A tangential milling cutter takes a roughing cut at the Akebono automotive braking plant in Elizabethtown, Ky. Retooling boosted edge life by 18 to 1, and eliminated a vibration problem on the machine that formerly caused four to five unpredicted line stops per shift.
Of course, cutting-edge security matters a lot in every machining operation, but never more than in synchronous machining cells or carousel arrangements. Sudden tool rupture or edge breakdown at one operation can affect the entire process. Moreover, the risk of failures is often the main cause of extra operator attendance.
“Especially in cells and carousels, the number-one priority in tool selection should be zero tool rupture or edge breakdown,” said Konrad Forman, North America milling tool manager for Ingersoll Cutting Tools. “Unless you are replacing an edge due to gradual wear only, you are missing an opportunity to improve cell-wide efficiency -- and even to run unattended.”
Forman cited three recent cases to illustrate what can be done.
Net Surfing to Longer Edge Life — At Busche-CNC in Albion, Ind., a simple retooling de-bottlenecked the rough turning operation for difficult-to-machine wrought 5130 and hardened 4140. Previously, cutting edges cratered after an average 20 pc on the 5130; toolbars snapped every other day. The Ingersoll Hex-Turn inserts improved edge life nearly 10 to 1, and eliminated completely the unpredictable, cutting-edge rupture and all the hazards and disruptions that followed.
Now, a single tool completes both roughing and finishing. Moreover, the machining operation has been able to raise its feed rates and throughput by 50% on the wrought stock, and 50% on the hardened material — with no trade-off in edge life.
Running 24/5, Busche uses seven two-lathe turning cells to produce 2.75 million/year automotive ring gears in a 400-person shop. Operations there include OD turning, ID turning and facing. As any Tier 2 automotive supplier knows, this is a very competitive business, turning on pennies per part and rock-solid delivery.
The switch was from 80-deg rhombic inserts to Ingersoll Hex-Turn inserts. “I found them the day they hit the market because I regularly surf the ‘net for new solutions we can use,” said Jerry Busche, vice president.
This retooling was essentially a drop-in replacement. The only processing changes were to modify the program to increase feed rates, decrease the scheduled stops for indexing, and write out all the steps associated with a separate finishing operation that is no longer needed. Standard parameters for roughing the 5130 are now 900 sfm, 0.0250 IPR, 0.150 DOC.
For the hardened 4140 stock, the feed is cut back only slightly. In each case, the DOC is backed off for the finishing passes.
The primary reason for the big improvement in cutting-edge security is the Hex-Turn insert’s stronger geometry, according to Ingersoll turning product manager Ed Woksa. “On the one hand, the insert has a 45-degree lead angle that thins the chip and reduces notch wear,” he explained. “On the other, the hex shape is closer to a true round, intrinsically the strongest shape due to the absence of stress-raisers.”