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Explore Microprinting and Micromolding for Miniaturization

Article-Explore Microprinting and Micromolding for Miniaturization

Image courtesy of Isometric Micro Molding Inc. micromolding-Part - Pellet of Resin.jpg
A micromolding expert examines the potential of 3D printed parts, parts molded from 3D printed mold inserts, and parts molded from traditional molds.

Isometric Micro Molding, known for its micro injection molding expertise, has expanded its use of 3D printing to further support development of miniaturized medical devices. Brent Hahn, Isometric’s VP Business Development & Strategy, shared the company’s progress during the IME West 2023 Medtech Theater session, “A Comparison for Micro Applications: 3D Printed Parts, Parts Molded from 3D Printed Molds, and Parts Molded from Traditional Molds.” 

Defining micromolding as “parts that are a fraction of the size of a resin pellet,” Hahn told the audience that Isometric “can make a thousand parts out of a single pellet of resin if there was no runner.” Larger parts, too, can be molded with microfeatures. For instance, he described molding a 3-in. part with 175 features that each measure only 25 microns—one-quarter the width of a human hair—using metal molds, in high volumes and with high cavitation. Another example entailed micromolding parts with a 400:1 aspect ratio and equally tight tolerances.

In addition to offering micromolding, Isometric can micro 3D print individual parts or full assemblies for prototyping as well as can 3D print micro mold inserts for use in an existing metal base for quick, short-run micromolding in the intended thermoplastic.

Isometric “started about three years ago with one printer and now we have three with super-high resolution and seven 3D printers overall to help our customers through their development processes in our new innovation lab,” Hahn said. For instance, “we have 3D printed an entire part’s thickness of 25 microns. That’s not a feature or a wall—that’s the entire size of the part.” Hahn said that was an extreme example, but if Isometric can print at that level, their work can help design engineers quickly go through various iterations. Isometric has been in business for more than 33 years and are experts in Design for Manufacturability (DfM) and Design for Automation (DfA), and that feedback is incorporated into 3D printed components or 3D printed mold inserts, to support designs that can become high volumes devices, he added.

As examples, he shared a catheter impeller wall thickness measuring 50 microns that “transitions to translucence because it is so thin” and “microneedles with 2-micron-tipped radii for sharpness,” he said.

“Getting down to the micron level of real precision so our customers can have parts in hand as quick as the next day in some cases helps R&D groups have all the bells and whistles to come up with the best design possible,” he continued. “It also leads to lower costs in development—you’re not waiting so long to try different designs with crisp features and fine surface finish.”

Image courtesy of Isometric Micro Molding Inc.micromolding-ISO_5inch_5011 V1.jpg

Hahn added that “there is an FDA-approved biocompatible resin for 3D micro printing” that allows for quick, low-cost design iterations of many performance characteristics that mimic those of thermoplastic parts. “We can do this in one day, and no mold is needed. It is a one-step process—take that CAD design, put it in, and print it directly. Multiple designs can be printed at the same time.” Such capabilities enable design engineers to test several micro part designs during early-stage development, he explained.

However, 3D microprinting uses a photosensitive polymer versus the intended thermoplastic. But if your project is looking at, say the design of air flow or water flow and the angle or shape of a nozzle, you don’t need a thermoplastic or a fluoropolymer or a bioresorbable material for your experimentation—you’re worried about the geometry—so a photosensitive polymer "would be fantastic for this kind of application," he said.

“But if you need a thermoplastic resin for the functionality of the part, here’s our new innovative approach—a 3D-printed high-resolution micromold insert that can be used in a master unit die (MUD) base with our micromolding process to mold in the intended thermoplastic,” Hahn told Design News. “So when the functionality of the resin is just as important as the geometry, this option now bridges the gap between a traditional prototype mold and a 3D-printed component. We can print this mold insert in about one day, and it is cost effective as no metal mold is required, and we can mold the parts in virtually any thermoplastic, even high-temperature thermoplastic.” It can be molded in LCP, and the team is working to see if it can get to PEEK as well, he added. Drawbacks to this option are the heating capacity of the photosensitive-polymer mold insert is not the same as that of a metal mold, and the inserts don’t have the longevity of metal molds, he said.

The third option would be to employ traditional metal molds, which can accommodate complex geometries including slides, mold any thermoplastic, offer longevity, and can allow more adjustments. “And the lessons learned can be directly translated into production molds in single or multi-cavities,” he said. “But it is slower because metal mold cavities need to be built and they are more expensive.”

Comparing Micromolding with Micro 3D Printing 

Hahn shared a study Isometric conducted comparing the use of micromolding using metal molds, 3D printed micro inserts for metal molds, and micro 3D part printing.

For this comparative study, the company 3D printed parts, 3D printed mold inserts, and built a metal mold with eight cavities to mold parts ranging from 25 microns (0.001 in.) to 200 microns (0.008 in.) thick. “Not to steal the thunder of this presentation, but we were successful,” he told the IME West audience. “All eight thickness options including 0.001 in. were able to be molded in the 3D-printed mold inserts and metal molds.” Micro 3D printing was also capable of printing the different part sizes. (Please see the table below for details from the study.)

Table courtesy of Isometric Micro Molding Inc.micromolding-3D Presentation Table.jpg

“We are excited to offer this bridge solution, where you can have that intended polymer in your hand in a week and in high-resolution versus 3D-printed photosensitive polymer versus the time it takes to build a traditional mold. Now having a viable second quick-turn development option allows the customer to make the right choice for their project scope, based on time, money, and priorities —such as a one-off or a large number of parts,” he concluded.

Donna Bibber, CEO of Isometric Micro Molding, will be discussing the future of miniaturization in the upcoming Design News webinar, It’s a Tiny World – The Future of Miniaturization, on Thursday, March 23, at 2:00 PM EDT. Please join us for an informative panel discussion with Bibber; copanelist Prabhakar Gowrisankaran, VP of Engineering and Strategy, Performance Motion Devices Inc.; and Design News Editor Daphne Allen.

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