mim precision ratchet wheel power tools - HR234

Metal Injection Molding (MIM) Process

The Metal Injection Molding process is a multi-stage process that converts fine metal powders into near full density, high strength metal components. MIM competes with cast, wrought, and machined metal components on the basis of both manufacturing cost effectiveness and material properties. The process consists of mixing fine metal powders with thermoplastic binders to form a feedstock which is injection molded into a closed mold. After ejection from the mold, the thermoplastic "binders"are chemically or thermally removed from the part so that the part can be sintered to high density. During the sintering process, the individual particles metallurgically bond together as material diffusion occurs to remove most of the porosity left by the removal of the binder. The sintering process shrinks the part, providing a net shape that can be used as-is or further worked to add additional features or improve tolerances.

Mixing

Metal Injection Molding feedstock begins with micron-sized metal particles. The metal powders are hot mixed with thermoplastics chosen to provide the necessary rheological properties for molding, mechanical properties for handling, and chemical and physical properties for ease of subsequent binder removal. Good feedstock formulations balance numerous conflicting cost and processing factors relating to both powder and binder selection.

Molding

Standard plastic injection molding machines are used to form Metal Injection Molding components. The feedstock is heated in the barrel to soften the powder/binder feedstock to a toothpaste consistency. This hot paste is injected into a closed mold cavity and cooled prior to ejection. Robotic pick-off is typically used to prevent handling damage. Runners and gates are reground and reused, minimizing scrap loss at the molding operation.

Debinding

Once the part is molded, the thermoplastic binders used to help the powder flow into the die are no longer needed and must be removed. First, a portion of the binder is removed to open up a pore network within the part. The remaining binder is subsequently removed through the open pore network that has been created. This two-stage process removes the binder without creating internal cracks or voids within the part. There are several effective binder removal methods in commercial practice, both thermal and chemical, each with its own set of advantages and limitations.

Sintering

After the binder is removed, the parts are heated in a protective atmosphere to a temperature high enough to create metallurgical bonds between the powder particles and cause densification. This process typically relies on solid state diffusion and/or liquid phase formation to drive the densification process. The parts typically shrink 15 to 20 percent from the original die size during sintering to achieve final component density of 96 to 98 percent of full density. Optimum sintering temperature depends on the material, typically 2200°F to 2550°F (1200°C to 1400°C) for ferrous materials.

Metal Injection Molding Applications

• Automotive Systems - Steering Columns (actuators, ignition lock components), Sun Roofs (stop cams), Seating Mechanisms, Solenoids, Fuel Injectors
• Orthodontics – Brackets, Buccal Tubes
• Medical and Dental Instruments – Endoscopic Surgical Instruments
• Firearm Components – Triggers, Sights, Safeties, Seer Blocks
• Ordnance – Guidance Fins
• Hardware and Lock Parts – Lock Cylinders, Bolts, and Sidebars
• Computers and Electronics – Disk Drive Components
• Electrical – Connectors, Switches

If you want us to produce your spare parts,pls kindly provide us the following information:

1.2D&3D drawings

2.the materials,surface treatment,and the hardness requirements

3,the quantities you want

4.the usage

5.any other requirements if you have any.