When considering metal part manufacturing technologies, metal injection molding (MIM) and traditional machining are two common and functionally diverse methods. To help understand the suitability of both methods and their advantages and limitations, this article will explore in detail the differences and connections between MIM and machining, as well as the key factors that should be considered when choosing a suitable production technology.
Comparison of technical principles
MIM Metal Injection Molding is a new process combining powder metallurgy technology and plastic injection molding technology. For mass production of precision, complex metal parts and some metals that cannot be produced by die casting (such as stainless steel and other low alloy steels).
Machining: Removing material from a metal block by cutting, drilling, milling, etc., to gradually carve out the desired part shape. This method is flexible and works with a wide range of materials, but can be less costly and efficient when producing complex shapes or high-volume products.
Main advantages and applicable scenarios
Advantages of MIM:
Complexity and precision: MIM can produce complex geometric shapes that are difficult to achieve by mechanical processing, such as internal hollow structures, fine meshes and complex three-dimensional shapes.
Economies of scale: For high-volume production, the unit cost of MIM decreases significantly as production volume increases because once the mold is made, it can be used repeatedly.
Material utilization: Since it is directly formed from the slurry, MIM produces almost no waste of raw materials and is more in line with the requirements of sustainable production.
Advantages of machining:
Material and design flexibility: Can process almost all types of metal materials, suitable for producing prototypes or equivalent production of smaller products.
Precision and surface treatment: High-precision processing capabilities make the surface of machined parts smooth and the details processed.
No upfront investment required: no specific molds are required, suitable for low-volume or customized production.
Cost, efficiency and environmental factors
Cost-benefit analysis:
MIM: The initial mold cost is higher, but it is suitable for long-term mass production. Particularly cost-effective when producing complex components.
Mechanical processing: The cost of a single piece is fixed, no additional mold costs are required, and it is suitable for small batch production. However, as the complexity of the parts increases, the cost rises sharply.
Productivity:
MIM: Once the mold and process parameters are set, the production speed is fast and large-scale production can be quickly achieved.
Machining: The processing speed depends on the complexity and quantity of the parts. For complex or large parts, the production efficiency is lower.
Environmental impact:
MIM: Lower material waste and energy consumption, better performance in terms of environmental sustainability.
Mechanical processing: produces more metal chips and cutting fluid waste, which puts greater pressure on the environment and resources.
Commonalities and Differences From MIM to Machining
MIM parts and machining parts are widely used in arms, aerospace, machinery manufacturing, medical and other industries. However, the MIM process offers many advantages for machining unsolvable precision components. Especially if the parts are likely to be smaller and require more maneuverability. Material selection, geometric design, purchase quantities, tolerances, and tooling costs are all important factors in the decision-making process.
1.Material
MIM materials are processed under high temperatures and pressure, which can efficiently mass-produce small, precise, and high-performance parts. It can ensure that MIM parts have good mechanical properties, excellent strength, and ductility. Can be customized according to the customer’s material composition. Such as low alloy steel, carbon steel, stainless steel, nickel alloy, tool steel, tungsten alloy, titanium alloy, etc. Especially for surgical instruments, artificial joints, cardiac pacemakers, etc.
2.Unique geometry
Many unique geometric shapes can be designed for MIM parts, and even several related parts can be designed into a complex part. Machining is often difficult to machine complex components. Also, as a component becomes more complex, the more machining time it takes to manufacture it, the more expensive the machining.
3.Quantity of parts
MIM is a high-quantity manufacturing product, especially a product with an annual purchase quantity greater than 50,000 pcs. Since the Machining process time is fixed, theoretically, from 5,000 pcs to 10,000 pcs, processing equipment needs to be doubled. But for the powder metallurgy process, it is only to increase the injection time of the product, increase the number of caves in the mold, and sinter several times. Therefore the quantity is larger because it can be machined at a much lower cost than comparable machined parts.
4.Tolerance
The tolerance in the case of MIM +/-0.3% (ie 1.000” +/-.003”). And these tolerances increase in proportion to the size of the features. Machining tolerances can be as low as +/-0.005, with capabilities as low as +/-0.001. As a result, CNC machines can produce fewer error-prone parts.
5.Mold Cost
The need for MIM parts is based on mold production. This means that there must be an upfront cost of tooling production, but this cost can be quickly recouped when amortized for high-volume production. Therefore, it is recommended that products with a quantity of more than 5000 pcs, be machined. Of course, it should be considered according to the actual product structure and processing cost.
Here is a table outlining the differences between Metal Injection Molding (MIM) and Machining:
| Characteristic | Metal Injection Molding (MIM) | Machining |
|---|---|---|
| Process | Uses a mix of metal powder and polymer binder, injection molded, then debinded and sintered to achieve full density | Removes material from a solid metal block through cutting, drilling, milling, etc., to form the desired shape |
| Applicable Materials | Suitable for various metals and alloys, such as stainless steel, titanium alloys, cobalt-chrome alloys, etc. | Suitable for a wide range of metals and alloys, such as aluminum, steel, stainless steel, brass, titanium, etc. |
| Production Efficiency | High efficiency, ideal for mass production of small, complex, high-precision parts | Medium to low efficiency, suitable for small batch or custom production of larger parts |
| Complexity and Precision | Can produce very complex geometries with high precision (±0.5%) | Suitable for high-precision parts, especially simple to moderately complex geometries |
| Material Utilization | High material utilization (minimal material waste) | Lower material utilization (significant material is removed) |
| Cost | Low-cost process for large-scale production, but high upfront mold costs | Low to medium cost, especially for small-batch or one-time production |
| Suitable Product Types | Ideal for producing small, complex, high-precision parts (e.g., medical device components, electronic parts) | Suitable for producing larger parts with higher requirements (e.g., aerospace components, automotive parts) |
| Production Speed | Time-consuming upfront mold production, but very fast production once molds are ready | Relatively slow, especially when parts are highly complex |
| Surface Finish | High surface finish, but may require post-processing to meet extreme surface requirements | Can achieve very high surface finish, usually without additional processing |
| Flexibility | Limited flexibility in design changes due to upfront mold production | Highly flexible, allowing for quick design adjustments as needed |
| Common Defects | Shrinkage, porosity, deformation, uneven sintering shrinkage | Burrs, tool marks, deformation due to thermal stress |
| Environmental Impact | More environmentally friendly, less waste, and lower energy consumption | More waste, high energy consumption, and environmental concerns with cutting fluids |
This table summarizes the main differences between Metal Injection Molding and Machining, helping you better choose the appropriate manufacturing process.
Therefore, the MIM process is very suitable for the production of products that meet the following requirements:
- Unique geometry;
- Large purchase volume;
- Miniaturized products;
- High precision;
- Stable product quality.
Tags Metal Injection Molding | MIM Materials | Design
Metal Injection Molding – Source: Wikipedia