Dissolvable Additive Molds for High-Pressure Injection Molding
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Solution Overview
Problem
Existing additive manufacturing technologies for molds lack durability and mechanical stability to withstand high temperatures and pressures in thermoplastic injection molding, and sacrificial molds are limited by materials and processing speed for complex geometries.
Innovation Solution
Development of dissolvable resin formulations for sacrificial molds that can withstand thermoplastic injection molding temperatures (70-450°C) and pressures (0.2-400 MPa), using materials like 4-(1-oxo-2-propenyl)-morpholine and trimethylolpropane(EO)9 triacrylate, with post-curing and vacuum-assisted filling to create molds suitable for STIM processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polymer additive manufacturing is used to create durable molds for repeated injection molding cycles, then the molds can withstand high temperatures and pressures, but the geometrical freedom from additive manufacturing is lost due to the need for drafts and parting lines
Solution Approach 1:
The patent employs sacrificial molds made from water-soluble polymers that are designed to be single-use or limited-use components. These molds are dissolved after a predetermined number of injection molding cycles (typically 1-10 cycles) to release the molded articles, eliminating the need for complex draft angles and parting lines that would be required in durable reusable molds.
Solution Approach 2:
The patent changes the material parameters by using water-soluble polymer formulations with specific solubility characteristics. The molds are designed to maintain structural integrity during the injection molding process (withstanding temperatures up to 450°C and pressures up to 400 MPa) but dissolve when exposed to water or aqueous solutions after use, enabling complex geometries without traditional mold constraints.
2Productivity
If thermoplastic injection molding is used for high-speed manufacturing, then production efficiency increases, but the molds require complex mechanisms like movable cores and sliders that cause rapid breakdown of additively manufactured polymer molds
Solution Approach 1:
The sacrificial mold approach eliminates the need for durable reusable molds with complex mechanisms. By using single-use water-soluble polymer molds, the system can employ aggressive injection molding parameters (high speed, high pressure, movable cores, sliders) without concern for mold longevity, as the molds are intentionally designed to be consumed after releasing the part.
Solution Approach 2:
The patent extracts the ejection function from the mold structure itself by making the entire mold water-soluble. Instead of using mechanical ejection mechanisms that require durable moving parts, the mold is dissolved in water after molding, automatically releasing the molded article and eliminating wear from mechanical ejection systems.
3Device complexity
If sacrificial molds are used for casting thermosetting materials, then complex geometries without parting lines can be achieved, but the manufacturing speed is considerably slower due to slower curing rates
Solution Approach 1:
The patent uses water-soluble polymer molds that can be rapidly manufactured via additive manufacturing and used for high-speed thermoplastic injection molding. The molds are dissolved quickly in water after use, enabling rapid turnaround between production batches, unlike thermosetting material casting which requires slow curing times.
Solution Approach 2:
The patent replaces the thermal curing process (slow, heat-based) with a mechanical/electrical additive manufacturing process (fast, layer-by-layer deposition and UV curing) for mold creation, and replaces chemical curing (slow) with water dissolution (fast) for mold removal, dramatically increasing manufacturing speed while maintaining complex geometry capabilities.
4Manufacturing precision
If additively manufactured molds are used for molded articles with delicate features, then high precision can be achieved, but the articles cannot be removed without breaking or distorting
Solution Approach 1:
The sacrificial mold approach allows molded articles with delicate features to be produced with high precision by using additively manufactured molds that capture fine details. The molds are then dissolved in water to release the parts, eliminating the mechanical ejection process that would otherwise cause damage to delicate features.
Solution Approach 2:
The patent introduces water as an intermediary substance that facilitates the release of molded articles from the mold. The water-soluble polymer mold dissolves in water, acting as a temporary holding structure during molding but automatically releasing the delicate part through chemical dissolution rather than mechanical force, preventing damage to fragile features.
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
Enables the production of complex, high-resolution molded articles with smooth ejection and high throughput, overcoming material limitations and ensuring durability under extreme conditions.
Implementation Method 1
capable of sustaining plastic melt temperatures in the range of 70-450 degrees C. and injection pressures in the range of 0.2-400 MPa
Implementation Method 2
capable of sustaining plastic melt temperatures in the range of 70-450 degrees C. and injection pressures in the range of 0.2-400 MPa
Implementation Method 3
whereby the mold is dissolved to release the molded article
Implementation Method 4
Vacuum pressure in the range of 0.08-0.95 bar may be applied to assist filling
Data Source
AI summary
Sacrificial additively manufactured molds having a dissolvable material for use in thermoplastic injection molding processes at plastic melt temperatures in the range of 70-450 degrees C. and injection pressure in the range of 0.2-400 MPa. A method of producing a molded article using said sacrificial additively manufactured molds is also disclosed.