Some ideas are worth waiting for. But seldom has a metal casting sojourned as long a path as the one traveled by AFS Corporate Member Mueller’s ductile iron monolithic bypass. Eight years after a lightbulb moment on a trade show floor, the long overdue casting conversion finally saw the proverbial light of day for an underground water works application. It also made its way to the winner’s circle as AFS 2025 Casting of the Year All Around Winner and Newcomer of the Year.

In its former life as a traditional assembly––comprising over 60 separate pieces––the bypass was as complex as parts come, and Mueller engineers Jason Bradley and Matthew Sutterfield had long pondered how to simplify the design. It eventually took an epiphany at an AFS Additive Manufacturing event and a dinner-napkin brainstorming session to bring a new solution to the table. 

The process and the casting itself were so innovative, its creators later realized it couldn’t have been produced by any other means than the one they chose––and it’s now protected by multiple patents. The new 10.5 x 10 x 7-inch casting weighs in at 24.2 lbs., 63% less than its 74.4-lb. predecessor. Mueller’s monolithic bypass has combined the function of four fabrications and three castings, reduced 16 bolts and nuts to 12 bolts, eliminated six flat gaskets, reduced 9 leak paths to three, and eliminated two weldments, all of which reduced assembly labor cost by 96%.
“Just looking at the complexity of the original assembly and all the alignment that went into making it work, you can see why it was an absolute nightmare going through our facility, said Bradley, who is senior director of engineering at Mueller today. “Being able to eliminate all of that complexity by bringing it down to a single casting was our epiphany.”
Active in the AFS Additive Manufacturing Division, Bradley was walking the exhibits at one of the its earliest conferences in 2016 when a bell went off in his head. First, he saw a GE presentation highlighting an example of metal printing a single part that had previously been 20 individual welded and brazed metal parts. Humtown Products was also at the show, Bradley said, demonstrating how a former nine-piece core assembly had been converted to a single-piece core through 3D sand printing. It was obvious the capability to 3D print molds and cores was going to be a gateway for transforming Mueller’s bypass into “a better mousetrap,” according to Bradley. 

“This kind of got the wheels turning for us,” he said. “Additive offers solutions that we’d never been able to consider. At dinner that night after the show, Matt and I couldn’t stop thinking how we could exploit this capability in our products. Originally, we came up with what we called a monolithic valve, which was a gate valve that contained a bypass, but later on, we moved off of the monolithic valve to just a monolithic bypass.

“It all started with getting exposure to the additive technologies that were out there and seeing how others were using them,” he continued. “And now we’re seeing additive make this transition to solve real world production issues and in a cost-effective manner. That’s what I’m excited about, and this project has been a perfect example. The transition is happening––additive is breaking into mainstream metalcasting as a production tool, and that just wasn’t the case before.”

Brake Then Accelerate

Then a timeout was called. Bradley was reassigned to project management on two large facility expansions, so the monolithic bypass “pet project” was temporarily tabled. Four years later when he returned to R&D, Bradley wiped the dust off the casting design and pursued production partners for the already patented concept. 

Once the gating was designed, the Mueller team had taken the monolithic bypass as far as they could, and it was time to bring in the molding cavalry––in this case, Matthews Additive Technologies. Specializing in mold design and 3D mold printing, Mathews employs a proprietary cold hardened phenolic (CHP) binder system (instead of the more traditional furan curing system), which allows loose sand to pour more easily out of a mold. 

“Brushing unwanted sand out of the mold leads to casting defects,” said Bradley. “That’s why we went with the Matthews approach; we wanted to do this as a closed blind box where the core itself is integrated into the mold rather than having multiple loose pieces.”

Matthews Additive Director of Business Development Dave Rittmeyer says the company employs an ExOne printer and ASK branded binder but over many years has developed unique processing that he calls their secret sauce. It eliminated numerous roadblocks, he says, but that’s not to say the mold was not without challenge: After the first version of the printed mold, operators couldn’t get all the unbound sand out of a few holes in the mold insert.
“People can get impatient and aggressive trying to get it out, and that was causing problems,” said Rittmeyer. “Time is money, and knowing that Mueller’s castings were only going to get bigger from here, we needed to find a way to get the sand out faster.”

Enter the skull cap solution. 

Rittmeyer produced what he called “the little skull cap. “We printed a separate little chunk of sand in the shape of a rectangle. We glue that piece on, then they pour it. But it’s removable so we can easily drain all the sand out after printing,” he said.

“We swung for the fences for our customer,” Rittmeyer added. “We didn’t give up and worked to come up with a creative solution for a very challenging project.”

Shooting for the Moon

Manufacturing the monolithic bypass prototype was almost like bringing Pinocchio to life, although Bradley and his colleagues weren’t wishing upon a star. However, eight years from head to paper to print and pour, they were definitely dreaming big. 

“Surprisingly, it went fairly smoothly for the most part,” Bradley said. “The design was simple; it was a pre-existing design that we just had to convert to a monolithic structure. We already had the dimensional requirements.
“But we decided shoot for the moon,” he added. “We went for 100% as cast. We cast in the O ring seal and all the bolt holes so that when it was degated, it was ready to be powder coated and assembled––no post processing. We incorporated everything into our design, ran it through FEA analysis and Magma simulation to gate it the way it needed to be gated and to ensure we ended up with a clean casting.”

Bradley says he’s convinced the complex casting could not have been produced without the 3DP mold approach, but Rittmeyer walked it around the block before agreeing with that assertion.

“I’m always very cautious about saying ‘could not be done any other way,” he said. “If somebody wanted to put enough time and effort and resources to make all the cores and make the traditional tooling, then sure, they could technically do it, but it would be so cost prohibitive.

“On the other hand,” he countered, “I’m picturing it all in my head right now, and to do what we did and how we did it, I guess really there’s no other way you could have done it. And to do it with no parting line across any machine face and hold everything in position with no flash, that’s truly impossible any other way. We were able to hold everything together perfectly, with no machining.”

All In The Family

Mueller outsourced the pour to a job shop foundry to avoid disrupting their own packed production schedule. The successful proof of concept now opens a flood gate for extended applications across the family of Mueller gate valves. The first version is a 2-inch bypass for 18- and 20-inch gate valves, but there are eight unique sizes, says Bradley. “As we get larger in our gate valves, the bypass itself gets larger all the way up to a 10-inch. The initial step will be to extrapolate that 2-inch bypass across the remaining sizes. 

With this scope of reimagined bypass casting work on the horizon, he’s got yet another major focus on his mind.
“Doing parts like this and getting it in front of our leadership, we’re showing what’s possible and adding to our business case development for actually bringing that technology in house,” he said. “It’s got real world benefits that can actually satisfy production-related issues today. We utilize this technology all the time for new products that we’re trying to bring to market, and we pay a lot of money to outsource. And so, this is just another chink in the armor to justify bringing the technology in house.”