Characteristics of MIM (Metal Powder injection Molding) products
Complexity.
MIM (Metal Powder injection Molding), like injection molding, has no restrictions on shape design.
Because MIM is a forming process, additional product features do not increase the cost, which makes MIM an ideal way to combine independent parts into multi-functional products.
MIM design rules are very close to injection molding, so they apply to almost all products.
Precision.
The reference design for the net forming accuracy of MIM (Metal Powder injection Molding 4) is usually ±0.5% of the size.
The net forming of some properties can reach ±0.3%.
As with other technologies, the higher the precision requirement, the higher the cost, so the appropriate relaxation of tolerance requirements is encouraged when the quality permits.
The tolerances that can not be achieved in one-time forming of MIM can be realized by surface treatment.
Weight and size.
MIM is especially suitable for parts weighing less than 100g, and less than 50g is the most economical.
However, parts weighing up to 250 grams can also be handled.
The main cost of MIM process is raw materials, so MIM uses new technology to reduce the weight of parts as much as possible.
Like plastic products, the weight of parts can be reduced through the core and bracket without affecting the integrity of the product.
MIM excels in tiny and miniature parts, and it is feasible to weigh less than 0.1g.
Weight is not a limiting factor, and products longer than 250mm can also be dealt with.
Thinning.
A wall thickness of less than 6 mm is most suitable for MIM.
A thicker outer wall is fine, but the cost increases due to long processing time and additional materials.
In addition, the extremely thin wall lower than 0.5mm can also be realized by MIM, but it has high requirements for design.
Output.
MIM is a flexible process, and the output with annual demand of thousands to millions can be realized very economically.
Like castings and injection molded parts, MIM requires customers to invest in moulds and tools, so cost estimates are usually affected for small batches of products.
Raw material.
MIM can handle many materials, including ferroalloy, superalloy, titanium alloy, copper alloy, refractory metal, cemented carbide, ceramic and metal matrix composites.
Although non-ferrous alloys aluminum and copper are technically feasible, they are usually treated in other more economical ways, such as die casting or machining.
The technological process of MIM
The MIM process combines the flexibility of injection molding design with the high strength and integrity of precision metals to achieve low-cost solutions for extremely complex geometric components.
The MIM process is divided into four unique processing steps (mixing, forming, degreasing and sintering) to realize the production of parts and components, and the surface treatment is required according to the characteristics of the product.
Mixing.
Fine metal powder with particle size less than 20 μ is mixed with thermoplastic and paraffin binder in a precise proportion.
The volume of metal powder and binder is about 60:40.
The mixing process is carried out in a special mixing equipment and is heated to a certain temperature to melt the binder.
In most cases, mechanical mixing is used until the metal powder particles are uniformly coated with a binder and cooled to form particles (called raw materials), which can be injected into the mold cavity.
Shaping.
The equipment and technology of injection molding are similar to those of injection molding.
The granular raw material is fed into the machine for heating and injected into the mold cavity under high pressure to form (green part) cooling and demoulding. Only when the binder is melted (fully fused with metal powder) at about 200C, the whole process can be carried out. The mold can be designed into multiple cavities to improve productivity.
The cavity size is 20% larger than that of metal parts to compensate for shrinkage during sintering.
The shrinkage change of each material is accurate and known.
Degreasing.
Degreasing is the process of removing binder from formed parts.
This process is usually done in several steps.
Most of the binder is removed before sintering, and the residual part can support the parts into the sintering furnace.
Degreasing can be done by a variety of methods, the most commonly used is solvent extraction.
The defatted parts are semi-permeable and the residual binder is easy to volatilize during sintering.
Sintering.
The degreased parts are put into a furnace controlled by high temperature and high pressure.
The component is slowly heated under the protection of the gas to remove the residual adhesive.
After the binder is completely removed, the component is heated to a very high temperature, and the gap between the particles disappears due to the fusion of the particles.
The part shrinks directionally to its design size and is transformed into a dense solid.
For most materials, the typical sintering density is theoretically greater than 97%.
The high sintering density makes the performance of the product similar to that of forged materials.
Surface treatment.
According to the specific requirements, some parts may need surface treatment after sintering.
Heat treatment can improve the physical properties of metals.
Electroplating and painting can be used in high density materials.
Provide welding or cooling treatment technology.
The article is for sharing only, does not represent the position of this site, if there is any infringement, please contact the editor to delete, thank you!
