Updated: Aug 6
Historically injection molding has been great for manufacturing large numbers of identical parts at low cost. However, if you are doing small runs of a piece, or you know your piece will evolve over time, a 3D printed mold can get you going at a fraction of the cost of traditional steel molds.
To create a 3D printed mold, you first need to choose a suitable material. The result when printing it on an FDM printer with ABS or PLA will most likely lack the detail needed and require too much cleanup to make printing the mold feasible. Every flaw in the 3D printed mold will be reproduced in the cast, so we need to create the mold with a material that produces greater detail with less need for cleanup.
Using resin 3D printer and resins with high-temperature resistance, stiffness, and resolution will give you the detail and durability to make molds for small injection mold runs.
If you plan to inject liquid plastic into a 3D printed mold, it shouldn't melt the mold! So have a look around for resins with high heat deflection temperature when making molds with 3D printing.
Every time you remove a cast from a 3D printed mold, there could be wear and tear on the mold. Using a stiff resin to create your mold helps it to remain accurate for longer, giving you the most out of each cast.
One can also add cavities in the 3D printed mold for steel rods to increase the durability of the mold even further.
We've all seen the layers in a 3D print - especially FDM 3D prints. If your mold has these layers, they will be reproduced, and I can't imagine that being anyone's preference. Resin prints can be more detailed as the layers are often not visible to the naked eye, but if you do see layering in your 3D printed mold, either increase the resolution the next time you print it or give it a quick sand with sandpaper.
Once you've established that your project or application is suited to low run injection molding and have a quality resin to print with, it's time to put some thought into designing your mold.
This can be a much more detailed process depending on how complex the cast is that you are making, but the foundations are;
Never put supports on the inside face of the mold. This only makes for more clean up time as they leave the surface of your mold marked.
A smaller layer height when slicing and printing your mold will mean increased detail and less cleanup time - especially on a resin 3D printer where the layering is often invisible to the eye.
.5mm air vents or exit holes in your 3D model allow for air to escape when printing so there aren't bubble marks in your part after molding.
Right angles are not your friend. Sharp corners within the cavity should be rounded to ease part removal.
Include interlocking tabs on the top and bottom of a two-sided mold to reduce the likelihood of flash, which is when the casting material leaks out between the two halves of the mold.
Text that you want to appear debossed on the final cast should be deeper than 1 mm. Sharp corners should be rounded to help with the release of the cast from the mold. If you pull out a casted part and the lettering on it stays behind in the mold, for example, you may have ruined it. Usually you can still clean it up, but you have still made more work for yourself.
Now you can start 3D printing your own ideas for great small run products and designs! I'm very much looking forward to discovering more unique designs and creations as low run injection molding become cheaper and more accessible to everyone.
With a high-speed resin 3D printer from Gizmo 3D, you can prototype molds incredibly fast. You can print a mold that fits in your hand within less than two hours, for example. You could then cure it and finish running final casting tests all within a day. Once you are happy with your final mold, you can set your machine up to print a higher resolution version of the mold during the night and use the mold the next morning to start manufacturing. Click on the image below to save this blog to Pinterest
Have any questions about the Gizmo 3D Printers? Feel free to book a call or email info@gizmo3Dprinters.com.au ___
About the author: Ryan Madden is a 3D printing enthusiast based in Brisbane, Australia. He has been printing on various FDM 3D printers for years as a hobby. He started printing on resin 3D printers for the first time in February 2019 when he was hired as 3D printing technician at Gizmo 3D Printers Pty Ltd.