Bar Feeder | Bar Feeder and Turning

Bar feeder cuts shop costs

Installing bar feed systems to complement turning operations helped reduce manufacturing costs and improve controls over the machining process for a large Tennessee job shop.

Southern Fabricators (Memphis) manufactures steel components, ranging from the size of a quarter up to 30' (9.1 m) and longer for OEM products, such as parts for trailers and rail cars, and large oil pans for locomotives. The job shop employs a wide range of machine tools with more than 230 machines, including 30 CNC machine tools, plasma and laser cutters, mechanical presses, and programmable press brakes ranging from 45 to 2000 tons (400 kN to 18 MN).

In order to meet demand, Southern Fabricators had subcontracted some parts to local machining vendors. Growing order levels, however, prompted management to expand its machining capability. "We needed to install a new lathe," says Norris Roberts, Southern Fabricators' tool engineer. "To justify the new expenditure, we had to bring those subcontracted parts back in-house."

With the majority of those parts machined from round stock, the company decided to install the lathe and the first of seven Rhinobar heavy-duty, hydraulic bar feed systems from Lexair Inc., (Lexington, KY). The Rhinobar systems handle 12' (3.7 m) stock and the bar feed systems are available in tube sizes ranging from 0.25 to 2.75" (6.4-70 mm) in quarter-inch increments.

Southern Fabricators paired the Rhinobar bar feed systems with Cincinnati Machine (formerly Cincinnati Milacron) CNC turning centers-a Cinturn, two Falcon 400s, two Falcon 200s, and two Hawk 150s. It produces a wide variety of parts, including dies, spacers, pins, form tooling, dowels, and bushings, on the turning centers.

Complexity is the watchword for Southern Fabricators, as the shop bores, turns, or faces many types of parts. Production parts include those with turned contours, angles, or steps, machined out of materials such as cold-rolled and hot-rolled stainless steel, brass, and D2 tool steel. Part sizes range from 4 to 18" (0.1-0.5 m) diameter form tooling to pins that are 0.25-0.35" (6.4-8.9 mm) in diameter and 0.5-8" (12.7 mm to 203 m) long. Typical operations include turning shafts and drilling a center hole, and after the part is cut, the bar feed system advances another increment of stock into the turning center, with the whole operation taking about 45 seconds.

"We've been able to reduce our manufacturing costs by about 50% by machining these parts ourselves," notes Roberts. Once the machine operator loads the bar and starts the operation, he or she is freed for other duties, reducing the need for additional labor, adds Roberts.

With the installation of the turning centers and bar feeders, Southern Fabricators' turning output has tripled. And because the bar feed system eliminates chucking and rechucking of the workpiece, the turning centers can run untended for long periods of time. An endof-bar signal and auto pusher retraction alerts the operator when the Rhinobar is empty.

Since the bar feed system provides a high degree of stabilization to the round stock, the quality of machined parts has improved, says Roberts, who adds that the basic print tolerance at the shop is 0.0005 (0.013 mm). In the Rhinobar's design, oil fills the gap between the bar stock and feed tube, acting as a noise-damping support that provides a high degree of stability. As the bar begins to turn, hydrodynamic forces move it toward the center of the feed tube, and centering forces increase as bar speed increases.

The system's oil recuperator also features a bearing-mounted revolving support bushing that helps stabilize the bar stock, eliminating vibration. This support, working with a dynamic bearingmounted pusher cone that maintains contact with the bar chamfer, allows much higher turning speeds than other bar feed systems, according to the company. At Southern Fabricators, application speeds typically range from 200 rpm to 4000-5000 rpm, according to Roberts, and the front swing-out mechanism includes a large barrel clamp to further reduce vibration.

The expanded capabilities have allowed the job shop to perform more secondary turning operations for customers, and enabled the company to add significantly more production work for manufacturers that are seeking to do less machining and fabrication and more assembly operations. Circle 224.0

Copyright Society of Manufacturing Engineers Feb 1999
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