What is Metal Injection Molding (MIM)?

What is Metal Injection Molding?

Metal Injection Molding (MIM) is established by fusing plastic injection molding and powder metallurgy techniques. The powder mix consists of a metal and a polymer binder. Using a standard injection molding machine, melt the powder and inject it into the mold. The part then cools and solidifies into the desired shape. The final product is used in many industries such as medical, dental, aerospace, and automotive.

Metal Powder Injection Molding Technology Basics:

Metal powder injection molding technology is the product of the penetration and intersection of multiple disciplines such as plastic molding technology, polymer chemistry, powder metallurgy technology, and metal materials science. MIM technology overcomes the shortcomings of traditional powder metallurgy products such as low density, uneven material, low mechanical properties, and difficulty in forming thin-walled and complex parts. It is suitable for the mass production of small metal parts with complex shapes, high precision, and high-performance requirements.

MIM metal powder injection molding is the addition of a metal, a ceramic powder is carried out in the production of plastic technology, which makes the product generally have high strength, and good wear characteristics. MIM manufacturing metal powder injection molding technology includes feed preparation, injection molding, computer simulation of the injection molding process, debinding, sintering, etc. The processing process is different from traditional injection molding, which requires vacuum sintering.

MIM, or metal injection molding, is a molding technique generally used to manufacture small, thin, lightweight, or complex metal parts that are used in a variety of industries and applications and possess several desirable metal properties. MIM is typically used by customers who require mass production of metal parts that are precise in size, shape, and weight, and durable in function or aesthetics. MIM technology is applied in powder metallurgy or through metal injection molding to metal rods. Equipment required for MIM injection molding: granulator, MIM special injection molding machine, degreasing furnace, sintering furnace, testing equipment, secondary processing equipment, etc.

MIM metal powder injection molding technology is a set of injection molding technology, polymer chemistry, powder metallurgy technology, metal material science, and other interpenetrating cross products. Which can use mold blanks for injection molding, and quickly manufacture high-density, high-precision, high-density through sintering strength, structural components with complex three-dimensional shapes. Especially for small parts that are processed by complex shape processing technology or are difficult to process, MIM metal powder injection molding technology can be freely completed. Metal powder injection molding is a new type of powder metallurgy technology with high technical content, making it more sensitive to the needs of mechanized production, good practicability, and good conversion rate, and has been widely used. The use of mold injection molding blanks and rapid production of high-density, high-precision, three-dimensional complex-shaped structural parts. Through sintering can quickly and accurately materialize design ideas into products with certain structural and functional characteristics, and directly mass-produce parts. It is a new revolution in the manufacturing technology industry.

The Whole Process of MIM Technology:

• Kneading: Mix the fine metal powder and organic binder uniformly to become an injection material with good rheological properties.
• Molding: The advanced MIM special injection machine is used to inject the injection material into the mold cavity with the shape of the part to form a blank. The process steps are similar to plastic injection molding.
• Debonding: The binder is removed from the green body by chemical solvent dissolution and thermal decomposition to become a gray body.
• Sintering: The ash blank is heated to a temperature lower than the melting point of the basic components in a certain atmosphere, so that the strength and density of the sintered body increase, and it becomes a product and material with good physical and mechanical properties.
• Post-processing: According to the needs of the product, follow-up processing, such as heat treatment, surface treatment, etc., is carried out.

MIM Technical Advantages:

• Added complexity, thinner, stiffer, denser, and more flexible designs.
• Better mechanical properties and strength than CNC machining and casting.
• More efficient than CNC machining, less waste is generated in the process, and most of them can be recycled or reused.
• Better surface finish than casting and traditional forging.
• Widely used in different metals and advanced materials.

Application Areas of MIM Technology:

• Computer and its auxiliary facilities: Such as printer parts, magnetic cores, striker pins, and drive parts.
• Tools: Such as drill bits, cutter heads, nozzles, gun drills, spiral milling cutters, punches, sockets, wrenches, electrical tools, hand tools, etc.
• Household appliances: Such as watch cases, watch chains, electric toothbrushes, scissors, fans, golf heads, jewelry links, ballpoint pen clamps, cutting tool heads, and other parts.
• Parts for medical machinery: Such as orthodontic frames, scissors, and tweezers.
• Military parts: Missile tail, gun parts, warhead, medical cover, fuze parts.
• Electrical parts: Electronic packaging, micro motors, electronic parts, sensor parts.
• Mechanical parts: Such as cotton loosening machines, textile machines, crimping machines, office machinery, etc.
• Parts for automobiles and ships: Such as clutch inner ring, fork sleeve, distributor sleeve, valve guide, synchronous hub, airbag parts, etc.

Difference Between MIM and Casting:

Metal injection molding is suitable to produce small and complex metal parts that cannot be produced by traditional processes. This is not a problem if the part has intricated, thin, or fine design details. The metal does not melt in the MIM process as you know it in the metal casting process, extending tool life.

Why choose MIM overcasting? The biggest difference between casting and metal injection molding is that casting uses aluminum alloys or zinc alloys as raw materials. Metal injection molding, on the other hand, uses steel or other types of suitable MIM alloys. The most common are stainless steel, titanium, nickel, tungsten, copper, and combinations thereof. At the end of the die-casting process, the excess metal must be trimmed manually or passed through a different mold. This creates a lot of waste and requires extra time, which is not the case with MIM processes. Both MIM and casting have their technical advantages and disadvantages, and the right solution can be selected based on product or part design, batch, and production run requirements.