Better engine machining at Honda Anna. (WIP).

Brief: Although one second may not seem like a whole lot, of time, in the case of engine block machining at Honda of America Manufacturing's engine plant in Anna, Ohio, it is a whole lot of time, given that they are producing more than one million engines per year at the plant. One second was gained by engineers at the facility through process and tooling changes.

Situation: Aluminum alloy blocks are machined on the V6 line at Anna. At about the midpoint of the machining line, there are two operations performed: (1) an arbor with six cutters plunges into the block to mill out a relief for the crankshaft; (2) an arbor with two cutters produces a pocket to seat a thrust bearing that's located in the same area. In both machining operations, the arbors were fitted with brazed carbide cutting tools. Because Honda believes in continuous improvement, manufacturing engineers tried to improve the relief milling operation. Explains Todd Drouhard of Manufacturing Technical Services in Honda's Anna Engine Plant, "This operation happened to be the bottleneck for that particular machining module, so we were looking to reduce our cycle time. But as we tried to increase feeds and speeds, we were getting spindle overload alarms." Each alarm forced a shutdown and inspection that interrupted production. "They were pretty frequent; almost a daily occurrence," recalls Drouhard.

In both operations, cutters had to be removed from the arbors and ground to resharpen. Or they were thrown away. One of the issues related to resharpening was that the steel cutters with brazed carbide edges changed shape as a result of the regrinding. So it was necessary to shim the tools, test machine, and check the accuracy. This was inefficient both in terms of time and scrap.

Solution: Indexable inserts replaced the brazed tools. The reasons: lengthened cutting edge life, the elimination of grinding, and faster tool changes. The Honda engineers wanted the new tools to replicate the original cutter dimensions and configurations, so engineers from tooling supplier Sandvik Coromant (Fair Lawn, N) were able to quickly create the tools using a proprietary software package that allowed them to create custom solutions from an array of standard products. The crank relief operation used four cutters with eight teeth and two cutters with 12 teeth. The thrust bearing operation was performed by two cutters with eight teeth. The indexable cutters use H13A and H10 grade carbide inserts optimized for aluminum and other non-ferrous alloys. However, Drouhard explains, "The Sandvik folks suggested off-setting the cutters so they were not all turning at the same part of the cut. That ended the spindle overload alarms." Despite the higher feeds, the new cutter array reduces spindle loads 11% compared with the same configuration using the original brazed cutters. To accommodate the greater volume of chips generated by the faster cutters, Sandvik engineers also suggested rerouting some machine coolant lines. "That was an easy fix to accommodate the freer-cutting inserts," notes. Drouhard.

To reduce cycle time, Sandvik and Honda engineers developed a new variable-step feed program for the crank relief operation. Feed rates for each step were increased 15%, starting the cut at the highest rate and finishing at the slowest rate, Increasing the feeds for all the steps trimmed cycle time by about one second.

Benefits: Honda calculates the advanced carbide inserts outlast the brazed carbide cutting edges by 133% in both the crank relief and thrust bearing operations. By itself, doubling the life of the cutting tools reduced the cost of the thrust bearing operation by half. Inventory cost for all the tower milling tools was reduced 50% compared with the original cutters for the same operations. Depending on the tool, indexing all the inserts on the cutter takes around half the 30 minutes once required to regrind brazed cutters. Reduced setup time on the production line trimmed tool-changing time 48% per month. Tool changing frequency fell from one change every 1.5 to two weeks with brazed cutters to less than one a month with indexable inserts. Significantly, the CoroMill cutters with their self-adjusting inserts have eliminated clumsy trial-and-error setup. According to Drouhard, "With easy pre-setability, we have better chance of making the first piece a good piece."

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