Sep 3, 2018 | By Thomas

Silicone molding is an affordable production method that can allow you to make a series of identical objects for prototyping and functional testing. Until now, however, fabricating molds for casting complex objects required a lot of experience and also involved manual work, which made the process slow and expensive. Scientists at the Istituto di Scienza e Tecnologie dell'Informazione (ISTI-CNR) and the Institute of Science and Technology Austria (IST Austria) have developed a new tool for fabricating digital objects through reusable silicone molds. The tool automatically finds the best method to design the molds, and also delivers templates for so-called "metamolds": Rigid, 3D printed molds used to fabricate the optimized silicone molds.

The metamolds (red pieces far left and right) are used to fabricate the silicone molds (greenish and white shapes in the middle). Credit: Luigi Malomo

Silicone molding is simple and accurate and will forgive many mistakes. Extracting the object from the mold generally requires separating the mold pieces without getting them caught in overhanging parts of the object. A careful cut is required to open the mold. "Until now, silicone molding of complex shapes was a craft that needed years of experience and a skillful hand. You needed to know where to place the cuts ideally, and the work was done manually. Our new tool makes this method accessible for everyone," says Bernd Bickel, an Assistant Professor, heading the Computer Graphics and Digital Fabrication group at IST Austria.

With their new tool, the user just needs to upload the desired shape to the computer. The tool then calculates where the cuts need to be placed for an optimal result. This implies that the smallest possible number of mold pieces is utilized, and that the object can be safely removed from the mold once it is finished.

After that the computer automatically creates the 3D-printable templates of the metamold, a container that is used to create the ideal silicone mold pieces. The 3D printed metamolds are then filled with liquid silicone to produce the last silicone mold pieces, which are reusable and can be used to cast multiple replicas.

Scientists believe that this tool will be useful for small series production, such as in jewelry design or art. "When you are not producing millions of copies, this is the method of choice," says Thomas Alderighi from ISTI-CNR, the first author of the study.

As noted by Paolo Cignoni, research director at ISTI—CNR, one possible application is the production of a small number of replicas for museums that could be handled by visitors for a deeper experience of the exhibition.

The final silicone mold pieces can also be used to create replicas from a variety of different materials, including traditional ones like resin, but also unconventional ones like chocolate or ice.

Their method, which can lower the cost of silicone molding technique, is presented at this year's SIGGRAPH conference and published in the journal ACM Trans. Graph.



Posted in 3D Printing Application



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Cindy leonard wrote at 9/6/2018 5:49:34 PM:

How much does the equipment cost? Thank you

Eric Askue wrote at 9/6/2018 12:31:13 AM:

I'm the lead artist at Collapse Industries (also the distributor for the MilkShake3D Printer US) and the creator of World Over Run (a tabletop terrain business). I would like to talk with the developers about there process, as well as share a few points and discuss features. One of the many things about this process is the amount of silicon needed. We use mold jackets and our molds are usually between 10 and 30mm. If this sort of feature was explored and could be done between an SLA for the mold and an FDM for the jacket would make it cheaper and more flexible. there are other concerns to consider as well. Most of the time we make a master (the first casting) for our vault to recast the mold once it starts to fail. The issue with this method is that prototypes from SLA are not entirely stable and with age can deteriorate. Again I'd really like to have a proper conversation because I find this process very exciting for us and the development of our production. Thank you ~Eric Askue

L T D wrote at 9/4/2018 9:46:19 PM:

This technique is called pattern making and has always been the standard way to make sand castings or other technical castings. Make patterns that make the molds. It's ridiculous to make a part and then use a razor blade to cut off the silicone mold. That is only done in art castings from a sculpture. Even then, if more than one reproduction casting is to be made, I think you will find that the the impression in plaster or silicone that came directly off the sculpture is used to make PATTERNS that them are used to make the molds that make the wax investments. Note that at each step specialty plasters that have extremely predictable shrinkage or even expansion can be used.this gives optimal control over finished dimensions.

Kyle Schiefer wrote at 9/4/2018 7:46:26 PM:

You still need to address the grow lines leftover from the printing process (a time consuming step without an easy-to-manipulate part, given that it's opposed halves are nested separately in planar surfaces), and the value of producing solid "molds" in both print time and material costs is ungodly. For roughly the same price, if not considerably less, you can print a single part, clean it up, and mold it in half of the time. After all.. pouring silicone is still an hours long task, and unless you have absolutely identical mold halves, your parting lines will cause a whole new slew of problems in the production realm.. not to mention that silicone tires out, and becomes brittle over time, meaning that even if you did everything right.. every part you cast will require an exponentially greater amount of final clean up and finishing before they can be sold or shipped etc.

Hammah33 wrote at 9/4/2018 1:02:21 AM:

Composimold also works really well and solves some of these issues...

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