Aug 28, 2017 | By Tess
Most makers will have experimented with using 3D printing to make molds for casting. Whether it’s making a 3D printed mold for festive chocolates, or using lost wax or PLA casting to make strong parts, the processes of 3D printing and casting have often been used in combination.
Now, 3D printing company Formlabs has introduced a new method for casting metal parts using 3D printed molds. Using its High Temp Resin material, makers can easily 3D print molds for direct pewter casting.
In a tutorial recently uploaded to its blog, Formlabs details the process of direct metal casting using resin molds, and it’s not nearly as complicated as one might imagine. So, if you’ve been hankering for some metal gaming figurines or want to make pewter jewelry within a certain time restraint, you might just want to read on.
First off, let’s look at how direct casting differs from other methods of metal manufacturing. Metal 3D printing is a perfectly good way to make a part directly from metal, though the cost of this process is only really accessible to industrial manufacturers. Not so helpful for most makers.
Lost wax casting (or lost PLA casting) for its part is a reliable method of creating metal parts, though the process requires more steps (and thus more time) than direct casting to make finely detailed, good quality parts.
Formlabs’ method of direct metal casting with a 3D printed mold is surprisingly straightforward and requires only a few basic components: a Form 2 3D printer, High Temp resin, a cure chamber, CAD software, and Autodesk Meshmixer.
To start, you’ll beed a model that you want to mold. In choosing a design, the 3D printing company suggests selecting a small figurine, a piece of jewelry, or something else small and detailed. With an STL or OBJ file of the model ready, you’re pretty much ready to start.
Next, you’ll have to decide whether you want to print a sacrificial mold or a pull-apart mold. The former involves creating a shell mold in Meshmixer for the 3D printed model, which can be printed, cast, and simply broken apart once the metal has cooled.
For this method, Formlabs recommends using a uniform shell (the same thickness all around) for models between 2 and 20 cm in height. To reduce the risk of shrinkage and expansion damage, it suggests having a shell of at least 3 mm in thickness. Smaller models might not require a uniform shell.
The pull-apart mold method, for its part, consists of printing a two-sided mold which can simply be pulled apart once the pewter has cooled. This method is useful if you need to make more than one metal part, as it can be reused.
A few things to be wary of before printing the mold: be sure to include some air vents in your mold and make sure they are facing upwards (relative to the position of the mold when it is being filled) so that as the metal flows downwards into the cavity, the air bubbles can go up through the vent. Also, ensure that your 3D mold is properly oriented on the print bed so that it does not require internal supports.
Once printed, the mold can be post-cured, which will enable the High Temp resin to reach its highest thermal properties. Once the post-curing is complete, you can begin to melt your pewter material.
In its tutorial, Formlabs used an R98 pewter alloy which melts at a temperature of about 260°C. When the metal was liquified and the top layer of oxide was removed from it, it was carefully poured into the mold, which itself was secured with a clamp.
The pewter should only take a few minutes to cool (up to 20 minutes for a larger part), and once it is solid, you can begin to remove the mold. For sacrificial molds you can chip it away with a small screwdriver, and for the pull-apart method, you simply have to pull the two halves away from the finished model.
If all goes well, you should be left with a finely detailed, solid metal part. The full tutorial can be followed here.
Posted in 3D Printing Application
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