Powder Injection Molding | |
Powder Injection Molding (PIM) Powder injection molding (PIM) is a manufacturing solution for producing intricate parts in medium to high volumes (10,000 to over 2,000,000 parts annually) using fine (<20 μm) metal or ceramic powders. PIM is capable of transforming complex concepts & designs into high precision, high final properties, and net-shaped products from a wide range of materials such as carbon steels, low alloy steels, stainless steels, low expansion alloys (kovar and invar), tool steels, soft magnetic alloys, super alloys, to conductive materials (copper), and ceramics. PIM is well suited for parts weighing from 0.1gm to 250 gm. Cross sections are typically less than 0.25 in. (6.35 mm). However, parts are not restricted to this combination of mass and cross section. Tolerances are on the order of ±0.3 to 0.5%, albeit specific dimensions can be held as close as ±0.1%. |
Mixing | |
Very fine metal or ceramic powders are mixed with thermoplastic polymer (known as the binder) to form a homogeneous mixture of ingredients that is pelletized and directly fed into a injection molding machine. This pelletized powder-polymer mixture is known as feedstock. | |
Injection | |
In this process, the feedstock is heated to melt the binder content in order to form the desired component geometry. The molded part is known as the green part. | |
Debinding | |
The polymeric binder is removed from green part by thermal heating to approximately 400°C or 752°F. The result is known as the brown part that still contains its original geometry and size.
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Sintering | |
In this process, the brown part is heated to approximately 85% of the material's melting temperature, allowing densification and shrinking of the powder into a dense solid with the elimination of pores. The sintered density is approximately 98% of theoretical. The end result is a net shape or near net-shape metal or ceramic component, with properties similar to that of bar stock. |
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