How to choose the Vacuum casting molding and low-pressure infusion processing methods for small-batch spare parts?

Vacuum casting molding and low-pressure infusion are common methods for spare parts processing. The principles of the two seem similar on the surface. Make an original version by CNC machining or 3D printing. If the structure is more complicated, you can use 3D printing to make the original version, and then use the original version to make a silicone mold, and then use this silicone mold to make batch copies, but in fact, there are still certain differences between the two. Let me analyze the difference between the two processing methods of Vacuum casting molding and low-pressure infusion.

  1. Vacuum casting mold

Vacuum casting molding is a relatively common processing method that uses the original template to make a silicone mold in a vacuum state, and pours it with PU material in a vacuum state, so as to clone the same replica as the original template. It is mainly used for small batch customization of plastic spare parts, generally dozens to hundreds of plastic spare parts, it is more cost-effective to process in this way.

Product material performance can simulate the performance of most existing engineering materials. Common materials include PU, transparent PU, soft PU, Saigang, ABS, PP, PC high-temperature-resistant ABS, etc. At the same time, transparent parts such as PC and plexiglass can be copied. , Thermoplastic elastomer TPR, TPR, TPU, etc. and various soft materials such as silica gel, rubber, etc.

There are hundreds of materials to choose from, and different design hardness and surface texture can be realized. The complex molded products can be completely opaque or translucent, or completely transparent, which can meet various design requirements.

At the same time, various colors can be added to the reproduction products to meet various appearance needs. Product replication is not affected by volume, complexity, various structures, etc. It is easy to open the mold, the cycle is short, and the effect is quick. Vacuum casting molding is a manufacturing method based on prototype opening and duplicating products, with low cost and stable product quality. Vacuum composite molds are ideal for rapid engineering testing, design proof of concept, sales and presentations, etc.

small batch spare parts vacuum casting
small batch spare parts vacuum casting

Vacuum casting

Step 1: Make a Prototype

First, we need a prototype or sample. Samples can be made of any stable material, provided by the customer or manufactured by 3D printing. Common prototypes are made of plastic or metal materials, and the only requirement is that the material needs to be stable for a certain period of time at a high temperature of 40°C. We suspend the prototype in a casting box and pour silicone. The pouring box is then placed in an oven heated to 40°C until the silicone is fully cured. Cut the fully cured silicone mold along the parting line and take out the prototype.

Step 2: Manufacture the product using the mold

During the mold manufacturing process, our skilled workers designed many fine holes around the prototype. These small holes can play the role of exhaust during the mold-forming process. After the prototype is taken out, a cavity will be formed in the middle of the silicone mold, and the shape of this cavity is exactly the same as the prototype.

According to your design requirements, use various complex molding materials to pour into the cavity of the mold. After the cavity is filled, put the mold into a vacuum environment to remove the air in the cavity and fill every position of the mold with liquid silicone to ensure that the shape of the molded product is completely consistent with the prototype. Finally, the mold has to be put into the oven to cure, so that a strong and stable replica of the prototype can be finally obtained.


The tolerances of duplicate molded products mainly depend on the accuracy of the prototype, the geometry of the product and the selected manufacturing materials. Generally, 0.15% shrinkage is acceptable.

low pressure perfusion

Low-pressure infusion (Reaction Injection Molding), also known as low-pressure reaction injection molding, is a new process applied to rapid molds. It mainly mixes two-component polyurethane materials and injects them into rapid molds at room temperature and low pressure. Chemical and physical processes such as polymerization, crosslinking and curing form products. It has the advantages of high efficiency, short production cycle and low cost. It is suitable for small-batch trial production in the product development process, as well as the production of small-batch production, relatively simple structure covering parts and large thick-walled and uneven wall-thickness products.

Advantages of Vacuum casting

Vacuum casting molding is the most ideal way of rapid manufacturing small batches:

No need to invest high initial cost to manufacture molds
Excellent reproduction of molds, excellent product surface detail, and little or no post-processing required
Many different molding polymer materials are available, and the required colors can be formulated according to the requirements
After the prototype is produced, the mold can be completed within a few days
Mold strength can meet 50 times production
Lagging allows plastics of different materials and hardness to be integrally formed

low pressure perfusion

European and American countries, where low-pressure perfusion is used most, have more mature perfusion technology than materials. China was the first to use low-pressure perfusion for the automotive industry. In recent years, there are relatively more low-pressure perfusion processes in domestic medical product production and instrument production…

Because the production quantity of instruments and medical products is not large, the sales volume of a product is dozens or hundreds of sets a year. If the steel mold injection molding cost is relatively high, there are many medical products with relatively thick wall thickness. If the wall thickness is not uniform, it is not suitable for the injection molding process, the surface is more complicated, and it is not suitable for the blister process, but the low-pressure infusion is different, it can be infused with thick-walled products, and the wall thickness can be uneven products, normal perfusion wall The thickness (5-6mm) can be about 30mm at the thickest.

There are many materials used in the mold (aluminum mold, resin mold, plastic mold, plaster mold, etc.), and there are many choices of pouring materials, including imported materials, domestic materials, materials close to ABS, and materials close to pp.

Advantages of Low-Pressure Perfusion

Low-pressure perfusion is relatively advantageous for large parts with relatively simple structures. But one thing is certain, the material performance of low-pressure infusion is relatively much better than that of vacuum casting. No matter the hardness. The toughness and temperature resistance are much superior, and the price will be more expensive.

For small batch production, it is recommended to choose the production method of Vacuum casting molding. For mass production, it is better to choose low-pressure perfusion. If you have more questions, please contact our engineers to provide you with better service.

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