Metal Injection Molding（MIM)

Preparing the feedstock
The primary raw materials Metal Injection Molding are metal powders and a thermoplastic binder. The binder is only an intermediate processing aid and must be removed from the products after injection moulding. The properties of the powder determine the final properties of the Metal Injection Molded product.
The blended powder mix is worked into the plastified binder at an elevated temperature using a kneader or shear roll extruder. The intermediate product is the so-called feedstock. It is usually granulated with granule sizes of several millimetres, as is common in the plastic injection moulding industry.
Feedstock can either be purchased ‘‘ready to mould’’ from a number of international suppliers, or it can be manufactured in-house by a MIM producer if the necessary skills and knowledge are available.

Injection moulding
The ‘green’ MIM parts are formed in an injection moulding process equivalent to the forming of plastic parts. The variety of part geometries that can be produced by this process is similar to the great variety of plastic components.

Binder removal
The subsequent binder removal process serves to obtain parts with an interconnected pore network without destroying the shape of the components. The types of binder removal processes applied are further explained later in this introduction.
At the end of the binder removal process there is often still some binder present in the parts holding the metal powder particles together, but the pore network allows the evaporation of the residual binder quickly in the initial phase of sintering, at the same time as sintering necks start to grow between the metallic particles.

Sintering
The sintering process leads to the elimination of most of the pore volume formerly occupied by the binder. As a consequence, MIM parts exhibit a substantial shrinkage during sintering. The linear shrinkage is usually as high as 15 to 20%.
If required, sintered MIM parts may be further processed by conventional metalworking processes such as heat treatments or surface treatments in the same way as cast or wrought parts.
For certain applications, such as the automotive, medical and aerospace sectors, Hot Isostatic Pressing (HIP) can be used to completely remove any residual porosity. As MIM parts are typically small, this can be relatively cost effective for critical components.

More similarities to the final product without any secondary processing
Complex features/minute details often need secondary machining, but these can be usually obtained directly from the Metal injection molding process, without additional operations. Features like Undercut, Knurling, Threads, Angular Holes, Calligraphy, and complex profiles are easily achieved in MIM from the mold itself.

The Superpower to design and manufacture small and complex parts quickly
Since the MIM process allows us to mold the near-net-shape in which most cases do not require any secondary operations , it is fairly a quick way to manufacture complex components since the basic shape with features can be molded with lower cycle time. MIM utilizes multi-cavity . We can achieve Tight tolerances in metal injection molding process.

Integration using MIM
Usually, metal processing requires manufacturing of parts separately and then combining through welding, brazing, or press-fitting operations because of the design constraints, also the conventional method involves lots of material and energy wastage, but the MIM process allows to mold the near-net-shape of the part with all the desired intricate features like angular holes, slots, 3D profile.

Cost-effective
MIM process has no parallels when it comes to manufacturing small, highly complex, and intricate parts with profiles that are either impossible or cost-prohibitive with conventional techniques. To understand more effectively how the MIM is Cost-effective metal manufacturing.

Precision manufacturing even for higher annual requirements
MIM can result in eliminating process steps, thereby reducing product cost, making it feasible to manufacture complex parts in high volumes without the need for additional machinery and investment in infrastructure. Easily we achieve Consistent size and shape in MIM technology.

Very wide and efficient range of materials
The range of materials that can be processed in MIM is really wide and effective. It could be anything from stainless steel to high-speed steel, magnetic alloys to copper alloys, and surprisingly Tungsten. Special Rare metals, precious metals, and other types of high temperature melting alloys can also be used. MIM has limitations when it comes to low melting alloys like Aluminium, Zinc as it is difficult to remove binders in the sintering process.
INDO-MIM offers a wide range of 85+ material options, ranging from Tool Steel, Carbon Steel, Stainless Steel, Soft magnetic Steel, Superalloys, Titanium, and Cobalt chrome. We also have the capability of customizing the feedstock as per our customer/application requirements to achieve specific mechanical properties.

Higher Strength and Density
During the process of sintering, the part is heated to its recrystallization temperature, resulting in intermolecular fusion. The sintered part is denser and stronger than the raw form. After heat treatment, the finished product can achieve up to 98% theoretical density and mechanical properties comparable to a wrought form of the same base material.