Bar Feeding Tip: Are You Using the Right Collet Chuck?
LNS bar feeders are known for flawlessly loading bar stock over and over again. That’s why they are the first choice for unattended and lights-out production. If users experience repeatability issues with 6-foot and short loader bar feeders, the first thing to investigate is the collet chuck. A push to close dead-length collet chuck, for example, will create problems for servo-driven automatic bar feeders.
Until LNS began using servo motors and absolute encoders to more accurately position bar stock 20 years ago, bar feeders relied on pneumatics and a mechanical stop. Because the servo-driven bar feeders are so much more accurate, they don’t require a mechanical stop. The problem with using a push to close dead-length collet chuck is that when the hydraulic actuating cylinder moves forward to close the collet, it pushes the material slightly forward, which is just enough to cause problems such as over feeding and incorrect part length.
The ideal collet chuck to use with any servo-driven bar feeder is a pull-to-close type. This type of collet chuck pulls the lathe draw tube back towards the bar feeder, keeping the material held against the bar feed pusher. Alternatively, using a simple 3-jaw chuck also eliminates the problem.