Metal Injection Molding vs Liquidmetal
Powder Metal Injection Molding
Powder Metal Injection Molding (PMIM or MIM) is used for steel alloys with high melting temperatures. A feed stock of the alloy is made into a fine powder and mixed with a polymer powder. A continuous mass of this mixture is conveyed with a rotating screw through a heated barrel.
The polymer is melted and acts as a carrier for the metal powder to be injection molded. A metering plunger presses the necessary material into a steel mold. The result is a metal part containing 20% polymer.
The polymer is removed from the molded part with a thermal/chemical process called debinding. After that, the porous metal part is compacted into a solid with a long heating process called sintering.
Liquidmetal Process
Amorphous Metal Molding uses a Non-ferrous alloy designed to have an amorphous atomic structure in a solid state. Small batches of feedstock are melted in a vacuum chamber to avoid contamination from Oxygen. The melted alloy is poured into the shot sleeve where a plunger pushes the material into a steel mold.
The Liquidmetal part comes out of the mold to net shape, great precision, and with full physical properties. Secondary processes to remove the part from the runner and overflows are necessary.
Material Properties
A molding process can influence the material properties of a part due to the resulting porosity or grain structure, but the main contributor to the properties is the type of material that can be used in a particular process. The melting temperature of a material and the final part geometry will dictate which molding process to use.
MIM
VS
Liquidmetal
MIM
VS
Liquidmetal
MIM
VS
Liquidmetal
730-1090 (106-158)
Yield Strength
Mpa (ksi)
1250 (181)
.44
Standard Elasticity
% Strain
1.6
High Elasticity
285-323 (285-320)
Improve with Heat-Treating
Hardness
HB (Vickers)
460 (500)
No Heat-Treating Available
0 to < 500 hours salt spray
(Dependent on alloy)
Corrosion
Resistance
> 500 hours salt spray
Molding Design Considerations
Parameters such as part geometry and size are dependent on the process used to make the part. Review the comparison of how these two manufacturing processes affect the capabilities.
MIM
VS
Liquidmetal
MIM
VS
Liquidmetal
MIM
VS
Liquidmetal
Complex Contoured Geometries
Limits on size and wall section
Design
Flexibility
Complex Contoured Geometries
Limits on size and wall section
+/- 0.075 mm
Dimensional
Tolerances
+/- .02mm (critical dim)
+/- .05mm (standard)
Draft preferred
Zero draft possible
Part Draft
Requirements
3 degrees internal features
1 degree external features
< 1g to 100g
Part Size
< 1g to 450g
0.08 – 1.1 Ra μm
Surface
Finish
0.05 to 0.35 Ra μm
0.30 mm
Min Wall
Thickness
0.3 mm
6 mm
Max Wall
Thickness
2.5 to 3 mm
Mold Process Considerations
It is advantageous to reduce the number of manufacturing post processes required to produce a finished part. This will reduce development time, and maximize yield rates once in production.
Liquidmetal’s net shape molding allows you to check critical dimensions right out of the mold. A MIM part cannot be measured until after several post processes. This can result in substantial scrap and time lost if there was a problem upstream. These manufacturing trade-offs may be offset by part cost and the speed at which you can make parts in high volume.
MIM
VS
Liquidmetal
MIM
VS
Liquidmetal
MIM
VS
Liquidmetal
Medium to Ultra-high
Mass
Production
Medium to High
Ultra-low to Low
< $0.10 to $5.00
Part
Costs
Low to Average
$1.00 to $20.00
Many alloys and ceramics
Alloy
Alternatives
Amorphous alloys only
Days
Process
Qualification
Minutes
High, $30K to $100K
Tooling
Costs
High, $30K to $100K
Molding Process Advantages and Disadvantages
The Liquidmetal molding process produces an amorphous metal part with high strength, high hardness, and final density. All properties and CNC precision are achieved directly out of the mold without manufacturing post processes such as heat-treating, coatings, or machining. This simple molding process can reduce cost and part validation time.
Metal injection molding is an economical molding process that can achieve high volumes for mass production. It allows you to mold steels and ceramics that would otherwise have too high of a melting temperature for injection molding. Removing the polymer in post processing causes a part to shrink up to 20%, affecting dimensional stability and part shape retention. Machining, heat-treating and coatings are common to achieve the final dimensions and properties.
