Nixing soft-jaw rebore boosts lathe output.
Most of the work run on the three lathes equipped with the quick-change chucks is produced in batch sizes of one or two pieces. Although the machining time cycles on these workpieces are unusually long, changeover occurs three to five times per 8-hour shift. Using the old chuck, a hard-jaw to soft-jaw changeover would take about 30 min or more. Removing the jaw clamping bolts took 5 to 10 min, and the balance of the time was spent mounting and reboring the soft-jaws.
The new chuck allows jaws to be changed, repositioned, or reversed in 1 min. Another chuck feature allows remounting previously bored soft jaws without the need of reboring them. Ingersoll Dresser's Willy Tosonowsky explains: "We used to require more than 30 rain for chuck changeover. Cutting it to 1 min now saves us an average of 2 hours of downtime per shift. When the net machine cutting time on a shift is taken into consideration, the elimination of 2 hours of downtime actually translates into an increase in machine output of about 50%."
The chuck's quick-jaw change procedure is simple: The operator inserts a hex key into a socket behind the jaw guideway. Rotating the key one-quarter turn clockwise disengages the jaw-actuating mechanism. The operator can then reposition or remove the jaw by sliding it out of the guideway. The new jaw (or reversed jaw) is then inserted into the guideway, positioned, and the key is turned one-quarter turn counterclockwise to reengage the actuating mechanism. Reboring is eliminated on remounted soft-jaws because of the jaw accuracy and the jaw-actuating mechanism. The serrated teeth on the bottom of the jaw mate with a set of serrated teeth at the bottom of the jaw guideway. The tolerances allow remounted jaws to run concentric with the spindle axis within 0.001[inch] tir, which mostly eliminates the need to rebored.
Features of the chuck improve productivity and reduce costs. The jaw adjustment range is comparatively wide using the same set of jaws. This reduces the number of hard-jaw sets required to cover the full clamping range by up to 90% compared to conventional chucks. In addition, the chucks are available with master jaws that permit using top jaws inventoried by most shops - when a chuck is retrofitted or purchased on a new machine, the buyer does not have to invest in a complete new inventory of jaws.
The Ultimate CNC Chuck has a nearly fiat grip-force curve that reduces grip-force loss at high spindle speeds. A high-low grip force permits roughing and finishing at two different forces in one machine cycle without having to stop the machine to rechuck the workpiece. Retrofitting the chuck takes less than 3 hours; the existing short-stroke cylinder and draw-tube purchased with the machine can normally be used.
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|Title Annotation:||new chuck eliminates reboring when soft-jaws are remounted optimizing production time|
|Publication:||Tooling & Production|
|Date:||Sep 1, 1997|
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