Mechanical face drivers may be the best way to turn parts, allowing increased flexibility in turning applications to lower cycle times, turn both the smallest and largest of parts, and even allow interrupted and heavy cuts. Parts that are routinely cut using face drivers include automotive transmission parts, crankshafts, cam shafts, pinion gears, electric motor shafts, and axles up to 36 in. diameter.
The major benefit of a face driver is its ability to let a part be turned completely, from one end to the other, in one operation. At one time, heavy cuts were thought to be an issue because of part slippage, but this is no longer true. Interrupted cuts, also considered unacceptable for face drivers, can today be done easily, with fast feeds and deep cuts, boosting productivity.
Andy Schaffer, manufacturing engineer tech at Baldor Electric Co in Ozark, AR, is responsible for the machine shop, including every CNC in the plant. In addition to tooling responsibilities, he does some CNC programming, and sets up each new machine from scratch. He also is the "go-to" guy when changes in product mix start to bog down production efficiencies. Baldor Electric designs, manufactures, and markets electric motors, drives, and generators.
"During the last five years, we've seen our production mix flipflop from about 80% standard motors with 20% specials, to 20% standard motors and 80% specials," Schaffer explains. "This has caused a lot of problems because we now have much shorter production runs. Often an operator will produce just one or two shafts, which leads to frequent changeovers and lost production time."
Impressive Cycle Time Reductions of 30%+
"We used to change setups just once or twice a day," Schaffer continues. "Now I've actually seen instances where an operator has changed from one part setup to another as many as 23 times in one day. In addition to lost production time, we had issues with runout quality (TIR improvements of 20% or more on most parts), and holding other tolerances on our more critical shafts, especially when we were machining harder materials."
To address these problems, Schaffer tested a Neidlein mechanical face driver on one of Baldor's CNC turning centers. Although previously he had been disappointed with the performance of a hydraulic and a mechanical face driver, he was pleased with the current results.
"I told the Neidlein guys to put their money where their mouths were and give us a chance to test it under production conditions . . . and they did," added Schaffer. "We ran it hard for a month and it convinced us.
"In addition to better part quality, on some of our shafts we reduced cycle time by 30%," Schaffer reports. "Since then, we bought a few more Neidlein face drivers and put them on other machines. Eventually we plan to have all of our CNC machines equipped with them because it will help our operators to get back up to the production speeds we had when we were running bigger lot sizes."
Schaffer was looking for a 25-30% cycle time reduction and actually got to a 30% cycle time reduction on most parts.
A Major Improvement On Longer Shaft Turning, Too
"Where we usually run into issues is with shafts 36 in. and longer," Schaffer says. "Sometimes we'll run into chatter problems, but if this happens, we just use an Atling Steady Rest to stabilize it. For example, on specific shaft ranges in length from 30-36 in., it was taking us some 30-45 minutes to machine this part because we were taking such light depths of cut.
"When we began using the Atling Steady Rest in conjunction with the Neidlein Face Driver, we were able to run the part in just nine minutes because we were taking about three times the depth of cut," Shaffer reports. "We went from a 0.100 in. to a 0.370 in. depth of cut with a speed of 1,000 rpm and a feed rate of 20 ipm. I think we had been running around 800 rpm with a feed rate of 10 ipm. We could get more aggressive with it because we were holding it on both ends. Not only did we cut cycle time by more than 67%, but TIR also is better."
One "Mistake" Leads to Impressive Results
"One time, we had an operator that was running 2¼ in. bar stock," Schaffer remembers. "He pulled up a 2¾ in. program and made changes to it to run his next order. But when he got done, he forgot to 'edit and quit' it so he put a 2¾ in. bar in the machine and ran a 2¼ in. program. It ran the shaft and did not throw it out -- it took off about 0.900 in. of material and held onto the part. And, that was without the steady rest, just strictly the driver. When I saw that, it really impressed me.
"Overall," Schaffer says, "we turn from 2¼ in. material, all the way up to 4 in. bar. Lengths vary from 16 in. to 42 or 44 in. Our heaviest shaft probably weighs around 70 or 75 lb."
Tackling the Difficult Jobs In Ozark, Capital Investments Key
"Baldor has always had a reputation in the marketplace for high quality, and we currently run the shortest lead times of anyone in the industry," observes plant manager Ryan Waite. "One of the things we have pushed in the last 10 years is that most of our competition has gone offshore in pursuit of cheap labor. Baldor has chosen the strategy of investing capital within our existing facilities to increase productivity. Incorporation of the Neidlein face driver is one aspect in that it reduced cycle times. Business is beginning to swing heavily to the custom side because we do run such short lead times, and we do produce such high quality product.
"Generally we are taking on business that a lot of people would not run -- lower volumes and more difficult items to produce," Waite says. "What we have seen with our shaft production is much more stringent tolerances, and much longer shafts machined out of more exotic materials. Because we have seen an increase in cycle times for these products, it has caused us to look at many other machining alternatives to reduce cycle time and set these products up offline so we can continue the standard production at regular flow rates."
Shaft machining, says Waite, has been the biggest change for Baldor in the past year in terms of difficulty, including exotic materials, tighter tolerances, and size of motors produced because of the size of the rotor they have to put on.
"We are starting out with 3 to 3 3/8 in. bar stock, and we are turning it down to a ¾ in. final diameter. This can be much more difficult than it sounds," Waite observes.
