Application of rapid prototyping manufacturing technology Ⅱ

The Master Mold of the Rapid Mold

Another major application of rapid prototyping is as a master mold for rebuilding rapid economic molds, such as silicone rubber molds, polyurethane molds, metal spray film tools, epoxy molds and other soft molds for single-piece small batch trial production and casting plaster , Ceramics, metal-based synthetic materials, metal and other hard molds for mass production of plastic or metal parts. The use of rapid prototyping as a master mold of rapid molds is an extension of the economic benefits of rapid prototyping manufacturing technology and another bright spot.

1. Master mold of silicone rubber mold

Silicone rubber molds have outstanding advantages in low-volumn production of samples with fine patterns and no draft angle or even reverse draft angle. Almost all rapid prototypes can be used as master molds for silicone rubber mold production. The following figure shows an example of using the LOM prototype to rebuild the silicone rubber mold and quickly produce the product.

silicone rubber mold

2. Wooden mold for sand casting

The wooden molds of sand casting have always been made by traditional handwork, which has a long cycle and low precision. The emergence of rapid prototyping technology provides a good means for the rapid and high-precision production of wood molds for sand casting, especially based on
The production of complex-shaped wooden molds designed by CAD, and rapid prototyping technology show its outstanding superiority. The following figure shows the products of sand casting and the wooden mold made by rapid prototyping technology.

sand casting and the wooden mold

3. Master mold of epoxy resin mold

Epoxy resin molds are suitable for low-volumn products because of their low cost and larger number of parts than silicone rubber molds.
Trial production. The production of epoxy resin mold also requires rapid prototype as a master mold, which is made by casting resin materials and additional materials. The life of the mold can reach hundreds of pieces. The surface quality of the mold mainly depends on the surface quality of the prototype master mold, and the dimensional accuracy can be Achieve ±0. The picture below shows an example of a product made by an epoxy resin mold.

epoxy resin mold

Application in the field of Casting

Since the emergence of Rapid prototype technology, in addition to the wider requirements in the new product development stage, the application in the casting field has become more active. In typical casting processes such as investment casting, it has brought significant economic benefits to the manufacture of single-piece or small batch casting products.

In casting production, the manufacture of templates, core boxes, wax molds, die-casting molds, etc. often rely on mechanical processing. Sometimes a fitter is required to repair it, which is time-consuming and expensive, and the accuracy is not high. Especially thin-walled castings with complex shapes, such as blades of aircraft engines, marine propellers, cylinder blocks and cylinder heads of automobiles and tractors, etc. Mold manufacturing is a common problem.

Although the foundries of some large enterprises have also introduced some advanced equipment, such as CNC machine tools, profile milling machines, etc. But in addition to expensive equipment, the mold processing cycle is also very long. And because there is no good software system support, the programming of the machine tool is also very difficult.
In the face of today’s world economic market competition, product upgrades are accelerating, and it is difficult to adapt to the status quo of mold processing. The emergence of rapid prototyping manufacturing technology provides a promising new way to solve this problem.
At present, the application of rapid prototyping technology in casting mainly includes the following three aspects:

• Direct pouring castings

This method is suitable for single piece production with complex shapes, such as special castings in the aerospace industry, or to make one or two castings for further testing in the trial production of new products.
The specific operation is to cast the scapular prototype or use the investment casting method to make the shell and cast the casting, or use the lost foam casting method to directly cast the casting.

• Use the prototype to remake the master mold before pouring the casting

This method can be used when the number of castings is large. It first uses silicone rubber method, plaster type method, etc. to turn over the master mold, and then make a wax mold or directly cast into a casting. For example, the raw materials used in the SLS method are paraffin, nylon or polycarbonate, etc. The prototype sintered with polycarbonate material is better than paraffin in many properties, and can be used to make many complex and high-precision parts.
Chrysler Corporation and General Machines Corporation of the United States applied the SLS method to reduce the development cost of new automobile engine parts. Chrysler uses the SLS method to make wax molds to produce car intake and exhaust pipes with complex shapes. General Machines also uses this method to manufacture complex parts on spacecraft. The Rorketdyhe company in the United States even uses wax and nylon to make a complex six-cylinder cylinder block pattern, and then uses investment casting to produce castings

• Using Prototypes to Make Molds

This aspect is the most widely used and can be used for mass production of castings.
The Ford Motor Company of the United States uses the LOM method to manufacture a 685mm long automobile crankshaft model, which is first divided into three pieces, and then assembled into a template for sand casting, with a dimensional accuracy of ±0.13mm.

Investment Casting

Investment casting, also known as lost wax casting, is a kind of net shape manufacturing gold that can be made from almost all alloy materials.
It is a precision casting process for parts, especially suitable for the manufacture of thin-walled parts with complex structures. The emergence and development of rapid prototyping technology provides a guarantee for faster, higher precision, and more complex structure for the production of investment casting lost patterns. In particular, the QuickCast process developed by 3DSystems has highlighted the superiority of Rapid Prototyping technology in the field of investment casting.

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