AMT | Contrast and Comparison with Other Net-Shape Technologies

Date：2025-06-05   Views：1017

Table of Contents

Capability Overview

Technical Factors

Competitive Cost Factors

Relative Advantages

Capability Overview

Competing technologies determine the viability of powder injection molding (PIM). The first step in competition is based on capability—identifying which shaping technologies can form the component with desired features and properties. The second step focuses on cost—determining which technology is the most cost-effective for the intended production batch size. Process capability is always the first hurdle to overcome.

In this chapter, we address the competitive arena of PIM by first focusing on capability-based comparisons and then on cost-based considerations. PIM is a primary forming process suitable for creating original shapes. It is most effective for three-dimensional geometries and requires an economic batch size typically exceeding 5,000 units. Many of the larger firms will not accept orders below 100,000 units. For comparison, Figure 12.2 shows how PIM stacks up against other net-shape production technologies with respect to the economic batch size. Larger quantities are not a problem in PIM, but eventually piece cost no longer falls with order size.

The geometric aspects of PIM were introduced in Chapter Three, noting that almost all production is below 1 kg (2.2 lb), and the mean is just 32 g (0.07 lb). Likewise, the largest dimension is generally below 200 mm (8 inch), and 25 mm (1 inch) is fairly characteristic of the technology. Processing costs are best justified by shape complexity, so most PIM products range from 10 to 100 geometric specifications. Finally, the material needs to be designed for performance, so plastics, wood, rubber, minerals, and other low performance materials are not candidates for PIM - it excels with metals, ceramics, composites, cermets, and cemented carbides. Even after meeting these considerations, there remain a large number of possible net-shape processes against which PIM might compete.

Technical Factors

The three general means to create a three-dimensional shape are additive, subtractive, or replication processes. Additive processes like selective laser sintering are not cost-competitive for production quantities over about 10. Subtractive machining and grinding processes excel when the shape is simple, and the amount of material removed is small. Replication technologies such as PIM are most useful for mass production of three-dimensional shapes.

The following replication and subtractive approaches are considered for comparison with PIM:

• Powder injection molding

• Compacted powder processes (cold isostatic pressing, powder forging, die compaction)

• Deformation processes (hot forging, cold forging, stamping, fine blanking)

• Casting processes (die casting, sand casting, investment casting, thixomolding)

• Machining processes (milling, grinding, turning, drilling, boring)

Key factors for comparison include:

• Surface Finish: PIM offers better surface finish than casting techniques but is surpassed by fine machining.

• Possible Materials: PIM excels with metals, ceramics, composites, cermets, and cemented carbides.

• Shape Range: PIM is versatile in shape complexity but is generally limited in size compared to forging, casting, and machining.

• Size Range: Most PIM products are small, typically below 200 mm in the largest dimension.

• Batch Size: PIM is most cost-effective for batch sizes exceeding 5,000 units.

• Tooling Cost: PIM tooling costs are comparable to plastic tooling and are justified by large production quantities.

• Tolerances: PIM is competitive with most other technologies in terms of tolerances, although machining can achieve much tighter tolerances.

Figure 12.3 compares typical allowed tolerance ranges for several net-shape technologies. On an absolute basis, PIM is competitive with most other technologies, although machining is capable of much tighter tolerances.

Figure 12.4 plots typical surface finish ranges for several net-shape technologies. For comparison, PIM is better than casting techniques, but is surpassed by fine machining.

Competitive Cost Factors

Competitive technologies serve as the best benchmark for measuring the value of PIM. Process yield and material utilization are immediate advantages of PIM when compared with subtractive processes. In replication processes, there tends to be less waste, resulting in lower costs.

PIM often succeeds in delivering features that are difficult using alternative technologies, especially for smaller products. It is cost-effective for complex shapes and can lower manufacturing costs by a factor of 6 to 10 for complicated geometries.

The high tooling costs of PIM make machining more successful at lower production quantities. However, for mass production situations, the low piece price of PIM is attractive. Figure 12.7 illustrates the relative tool cost for PIM and several alternative net-shape technologies. At the lower production levels, PIM has a disadvantage; however, for mass production situations the low piece price is attractive.

Figure 12.5 is a schematic of the interplay between component complexity and production volume for several forming approaches. For a given complexity, a vertical slice through Figure 12.5 would show economic merit for PIM at higher production quantities. Advantages for PIM occur at lower quantities when the material is expensive or difficult to process by alternative techniques. Titanium fits this niche, because it is very difficult to machine. As an illustration of the underlying cost curves, Figure 12.6 plots the unit cost versus shape complexity for a batch size of 1 million units. It is the lower slope of the PIM curve that makes it attractive.

Relative Advantages

PIM has several advantages that make it a valuable manufacturing option:

• Overcoming Property Limitations: PIM overcomes the property limitations inherent to plastics, providing higher strength, stiffness, and thermal conductivity.

• Shape Complexity: PIM expands shape capabilities beyond stamping, forging, and fine blanking, allowing for intricate geometries.

• Material Versatility: PIM exceeds the property and shape range limitations inherent in powder compaction, offering a wide range of materials including metals, ceramics, and composites.

• Cost Efficiency: PIM provides lower costs compared with machining, especially for complex shapes.

• Productivity: PIM offers productivity levels not attainable with isostatic pressing and slip casting.

• Avoiding Defects: PIM avoids the defects, surface finish limits, and tolerance limits associated with casting.

The best applications for PIM are where plastic molding would be capable of forming the shape, but plastics lack the necessary mechanical, thermal, or other properties.