TECHNOLOGY
MIM vs. ...
Metal injection moulding has much in common with the well-known plastic injection moulding. MIM technology allows designers to combine the freedom of form of plastic injection moulding with the superior properties of metal. The diagram shows the cases for which MIM is the optimal production technique: high product complexity in relatively large quantities. During the process, MIM’s great freedom of form makes it possible to combine functionality and aesthetics in parts with high-quality material properties.
The following briefly describes the differences between MIM and other production techniques and the advantages – with the emphasis on the differences with MIM. Obviously, the optimal production technique for a specific part depends on the requirements, quantities and numerous other aspects.
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comparison with other techniques.
MIM vs. additive manufacturing (AM).
3D printing, or additive manufacturing (AM), is the technology everyone is talking about. Metal powder is melted, either directly with a laser or with the addition of a binder to first print and then debind and sinter the part. So, a complex metal part can be made quickly and without additional tools. Will AM completely replace MIM? We don’t think so. In fact, AM will increase the use of MIM because the two techniques are complementary and start from the same base material (powdered metal).
With AM, designers can quickly create complex prototypes to see, feel and test their designs. Once the prototyping phase is complete, the product is launched and demand for the complex parts increases, production can be switched from AM to MIM. When parts move from single pieces and prototypes to series production, MIM then has further advantages: higher surface quality, homogeneous material properties and the fact that post-processing requires less work.
| MIM | AM | |
|---|---|---|
| Freedom of form | ++ | +++ |
| Part size | 1-100 mm | 1-100+ mm |
| Batch size | 1000-1M+ | 1-1000+ |
| Surface quality | ++ | – |
MIM vs. CNC milling.
Rapid production of prototypes and medium quantities is possible with CNC milling because no mold is required. Large quantities can be produced economically with CNC milling when the part design is simple. When tight tolerances over larger distances are required, CNC milling is the optimal production technique. However, MIM can be more beneficial when part design becomes more complicated and production numbers increase. A typical reason to switch from CNC milling to MIM presents itself when multiple CNC parts can be merged into a single MIM part.
| MIM | CNC | |
|---|---|---|
| Freedom of form | ++ | + |
| Part size | 1-100 mm | 1-1000+ mm |
| Batch size | 1000-1M+ | 1-1000 |
| Material properties | ++ | ++ |
MIM vs. die casting.
MIM and die casting have many similarities: both techniques use a die and produce high-quality, complexly shaped metal parts in large quantities. The main difference is in the materials. Injection moulding is limited to aluminum, magnesium, zinc and related alloys, while MIM works with (stainless) steel, nickel and cobalt-based alloys, titanium, copper and various other (exotic) materials. This difference is related to the casting process. In die casting, a liquid material is injected directly into a die. In MIM, on the other hand, a metal powder is injected using a polymer bonding system, followed by a debinding and sintering step.
| MIM | Diecasting | |
|---|---|---|
| Freedom of form | ++ | ++ |
| Part size | 1-100 mm | 1-500+ mm |
| Batch size | 1000-1M+ | 1000-1M+ |
| Material properties | ++ | + |
MIM vs. investment casting.
In investment casting, a copy of the desired part is made in wax for one-time use as the basis for producing a die. Liquid metal is poured into this mold, the part is removed and reworked. In terms of dimensions, accuracy, typical production numbers and material selection, lost wax casting and MIM are very similar. In general, MIM is slightly more cost-effective for production numbers above 100,000 pieces per year. For large wall thicknesses and parts with a relatively large mass, investment casting is preferable, while MM stands out with a better surface finish and the ability to make thinner walls.
| MIM | Investment casting | |
|---|---|---|
| Freedom of form | ++ | ++ |
| Part size | 1-100 mm | 1-200+ mm |
| Batch size | 1000-1M+ | 1000-100k |
| Material properties | ++ | + |
MIM vs. powder pressing.
In Powder Pressing, a fine metal powder is pressed into a mold using a die and then sintered. This results in a repeatable process for producing large quantities of precise parts. This technology is primarily used to produce gears, pulleys and levers. These are examples of parts that require high accuracy in the X and Y directions but have fewer requirements for accuracy and other properties in the Z direction, the direction of pressing force. However, pressing limits the design freedom for this technique: undercuts, accurate dimensions in the pressing direction and varying wall thicknesses are not possible. After sintering, the residual porosity of pressed parts affects their material strength and suitability for applications requiring fully dense material.
| MIM | Perssintering | |
|---|---|---|
| Freedom of form | ++ | – |
| Part size | 1-100 mm | 10-500+ mm |
| Batch size | 1000-1M+ | 1000-1M+ |
| Material properties | ++ | ++ |
MIM vs. stamping/extrusion.
When large numbers of parts with a flat or continuous profile are required, nothing beats stamping/extruding for cost effectiveness. However, the design freedom for this technique is limited. It is not unusual for a stamped part to be combined later in production with other parts, such as rivets or bolts, to form a sub-assembly. The total cost for such a composition usually exceeds the cost of a single MIM part that combines all these functions.
| MIM | Stamping / extrusion | |
|---|---|---|
| Freedom of form | ++ | – |
| Part size | 1-100 mm | 1-1000 mm |
| Batch size | 1000-1M+ | 1000-1M+ |
| Material properties | ++ | + |