Rapid Manufacturing of Soft Mould Based on Rapid Prototyping

Resin products made by vacuum casting of silicone rubber molds
Resin products made by vacuum casting of silicone rubber molds

Rapid prototyping cannot completely replace the final product due to the limitation of the materials used in its manufacturing method. Therefore, products made of actual materials are still needed in terms of new product function inspection, market trial operation to obtain feedback from users after use, and low-volumn production. Therefore, the use of rapid prototyping as a master mold to remake molds and produce products with actual materials has produced Rapid Tooling-RT based on rapid prototyping.

The outstanding feature of using Rapid Tooling technology is its significant economic benefits.  Compared with the traditional CNC machining mold method, the cycle and cost are reduced by about 1/3~1/10, as shown in the following table. In recent years, the industry has invested more and more manpower and funds in the research and development of Rapid Tooling, and Rapid Tooling’s revenue has also grown tremendously.

Comparison of rapid tooling and traditional machining methods

Molding methodProduction cost/USDProduction cycle/weekMold life
Silicone rubber casting5230
Metal resin casting94~5300
Arc thermal spraying256~71000
Nickel Evaporation Deposition306~75000
Traditional machining6016~18250000

Classification and process of Rapid Tooling

Rapid Prototyping-based rapid mold manufacturing methods are generally divided into two categories: direct method and indirect method.
Direct molding method is to directly use RP technology to make molds. In Rapid Prototyping technology, the selective laser sintering method (SLS method) can be used to directly produce the metal mold. The steel-copper alloy injection mold made by this method has a life span of more than 50,000 pieces. However, in this method, the material shrinks greatly during the sintering process and is not easy to control, so it is difficult to quickly obtain a high-precision mold.

At present, most of the methods for rapid manufacturing of molds based on Rapid Prototyping are indirect molding methods. Indirect molding method refers to the use of Rapid Prototyping prototype to indirectly rebuild the mold. According to different materials, the molds produced by the indirect molding method are generally divided into two categories: Soft Tooling and Hard Tooling.

The soft mold  (such as silicone rubber, epoxy resin, etc.) used in it are different from the traditional steel materials. Due to its low manufacturing cost and short production cycle, it is highly valued in the development of new products as product function testing and market trial operation, as well as the production of single-piece and small-batch products in the fields of defense and aviation.  It is especially suitable for the modern manufacturing mode with small batches, many varieties and quick modification.
At present, the soft mold manufacturing methods proposed mainly include silicone rubber casting , metal spraying , resin casting and so on.

The number of soft mold production products is generally 50 to 5000 pieces. For tens of thousands or even hundreds of thousands of products, traditional steel molds are still needed. Hard molds refer to steel molds. RP prototypes are used to make steel. The main methods of molds include investment casting, electric discharge machining, and ceramic precision casting.

making molds based on RP master mold

Making prototypes or forming molds based on the one-time conversion casting of Prototype master mold

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