Excerpt from the May 2020 Issue of Modern Casting
This year’s annual AFS Casting Competition is a rare one. Two submitted castings tied for the top honor, and for very different reasons. The opener main body casting by Lethbridge Iron Works Co. (Lethbridge, Alberta, Canada) showcases the opportunities in converting from fabrication to casting, while the V6 engine block by BRP-US (Spruce Pine, North Carolina) exemplifies the ultra-complexity achievable with the lost foam casting process. Eight additional castings also have been honored for their exemplary work in achieving customer benefits and advancing the metalcasting industry.
BRP Pushes Envelope of What Lost Foam Casting Can Do
At first, the senior process engineer at AFS Corporate Member BRP-US Inc. (Spruce Pine, North Carolina) didn’t really want anything to do with the 300-HP V6 engine block for a marine outboard engine. The block was so large and complex, featuring a water jacket which sequences cooling water through nine separate targeted passageways within the block, cylinder bores, and exhaust. It was not a simple tube within a tube water jacket design.
“When we looked at this part, I knew it would be a difficult part, and I didn’t really want to sign off on it,” said Willie Anglin, senior process engineer. “But now, five years later, it is running better than many of our other blocks. The truth is, I never thought we would see it run as well as we do.”
GS-Snipe 300 HP V-6 Aluminum Block
BRP-US Inc. (Spruce Pine, North Carolina)
Process: Lost Foam
Weight: 83.3 lbs.
Dimensions: 20x15x20 in.
Application: Marine outboard engine
The two-stroke 300HP V-6 marine engine block called the G2 Snipe is cast in aluminum via the lost foam method. Nine foam tools are required to produce 15 individual foam patterns and the runner. The cast walls are as thin as 4mm for weight savings. Plus, rather than bolt a welded exhaust to the block, the engine designers wanted to incorporate those features into the single aluminum casting.
The one-piece design eliminated the need for multiple castings, weldments, and their assembly.
“The internal passages in this part are too delicate or too small to be made with sand cores,” said Curtis Taylor, plant manager. “Lost foam internal passages, complicated internal passages is our claim to fame. We hold tight tolerances, and we make parts where people need a lot of cooling passages or oil passages.”
This type of marine engine block is not so off base for BRP, which poured the first V-block two-stroke engine in production using lost foam. But succeeding at casting this part depended on process improvements at BRP that ultimately benefitted many other parts in production.
Casting Conversion Frees Up Customer’s Internal Resources
The opener main body casting by Lethbridge Iron Works Co. was a textbook case for a casting conversion from a steel fabrication. The cast design reduced the part count from 12 to 1, reduced labor and equipment time for the customer, decreased overall cost, and improved the performance through increased strength and tighter tolerances.
Opener Main Body
Lethbridge Iron Works Co. Ltd. (Lethbridge, Alberta, Canada)
Material: Ductile iron ASTM A536 Grade 65-45-12
Process: Green sand molded with nobake and shell cores
Weight: 39 lbs.
Dimensions: 36x16x8 in.
Application: Main body for components on a coulter seeding drill
Converted from: 12-piece steel fabrication
“For the customer, what makes a good candidate for conversion is the ability to save both time and money,” said Mark Mundell, director of sales, Lethbridge Iron Works. “Everything written about conversion is true. If you can make a casting out of a multiple piece component, it is going to provide for a cheaper, more consistent and repeatable part, and it will lean out the manufacturing process.”
Some casting conversions are more challenging than others. In the case of the opener main body for a coulter seeding drill, the design included varying section thicknesses and several functioning features located on different planes. A zipper-shaped depth adjustment feature is cast perpendicular to the mold parting plane, with other features being located on the horizontal parting plane.
“The success of a conversion comes down to being able to work with the engineer to create a casting that is both castable and still meets their design needs,” Mundell said.
Incorporating the numerous adjustment features into the casting was critical to making the conversion a reality. Through the use of multiple cores, parting design, and draft allowances, all features were castable and achieved the necessary results.
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