drives and absolute encoders, quick-change guide channels and pushers, and automatic diameter adjustments, these hydrodynamic bar feeders continue to be the industry standard for loading 12-ft. barstock.
Space-Saving Short Load Bar Feeders
As automatic bar feeders enabled operators to make better use of their time through untended production, the demands for efficiency grew even more intense as the manufacturing world became more globally competitive. Thus, the need to “do more with less” extended to maximizing the use of factory floor space. Customers wanted to reduce the footprint of machining operations, and LNS responded in 1991 with the first automatic magazine bar feeder for loading headstock-length barstock. The Quick Load requires only a third of the space used by 12-ft. bar loaders. Over time, these short-load machines have been enhanced with the same time-saving enhancements found in the 12-ft. bar feeders and, to meet the changing needs of customers, offer an expanded range of diameter capacities from ¼ inch to 4 ¾ inches with virtually no spindle speed limits.
For increasing numbers of today’s manufacturers, efficiently feeding barstock into their turning machines is no longer a question of “Should I?” but rather “What is the best solution?” Is a short-load bar feeder the best choice, or is a 12-ft. model a better solution? It depends on the kinds of parts and production runs you are making and whether or not floor space is a major concern. That’s why it’s best to consult a bar feeding applications expert before deciding.
More important, simply choosing the right bar feeder is only part of the productivity equation. To make machining processes as efficient as possible, machine operators should consider the entire operation from raw material to completed part. The primary factors include:
Loading barstock. What are the options? Robots or overhead gantry loading systems tend to take more time to load and unload parts than properly applied bar feeders. Moreover, robots don’t provide the support and guidance many applications require. Manual loading is tedious, time consuming and virtually guarantees downtime. Only automatic bar feeders provide optimum, continuous loading and support of barstock to maximize turning machine productivity and enable lights-out operation.
Workholding solutions. This includes chucks, collet chucks, spindle extensions and automatic work support systems using steady rest technology. They enable the accurate machining of large and complex parts without sacrificing spindle speed or inhibiting production flow.
High-pressure coolant systems. They extend tool life, enable higher cutting speeds and improve surface finish, which means less work interruption and the opportunity for longer untended operations.
Part unloading. Again, there are a number of options including robotics, manual unloading, gantry systems and collet-type unloaders. The choice depends on the specific application and productivity goals. For most cell-based operations, nothing is faster, more dependable and easier on part finishes than unloading through a vacuum.
Proper chip and coolant management. This is essential for eliminating productivity-robbing bottlenecks and reducing coolant costs. Unfortunately, many operations don’t consider the issues associated with using a mixture of materials and multiple machining operations. Basic hinge-belt conveyors can’t handle all of these problems, and that’s why LNS developed the MH series of filtering chip conveyors.
Advanced communications between manufacturing components. In addition to the many technological advancements in bar feeding, support and unloading in recent years, the advent of Ethernet-based communications between the machine tool, bar feeder and parts unloader improves productivity.
Air quality issues. In addition to addressing workplace safety issues, it makes good economic sense to keep the workplace clean and free of dangerous oil contaminants and mist. Tramp oil removal systems, oil mist collectors and other air quality products help shops comply with OSHA requirements while reducing operator downtime.
Yesterday, Today and Tomorrow
The bar feeder has steadily evolved from a stand-alone component that has been refined over the past 35-plus years with mechanical and electronic enhancements into an essential element of a much larger productivity improvement scenario. They contribute to more efficient manufacturing through smooth, reliable loading and guiding of a range of barstock diameters, by providing excellent bar support that eliminates vibration and enables turning machines and machining centers to run at peak speed, and by making untended and lights-out operation practical.
As for the future, according to Damien Wenisch, director of technology for LNS America, “Coupled with the issues outlined above, bar feeders will continue to evolve to meet the needs of manufacturers around the world. What new developments are in store? For one, we’ve only begun to exploit the potential of e-Connect communications to boost productivity, troubleshoot problems and enable remote control of manufacturing activities through the bar feeder, machine tool and other components. And while some may say that bar feeders have peaked technologically, LNS is exploring exciting new ways to make bar feeding even more efficient while becoming more ecologically friendly.
“By continuously probing the needs of customers in North America, Europe and the Pacific Rim and sharing that information throughout the LNS organizations, opportunities and challenges emerge that lead to greater manufacturing efficiencies for all.”