When AFS Corporate Member Mercury Marine headquartered in Fond du Lac, Wisconsin, began laying out plans for its first-to-market V12, 600 hp, 7.6-liter Verado premium outboard engine, Buyer Nick Adelman knew that close geographic proximity to a foundry partner was going to be a top priority. But it wasn’t until AFS Corporate Member Watry Industries was awarded eight castings––including a highly-complex aluminum oil sump––it became apparent the collaboration would give new meaning to the term “inside job.

Situated on Lake Michigan in Sheboygan, Wisconsin, just 45 minutes east of the Brunswick-owned marine engine-maker, Watry became deeply intertwined in the design-for- manufacturability (DFM) process beginning in 2019 through production start-up in 2021––so much so that Watry Engineer Larry Bartol became almost a permanent fixture onsite at Mercury for a few months. Three or four days a week, he brought his laptop with CAD software to an onsite workstation at the customer’s office, where he had direct access not only to the engineers assigned to the oil sump casting, but also to each of the design engineer leads for seven other related castings Watry was producing for the engine.

“Our proximity was important for a couple different reasons,” said Watry General Manager Ryan Silva. “It’s a premier product line, so having someone there who can collaborate quickly and easily, or for them to come here for PPAP and other evaluations, was really important for this program.”

Although Watry has been a supplier to Mercury for over 30 years, ranging across numerous, diverse platforms and programs, the oil sump casting would put the foundry’s well-regarded technical expertise to the test. 

Jason Dannenberg, president of Watry’s parent company, Ligon Permanent Mold Group, said, “The technical level of difficulty for this casting was so high that the solutions provided were not historical solutions—we had to come up with new ways to solve problems to make this casting. That’s really the key, and how well our team pulled together at Watry to solve several unique problems.”

Serving as a reservoir for the motor’s engine oil (and housing for the transmission), the sump casting weighs 51 lbs. and measures 23 in. long x 18 in. wide x 15 in. high. Poured in A356.2 T6 to support hardness and elongation mechanical properties as well as corrosion resistance, the casting was produced with the reverse tilt semi-permanent mold process. Mercury specified the requirements of AA 356.0 T6 for the casting, which also had a strict cleanliness requirement. Adelman, who is now category manager for casting and machining at Mercury Marine, added that time was tight, too.

“We always have aggressive project timelines and they hit them all,” he said. “We frequently don’t give our suppliers quite as much time as they ask for. If I tell our designers they have 18 weeks, they’ll design right up to the quoted lead time, trying to perfect the first revision.”

Watry Sales Manager Luke Czaplewski recalled, “Not only were we launching those eight structural castings simultaneously under the customer’s tight timeline, but you throw in a global pandemic that increased business throughout Watry Industries and it was pretty impressive to come out and develop this complex casting and get it into production on schedule.” 

The Cleanliness Conundrum

The new engine represented a series of industry precedents, from its high horsepower and 7.6-liter displacement to being the first V12 design and two-speed transmission in any outboard marine application. A giant in its industry, the engine is taller than most humans. Inside, its large, complex midsection castings are all anodized by American Metal Finishing in Green Bay to protect components from the corrosive environments in which they’ll live––and some, excluding the oil sump, are powder coated by Watry, according to Adelman. 

“It was a pretty challenging program, and having a good general manager at Watry with a strong engineering background was a key factor in choosing the foundry we were going to work with,” he said. 

An ongoing program that continues today, the volume of 2,500 engines per year isn’t huge, he noted, but the large, complex castings represented good business for the right foundry. Watry proved they were it by assigning and acquiring necessary assets such as its two gravity tilt casting machines, adding a fourth machining center, and creating a clean room.

“One of the biggest challenges was cleanliness, this being a horseshoe-shaped oil reservoir that feeds the engine,” said Adelman.

To achieve the stringent requirement, the engineers from both companies initially developed a three-piece, glued-joint sand core to form the unusual and complex geometry. However, it didn’t take long for Watry’s team to recognize and advise this wasn’t the most effective route to meet the cleanliness demand.

Watry’s solution: 3D printing the baffle core to avoid core fin seam lines in the oil reservoir. And once that decision was made, the team reasoned that simultaneously printing the large 70-lb. body core used to create the transmission cavity logically made best use of the 3DP process, which was outsourced nearby.

“What became evident is the seam lines from the three segments ended up all having to be in oil passageways where oil would flow back to the main pickup for the engine,” said Silva. “The risk we identified was that those seam lines, if they had any penetration from molten aluminum, would end up being flash or debris in this blind cavity, and there would be no way to inspect for it. And even if you could, there’s no way to rework it. Ultimately, it was a risk to engine operation in the long run. We decided the best approach was to eliminate the core fin possibilities by eliminating the seam lines and going to a one-piece core. And that really fit the 3D printing process perfectly.”

Bartol at Watry added that the body core they eventually designed could not have been made with conventional methods. 

“Once we determined we were going to be 3D printing that body core as well, we were able to work with the interface between the two cores and create features that helped register the two cores to each other to minimize any potential wall thickness issues,” he said. “It also allowed us to provide a better method of holding the core robotically and placing it. So, we had some fortunate, unintended consequences we were able to take advantage of thanks to 3d printing.” 

