Production Machining

OCT 2016

Production Machining - Your access to the precision machining industrial buyer.

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bar feeder requires tools to change guiding elements and pushers or to make other adjustments. • How realistic is the stated diameter range? Even bar feeders that use the hydrodynamic principle by surrounding the bar with oil cannot change the laws of physics to arbitrarily expand the range of diameters. Barstock that is not properly supported through appropriate guides will create vibrations that can harm machine tools and impact part quality. • H ow rigid is the construction? To further reduce vibra- tion, a 12-foot bar feeder must be built of substantial materials that provide the same kind of rigidity found in high quality CNC machine tools. Spinning a 12-foot bar at high rpm requires stability for smooth and reliable bar feeding, extending the life of the bar feeder and providing safety for the machine operator. • W ill remnants be retracted back to the bar feeder or pushed through the lathe chuck? Remnants are longer when pulled back to the bar feeder than if the remnant is not held by the pusher collet. Bar loading time is also affected. • C an the bar feeder be easily converted from one remnant application to another? • D oes it make use of advanced technology? Smoothly operating servomotors, absolute encoders and sophis- ticated yet easy-to-use controls help to guide operators through programming and operation. • C an the bar feeder's capacity be expanded to enable longer production runs? Short Loaders Perhaps the least expensive form of automation for a CNC lathe is a short load bar feeder. ese versatile machines load spindle-length bars into the lathe for automatic operations, and they're perfect for applications calling for production lots as small as 20 to 30 parts. e key here is to choose a bar feeder with quick setup times, ideally in the range of two to three minutes or less. Primary consider- ations for determining if a short loader is right for certain applications are part length, material shape, material cost and the length of desired unattended operation time. Most short loaders provide three modes of operation: • Feeding to a programmed length without the help of the turret stop • Feeding to a turret stop • Using the subspindle to extract material when transfer- ring the part from the main spindle to the subspindle for back-side machining Short loaders are cost-effective, take up minimal floor space, do not require bar end preparation, and enable unattended operation. Because the entire length of barstock is contained within the lathe headstock, a short load bar feeder has virtually no rpm limits. is design is also an excellent choice for running profiled material or bars that are not perfectly straight. Used in conjunction with a shaped spindle liner and custom workholding, short loaders are capable of running a variety of extruded shapes as well as square and rectangular bars. A short load bar feeder can be used for unattended machining of a part that previously would only be a candidate for milling. Some short loaders can be converted for high-speed shaft loading in which precut shafts may be loaded in less than four seconds. Short loaders may not be the best choice for longer part runs because they do not hold as much material as a 12-foot bar feeder. Another concern is that the maximum barstock length is limited to the headstock length of the machine tool. is length is typically no more than 4 feet and, because machine spindles are getting shorter, in some cases, less than 3 feet. Being limited to shorter lengths may create additional remnants that can be costly, especially with expensive materials. In this case, a 6-foot bar feeder may be the best choice. BAR FEEDERS/MATERIAL HANDLING 34 PRODUCTION MACHINING :: OCTOBER 2016 :: While bar feeder size and capacity are key considerations, other factors such as reliability, customer support, and ease of setup may be equally important.

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