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Metal Injection Moulding (MIM) Slide Image 1

What is MIM?

MIM is a manufacturing process which is able to deliver near net-shape metal components by compressing metal powder in a special sintering process.

MIM offers significant cost savings compared to the use of conventional machining or electrical discharge machining. Used especially in the medical and automotive sectors, it can offer significant savings to customers.

Material cost savings and reduced cycle times

With minimal raw material waste, as well as reduced cycle times, MIM can reduce costs by more than 50%,it is currently seen as a strong and reliable solution for overcoming several important economic challenges. MIM offers high volume manufacturing of tightly-toleranced small metal components. Automotive and medical applications are two of the main sectors driving the increase in the demand for MIM components.

By using this MIM process, it is possible to combine several separate parts into one. This significantly reduces development time and effort and improves supplier tracking.

Using MIM it is possible to produce complex, three dimensional shapes that are difficult or near impossible to manufacture using conventional fabrication technologies. MIM provides for complex shapes in medium to high volume manufacturing process.

Metal Injection Moulding (MIM)

Metal Injection Moulding is an innovative manufacturing process in which fine metal powder mixed with a special thermoplastic binder is injected into a mould to form the required shape. The MIM component is ejected from the mould, the binder is then removed and then the component is sintered, to produce a high-density metal component. Whilst the design principles are broadly similar to those used for plastic injection mouldings and pressure die-castings, the properties that can achieved using the MIM process are far superior. MIM is ideal for high volume, small, complex geometry, thin wall metal components. Being a net-shape process, MIM is most competitive where costly machining operations can be avoided and where the number of parts required is sufficiently high to justify the cost of the mould.

The Four Stages In The MIM Process

    This involves the mixing fine powdered metal, typically less than 20 microns in size with a thermoplastic binder, to form a homogeneous mix. The ratio is typically 2/3 metal to 1/3 binder. This mix is then granulated to form an MIM feedstock which can be injected into the mould.
    The granulated mix (pellets) can now be loaded into an injection moulding machine. The machines used for Metal Injection Moulding, are very similar to those used in Plastic Injection Moulding, however the mould cavities are deliberately larger than the required finish dimensions to allow for contraction / shrinkage during the final sintering process. The mix is heated to give a soft consistency prior to being injected into the cavity. The component is cooled prior to being ejected then cleaned, de-flashed and laid out in trays ready for de-binding.
    The injected MIM parts in their ‘green state’ go through a two stage process to remove the Thermoplastic binder which was required to aid the injection moulding process. In the initial stage of de-binding, a proportion of the binder is removed to form an open pore structure. In the second stage a thermal de-binding / low temperature pre-sintering operation is carried out to remove the remaining binder leaving the MIM parts in the ‘brown state’ ready for sintering.
    The final stage is to sinter the brown MIM components in a high temperature sintering treatment furnace (typically 1200° to 1400°C), either in a controlled atmosphere or under a vacuum. This densification process causes the parts to shrink to 80-85% of their moulded size in a controlled manner, whilst releasing the surface energy stored in the fine powder and fusing the metal particles together to achieve components with a component density of around 97% of full density. This results in high density, high strength MIM parts.

Post Sintering

As with other primary metal manufacturing processes, a number of other secondary operations could be carried out to MIM components to add features or enhance properties.

Features of MIM Components.

Metal Injection Moulding applies the principals of injection moulding to the well-established technology of powder metallurgy and to produce complex components in steels and high strength materials with tight tolerances, fine surface finish and finely reproduced detail.


Complex Shapes, combine a number of simpler components together into a single component

Good Surface finish typically around 1.6µm.

Improved Mechanical Properties, with densities approaching that of wrought materials

High Production rates


Small Components Typically less than 0.1kg

Thin components typically 6mm max

Tooling costs and lead time.

Characteristics MIM P/M Die Casting Investment Casting Machining
Complexity High Low High Fair High
Min. Wall Thickness 0.5 mm 1mm 0.8mm 2mm 0.5 mm
Surface Roughness
1.6 μ m Ra
Fine Coarse Medium Medium
5 μm Ra
Mechanical Properties Good Fair Medium Fair Good
Varieties of Materials Many Many Few Average Many
Density 95 - 99% < 95% 99~100% 99~100% 99~100%
Accuracy High High Medium Medium High
Plating Quality Good Poor Medium Good Good
Productivity High High High Medium Low
Cost Medium Low Low Medium High

Suggested Tolerance for MIM parts

Dimensions in mm Suggested Tolerance
25.0 + / - 0.100
12.0 + / - 0.050
6.0 + / - 0.040
3.0 + / - 0.030
1.0 + / - 0.030