Tight Squeeze

Much of the engine’s internal workings had already been designed once the Watry team came into the DFM picture, and space was non-negotiable. Everything in Mercury’s outboards is typically tightly packaged with real estate at a premium, Adelman said, which made the Magmasoft simulation Watry used invaluable. Over 50 simulations were run to get the reverse tilt orientation right, followed by dozens of simulations to arrive at the best gating entry points, according to Bartol. 

Many simulations were also done to evaluate wall thicknesses and solve metal feed problem areas. Through dynamic daily collaboration with the customers mechanical and industrial engineers, Bartol walked a tightrope of design restrictions that prohibited adding wall thickness inside or adding metal outside because of a cosmetic cowling––creating potential interference with stack-up, according to Adelman.

“The real challenge here was that everything was pretty much locked in,” he added. “We had a very specific window. They had oil volume to worry about, they had a mating component on the inside, they had a cowl on the outside. So, there wasn’t a whole lot of latitude to say, ‘Okay, we could just add some draft here, and we’ll be good.’ We had to figure out a way to do things without making dramatic changes to their design, or the envelope we were working in.”

“You have to consider the metal velocities as the machine is tilting and how it might impact the sand cores because we are actually pouring right onto the top a sand core,” he said. “And we had to work around the holding points for robotically loading that 70-lb. sand core into the into the mold. There were all sorts of interesting challenges.

Adding to the many puzzles of the project such as the casting’s complex shape, engineers were also dealing with a zero-degree draft in the transmission cavity, as well as sound mitigation and corrosion resistance.

Reverse Tilt Pour

Not new but fairly uncommon in the metalcasting industry, the reverse tilt process allows metal to be poured in a way that’s similar to low pressure or static pouring.

A complication Watry faced was that the entire outside of the mold was made from steel cores that slide in and out, making it difficult to get metal to the part without gating underneath cores. The operational challenge with that, according to Silva, is if hot metal runs underneath a seam line on steel cores, the result is flash, which obstructs how the mold closes.

What they needed was some out-of-the-box ingenuity. 

“Typically, in the permanent mold tilt process, your pour cup would be at the parting line, and most of your gating would run along the parting line and around the perimeter of the part. But we didn’t have that option,” said Bartol. “Everything contacting the parting line on this mold was moving steel core, which you can gate along the surfaces of those cores, but it creates multiple issues. Basically, what we did was turn the mold 90 degrees so we’re pouring through the moving platen of the casting machine. We took advantage of the machine’s openings and put our pour cup behind that platen, and poured in between the structure of the casting machine to get metal to the part. That allowed us to gate into the center of the part––basically dropping metal down to the center in a sort of fan pattern––it looks like a bat wing. We’re able to get to the outer walls of the part and the heavy part sections we needed to feed. 

Reverse tilt also allowed the team to vent at the highest part of the mold, Silva added. “Instead of laying the part down flat, we were able to cast it in a vertical position where the highest point allowed air to escape properly.”

Customized Robotics

Custom-programmed robotics made the unique pour-cup positioning possible. In fact, without Watry’s robots, no human could have physically poured molten metal, and the reverse tilt process itself could not be achieved. Silva says the credit goes to a key problem-solver at Watry, Maintenance Supervisor Earl Rollins.

“The big thing for us at Watry is that we do all of our own integration,” said Silva. “We buy the robots and then design, build, program, everything from the ground up, in house. That allows us to have a lot of flexibility to accomplish exactly what we want with the robot. There’s obviously a lower cost of integration, too, which is a big benefit for us and our customers. 

Specific to the reverse tilt casting cell, Watry achieved an automation feat not previously performed: The foundry used robots to position and hold the 70-lb. core used to create the transmission cavity. “It’s essentially being set into a blind pocket where there’s no physical way for a human to load the core,” said Silva. “So, the solution we came up with is, we put some blind holes on the top of the sand core.”

Loading with the robot makes the operation safe for the operator, he noted, as well as perfectly consistent.

Testing, Testing

Several testing and post-casting services round out the full gamut of value Watry brings to the Verado oil sump project. These include alloy chemistry inspection through spectrometer analysis, heat treating (which bakes out the cores), mechanical testing, CNC machining, CMM checks to ensure CNC tolerances are in specification, anodizing, powder coating, leak testing, and cleanliness testing to assure the milipore requirement is met.

Seeing the powerful engines out in the marketplace gives the Watry team a special pride, but at the end of the day, Silva says it’s his team itself that makes him most proud when reflecting on the collaborative development of this casting. 

“We’ve spent a lot of time talking about this project and the hard work we put into it, but this probably doesn’t even touch 1% of the challenges and the hundreds of hours working with the customer, designing solidification, making robot cells, and the process development,” he said. “And there were many more people we haven’t named who were involved. The whole team really stayed positive and focused on how we were going to take the next step and make good parts for our customer. I’m incredibly proud of how solution-focused they were throughout the process.