MIM Additive Manufacturing
Table of Contents
mim additive manufacturing refers to an industrial process to produce small, complex metal parts at high volumes. A composite metal powder feedstock is molded into a green-state shape using injection molding equipment, debound, and then sintered to achieve full density.
MIM leverages the geometric flexibility of polymer injection molding and green-forming with the performance capability of metal alloys. With additive manufacturing processes expanding options, this guide covers MIM compositions, properties, applications, specifications, process flows, suppliers, tradeoffs, and FAQs.
![MIM Additive Manufacturing 1 mim additive manufacturing](https://met3dp.com/wp-content/uploads/2023/10/H13-Powder.jpg)
Composition of MIM Alloys
Many compositions are available as MIM feedstocks:
Material | Common Alloys | Overview |
---|---|---|
Stainless steel | 316L, 17-4PH, 420 | Corrosion resistant, high hardness, for medical uses |
Tool steel | H13, P20 | High strength, heat resistance, for molded tooling |
Aluminum alloy | 2024, 6061, 7075 | Lightweight, high strength-to-weight ratio |
Titanium alloy | Ti-6Al-4V | Lightweight with corrosion resistance and high strength for aerospace uses |
Nickel alloy | Inconel 625 and 718 | Heat/corrosion resistance suited for turbo machinery |
Tungsten | WHA, WC | Extremely high density perfect for balancing applications |
Both standard and custom formulations are available depending on needs.
Properties of mim additive manufacturing
In addition to composition tailored to performance requirements, key resulting properties include:
Property | Description |
---|---|
Density | Ranges from near pure metal density to greater than 95% theoretical density |
Tensile strength | 250 MPa to over 1300 MPa depending on reinforcement strategies |
Hardness | Up to 70 HRC achieved based on alloy choice |
Corrosion resistance | Varying resistance levels possible based on compositions selected |
Surface roughness | As molded <6 μm Ra up to <0.2 μm Ra after plating/polishing |
Complex geometry | Molding allows intricate shapes unachievable with other processes |
Feature resolution | Small slots, holes, threads down to ~100 μm » achievable |
Wall thickness | As low as ~0.25 mm walls molded based on geometry |
Tolerances | Tighter tolerances than metal AM, typical ±0.3% of dimensions |
These capabilities make MIM suitable for end-use precision components.
Applications of MIM Additive Manufacturing
MIM’s geometric flexibility and tailored composition suit various industries:
Industry | Component Examples |
---|---|
Automotive | Gears, rocker arms, turbocharger components |
Aerospace | Turbine blades, impellers, nozzle guide vanes |
Firearms | Triggers, safeties, slides, ejectors, muzzles |
Medical/Dental | Scalpel handles, forceps, skull plates, crowns |
Oil and Gas | Valve parts including bodies, stems, actuators |
Micro Electronics | Shields, connectors, pins, spacers, actuators |
MIM also helps create tooling inserts capable of mass production molding/forming operations.
MIM Feedstock Specifications
Feedstock properties require careful control for tolerance and feature capability:
Parameter | Typical Specification | Test Method |
---|---|---|
Powder particle size | 3 – 20 μm | Laser diffraction |
Powder loading | >55 vol% | Thermogravimetric analysis |
Powder apparent density | 2.5 – 4 g/cm3 | Hall flowmeter |
Tap density | >4 g/cm3 | Tapping volumeter |
Viscosity curve | Shear rate dependent | Capillary rheometry |
Pellet size distribution | 2 – 4 g sensitive to shape | Sieving |
These specifications promote mold flow while ensuring green-body and sintered strength.
Overview of the MIM Manufacturing Process
- Develop composite feedstock with desired powder + binder system
- Pelletize feedstock for precision volumetric shot control
- Injection mold parts with tight tolerances and surface finish
- Chemically debind and remove polymer content
- Sinter pellets at >92% theoretical density
- Machine features as needed if geometry allows
- Apply supplementary plating, heat treating, coating, etc. if necessary
- Quality assurance testing and validation for production
This continues to be optimized for reliability at high volumes.
MIM Equipment and Feedstock Suppliers
Company | Materials | Capabilities |
---|---|---|
BASF | Wide range of MIM alloys | Complete quality feedstocks |
Sandvik Osprey | 316L, 17-4PH, more | Atomization expertise transferred to MIM |
MPP | Tool steels, stainless steels, custom | Leading MIM equipment too |
CN Innovations | Custom alloys | Specialists in novel compositions |
Parmatech Corp | Ti alloys, tool steels, Fe alloys, exotics | Equipment and feedstocks |
Suppliers offer complementary equipment like molding machines and furnaces to enable turnkey production.
Tradeoffs When Considering MIM AM
Pros:
- Highly complex geometries and assemblies consolidated
- Excellent mechanical properties from uniform fine grains
- Great surface finish resolution as molded
- Proven mass production scalability once qualified
- Low wasted raw material relative to metal printing
- Leverages existing injection molding know-how
Cons:
- High up front costs for feedstock formulation and tooling
- Intensive qualification for new parts and applications
- Limited size range to under several pounds
- Restricted to alloys available as powders
- Generally lower ultimate strength than forgings
- Per-part cost higher than other processes until >10k volume
MIM hits the sweet spot for small complex metal components with its established track record.
![MIM Additive Manufacturing 5 mim additive manufacturing](https://met3dp.com/wp-content/uploads/2023/10/D2.jpg)
Frequently Asked Questions
How small of features can MIM practically mold?
Typical lower range limits fall around 100-150 microns for hole diameter and mold wall thicknesses around 0.3 mm (~12 thou), thinner in certain geometries.
What determines the size range limits for MIM parts?
General difficulty handling thin-walled shapes over approximately 5” flow length without sagging or distortion. Maximum thickness typically under 0.5” and weights up to 5 pound range.
Does MIM allow functionally graded (FGM) composites?
Yes, advanced molding processes now support tailored porosities or spatially graded multi-powder feedstocks within a single molded component during manufacturing.
How many alloys are commercially available as MIM feedstocks?
Over 60+ base formulations exist – 300 series stainless steels comprise over 50% of the total market, followed by tool steels, titanium alloys, and nickel superalloys seeing growth.
What finishing processes typically follow MIM?
Common secondary operations include barrel finishing/vibratory deburring, surface grinding, shot peening, laser marking, passivation, plating, heat treating, joining, and inspection.
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