Characteristics of MIM (Metal Powder injection Molding) products
Complexity.
MIM (Metal Powder injection Molding), like injection molding, has no restrictions on shape design.
Because MIM is a forming process, additional product features do not increase the cost, which makes MIM an ideal way to combine independent parts into multi-functional products.
MIM design rules are very close to injection molding, so they apply to almost all products.
Precision.
The reference design for the net forming accuracy of MIM (Metal Powder injection Molding 4) is usually ±0.5% of the size.
The net forming of some properties can reach ±0.3%.
As with other technologies, the higher the precision requirement, the higher the cost, so the appropriate relaxation of tolerance requirements is encouraged when the quality permits.
The tolerances that can not be achieved in one-time forming of MIM can be realized by surface treatment.
Weight and size.
MIM is especially suitable for parts weighing less than 100g, and less than 50g is the most economical.
However, parts weighing up to 250 grams can also be handled.
The main cost of MIM process is raw materials, so MIM uses new technology to reduce the weight of parts as much as possible.
Like plastic products, the weight of parts can be reduced through the core and bracket without affecting the integrity of the product.
MIM excels in tiny and miniature parts, and it is feasible to weigh less than 0.1g.
Weight is not a limiting factor, and products longer than 250mm can also be dealt with.
Thinning.
A wall thickness of less than 6 mm is most suitable for MIM.
A thicker outer wall is fine, but the cost increases due to long processing time and additional materials.
In addition, the extremely thin wall lower than 0.5mm can also be realized by MIM, but it has high requirements for design.
Output.
MIM is a flexible process, and the output with annual demand of thousands to millions can be realized very economically.
Like castings and injection molded parts, MIM requires customers to invest in moulds and tools, so cost estimates are usually affected for small batches of products.
Raw material.
MIM can handle many materials, including ferroalloy, superalloy, titanium alloy, copper alloy, refractory metal, cemented carbide, ceramic and metal matrix composites.
Although non-ferrous alloys aluminum and copper are technically feasible, they are usually treated in other more economical ways, such as die casting or machining.
The technological process of MIM
The MIM process combines the flexibility of injection molding design with the high strength and integrity of precision metals to achieve low-cost solutions for extremely complex geometric components.
The MIM process is divided into four unique processing steps (mixing, forming, degreasing and sintering) to realize the production of parts and components, and the surface treatment is required according to the characteristics of the product.
Mixing.
Fine metal powder with particle size less than 20 μ is mixed with thermoplastic and paraffin binder in a precise proportion.
The volume of metal powder and binder is about 60:40.
The mixing process is carried out in a special mixing equipment and is heated to a certain temperature to melt the binder.
In most cases, mechanical mixing is used until the metal powder particles are uniformly coated with a binder and cooled to form particles (called raw materials), which can be injected into the mold cavity.
Shaping.
The equipment and technology of injection molding are similar to those of injection molding.
The granular raw material is fed into the machine for heating and injected into the mold cavity under high pressure to form (green part) cooling and demoulding. Only when the binder is melted (fully fused with metal powder) at about 200C, the whole process can be carried out. The mold can be designed into multiple cavities to improve productivity.
The cavity size is 20% larger than that of metal parts to compensate for shrinkage during sintering.
The shrinkage change of each material is accurate and known.
Degreasing.
Degreasing is the process of removing binder from formed parts.
This process is usually done in several steps.
Most of the binder is removed before sintering, and the residual part can support the parts into the sintering furnace.
Degreasing can be done by a variety of methods, the most commonly used is solvent extraction.
The defatted parts are semi-permeable and the residual binder is easy to volatilize during sintering.
Sintering.
The degreased parts are put into a furnace controlled by high temperature and high pressure.
The component is slowly heated under the protection of the gas to remove the residual adhesive.
After the binder is completely removed, the component is heated to a very high temperature, and the gap between the particles disappears due to the fusion of the particles.
The part shrinks directionally to its design size and is transformed into a dense solid.
For most materials, the typical sintering density is theoretically greater than 97%.
The high sintering density makes the performance of the product similar to that of forged materials.
Surface treatment.
According to the specific requirements, some parts may need surface treatment after sintering.
Heat treatment can improve the physical properties of metals.
Electroplating and painting can be used in high density materials.
Provide welding or cooling treatment technology.
The article is for sharing only, does not represent the position of this site, if there is any infringement, please contact the editor to delete, thank you!