For more than a decade, many rapid prototyping techniques have been used to make shells for Investment Casting. These techniques often involve direct molding (the mold is directly manufactured without processing).
The cost of direct molding and casting wax is significantly higher. However, without the processing requirements, the shell can be produced within a few days. As a result, the direct molding used for shape casting is used more and more in the industry. In fact, almost all foundries use this method.
1. Direct molding technology
Many rapid prototyping techniques can be used to make direct molds. The following four technologies are the main techniques for producing such molds, including:
Aluminium castings made from the shell shown in the picture
(1) Stereolithography light-curing stereoscopic molding technology - this process is often used to make a hollow member structure with six metal rib structures inside. When the hollow member is manufactured, the interior of the heated mold is cracked. In addition to this, the method of manufacturing the hollow member structure saves raw materials more than other conventional investment mold manufacturing methods. Although the resin used in this method is a thermosetting resin material and is not easily melted like a wax, it is still heated to melt.
(2) Thermal spray technology - This system is no longer used in the manufacture of workpieces is the use of inkjet technology to spray droplets of molten wax. Because it is still waxed, its use is very similar to that used by many foundry manufacturers today, and their casting process is very simple.
(3) Laser sintering technology - The laser sintering system mainly uses polyethylene powder when manufacturing molds. Although the finished workpiece is porous, wax is used to seal the shell when used as investment casting. The thermal spray mold must also completely melt the shell.
(4) SolidScape spray-wax three-dimensional forming system - another system that uses inkjet printing technology to make wax patterns. It can be used to make small, complex, high-precision workpieces. The Solidscape system is widely used to shape jewelry products.
2, advantage
The initial limitations regarding direct mold accuracy and surface smoothness limit the use of form casting. However, in the past five years, direct molding technology has been greatly improved in quality, which has a huge impact on the traditional wax molding technology. In this way, direct molding technology is used to cast products. It is estimated that more than 50,000 direct molds are cast every year in the world, and 40% of its market share has exceeded that of form casting.
For example, one customer asked Nu-Cast, of Londonderry, New Hampshire, to produce three sets of gimbals for securing camera equipment under an aircraft. Due to its strict weight limitations, the structure of the workpiece must be as hollow as possible, which complicates the structure of the workpiece. This workpiece cannot be manufactured by ordinary machining procedures unless many different parts are machined first and then welded together. Many fusible workpiece cores have to use wax mold technology. The total cost is about $85,000. After using direct molding technology, Nu-Cast not only simplifies the processing, but also delivers four weeks ahead of time while saving costs.
As expected, direct molding is used in those small quantities of processing because the total cost is much lower than the processing cost. In this case, for the foundry, not only the cost of the workpiece is reduced, but also the delivery time is greatly shortened.
More interesting, however, is the emergence of direct molding that allows foundries to enter the small-volume metal parts processing market that has never been seen before. These industries include military, aerospace, customs equipment, and the racing industry, as these industries often require metal parts that are small in number but complex in structure.
As a primary use for such use, investment casting can meet this requirement very easily. This requirement includes requirements for mold accuracy, surface finish requirements, and material properties. However, the higher cost of processing in the conventional manner makes the original molding technique unsuitable for investment processing.
Because there is no processing cost, low-cost direct molding technology is best suited for this type of processing. As a result, many large processing companies have the ability to process small batches of workpieces.
The development of product grade investment casting is changing the cost structure of investment casting. Although the cost of direct molding is higher than the cost of wax molding, direct molding eliminates the need for processing, so for the total cost of processing, direct molding is slightly less than wax molding, and this It often makes parts processing even more simple parts more competitive in the market.
Direct molding also has the advantage that other rapid prototyping methods do not have, that is, it can be used to machine parts with very complicated structures. As long as you can think of it, it can be manufactured, which is simply impossible with other rapid prototyping methods. Therefore, direct molding is often used to make those composite parts that were previously produced separately. And its benefits include a lot of cost savings.
3. Market development
At present, many foundries in the United States are vigorously developing this market. This is not only because this new approach can be a strong competitor to traditional processing, but also because they are filling the gap in this huge processing market.
In addition, this market is less susceptible to the fierce competition caused by the entry of foreign foundry companies. Unlike the injection molding market, foreign competitors have taken up a very large share of this sector due to the cheap labor structure. Due to the small size and increasing requirements for the production cycle, this processing market is difficult to be influenced by foreign foundries.
A few years ago, few people predicted that adding manufacturing technology would have such a large impact on existing processing procedures, and the market scope of its development was never before. But today, we are beginning to wait and see what impact it may have on other processing areas.
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