barfeeder
A type of feed (feeder) for machine tools such as lathes, turning centers, and Swiss-turns, which holds multiple bars of bar stock and feeds each bar, in turn, into the machine.
barfeeder: automatic stock loader for high-volume turning
A barfeeder is an auxiliary attachment that mounts on a lathe or turning center and automatically feeds lengths of bar stock through the spindle during production. Instead of an operator manually loading each bar, the barfeeder holds a magazine of material, ejects the finished part, and pushes a fresh bar into the chuck for the next cycle. This eliminates dead time between passes and is essential for efficient piece-part production where setup time would otherwise dominate the job.
The mechanism consists of a motorized pusher arm, a collet or chuck grip, and a multi-spindle magazine that typically holds 6 to 12 bars of stock in parallel arrangement. As the machine finishes a part, the barfeeder retracts slightly, the finished workpiece drops clear, and a pneumatic or servo-driven pusher advances the next bar into position. The stock diameters range from 0.125 inches to 2 inches or larger, depending on the machine and the barfeeder model. Swiss-type machines and CNC screw machines are the primary users; smaller manual lathes rarely justify the cost.
Feeding pressure and push distance must be carefully set to match the material and the machine's cycle time. Too much force bends or marks the bar; too little leaves a gap at the spindle. Carbide and aluminum feed quickly and predictably, but stainless and cast iron require slower feed rates and more frequent pusher pad changes because the bars slip or drag. The pusher pads themselves wear constantly and are consumable parts.
Common problems and setup
Bar runout, or wobble, is the most frequent complaint; bars must be reasonably straight and concentric to the magazine bore, typically within 0.010 inches TIR. Bent or kinked bars jam the magazine and can damage the pusher mechanism. Magazine spring tension must be adjusted as bars are consumed, otherwise the topmost bar may not align with the pusher. Some models include a bar sensor that stops the machine if a bar is missing or misaligned.
Barfeeders became standard in the 1970s with the rise of CNC screw machines and are now integral to Swiss-type turning. They are sold as either integral components of new machines or as retrofit kits for existing spindles. Operating costs are low beyond the initial purchase and occasional maintenance, which makes them economical even for small production runs of a few thousand parts.