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Comparison for PM&PIM
The following is a multi-dimensional comparative analysis of Powder Metallurgy (PM) and Powder Injection Molding (PIM) processes, combined with the latest technological advancements in the industry (up to 2025):I
I. Comparison of Core Processes
PM | PIM | |
Process steps | Mixing → Uniaxial pressing (using a 300-800 ton press) → Sintering (at 980-1100℃) → Optional finishing / Oil immersion | Mixing (with twin-screw extruder) → Injection molding (at 80-200 MPa pressure) → Degreasing (chemical / thermal degreasing) → Sintering (at 1100-1400℃) |
Material properties | Particle size: 50 - 100 μm, density ≤ 92%, high porosity | Particle size: 2 - 15 μm. Density: ≥ 95%. Extremely low porosity. Capable of processing complex materials such as titanium alloys and ceramics. |
Production equipment | Mechanical press machine (production speed: 10 - 50 times per minute) | Special injection molding machine (locking force 50 - 500 tons), multi-cavity mold (128 cavities) achieving a cycle time of 20 seconds per piece |
II. Performance and Cost Comparison
Dimension | PM | PIM |
Part complexity | Suitable for two-dimensional symmetrical structures, but difficult to achieve thin-walled sections (less than 0.5mm) and internal structures | It can form complex structures such as 0.1mm thin-walled, cross-shaped holes, and three-dimensional hinges. The design freedom is close to that of plastic injection molding. |
Dimension accuracy | IT6-IT7 grade (±0.05mm to ±0.15mm), after sintering, the finishing process can achieve ±0.02mm | IT5 grade (±0.03mm), the precision of small parts is higher. It requires mold compensation technology to control the 15-20% sintering shrinkage rate. |
Surface quality | Surface roughness: Ra 1.6 - 6.3 μm. It requires polishing treatment. | Surface roughness Ra is less than or equal to 0.4 μm, which can directly achieve a mirror-like effect. |
Mould cost | The cost of simple molds is $300-$3000, while that of complex molds is $5000-$10000. | The cost of the mold ranges from $2800-$8500. With the division of the cost among multiple cavities, the cost per unit is significantly reduced. |
Unit cost | Simple parts cost $0.05-$3.50 (in large quantities), while complex parts will incur an additional 30% processing cost. | Complex parts: $0.1-$17.50 (for large quantities), integrated design saves assembly costs by over 40% |
IV. Technological Development Trends
• Powder Metallurgy:
1. Breakthrough in low-cost coarse-grained iron-based powder processing technology, resolving the problem of traditional MIM feeding fluidity
2. Digital Transformation: AI-driven pressing parameter optimization system, yield rate increased by 4.2%
3. Lightweighting: Expansion of aluminum-based composite material application, density reduced to below 2.5g/cm³
• Powder Injection Molding:
1. Titanium alloy 3D printing - Injection molding composite process, achieving integrated manufacturing of complex internal cavity structures
2. Green Manufacturing: Hydrogen-based direct reduction iron technology reduces carbon emissions by 35%, and the recycling rate of recycled powder reaches 80%
3. Ultra-precision: Minimum feature size of 0.05mm, meeting the manufacturing requirements for 5G radio frequency components.
V. Decision-making Recommendation Matrix
Scene | Recommended Process | Core Advantage |
Simple symmetrical structure, annual output > 100,000 pieces | PM | The mold has a low cost and a fast production speed (50 pieces per minute). The cost per unit can be as low as $0.07 |
Complex thin-walled structure, annual output > 1 million pieces | PIM | The design has high flexibility, and the integration reduces the number of components by 70%, while the overall cost is reduced by 30-50%. |
High-precision medical implants | PIM | Tolerance: ±0.03mm, Surface roughness: Ra ≤ 0.2μm, Compliant with ISO 13485 certification requirements |
High-temperature wear-resistant tools | PM | The hardness of sintered hard alloy is HRC 65+, and its cost is only 60% of that of the forging process. |
Titanium alloy lightweight parts | PIM | Can handle ultrafine titanium powder (5μm), with a density of 98% and tensile strength greater than 800 MPa |
Conclusion
I. For the mass production of simple-shaped parts: The efficiency of traditional powder metallurgy is often higher than that of powder injection molding. Traditional powder metallurgy commonly uses compression molding, which has a simple process. For example, to produce simple cylindrical, block-shaped or gear-like parts, the powder is compressed into the mold by a mechanical press and then sintered. The mechanical press compression molding is fast, capable of pressing multiple pieces per minute, making it suitable for quickly blanking a large number of standard parts. However, powder injection molding requires additional steps such as mixing binders and degreasing, and even though the single-piece molding is fast, the overall cycle is more time-consuming for simple parts.
II. For the mass production of complex small and precise parts: The efficiency and overall benefits of powder injection molding are superior. It can mix the powder with the binder to form a highly fluid feedstock, and then precisely inject it into complex cavities using an injection machine. It can produce complex shapes in one go, reducing the need for multiple processing and assembly steps. For example, when making small parts with deep holes, slots, or multiple curved surfaces, traditional powder metallurgy often requires multiple sets of molds for staged pressing or a large amount of subsequent processing. However, powder injection molding can achieve batch and rapid molding, with a single mold forming speed of about 1 to 10 pieces per minute.
III. For small batch production: Traditional powder metallurgy is highly flexible and has higher production efficiency. It does not require high upfront investment for small batch manufacturing. Based on the simplicity of the part, it can produce products through simple mold pressing and sintering processes. While powder injection molding can also produce small batch parts, the preparatory work for preparing the feedstock, designing the mold, and adjusting the degreasing and sintering parameters is cumbersome, and the cost and time consumption are not conducive to improving the efficiency of small batch production.
