Soligen Technologies, Inc., of Northridge, California, spent three years developing its CAD casting technology before entering the market as a rapid casting service provider. At the beginning of the fourth year, Soligen introduced Direct Shell Production Casting (DSPC®), turning the heads of the largest target customers and converting them into clients.

Soligen actually began in a garage. Believing in a new technical direction, Soligen obtained the exclusive worldwide license for 3D printing from MIT in the field of metal casting. The founder of Soligen, also a founder of one of the first service bureaus, then built proprietary technology based on 3D printing. The result was DSPC, a process that creates a first article metal part, of any complexity, faster and more cheaply than conventional methods.

DSPC adds significant value to the rapid prototyping and rapid manufacturing processes, improving quality and saving time and money. DSPC creates a first article metal part without the extra steps, expenses and time related to rapid prototyping in a polymer, powder or paper, and then developing tooling for a metal part that may not even be approved. More simply, rapid prototyping of patterns and core boxes for metal casting of a simple automotive intake manifold can run upwards of US$40,000 - and there is no guarantee that the casting tooling will work. If it does not, or if the design is altered during the process of preparing the patterns and core boxes, the majority of that investment in the first set of tooling will go down the drain and the majority of the original cost will be respent on the next set of tooling. This process continues until the client has an approved metal part. Each iteration can take up to nine months depending on the size and complexity of the part.

DSPC takes a CAD file and translates it into a ceramic mould, which can then be poured with any molten metal. Soligen can produce an accurate part, regardless of geometric complexity, in six to eight working days at a fraction of the cost of traditional methods. Each design iteration follows the same process, keeping time and expenses to a minimum.

DSPC is also extremely versatile. New, more effective and efficient parts, such as engine blocks, manifolds, and many other components, can be created by DSPC's ability to ignore parting lines, draft angles and core print considerations while iterating the design. A DSPC of cored parts may contain integral ceramic cores, allowing a hollow metal part to be produced. It may also be made for highly complex parts of any size. DSPC can also make 'lost foam designs' including parts and tooling. Furthermore, virtually any molten metal can be used. Engine parts have already been manufactured in aluminum, magnesium, iron, ductile iron, alloy steels and stainless steel.

Within 10 days, the customer had a functional aluminium intake manifold in his hand.
An extreme example of the flexibility and versatility of DSPC comes from an intake manifold Soligen made for a truck. The customer originally designed the intake manifold in plastic. At the last minute, he realized that the plastic design was very marginal and would therefore not meet his standards for durability. He decided to change to metal. However there was no time left in the program to redesign the manifold for metal casting. Desperate, and slightly embarrassed, he called Soligen to see if it could make a plastic design in metal. Soligen was able to take the CAD design, made for a thin-walled plastic manifold, and then produce cast it in aluminium - complete with the intricate details commonly found in plastic manifolds. Within 10 days, the customer had a functional aluminium intake manifold in his hand.

Producing prototypes, first article parts and short runs via DSPC eliminates the need for temporary tooling, thereby expediting the design and functional testing phases of cast parts. It enables the customer to perform an unlimited number of design iterations, including testing with different materials or alloys, without the cost and time consumption associated with single or multiple tooling productions. Additionally, DSPC's reliance on CAD files provides forr stringent configuration control, ensuring that all design changes are properly documented.

For the mass manufacturing phase, production tooling (permanent molds, steel or aluminum patterns and core boxes) can be cast as net shape tools from the same CAD file as the tested and approved part using DSPC. This not only continues to offer time and cost savings, but also significantly reduces potential geometrical inconsistencies from incongruous manufacturing phases.

How it works
The DSPC machine prints the designer's CAD file, layer-by-layer, to create the ceramic casting moulds. Soligen's casting engineer adds a gating system to the designed part's CAD file and adjusts it for alloy shrinkage, converting it into a cavity file of a ceramic mould in CAD space. This is a one-off process which is performed off-line on the DSPC machine. The computer file of the ceramic mould is then used to generate automatically the actual ceramic mould in layers in the DSPC system.

The DSPC fabrication process involves three steps per layer. First, the ceramic shell model is 'sliced' to yield a cross-section of the ceramic mould. Second, a layer of fine, powder is spread by a roller mechanism on a separate building platform. Third, a multijet printhead moves across the layer of powder, depositing binder in regions that correspond to the mold's cross-section. The Binder adheres the particles together into a rigid structure. Once a given layer is completed, the ceramic shell model is sectioned again at a slightly higher position, and the building platform is lowered, repeating the process until all layers are formed. The DSPC mould is then cleaned of excessive powder, fired and poured with molten metal.

If a small company like Soligen can deliver accurate parts, and at a fraction of the time and cost of parts made the traditional way, repeat orders are bound to follow.
Soligen has cracked tier one, two, and three automotive OEM suppliers the same way - by producing a part when they were up against a deadline and all other options had failed. The same doorway is open for the company's other target industries: marine, aerospace, hand tools, pumps and valves. If a small company like Soligen can deliver accurate parts, and at a fraction of the time and cost of parts made the traditional way, repeat orders are bound to follow.

As a user of RP and rapid manufacturing technology, the slashing of production time on a transmission housing from 14 to four weeks is certain to be of interest.

For further information please contact:
Yehoram Uziel, Soligen Technologies Inc.,
19408 Londelius St, Northridge, California 91324, USA,
Tel: (818) 718- 1221 or Fax: (818) 718-0760

Originally published in Prototyping Technology International, Issue 4 April/June '98