Cranking Up Crankcase Production

May 20, 2023

Success in high-volume engine manufacturing requires the utmost in precision machining, reliability, intelligent engineering, and, above all, automation.

Shannon Walter, manufacturing process engineer, and the team at Kawasaki Motors Manufacturing Corp., U.S.A. (KMM) of Maryville, Mo., where hundreds of thousands of lawn mower/tractor crankcases are churned out annually, will be the first to attest to this. The results of precision machining automation contribute mightily to one of Kawasaki’s top goals: quality.

In a crowded consumer market with popular brands, quality is by no means a small factor. “Every year our customers want more of our engines because our quality is highly respected in the marketplace,” Walter said. And more is what they get. “In 2022, we are again on track to break our year-over-year production records,” he added. The growth has also led Kawasaki to open a second plant, 200 miles away, in Boonville, Mo.

Established in 1989, and the only operation dedicated to Kawasaki engine manufacturing in the U.S., the company has some 1,000 employees, more than 900,000 sq-ft [83,613 sq-m] of manufacturing space, and a staggering 470 CNC machines—ranging from VMCs and HMCs to lathes and washers—featuring a who’s-who list of leading brands.

Another strength of Kawasaki’s Maryville Plant operation is vertical integration, with 95 percent of its products (beginning with the die casting of the crankcases) being fully made and assembled within the plant. This ensures control of manufacturing all engine parts (crankcases, cylinder heads, shafts, covers, and flywheels) from start to finish.

Even the most efficient manufacturing operations aren’t immune to the challenges that increased demand, labor shortages, and shrinking customer lead times can present. This was the case for KMM, despite its three-shift, seven-day operating mode. Outsourcing the manufacturing of nearly 200,000 crankcases per year was necessary to meet demand before a new machining solution was developed. In an effort to save costs, retain quality standards and eliminate downtime, KMM sought a more robust way to address this problem.

“We set a goal, our number one vision, to eliminate operator time and error and to fully control our quality,” Walter said. “We formed a six-person committee to evaluate the options. Unquestionably, the committee decided that all roads would lead to full automation.”

According to Walter, robots were initially high on the committee’s list, primarily due to KMM’s existing (semi-automated) CNC-machining lines consisting of eight machines (multi-pallet HMCs, VMCs) in which two cells were dedicated to one employee in each full shift who had to manually load aluminum crankcases weighing 19 to 28 lbs [8.6-12.7 kg].

“We analyzed the situation and the problem it created, including quality issues and downtime caused by misplaced parts, which can easily occur without full automation,” Walter explained. “We determined that to meet our target, we needed a fully automated solution to eliminate downtime and machine the engines with precision at least as fast as our existing semi-automated lines.”

Considering the goal to complete each engine, requiring many holes, cylinders, and features that need to be either bored, drilled, tapped, and face milled within a few minutes, KMM knew it needed a dynamic technique. To this end, it turned to Grob Systems Inc., manufacturers of advanced CNC machining centers with comprehensive automation possibilities.

After KMM issued its demanding requirements, Grob evaluated the best way to reduce cycle time, while ensuring quality and eliminating downtime. The Grob team conducted in-depth analysis and determined that instead of having two cells consisting of eight machines per line with one person manually loading parts—which was fraught with problems—a better solution would be a line of four machines in two cells with a custom overhead gantry that would automatically load and feed the entire line and each machine. The result even improved upon KMM’s cycle time requirements.

“We were trying to achieve maximum speed along with high accuracy. Grob invited us to their manufacturing plant in Bluffton, Ohio, to demonstrate its runoff capabilities, which achieved a cycle time reduction of over five percent faster than our target goal. Actually, we didn’t think they could do it, but amazingly they did. We were very impressed and gave them the nod,” Walter said.

In late 2016, the first Grob line was installed in the Maryville plant, and KMM was off to the races cranking out crankcases. The new line, consisting of four G500 CNC machining centers arranged in two cells with a Grob automated overhead-loading gantry, has a load-in station at the beginning of the line and a station at the end of the line where the crankcases are honed, leak tested, and washed. The setup requires just one worker.

The process was so successful in eliminating downtime and increasing engine throughput that KMM ordered a second Grob line for the following year. Since then, KMM has added a new line every year to meet its continually increasing demand for engines. The lines currently take up about 10 percent of the plant’s cavernous footprint.

Now, instead of dedicating one worker to manually load each eight-machine, two-cell, semi-automated line, KMM has one worker responsible for two lines. This has significantly reduced manual loading while dramatically increasing accurate, finished part throughput without downtime.

“Since the lines have been installed, Grob has helped us meet our demand internally without outsourcing, saving us over $5 million annually alone,” Walter said. Chief among the gains has been reduced labor and downtime, which has also led to improved quality.

“Due to the reduced number of manual setups, we have saved over $160,000 yearly in our labor cost and realized an additional $32,000 in annual savings through the elimination of downtime caused by misplaced parts,” Walter continued. “And the savings doesn’t even include avoided costs such as when major machine components are damaged. Also, the over five percent time reduction per cycle has led to a substantial increase in production throughput of our engines.”

There have also been other benefits, such as how Grob has helped KMM address labor logistics. “We have been struggling to hire and retain enough workers for our Maryville plant,” Walter said, “and the Grob lines have been instrumental in allowing us to keep pace with demand while reducing manpower by 50 percent in our crankcase machining area.”

At the heart of the system are Grob’s rigid, compact G500 5-Axis CNC Machining Centers that are manufactured in the company’s 400,000-sq-ft facility [37,161-sq-m] in Bluffton. With quick spindle ramp-up times, a fast chip-to-chip time of 2.6 seconds and an automated gantry loading system, these machines are ideal for high-production, around-the-clock operation.

As for accuracy, the machines have a linear-axis repeatability of 0.0001” [0.0025 mm], which Grob said ensures continual reliability and precision.

Utilizing a horizontal spindle design, constant milling conditions are maintained throughout the Z-axis stroke due to the axis’ bearings traveling with the spindle, and the chips fall away from the part being machined.

Chip control and evacuation is further enhanced in other ways as well. For example, parts are machined directly above the chip conveyor, and tool changes occur outside of the work area, which eliminates chip interference during tool changes. In addition, a brush cleans the tool shank prior to the tool being inserted into the spindle and a coolant flushing system pushes chips out of the work area and through the conveyor.

“These features are all mission critical in operations such as ours, where stopping machining to clear away chip piles is simply not an option,” said Gary Wilmes, a maintenance engineer at KMM. “One machine can even be locked out while the rest of the line continues to run,” he added, “and there is open access to the hydraulics and pneumatics cabinet, which is easy for maintenance.”

An operation of KMM’s magnitude and its strategy to invest significantly in an automated machining project couldn’t be fully realized without a high level of trust and confidence and collaboration between both parties. This includes prompt service as needed.

“We were very pleased with the support during the Grob implementation process. We were green when it came to Siemens controllers, and the Grob staff has been outstanding when we needed help. I cannot praise their project manager and service engineer enough on how they have treated us with every problem or request we have had on the Grob lines,” Walter said.

“In addition, with their factory being in the U.S., we felt like we wouldn’t have to wait for parts if the machines needed service. Their full-service capability is excellent, and we have found that 98 percent of the time any issue that might arise is solvable by using their remote diagnostic service,” added Wilmes.

And that’s time Kawasaki can use to crank out even more crankcases.

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