Injection Molds & Metal Parts Continued...
Commercially-available Processes

Direct Additive Fabrication of
Injection Molds and Metal Parts

Alternative Approaches

Space Puzzle Molding^TM
Space Puzzle Molding^TM is a hybrid approach from Protoform GmbH (Germany). Molds are made as a complex series of small pieces and fit together in a special frame like a three dimensional jigsaw puzzle. CNC is typically used to make the puzzle elements. However, aluminum-filled epoxy casting, and other methods have also been used, as have direct RP fabrication processes such as selective laser sintering. Molds are manually removed and disassembled after each shot to eject a part, resulting in a higher piece-part cost than fully-automated processes. The molds can be used to produce hundreds of parts.

Protoform is not the only company to use such a hybrid approach. Some mold fabricators routinely use machined sections for appearance surfaces and RP-fabricated sections for cores and other surfaces where appearance is of secondary importance.

STAT^TM [Sample Time Acceleration Technology]
STAT^TM is available from Catalyst PDG, Inc. While few details of the technology are public, indications are that it is based on the CNC machining of composite materials to directly form injection molding inserts. The process is aimed toward reducing the time to obtain parts in final materials and the company says that a tool can be finished in as little as six to fifteen days, depending on the size of the part. Standard injection molding presses and parameters are used, but with a diaphragm added which limits stress on the composite tool. The composite tool is also tempered in a proprietary process step.

Typical tolerances promised are +/- 0.005 in and it's possible to obtain +/- 0.002 in for smaller parts. Tool life is typically 1,500 pieces, but that can be extended by tool maintenance. Nearly any plastic can be used and good geometry detail can be obtained because it's basically a machining process.

Laminated Tooling and Part Fabrication
Another technique which has received quite a bit of development over the years is laminated tooling. Several laminated tooling methods have been available for years on a limited basis, or have been used strictly in-house as proprietary technologies, particularly in Europe.

Laminated tooling is essentially the adaptation of the laminated object manufacturing (LOM) process to the problem. Work dates back to the earliest days of the RP field circa 1986 when LOM pioneer firm Helisys, then know as Hydronetics, was being in part supported by the John Deere Co. In general, profiles are cut using various means from metal strips or sheets which are then either bonded layerwise or tightly held in a frame to form injection molding, stamping or other tools. Work has also been carried out at universities in the UK, the Fraunhofer Institutes in Germany (Metal Laminated Tooling process - MELATO), and in the US at MIT and elsewhere on similar technologies. One advantage is that the method can provide somewhat larger tools than other additive technologies.

Solidica's Ultrasonic Consolidation Process^TM
Solidica has developed a laminated approach that is based on CNC cutting of thin, metal strip material. The strips are subsequently bonded together ultrasonically to form the final part. Solidica uses the tradename Formation for the machine itself. Among the advantages compared to laser powder forming methods are said to be the avoidance of expensive high-power lasers and powder materials both of which can be expensive and potentially hazardous. Another claimed benefit of the Ultrasonic Consolidation^TM (UC) process is that EDM is reduced or eliminated.

The process can also be used as a manufacturing method to make composite materials, or to imbed fiber optics in metals for smart structures and communications applications. Material strength can be improved in this way for structural applications or for the fabrication of protective armor. Features such as small holes for vacuum forming tools can be incorporated in the base material used which eliminates secondary machining operations. These techniques have been described in the company's intellectual property and work is also being pursued in university labs.

The technology can be used for tool repair, as well, but may find its major use in the repair of high value military and aircraft parts. The ability of UC to save money and time by repairing such parts right in the field is being evaluated.

The company says feature-to-feature accuracy is within +/- 0.002 to +/- 0.005 inches depending on geometry, over the machine working area of 24 x 36 inches; density in the range of 98 to 99 percent. The initial development focused on the use of aluminum alloys, but this is being extended to a wide variety of metals, including stainless steel, copper, nickel, titanium, and combinations of materials.

Fast4m
Fast4m offers a laminated tooling process for building injection molds, lost-foam molds, and similar items such as compression molds. Conformal and flood cooling techniques are specialties of the company, and molds can be built from steel or aluminum. Fast4m says that appreciable savings in time and cost can be realized and offers numbers and case studies on their web-site.

The approach offers CNC-level accuracy, a long tool life and the ability to make truly enormous tools. Some tools made by Fast4m have weighed as much as 15,000 lbs.

Protomold Company, Inc.
If the need is for a relatively simple part, certain types of subtractive fabrication can be quite cost-effective. For example, Protomold Company of Maple Plain, MN says it's able to deliver parts in as little as three days for tooling charges as low as $1,795, including 25 sample parts. According to Protomold's President, Brad Cleveland, not only can they create the tooling, but they can ship parts as quickly as the day after receipt of a customer's CAD file. He says in some cases they've delivered 500 parts in just eight hours. The molds must be capable of being CNC machined in aluminum. Any plastic can be used and the tool life can be as great as 100,000 parts.

Limited side-action capability is available for parts with undercuts. At present, the process supports up to two side actions per mold which must be on the parting line. There are also limitations on the maximum dimensions for sides where the pulls are located as well as the pull length. Delivery time for these more complicated molds is also greater than for simpler tools.

Advanced Technology's TCT^TM Technology
Advanced Technology of Corona, California has been providing injection molding tools and sample parts in less than 10 days to its largely medical industry customer base for more than a decade. According to the company, about 50% of their jobs are completed in 5 days or less.

The tools that the company produces are guaranteed for 2 million parts and can use any production thermoplastic with tolerances and mold parameters identical to standard injection molding procedures. Typical quantities are in the range of a few hundred thousand parts.

The company says this is the result of two things: the use of a proprietary mold material and operator cross-training that allows one person to carry through complete jobs if necessary from start to finish. The material is a trade secret, but it's said to be easy to modify and weldable. It's worked using traditional CNC technology and any complexity of part can be produced, including features that need slides and other accessories which may be difficult with some rapid tooling methods. One advantage of CNC compared to tooling made by RP, they say, is that there is much less time-consuming hand finishing to bring the master into tolerance and finish specs.

There are a few limitations: Parts have to fit within a 7.5 inch cubic envelope and it's not possible to do optical grade finishes. Also, RP technology can more easily provide conformal cooling and gradient, or multi-material molds for thermal optimization.