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Product Details

1，什么是MIM？

 

 

 

MIM（金属注射成型）是金属注射成型的简称。将金属粉末及其粘合剂的增塑混合物注入模型中是一种成型方法。它是将选定的粉末与粘合剂混合，然后将混合物制粒然后注塑的形状。

 

 

 

您可能不知道MIM技术，但是您必须了解手机的金属卡夹。目前，手机的金属卡夹主要由MIM技术制成。

 

 

 

手机金属卡

 

 

 

 

 

2，MIM流程

 

 

 

MIM process combines the flexibility of injection molding design and the high strength and integrity of precision metals to realize the low cost solution of extremely complex geometric parts. MIM manufacturing process generally includes: mixing granulation, injection molding, degreasing, sintering and surface treatment to realize the production of parts, and determines whether surface treatment is needed for product characteristics.

 

 

 

MIM process flow

 

 

 

 

1. mixing and granulation

 

MIM is mainly made of fine metal powder, thermoplastic plastics and paraffin binder mixed in exact proportion. The mixing process is carried out in a special mixing equipment, and the binder is melted by heating to a certain temperature. Most of the time, mechanical mixing is used until the metal powder particles are uniformly coated with binder to cool, forming particles that can be injected into the cavity.

 

 

 

MIM mixing granulation

 

 

 

 

2. injection molding

 

The equipment and technology of injection molding are similar to injection molding. Granular materials are fed to the machine for heating and injected into the cavity at high pressure. The whole process can be carried out only when the binder is melted (fully integrated with metal powder) at about 200 ° C. the mold can be designed as multiple cavities to improve the productivity. The shrinkage of metal parts during sintering should be considered in the design of cavity size. The shrinkage changes of each material are accurate and known. MIM injection will produce a large number of nozzle materials, which can be reused by mixing with new materials.

 

 

 

injection molding

 

 

 

 

3. degreasing

 

Degreasing is the process of removing the binder from the forming parts. This process is usually done in several steps. Most of the binder is removed before sintering, and the remaining part can support the parts to enter the sintering furnace.

 

 

 

Degreasing can be done by many methods, and the most commonly used method is solvent extraction. The parts after degreasing have semi permeability, and the residual binder is easy to volatilize during sintering.

 

 

 

Degreasing

 

 

 

 

4. sintering

 

Degreased parts are put into a furnace controlled by high temperature and high pressure. The component is heated slowly under the protection of gas to remove the remaining adhesive. After the binder is completely removed, the part will be heated to a high temperature, and the void between particles disappears due to the fusion of particles. The component is oriented to its design size and transformed into a dense solid. For most materials, the typical sintering density is more than 97% theoretically. The high sintering density makes the product performance similar to the forging material.

 

 

 

sinter

 

 

 

 

5. surface treatment

 

The sintered parts will have certain flying edge. The main parts of the fringes can be removed by laser first, and then the surface treatment is carried out after sintering according to the specific requirements. Heat treatment can improve the physical properties of metal. Electroplating and coating can be applied to high density materials.

 

 

 

surface treatment

 

Before (left) sand blasting (right)

 

 

 

3、 MIM product features

 

 

 

1. complexity

 

MIM is the same as injection molding, and there is no limit to shape design. Because MIM is a forming process, additional product characteristics will not increase cost, which makes MIM an ideal way to combine independent parts into multi-functional products. MIM design rules are very close to injection molding, and are suitable for almost all products.

 

 

 

2. precision

 

The reference design of MIM net forming precision is usually ± 0.5% of the size. The net forming energy of some properties can reach ± 0.3%. As with other technologies, the higher the accuracy requirements, the higher the cost, so the tolerance requirements are encouraged to be relaxed appropriately when the quality permits. The tolerance that MIM primary molding cannot achieve can be realized by surface treatment.

 

 

 

3. weight and size

 

MIM is particularly suitable for parts with a weight of less than 100 grams, and less than 50g is the most economical. However, parts weighing 250 g can also be processed. The main cost of MIM process is raw materials, so MIM reduces the weight of components as much as possible through new technology. Like plastic products, the weight of parts can be reduced by means of the core and bracket without affecting the product integrity. MIM is outstanding in the aspect of small and micro components, and it is feasible to weigh less than 0.1g. Weight is not a limiting factor, and products with a length of more than 250mm can also be treated.

 

 

 

4. thinness

 

Wall thickness less than 6 mm is the best fit for MIM. Thicker outer walls can also be used, but the cost will increase due to the long processing time and the increase of additional materials. In addition, the thin-walled system with less than 0.5mm can also be implemented for MIM, but it has a high requirement for design.

 

 

 

5. output

 

MIM is a process with high elasticity, and the annual demand of several thousand to millions of production can be realized very economically. Like casting and injection molding, MIM requires customers to invest in tooling and tooling costs, so for small batches of products, it usually affects cost estimation.

 

 

 

6. raw materials

 

 

 

MIM可以处理许多材料，包括铁合金，超合金，钛合金，铜合金，难熔金属，硬质合金，陶瓷和金属基复合材料。尽管有色合金铝和铜在技术上是可行的，但通常以其他更经济的方式进行处理