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3D Keltool is one of the most popular methods of creating a moderate to high volume tool. The process was developed over twenty
five years ago by 3M, but languished for years until the ability to make accurate patterns economically by RP came into being.
Although it's presently owned and licensed by 3D Systems, a leading stereolithography system producing company, any type of
RP-generated pattern can be used. The process is available from several licensees in the US and Europe. It offers good accuracy
and finish from a long-lasting steel tool, and many users have made more than a million parts from a Keltool mold. The main
limitations are that the size of mold inserts that can be created are fairly small, on the order of a cube six inches on a side,
and thin walled sections may not be possible to fabricate. Some have used multiple molds joined together to get around the size
limitation.
The process starts with an RP pattern from which a rubber mold is created. The rubber mold is then used to cast a steel powder
and polymer binder mixture into the mold geometry which after hardening is in a green state. The green mold is fired and copper
infiltrated resulting in a tool with about 70% steel and 30% copper content. Ejector pins, cooling lines and other accessories
may be added in final machining and polishing steps. In some cases little or no finishing is required.
The inserts are strong enough to withstand typical injection molding temperature and pressure conditions, and it's possible to
use filled plastics and perform die casting with them. The method is advantageous for small, complex molds that would require
much time to make with CNC or EDM techniques.
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