3D printing is a wonderful technology by itself, but it also enhances other manufacturing technologies when combined with them. There have been many cases in which 3D printing and investment casting were used together, and 3D printing and CNC machining are often both required to create a single part – hence the growing number of machines that combine the two technologies into one. One of the most reliable manufacturing techniques is injection molding, and it’s injection molding that 3D printing is often compared to. It’s still the standard when it comes to plastic manufacturing, particularly large volume manufacturing.
3D printing is catching up, though, as 3D printers get faster and materials get stronger and more durable. Will it ever replace injection molding? Probably not – but 3D printing can improve injection molding, as a team of Formlabs researchers found and described in a white paper entitled “Injection Molding from 3D Printed Molds.” The white paper is available for free here.
Molds for injection molding are typically costly and take time to make, so 3D printing the molds instead of tooling them can save both time and money for low-volume production. In the study that led to the white paper, the researchers used a Form 2 3D printer to print molds for several small parts, which were then fabricated using a Galomb Model-B100 Injection Molder.
“There is a lot of interest in 3D printing injection molds but it’s an application that’s been out of reach for a lot of people,” Jennifer Milne, one of the paper’s authors, told 3DPrint.com. “Most people are familiar with 3D printing for prototyping and development, but this application starts to bring 3D printing into pre-production and production phases. To do that with a printer that costs $3,499 is unheard of, and so injection molding from low-cost desktop SLA 3D prints is an application that product designers and engineers are interested to learn more about and try for themselves.
Injection molding is a demanding application and there are of course limitations. Our High Temp resin has the highest HDT of any SLA resin on the market, but for injection molding it must also withstand high pressure, and thermal cycling for multiple shots. In this whitepaper we demonstrate that our High Temp resin is suitable for prototying injection molds, or producing low-volume low-pressure molds, for use with desktop manual injection molding machines.”
The team tested both High Temp Resin and Clear Resin for the experiment, printing molds of the Formlabs butterfly logo as well as a USB device enclosure. Galomb then tested the molds with 25 shots of LDPE, a thermoplastic with a relatively low melt temperature. After the shots were injected, there was no noticeable surface deterioration of the molds, according to the white paper.
“This is one of the first projects that came form our Applications Engineering team where we pushed the material to its limits and then shared what worked,” said Milne. “While the examples in the whitepaper were successful, we also tried many things that didn’t work. However, by putting this whitepaper out into the world, we’ve since seen Fortune 500 companies find ways to use High Temp parts printed on the Form 2 to tune their injection molding process saving them significant time and money. We’ve also seen smaller companies like Stickybones use Form 2 printed molds to produce end-use plastic parts. We’re excited to create content that inspires others to try to integrate Form 2 printed molds into their production processes in new ways, and for those willing to experiment we’ll start to see more and more success stories.
One surprise was that our standard resins (Clear, White, Black, and Grey) could also work for printed molds in some examples, like the Stickybones case where they used Black resin, or for the simple test case of the USB enclosure which was successfully shot in PP. It was only with higher melt temperature materials like ABS that we started to see crazing and the need for High Temp was apparent.”
The white paper goes on to detail several common problems that can happen when 3D printing molds for injection molding, as well as steps that can be taken to solve them. It also offers design guidelines for creating 3D printed molds. The paper is a good read with a lot of useful information; if you’re interested in checking it out, you can request a free copy here.
“Formlabs continues to be interested in Injection Molding as an application,” concluded Milne. “This is the second version of this whitepaper updated to include our High Temp resin and its capabilities, and we’ll continue to work on materials development and share best practice when we connect with companies successfully implementing these techniques into their workflow.”
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