Injection Molding Feedstock Delivery System with Buffer Chamber
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Solution Overview
Problem
Metal injection molding (MIM) techniques, particularly high pressure and high temperature methods, face challenges such as inconsistent results, long cycle times, equipment wear, and significant volume shrinkage leading to defects like warping in orthopedic and aerospace applications.
Innovation Solution
A feedstock delivery system for injection molding that includes a vessel unit with a fluid jacket to maintain constant temperature and a dispensing unit with a buffer chamber and valves to control the flow of feedstock slurry, ensuring consistent temperature and pressure during the molding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high pressure injection molding is used to dispense viscous feedstock, then the feedstock can be sufficiently propelled into the mold, but transient feedstock properties lead to inconsistent results and long cycle times
Solution Approach 1:
The patent changes the physical state of the feedstock from a viscous paste to a low-viscosity slurry by transforming the binder from solid to liquid state. This parameter change allows the feedstock to flow easily under low pressure, eliminating the need for high pressure cycles and enabling consistent results without transient property variations
Solution Approach 2:
The patent uses a fluidized bed approach where air is introduced to fluidize the metal powder and binder mixture, creating a slurry that can be pumped and injected at low pressures. This pneumatic approach replaces the mechanical high-pressure screw injection system, reducing cycle times and eliminating equipment wear
2Productivity
If high pressure and high temperature are used in MIM, then the viscous feedstock can be dispensed, but it contributes to long cycle times and wear and tear on expensive equipment
Solution Approach 1:
The patent fundamentally changes the temperature parameter from high temperature (above 150°C for melting polymer) to low temperature processing. The binder is transformed from solid to liquid state at lower temperatures, eliminating thermal stress on equipment and reducing cycle times while maintaining feedstock flowability
Solution Approach 2:
The patent replaces the high-pressure mechanical screw injection system with a low-pressure pneumatic or hydraulic pumping system. This substitution eliminates the need for expensive high-pressure equipment, reduces wear and tear, and improves reliability while maintaining productivity
3Quantity of substance
If high pressure MIM is used, then feedstock can be injected into the mold, but it limits the volumetric loading of metallic powders to less than 65%, resulting in significant shrinkage and warping
Solution Approach 1:
The patent changes the rheological parameters of the feedstock by transforming the binder from solid to liquid state, creating a slurry with optimized viscosity. This allows for high metal powder loading (exceeding 65% volumetric) while maintaining flowability, thereby reducing shrinkage and improving dimensional accuracy after sintering
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves consistent quality by maintaining the feedstock at a constant temperature and controlling pressure, reducing volume shrinkage, and minimizing equipment wear, thereby improving the accuracy and reliability of metal injection molded parts.
Implementation Method 1
a fluid jacket that encloses at least a portion of the vessel and at least a portion of the first dispensing unit conduit of the dispensing unit such that heated fluid flowing through the fluid jacket transforms the feedstock into a feedstock slurry and maintains the feedstock slurry at a constant temperature
Data Source
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AI summary
A feedstock delivery system for injection molding includes a vessel unit that includes a vessel with an internal volume and an inlet for receipt of a feedstock. First and second dispensing units are alternatively connectable to the vessel unit and each include first and second ends, first and second valves, and a buffer chamber. The first end is connectable to the dispensing unit such that the buffer chamber is in communication with the internal volume of the vessel. The second end is connectable to an injection mold and defines an outlet of the feedstock delivery system. The outlet is in communication with the buffer chamber, and the buffer chamber is positioned between the first and second valves. The buffer chamber of the first dispensing unit defines a first chamber volume, and the buffer chamber of the second dispensing unit defines a second chamber volume greater than the first chamber volume.