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Producing 'Unmoldable' Parts with 3D Printing

Image by Gerd Altmann from Pixabay possible-379215_640-web.jpg
Additive manufacturing helped deliver an intricate design not limited by traditional manufacturing constraints.

In the Virtual Engineering Week presentation, How Do You Prototype & Produce the Unmoldable?, the story of producing a difficult-to-mold consumer product using 3D printing technology was told from three perspectives—the product OEM, the component manufacturer and printer, and the 3D printing technology supplier.

Gage Cutler, owner of FinMan Fishing Innovations, had a great idea for a new product that would help address concerns people encounter when fishing. This is no fish tale—it is the story of additive manufacturing technology delivering a flexible, durable, intricate product that may not have been possible with traditional manufacturing.

The FinMan Original is a rod-mounted tool that slices, snips, and stows gear. It has an intricate design, which made manufacturing a challenge. “For reference, the parts are around 1¾ in. long, around ½ in. tall, and just by looking at it, you can see there's a ton of detail,” Cutler said. Another big requirement for the product is that it be flexible, yet strong.

Aesthetics were also a consideration as the product is meant to look like a fish.  

When it came to manufacturing the FinMan, Cutler said he and his engineer did not want to be limited by traditional manufacturing constraints that would have taken away from both the functionality and the aesthetic qualities of the product.

“That's really what pushed me in the 3D printing,” he said. “For example, from the financial point of view, I didn't want to have to spend $15-, $20-, $25 thousand for a Gen 1 part and then immediately want to go to a Gen 2, and have to pay for another $20,000 mold,” he explained. “With 3D printing it was a $250 non-recurring engineering charge to change the digital file,” he said, enabling Gen 2 parts to be processed the next day, if needed.

Time to market was also reduced, he said. “We were able to use the same technology from prototype to production really at any scale,” he said. This would also allow for customization opportunities, which Cutler said opens up white labeling and private labeling opportunities for his company.

John Gallagher, president of the Gallagher Corp, described the manufacturing process for FinMan. The first thing they looked at were some design features, the first of which was texture. Another thing was the width of a horizontal slot on the bottom of the FinMan where a razor blade is inserted.

“That slot is 1 in. long, and 0.0048 in. wide, and we're holding that width to better than +/-0.005 in.,” Gallagher said. “Early on, it was unknown what width was needed to get the right fit for the razor blade. So we used prototyping to look at different slot widths.”

Gallagher mentioned that they also wanted to add a logo on the bottom of the FinMan and did a couple of iterations of this quickly to see what looked the best. “We print the same way, same process, same material, whether we're making prototype or production parts,” he said. “I think everyone recognizes the benefits of 3D printing for prototypes, but sometimes they're surprised that 3D printing can be a viable option for production.”

Gallagher explained that his company evaluates production viability in three ways. First, he said, was efficiency. “Is the part size within the printer’s envelope, and are the parts geometry printable? Assuming yes to both of those, then efficient printing is all about cycle time and number of parts per cycle,” Gallagher said.

Cycle time depends on how tall the part is, and parts per second depends on how many parts can fit on the platform. “So, in general, things that are FinMan-size or smaller can be efficiently produced," he said. 

The second question revolves around economics. “Often the comparison point here is between injection molding and 3D printing,” Gallagher said. “It's all about cost per part and I expect honestly that 3D printing is going to have a higher part cost.” However, he said what is likely not being included in the part cost is the cost for tooling, which can be significant for injection molding, especially as designs evolve over time.

The cost of lead time is also not included in that part cost. That can be significant for injection molding, but only days for 3D printing, he said. “For injection molding, there could be eight, twelve, sixteen weeks required just to fabricate the mold. So, saving the upfront investment in tooling and saving time is valuable. And that can really flip at the economics advantage to 3D printing,” Gallagher noted.

His third criteria is that the printed material can meet requirements such as strength, durability, or ability to handle high temperatures.

Gallagher concluded his remarks by saying that FinMan answered yes to all of these questions. “FinMan is a design that Gage was having trouble even making, and yet we've optimized it to print 100 at a time, in a 105-minute print cycle.”

Bob Gafvert, production partnership sales manager at Carbon, then spoke from his years of experience in injection molding as well as additive manufacturing. He said that when looking at materials, it is not only the cost that should be considered but mechanical performance is more important.  

For FinMan, because it needed to be flexible and strong, they ended up using Carbon’s rigid polyurethane 70, which is similar to ABS, and has a UL 94 horizontal burn flame resistance classification.

“The advantage mechanically with Gage’s product with a Carbon material is the process that the material goes through,” Gafvert said. “These are dual-cure materials, so it's a two-part material, whether it's a two-part urethane or two-part epoxy.”

In the company’s process, the shape of the part is set up with UV light and then it is cured in a thermal oven where the mechanical properties are set, Gafvert said. “It's where the UV cross links that were established in growing the part from a liquid resin, from an STL file, and taking advantage of all the different cross sections into a fully functioning mechanical part, similar to ABS.

“One of the keys to that process, why Gage is able to have that flexibility and that strength, is isotropic properties of that rigid polyurethane 70,” Gafvert continued. “The process with Carbon really allows you to develop an isotropic part because you don't have the traditional layering that you do with traditional additive. You don't have the porosity that you do with say a powder system. When you're working with liquid, you're able to achieve fully dense parts in the X, the Y, and the Z dimensions,” he concluded.

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