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Pushing two inches

Dec. 1, 2001
Barfeeding automates more than long-run lathe work.

Barfeeding automates more than long-run lathe work.

The Boss 547's quick-change-style guide channel system absorbs shock and vibration so shops can run 2-in.-diameter stock at full machining rpm.

A Bell Group machinist loads 2-in.-diameter barstock into the Boss 547 to run multiple short-run jobs unattended.

The Bell Group's Boss 547 barfeeder from Iemca is integrated to a Mazak SQT-200 lathe.

On some of its 2-in.-diameter bar work, Bell machines down to 0.250 in. in diameter, making a rigid barfeeder crucial to the operation.

With its own CPU, the Boss 547 offers users two settings for pushing barstock.

The Bell Group produces parts from 2-in.-diameter stock for small milling tables used in the jewelry-making industry.

Lathe work at the Bell Group doesn't involve tens of thousands of pieces per job. Instead, it's a lot of short-run parts from different sizes of barstock — a situation most would consider less than ideal for automating. However, by incorporating a barfeeder with a 2-in.-diameter push capacity, Bell sets up its Mazak SQT-200 lathe for multiple jobs and, with a little careful planning, runs them unattended.

The Albuquerque, N.M., company, which manufactures products for jewelry making, uses an Iemca Boss 547 magazine-style barfeeder that handles twelve 1-in.-diameter, 12-ft-long bars. For Bell's 2-in. work, the capacity is six bars with an additional one loaded in the lathe.

A quick-change-style guide channel system lets the shop switch from one diameter to another easily. And while the bar is spinning at full machining rpm, the system absorbs shock and vibration using a vulcanized rubber channel that holds 150-weight hydraulic oil to form a cushion around the stock.

At the front of the feeder, there is a bushing device consisting of a stabilizer along with a set of nylon liners that Bell changes for different bar diameters. These liners surround the material and restrict excessive movement.

The 547's liners each have a 3 /4-in. range. Bell runs its smallest jobs with the liner, then progresses to the 5 /8 to 1 /4 to 7 /8 in., 3 /4 to 1 1 /4 in., and on up to the 1 to 2-in. liner for its large work. "Which liner to use depends on the stock," says Jeff Zirwas a manufacturing engineer at Bell. "When running hex stock, for example, liners should be close to material size, but for light materials such as plastic or aluminum," he says, "we run 1-in.-diameter stock in a 2-in. liner with little whip."

The company has four sets of liners. During any given day, machinists may change liners as much as twice, but normally, it happens just once a week, says Zirwas. The reason is that machinists plan jobs around families of parts. This planning, he says, is the key to automating short-run jobs with a barfeeder.

The company has four sets of liners. During any given day, machinists may change liners as much as twice, but normally, it happens just once a week, says Zirwas. The reason is that machinists plan jobs around families of parts. This planning, he says, is the key to automating short-run jobs with a barfeeder.

Four or five different jobs may be made from the same size stock, so they are run together. "Our machinists may get 10 to 15 jobs due within two weeks," says Zirwas. "They are permitted to arrange them the best way they see fit to get the most production out of the machine."

In addition to the family-of-parts approach, Bell keeps track of what guide channels work best for which jobs. The information is then documented in a "process book" that machinists can reference when the same or similar job comes up again. Specific information includes recommended channels and pushers and whether or not the remnant is retracted or sent through the machine spindle. With this knowledge, machinists then set the parameters of the lathe.

Because of the process book, barfeed setup time has gone from 3 to 4 hours down to 30 or 40 min. "And with the work being done in families of parts," says Zirwas, "that 30 or 40-min setup is good for 3 or 4 days worth of work."

Setup also goes smoothly because of the interface between the 547 and the Mazak lathe. "Not every barfeeder integrates with every machine," points out Zirwas. The 547 has its own CPU, and there are basically two settings. One is simply letting the feeder push stock until it contacts a stop within the lathe, and with the other, the feeder pushes an exact predetermined amount of stock into the lathe without a set stop. This second option, he says, frees up another tool station in the lathe.

Two-in.-diameter work
The biggest consideration when working with large-diameter bar-stock is weight, says Zirwas. But once the 547 is loaded, he adds, it's no longer a problem.

The unit's construction is a heavy-duty weldment fabrication as compared to smaller feeders. "The machine is significantly stronger than a tube feeder, which has to be light enough to pivot for loading from the front," notes Andy Pennington of Iemca in St. Louis.

Bell has two or three regular 2-in.-diameter-stock jobs, all involving live tooling. "And a single bar of cold-rolled stock," says Zirwas, "weighs about 150-200 lb. That's not something a shop wants to see whipping around wildly during high-rpm machining."

Two-in. stock sits snugly in the feeder's guide, which has as little as 0.078 in. of clearance to keep things stable — so much so that Bell did not have to change any machining parameters to accommodate the feeder. Jobs still run just as fast as they did prior to the 547 — 2,500 rpm and 20-in./min feedrate, comments Zirwas.

When the shop began producing 2-in. parts, the raw material did not fit in any of the company's CNC lathes, so stock was cut into chunks that would fit. A machinist would have to face, or prep, each one prior to machining. For one particular part made from 12L14 free-machining steel, barfeeding with the 547 slashed machining time from 15 to 2 min.

According to Zirwas, remnants are another consideration in large-stock feeding. They can be heavy, so it may not be a good idea to simply drop them onto a machine's chip conveyor. The 547 pulls stock remnants out of the machine spindle and drops them into a bucket.

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