The Mold has always been a vital part of the manufacturing process. Over the years as production methods changed so did the mold. The essence of the mold remains “a pattern or model by which something is shaped or made” but technology enables different mold capabilities. Here is a historical look at the mold over the years, from pre-historic craft to contemporary digital (virtual) molds.
There is documentation of the use of molds since as early as 5th century BC. Molds were used to create weapons, clay figurines, coins, as well as baked goods. This stone mold was used to produce spear tips during the Bronze Age (first below) and another was used for molding and baking gingerbread during the 15th century (second below).
The lost wax process starts from making a model of the final shape out of wax, the wax shape is then covered in clay. The clay is burned creating a rigid shell and allowing the wax to melt leaving a hollow shape of the model. The metal poured into the mold fills the hollow shape creating an exact copy of the wax item in metal. The lost wax casting process dates back to 4500–3500 BC but is still used today. Combined with 3D printed wax or other soft materials, 3D printing provides an efficient and fast way to produce the model to be lost in this casting process. Schmolz+Bickenbach together with Voxeljet use PMMA, a material which softens at 73° C and burns out without residue at temperatures over 700° C. This means that the material is ideally suited for use as lost models for investment casting purposes (below the item after casting and finishing).
Sand casting is another ancient technique based on simple principles. Basically, the wanted shape is imprinted in sand, and the metal is poured into the cavity created. Over the years, this simple method has been adapted to the needs of the industry. Today over 70% of all metal castings of industrial parts are produced via the sand casting process (below and in video).
Sand casting is also used in conceptual design projects such as Can City by Studio Swine. The studio utilized the sand casting process, creating a mobile foundry in the streets of Sao Paulo. Using the metal of discarded cans they turned the street into an improvised manufacturing line.
As plastic became a more prevalent material for production, injection molding took its place as a highly popular manufacturing method. The technique has evolved steadily since its beginnings in the late 1800’s, from the production of combs and buttons to major consumer, industrial, medical, and aerospace products.
Lego, for example, processes 60 tons of ABS material every 24 hours, producing more than two million pieces per hour. Injection molding allows for a very high level of accuracy, as every piece must fit perfectly to any other. In fact, all Lego elements are fully compatible, no matter when and where they were made from 1958 until today. The injection molding process uses large, heavy metal molds that are manufactured in Germany (above). Below is a retired Lego mold after making 120,000,000 Lego bricks.
Keter is a leading plastic manufacturer known for their manufacturing expertise and excellence, including intricate molds and production systems. For their latest Knitted collection (below), Keter developed a method in collaboration with designer Maya Ben David, in which they could apply the process of injection-molding to create a deep surface finish that results in a soft 3D woven appearance.
These intricate structures must need very advanced molds in order to create the 3 dimensional knitted patterns. Part of the process included 3D printed tests (above) of the structure connections and details in order to provide the most accurate look.
3D Printed Molds
As 3D printing technology evolved, many injection molding companies find themselves turning to 3D printing just to stay competitive. For a large company, additive manufacturing can assist in more than just the prototype phase. Incorporating 3D printed parts in molds can cut costs and time dramatically. An aluminum or steel mold can take weeks to get from CAD file to delivery, however, a 3D printed mold can be produced in a matter of hours. Here is an example of 3D printed mold inserts by Polymer Conversions (below) and an injection molding tool made with 3D printing by Stratasys and Worrell Design Inc. (up top).
Apple filed a patent application for a new method of forming electronic device components using liquid metals and 3D printed molds. Apple researched ways to mold amorphous, glass-like alloys while reducing cost, reducing material waste, and maintaining an optimized cooling rate. This method could potentially be used to replace costly and wasteful traditional investment castings (such as lost wax casting). These molded products have desirable strength and impact-resistance properties, and can be used in a wide range of electronic devices.
Enter the Virtual World
Physical molds are usually used for repetitive use (excluding the last wax method), they offer great accuracy and are cost efficient for mass production. As the world moves to utilize more and more virtual and digital techniques, we would expect no less from a virtual, digital, mold. In fact, as production moves to the virtual world, requirements only grow. We would still want repetitive production but with added customization capabilities – which is practically impossible in the traditional way of producing physical molds. Metal injection molds are made with complicated machines, they’re expensive and take a while to make. In contrast, the virtual world calls for molds which are easy, cheap, and fast to produce, as well as locally available. On the other hand, brands must be able to control and monitor the eventual manufacturing from these digital molds, without any information leakage or changes. Brands also want to make at least as much money as they do when using injection molds in this new distributed manufacturing world, utilizing virtual molds and Additive Manufacturing. I can’t resist a small plug: Make it LEO provides just such virtual molds that are preserved, protected, and tracked. With virtual molds and Distributed Additive Manufacturing brands can achieve on demand manufacturing, drastically cut inventory and logistics costs, and enjoy additional income from new business models. Exciting!
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