Injection Molds & Metal Parts Continued...
Under Development, Dormant or Abandoned Processes

Indirect Processes that Use RP-generated
Patterns to Mold Plastic Parts

3D Keltool^TM
3D Keltool^TM is a method 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. It's presently owned and licensed by 3D Systems, but is now only available from a handful of licensees in the US and Europe.

Any type of RP-generated pattern can be used. 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 customers 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.

3D has been treating 3D Keltool^TM with benign neglect, concentrating its efforts on other technologies it has since acquired such as selective laser sintering.

PHAST (Prototype Hard and Soft Tooling)
A process under development with similar fabrication steps to aluminum-filled epoxy tooling may be worth considering for parts requiring volumes in the hundreds of thousands, or for more complex or multi-cavity tools. An RP-generated pattern is used to form a metal-matrix composite tool made from tungsten and bronze, and is good for producing fine details and avoiding the use of EDM.

PHAST is available on a limited basis from the Milwaukee School of Engineering. It's based on initial work by Procter & Gamble. The company donated the patents for the process to the school after deciding not to pursue commercialization itself.

RMT Spark^TM
The process was originally developed by Swift Technologies Ltd. of the UK and was called SwifTool^TM. Swift's assets and intellectual property were purchased in 2003 by start-up, Rapid Moulding Technologies, Ltd. That company subsequently combined with several others in 2005 to become a division of vertically-integrated European Plastics Technology Solutions, Ltd.

It's an indirect process that uses any form of RP-generated or other pattern, and can produce molded plastic parts in a day or even less. The pattern is embedded in the surface of a bed of clay-like modeling compound held in a box frame. Parting lines are defined for the final mold by manually sculpting and kneading the modeling compound into the desired geometry. Once a satisfactory parting line is established, the up-facing surfaces of the pattern and modeling compound are sprayed with mold release, and the entire assembly is covered with a mass of proprietary fiber-filled, thermoset composite material. This material is then cured against the model in a special vacuum press over the course of an hour. After curing, the second half of the mold is then poured and cured against the first in the same way. Ejection pins and accessories are put in during secondary machining operations. The net result is a tool that is similar to those made with aluminum-epoxy, but more sturdy because less brittle. The number of parts that can be molded depend on the particular part geometry and plastic used: 50,000 are possible with polypropylene, but temperatures needed for ABS limit the number to about 1,000 to 2,000. Plastics that require temperatures above 300 deg C lower this further to 10 to 100 pieces. The company has also purchased technology from Swift for adding surface textures in the process.

The company claims to have improved surface quality, reduced tooling costs by 30% and system costs by 75% after taking over the product line from Swift Technologies. Cost reduction was accomplished by making it possible to use the technology with standard presses and tooling systems.

The commercial availability of the process is not known, and it may now be abandoned.

EcoTool^TM
The process uses similar construction steps as aluminum-filled epoxy tooling, but uses a steel powder-binder system which is ecologically safe and hardens at room temperature. An infiltration cycle is required as in several similar processes such as 3D Keltool^TM and PHAST. One intriguing and unique aspect is that the tools are robust enough to produce glass parts. Up to several thousand glass parts have been produced from an EcoTool^TM mold.

Dr. Stuart Clyens of DTI says the shrinkage of the binder is very low, only 0.1-0.3%. There appears to be no upper limit on the size of tool which can be manufactured, but they generally do not exceed 20 Kg simply because of the difficulties in handling. The EcoTool^TM process has been used successfully to manufacture plastic injection molding tools, tools for superplastic forming of aluminum, blow and vacuum forming tools and high pressure aluminum die casting tools.

TNO in the Netherlands and the Danish Technological Institute were jointly developing the process, but it has become temporarily dormant until workers can be found who can devote more time to it.

MetalCopy^TM
MetalCopy^TM, formerly WibaTool, is a powder-based process developed jointly by IVF - The Swedish Institute of Production Engineering Research, and service bureau Prototal. It's similar to KelTool^TM and related processes, featuring high reproducibility of small part features, 99.5% density and a 1.5 micron surface finish. It is claimed to work well for injection molding bridge tooling of complex parts and has also been marketed as a turnkey system for $80,000.

Molds are said to show no significant wear after producing more than 20,000 parts in polyamide with 30% glass fill. Depending on the geometry, typical lead times from CAD model to finished tooling is about two weeks, and costs are said to be reduced by 50% in comparison with traditional methods.

A master of the tool is produced by RP and a silicone negative is cast from it. This silicone negative is used to produce a green secondary master using a mixture of steel powder and binder. The green part is sintered and infiltrated with a low melting-point metal. The mold may be finished by traditional machining methods. The maximum tool size for best quality is 4.7 x 4.7 x 2.7 inches (120 x 120 x 70 mm). Larger sizes are possible for less demanding applications and molds can be made from more than one section. Surface finish without polishing is 2 microns and the tool can be machined similarly to aluminum. Dimensional accuracy is dependent on the master and is said to be better than +/- 0.2% or 0.002 inches (0.05 mm) for small features.

The commercial availability of the process is not known, and it may now be abandoned.

Direct Additive Fabrication of
Injection Molds and Metal Parts

ExpressTool^TM
ExpressTool^TM isn't really an additive fabrication method at all and is said to take about the same lead time as typical CNC processes. It was purported to provide similar benefits as additive fabrication such as conformal cooling, higher thermal conductivity and resultant reduced cycle time. The method starts by CNC machining mold faces from a soft, conductive material such as a graphite block. This soft material is much quicker to machine than steel, of course, which saves time. The graphite then undergoes a plating operation to build up a thick layer of nickel-copper, or other hard metal surface. The nickel-copper shell is removed from the graphite and is then backed with steel to form the final mold. Experimental ExpressTool^TM molds have produced hundreds of thousands of parts.

ExpressTool^TM was being developed by a division of the Infinite Group, Olsey & Whitney which was dissolved in 2001, suspending additional work on the process.