MIM technology has added advantages with reference to design flexibility, dimensional accuracy, and material performance capabilities for applications in the automotive segment. Engine components such as turbochargers, fuel injectors, automotive access controls and also components for vehicle safety system are few such examples of MIM components used in automotive applications. Complex geometries with close dimensional tolerances along with superior material properties and shape making capabilities drawn from plastic injection molding can be manufactured through Metal Injection Molding . A wide range of materials – from low alloy steels to high-temperature steels and superalloys – that are hard and expensive to machine, can be processed.
Typical applications of MIM components used in an automotive are as shown in Figure 1. MIM components are also used in applications such as lock caps and lock shafts, housings, cams for electric seating and bonnet lock parts. MIM components could potentially replace multiple single engine components made from conventional technologies to an integrated assembly, resulting in significant cost savings.
Selection of the proper material for a particular application is decided based on the functional and technical requirements of the component. Table 1 lists the materials used for applications with their properties.
Typical properties & application
|Low alloy steels||Low Carbon, Case Hardening||4600 series (Fe-Ni-Mo)||Value High toughness & good surface wear resistance|
General engineering applications
|Med Carbo, Through Hardening||4630-4605 (Fe-Ni-Mo-Cr)||High strength General engineering applications|
|High Carbon, Through Hardening||4680, 52100||High strength & high wear resistance Bearing steel|
|Stainless steels||Austenitic||304L, 316L||Column 4 Value 4 Best corrosion resistance, High ductility|
watch links, medical devices parts, food processing equipment parts,Medical & dental device, marine components & non-magnetic housings
|Martensitic||410, 420, 440A/B/C||High strength & wear resistance and medium corrosion resistance|
Multi-utility hand tools, mobile phone components
|Precipitation hardening||17-4PH||Medium strength & wear resistance and good corrosion resistance|
Sporting weapons, mobile phone
Components, general engineering applications
properties with medium corrosion resistance
Magnetic probes, sensors, armatures and pole piece
|Tool steels||Die steels||S-7, D-2||High strength & wear resistance|
Hydraulic slides, high wear-resistant applications
|High-speed steels||M-2, T-15, 10-V|| High strength & wear resistance|
Hydraulic slides, high wear-resistant applications
|Non-ferrous||Copper||Cu + Ni-Sn combinations||High thermal and & electrical conductivity|
|Titanium||CP Ti, Ti6Al4V||Lightweight, high strength, and best corrosion resistance|
|Refractory alloys||Tungsten base||W+ Cu-Ni-Fe combinations||High density|
|Specialty and superalloys||Magnetic materials||Si-Fe, Fe -49 Co-2V||Good Soft magnetic properties|
|Electronic packaging materials||Kovar, Fe-Ni (Invar)||Low thermal expansion|
Following examples show how MIM has effectively introduced value addition and value engineering in few of the critical automotive applications.
1. Proportional Valves in Off-high way Vehicles:
Catcher, tension bar, new base cap & body—. These automotive components are used in proportional valves found in hydraulic circuits of off-highway and farm equipment. The two parts forming the new base and body are made of MIM 17-4 PH stainless steel, while the catcher and tension bar are formed of 4605 low-alloy steel. These parts were formerly produced via machining, welding, conventional PM, and fastening. The conventional manufacturing method led to multiple operations, resulting in increase in the lead time for manufacturing and wastage of raw material. All dimensions of the two parts forming the new base are achieved in the as-MIM condition, including the internal thread in the body. The catcher receives a grinding and burnishing operation to attain the OD tolerance and surface finish, while the tension bar needs no secondary operations. The external threads are also achieved as MIM. Heat-treated properties include a minimum density of 7.5 g/cm³, 1,550 MPa ultimate tensile strength, yield strength of 1,400 MPa, 3% elongation, and 42–48 HRC hardness range. By completely re-designing the parts to maximize the advantage offered by Metal Injection Molding, the customer obtained cost savings estimated at 65% of previous manufacturing route, with annual production of 350,000 pieces.
Fig 1: MIM components in proportional valves for off highway vehicles
2. Shock Absorbers:
The steel top plate that goes into shock absorbers of a particular automobile is developed by MIM. The complexity of the part with its 18 holes and six thin ribs connecting to a ring around a central hole presented a challenge to complete filling. The gating and venting system played a key role in producing this part defect free. It is produced close to net shape, with surface grinding to achieve flatness and a facing operation to achieve height tolerance being the only additional secondary operations performed. The material used is MIM 4605 low carbon alloy. After heat treating, the part has a density of 7.5 g/cm³, ultimate tensile strength of 1,550 MPa, yield strength of 1,400 MPa, elongation of 3%, and a hardness range of 42–48 HRC. This application is a new design for MIM and delivers increased repeatability/accuracy of the shock absorber over the previous machined version, with estimated cost savings of 25%.
Fig 2: Steel top Plate – Shock absorber Application
3. Diesel Fuel Pump
The pinion ring that goes into the metering valve in diesel fuel pump is manufactured through MIM. The material used is MIM 8620, which is a low carbon steel. The critical profile with multiple functional features make it an excellent candidate for MIM. This component was previously manufactured through the machining route and had to go through the operations of bar stock machining, slot cutting, gear cutting, chamfering and threading. These multiple machining operations resulted in increased cost and lead time, which was a pain point for the customer as the components were required in large volumes. The entire profile is now produced in MIM without any secondary operation, including the internal thread made possible through the thread inserts used in the molding tool. The following advantages are realized after migration to MIM: 1. higher repeatability 2. reduction in raw material wastage by 60% 3. No machining burrs on functional area 4. Cost savings of 40% MIM as a technology is very adaption friendly and could be applied to any sector with ease.