Heavy Bikes bike frames cast in aluminum with 3D printed molds | VoxelMatters - The heart of additive manufacturing

Heavy Bikes, a company specializing in bike frame manufacturing, now offers single-piece aluminum frames made with 3D printed molds. This approach, uncommon in traditional metal casting, combines modern technology with a centuries-old process to deliver a disruptive solution for custom, high-performance bicycles. By leveraging advanced 3D printing techniques, Heavy Bikes is revolutionizing how metal bike frames are designed, tested, and produced—making customization more accessible and efficient.

While many wouldn’t associate the foundry industry with innovation, Charlie Murray, co-founder of Heavy Bikes and Foundry Casting Systems (FCS), saw an opportunity to bring modern technology into metal casting. A seasoned entrepreneur with expertise in industrial controls and automation, Murray recognized that casting inconsistencies like porosity and shrinkage could be minimized through process improvements.

Instead of using traditional methods like CNC machining from billet aluminum, Murray envisioned a more efficient solution: using 3D printed molds to create castings with enhanced mechanical properties. Through collaboration with foundry experts, FCS developed the Pascal Process, a unique method that optimizes the casting environment using pressurized solidification. This process ensures that molten metal properly fills the mold, reducing defects and producing high-quality, repeatable results.

At the heart of Heavy Bikes’ production process is the S-Max 3D printer from ExOne, which uses sand binder jetting technology to create precise molds from silica sand and furan binder. The use of 3D printed molds opens new possibilities in casting, enabling complex shapes and intricate designs that would be challenging or impossible with traditional tooling.

Binder jetting technology, which eliminates the need for expensive, time-consuming hard tooling, allows Heavy Bikes to iterate designs rapidly. For Murray, this was a game-changer: “3D printing enables people to explore casting,” he said. “They might have been shunned away because of the tooling costs or because of the iteration costs in the past. Binder jetting opens that door.”

Through this process, Heavy Bikes can produce single-piece, solid aluminum frames without welds, a design that provides unique benefits in strength and durability compared to traditional tube-welded bikes.

Foundry Casting Systems’ Pascal Process improves the mechanical properties of Heavy Bikes’ aluminum frames. By pumping inert gas into the mold during solidification, the process creates positive pressure, which helps ensure the molten metal fully fills the mold’s intricate passages, resulting in a dense, solid structure.

The key to the Pascal Process is its ability to increase the mass feeding rate during casting. While a traditional 12-inch riser at atmospheric pressure would offer a certain amount of head pressure, the Pascal Process delivers the equivalent of a 70-foot riser using just a 1-foot riser. This innovation translates into fewer defects, such as porosity, and stronger, more durable cast parts.

One of the most significant advantages of using 3D printed molds is the ability to customize each bike frame to suit the rider’s needs. Murray, who has a background in competitive cycling, realized the importance of bike frames tailored for specific body types and riding styles. The digital nature of 3D printing means that adjustments can be made quickly and easily, without the cost and time associated with traditional mold-making methods. This flexibility also allowed Heavy Bikes to experiment with different shapes and configurations.

The first Heavy Bikes prototype dubbed the “Hypocrite,” was cast using a 3D printed mold from Liberty Pattern, a leading provider of complex sand casting molds. Liberty Pattern operates a fleet of five ExOne S-Max 3D printers, making it possible to produce intricate molds without hard tooling. This flexibility enabled Heavy Bikes to bring the Hypocrite bike frame from concept to reality quickly and cost-effectively.

Craft Pattern and Mold, another key partner, utilized the Pascal Process to cast the prototype, pumping inert gas into the mold at 150 psi to ensure the aluminum filled even the smallest, most detailed sections of the frame. The result was a single-piece bike frame with no welds—eliminating traditional weak points—and with enhanced strength due to the Pascal Process’s pressurization method.

With each iteration, Heavy Bikes refined its design, reducing the weight of the frame while maintaining structural integrity. The latest frames, poured in September 2024 at Denison Industries, weigh approximately 1.1 lbs less than earlier versions, thanks to continuous improvements made possible by digital design and 3D printed molds.

Murray believes that Heavy Bikes frames are more than just functional—they are also works of art. The design freedom provided by 3D printing means that each frame can be customized with unique surface designs, such as dimpling or logos, that would be difficult or expensive to achieve with traditional tooling. Whether painted, anodized, or left raw, Heavy Bikes frames offer a level of aesthetic customization that sets them apart from other bikes on the market.

The complete case study can be downloaded here.