Mantle is launching a new series of $350,000 machines that can 3D-print the mold inserts that are used to produce injection-mold plastics. It’s hard to overstate how important this will be — I caught up with the company’s founders to find out how and why this tech is going to put a serious dent in the speed-to-market for manufacturing.

Okay, let’s go deeply geeky for a moment, and take a look at one of the most interesting uses of 3D printing I’ve seen in a long while. To understand why this matters so much, you need to understand how manufacturing works; specifically, how injection molding works. Most plastic parts can be made by the hundreds of thousands, by injecting liquid plastic goo into a mold. This mold typically has water-cooling lines running through it, to bring down the temperature of the liquid, molten plastic quickly, so it solidifies. The mold opens, the plastic part is ejected, and you can go to the next cycle. Almost every small (and many large) plastic parts are made this way. The tools are usually made of extra hard “tool steel,” which needs to be extremely precise. The surface of this steel mold can be anything — smooth, textured, you name it — and anything that’s part of the mold cavity becomes part of the final plastic part. As you might imagine, creating these steel molds is extremely precise work, and it takes a long time (years) to become a tool maker. To become a truly excellent tool maker is a lifelong profession, at least as much art and experience as it is technology.

We’re seeing about a 70% reduction in the time to create these type of inserts and a 50% reduction in cost. Ted Sorom, CEO at Mantle

While injection-molded parts can be made by the tens of thousands in a negligible amount of time, the tools can take weeks, especially if your company is small enough that it doesn’t have dedicated toolmaking resources. Six to eight weeks is common, and during the global pandemic, I’ve heard quotes of up to 12 weeks. A three-month delay in manufacturing that can’t be worked around easily is, obviously, a nightmare.

You might ask yourself, “why don’t we just 3D-print these molds?” and the answer to that is complicated — the tools need to be extremely hard-wearing, precise, temperature-tolerant and the surface finish needs to be nigh-on perfect. There aren’t a lot of 3D printing technologies that tick all the boxes, but that’s exactly the space where Mantle is, erm, injecting itself.

“I was introduced to my co-founder who had started printing with silver conductive traces that were used to connect the backside of solar panels. From there, he started to try to print a physical object, not just the traces. When he started printing silver, I wasn’t interested in starting a jewelry company,” recalls Ted Sorom, CEO and co-founder at Mantle, excitedly sharing the genesis of the company. “About a month and a half later, he was printing low-carbon steel on very inexpensive equipment before anybody else had gotten close to doing that. I joined him to bring the technology to market back in 2015. We’ve been developing the technology for the last six years.”

The tech is interesting because they found a technology that connected with Sorom’s background in manufacturing. When the duo started printing in low-carbon steel, Sorom immediately realized that there would be a very important niche that could use this tech. Instead of using the 3D printer to print low-volume parts (as, say, automotive manufacturers tend to do) or prototype parts (as every manufacturer does these days), they would instead be using the 3D printers to create parts crucial to the mass-manufacturing process, whether that’s stamping dies or injection molding tools. Both need extremely precise surface finishes and longevity.

“Surface finish, tolerances and material durability requirements in the tooling space are extreme,” Sorom volunteers. “These tools are used millions of cycles to mass produce products. We’ve created a technology that the portion of the injection mold where the plastic hits the metal right. The insert that creates the final part. The materials we print today is similar to P20 tool steel — we call it P2x. The other is H13 steel.”

Now, if you’re not enough of a tool steel nerd to know what P20 and H13 are, these are two of the commonly used steel types for injection molding uses, which can be used hundreds of thousands, if not millions, of times before they need to be replaced.

The technique for printing is really interesting as well. The company has developed an FDM-style process — much like the filament printers you may have seen from MakerBot etc. — that uses a paste-like material that uses a liquid carrier that carries metal powders. After printing a layer, the company goes through a drying process that gets rid of the liquid component, resulting in a densely packed body of metal powders. After 10 layers or so, the process then uses a high-speed cutting tool (much like a CNC mill) to cut away tiny amounts of the material, which creates the surface finish and tolerances needed. That happens every 10 layers or so.

“At the end of the process, we have a body of densely packed metal powders held together by a tiny bit of glue or binder. We put it into a furnace and densify it into a solid metal part,” explains Sorom. “It’s a two-step process. We print and shape in one machine and then sinter the part in a furnace.”

The cool thing about doing it this way is that CNC machines are extremely good at getting high-precision parts, but the challenge is that the tool steel is so hard, that the CNC machine’s cutting tools cut it only very slowly. By shaping the parts before sintering, the company gets the best of both worlds: they do the precision shaping on a much softer material, and then “bake” the part to harden it afterward.

“That is how we are able to get a product that has the surface finish and detail to go directly from the 3D printer into an application,” Sorom says. “That’s where we save a ton of time and cost for our customers. We’re seeing about a 70% reduction in the time to create these type of inserts and a 50% reduction in cost.”

Mantle announced a year ago that they were going to build tool-making machines, and today it announces that the company is starting to sell its hardware, which includes a printer and a furnace solution.

The machine solutions will cost around $350,000, which might sound expensive, but for the metal fabrication shops that make tooling, this is roughly in line with the EDM and high-end CNC machines they already use. They also operate in industries where a $350,000 machine to cut production time by 70% is an absolute bargain, so it’ll be interesting to see the adoption of these machines out in the world. Delivery of the first production systems is planned for the first half of 2023.

The company produced a video showing how its tech works: