Sand 3D printing has been used by foundries to make tooling for decades. Traditionally, binder jetting with silica sand, an affordable and readily available material, creates the tools for pouring a metalcasting.
Molds to shape the exterior form of a casting and cores to create the interior geometries of the metal part are 3D printed straight from CAD files. This eliminates the monthslong lead times and high costs of traditional patterns and coreboxes created from wood or metal.
The fast delivery times afforded by binder jetting attracted the attention of other manufacturers in need of tooling for forming processes—from composite layup to thermoforming plastics. Traditional tools, often made of materials like epoxy board or aluminum, require CNC machining. The long lead times and high prices associated with this traditional process made the tooling sector ripe for innovation and manufacturers have implemented 3D printed sand tools into production for critical and cosmetic applications alike.
Binder jet 3D printing deposits binder in designs across a bed of powdered material one layer at a time. Precise, near-net shapes are built in a large-format machine in under 24 hours. 3D printed sand forms are then strengthened with resin infiltration and finished with coatings tailored to the stability and durability requirements of a variety of tooling applications.
The design freedom of additive manufacturing allows companies to innovate products without the design-for-manufacturability concerns of traditional production methods—and often at a fraction of the cost.
Striking Gold with X1 ThermoForm 3D Printed Tooling
In the world of consumer products, speed is the name of the game. The faster products get to market, the faster they can be purchased by consumers with ever-changing tastes. And in the world of aftermarket products with a focus on maintaining a true-to-factory appearance, product quality is a must. That’s why Original Appearance Manufacturing turned to ExOne 3D printed tooling for its thermoforming tools after traditional methods proved to be unsustainable for business.
The company was born in an auto body shop in Ames, Iowa, to supply a new, cost-effective cosmetic option to cover vehicle rust damage without budget-busting structural repairs. OAM grew the idea and today manufactures Quick Covers exterior automotive panels from vacuum formed ABS plastic.
Zach Kowalik, CEO and cofounder of OAM, explained the challenges of the company’s original handmade tooling of steel, composite or wood. “They required a lot of repair and maintenance, and we often struggled to place vacuum holes in precise locations due to the material and design constraints.” Although seen as the gold standard of thermoform tooling, OAM avoided aluminum because it was cost-prohibitive in terms of money and time.
With speed to market in mind and in need of a tooling option that increased durability while also offering more flexible vacuum-hole routing, the company researched alternative manufacturing technologies, including binder jet 3D printing. “When we finally discovered 3D printed tooling, we felt like we struck gold,” Kowalik said.
OAM typically receives its X1 ThermoForm tooling delivery about two weeks after finalizing its design. The sand tool is produced in Leetonia, Ohio, at a production sand 3D printing facility. After the shape is built layer by layer in sand in under 24 hours on ExOne 3D printers, the tool is infiltrated on-site and coated to provide the durability to withstand vacuum forming production. Compared to past aluminum tools ordered by the company, the X1 ThermoForm tool was half the cost and saved over three months of lead time.
“This is a game changer for the industry,” Kowalik said. Emphasizing the role rapid tooling plays in speeding OAM’s time to market, he continued, “Our product launch times are an order of magnitude faster than we could have ever dreamed of before.” The company used to target one product launch per quarter, but Kowalik now sees the company launching a product each month with the speed and cost-effectiveness of the sand tooling.
While speed is what attracted OAM to binder jet 3D printing, Kowalik emphasized the importance of the quality of the tooling to result in high-quality products. “We require a very smooth finish. Our parts are typically painted, so we require something akin to Class A automotive standard on all our finished parts.” Precision tooling is also a must to maintain a true-to-factory appearance for panels that install seamlessly to customers’ vehicles.
With its in-house 3D scanner, OAM runs quality-control scans to verify the accuracy of the tool over its production lifespan. Panels are produced in four-minute pulls at around 300°F and the team rescans the tool after increasing production cycles. The tool’s durable surface shows no visible sign of degradation and comparison of scans after 100, 200 and 500 cycles proved an accuracy of 99.99 percent or better across the tool as it continued production without any quality issues.
The OAM team routinely monitors the durability of the tool, with testing to continue even after 1,000 pulls. “So far we’ve seen incredibly high accuracy,” Kowalik said. “The part quality hasn’t changed—the tool is still making high-quality parts consistently. We’re looking for tools that can make up to several thousand parts per year over a multiple year lifespan. We’re hoping for five-plus years.”
OAM is also researching other additive methods to create tooling, but the “near-net shape” approach of other large-format processes require a finishing path on a CNC machine, greatly increasing the cost compared to infiltrated sand tooling from ExOne. “After success with our initial X1 ThermoForm tools, we’re excited to be moving forward with additional projects that are larger in size,” Kowalik said. “Product volumes that were not previously profitable are now viable, and variations previously cost-prohibitive are now opportunities for expansion.”
National Laboratory Focuses on Even Stronger Tools
While sand 3D printed tooling is being used successfully by manufacturers, work is underway to make these fast and easy tools even stronger to expand their use.
Amy Elliott, group leader of robotics and intelligent systems at the Department of Energy’s Oak Ridge National Laboratory, acknowledged, “There is a need for strong, cheap tools.” Manufacturers are looking to reduce costs and operate more efficiently, yet tooling must withstand processes that apply heat and pressure that can cause tooling to fail.
A research team including Elliott designed a novel polymer binder to produce increased-strength silica sand parts. “The project actually originated with a focus on finding a strong binder with less carbon for some metal binder jetting applications,” she said, alluding to the team’s extensive work with the binder jetting technology.
The bond their polyethyleneimine binder had with the oxide surface of the sand doubled the strength of sand parts compared to prints with conventional binder. The parts exhibited an additional eight-fold increase in strength after a special infiltration.
The combination of polymers gives the sand strength with the flexibility to tailor the properties to fit the requirements of the tool. Working closely with ExOne to identify areas where development of their findings could benefit the industrial market, the team focused on the water-solubility of the binder to provide washout properties for hollow-geometry designs.
A 3D printed washout tool is durable enough for winding, layup or autoclaving, yet the binder remains water soluble. This allows the sacrificial sand tool to be washed out of the form with tap water, leaving behind a hollow composite form. Customer projects have produced carbon fiber ducting, mandrels and other designs with trapped geometries.
Increasing the strength of ever-more complex designs helps spur adoption of binder jetting for new manufacturing and tooling applications, and beyond. Indeed, Engineered Particulate Infiltration Composite products using a similar technique are already used for architecture, restoration and consumer products.
As supply-chain disruptions and material shortages become increasingly common and prices continue to rise, manufacturers are looking to innovative solutions that de-risk supply chains and offer new cost-savings. 3D printed sand tooling is answering the call to help get to market faster with optimized product development life cycles and decreased tooling costs.