Microstructured Mold Casting with Polymer Release Layer
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Solution Overview
Problem
Existing methods for molding microstructured three-dimensional free-form surfaces face challenges with poor dimensional accuracy and high internal stresses due to material selection and processing issues, such as those encountered in silicone molds and sintering processes.
Innovation Solution
A method involving the use of a polymeric material with release agent properties to create a mold, followed by deposition of a hard material layer using techniques like vapor deposition and reinforcement, ensuring precise reproduction of fine shapes with dimensionally stable cores and minimizing manufacturing inaccuracies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silicone molds are used for molding microstructured surfaces, then ease of manufacture is improved, but manufacturing precision deteriorates due to poor dimensional accuracy and distortions from internal stresses
Solution Approach 1:
The mold is divided into two distinct parts: a silicone mold for capturing the surface pattern and a dimensionally stable core for maintaining geometric accuracy. This segmentation allows each component to fulfill its specific function without compromising the other - the silicone provides ease of demolding while the core ensures precision
Solution Approach 2:
The invention uses a composite structure combining silicone material with dimensionally stable materials (such as metals or rigid plastics). This composite approach leverages the advantages of both materials - the flexibility and release properties of silicone combined with the dimensional stability and stress resistance of the rigid core
2Strength
If sintering process is used for molding hard material layers, then strength is improved, but manufacturing precision deteriorates due to poor dimensional accuracy and high internal stresses from volume changes
Solution Approach 1:
The microstructured surface pattern is captured in advance using the silicone mold before the sintering process. The dimensionally stable core is prepared beforehand with the exact desired geometry. This preliminary action ensures that the final sintered product inherits the precision of the core without undergoing dimensional changes during the sintering process
Solution Approach 2:
The silicone mold creates a negative impression of the desired surface pattern, which is then transferred to the positive form using the dimensionally stable core. This copying process allows the microstructured surface to be reproduced without subjecting the core geometry to the detrimental volume changes of sintering
3Strength
If chemically deposited shells with large wall thicknesses are used, then strength is improved, but manufacturing precision deteriorates due to poor dimensional accuracy during molding
Solution Approach 1:
The invention applies different material properties to different parts of the mold structure. The surface layer captures the microstructured pattern with high fidelity, while the core provides overall dimensional stability. This local differentiation of material functions allows thin-walled microstructured surfaces to be produced with high precision without requiring thick walls for strength
4Device complexity
If a single molding process is used for microstructured surfaces, then device complexity is reduced, but manufacturing precision deteriorates due to inability to compensate for material defects
Solution Approach 1:
The molding process is segmented into distinct steps: creating the silicone mold, preparing the dimensionally stable core, and combining them. This segmentation allows each step to be optimized for its specific function - the silicone for pattern capture and the core for precision maintenance - resulting in superior overall accuracy despite the increased process steps
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
This approach enables the precise and wear-resistant reproduction of microstructured surfaces with high variability in material properties, avoiding distortions and internal stresses, and allowing for the production of tools for intaglio printing, injection molding, and other applications.
Implementation Method 1
coating the impression with a layer of polymeric material... bonding the layer of polymeric material to the core
Implementation Method 2
application of one or more layers of homogeneous layer thickness made of metallic material to the exposed layer made of polymeric material
Data Source
Figure 1~3
Figure 4~7
AI summary
The modelling of microstructured, three-dimensional free-form surface (12) for the production of mold and mold basins, casting models and/or core sockets, comprises preparing a core (30), whose surface is adapted to contour of the free-form surface, coating the free-form surface with polymer layer under external pressure with a thickness corresponding to the depth of the micro-structured surface, placing the coated surface on the core, and removing the coated surface as model from the core by which the polymeric layer remains on the core. The modelling of microstructured, three-dimensional free-form surface (12) for the production of mold and mold basins, casting models and/or core sockets, comprises preparing a core (30), whose surface is adapted to contour of the free-form surface, coating the free-form surface with polymer layer under external pressure with a thickness corresponding to the depth of the micro-structured surface, placing the coated surface on the core, removing the coated surface as model from the core by which the polymeric layer remains on the core, chemically, electrically or physically depositing metallic layers on the free-lying polymeric layer by evaporation of first metallic layer with minimal layer thickness of 10 mu m and reinforcement of the first layer by the second metallic layer with homogeneous layer thickness of 50-150 mu m, chemically, physically or electrically depositing a hard material layer with intermediate layers directly on the polymer layer by high-velocity gas flame spray coating, plasma spray coating, kerosene flame spray coating or other spray-coating techniques, preparing a prototype, whose contour corresponds to the free-lying surface of the hard material layer and/or to a reinforcement of the hard polymer layer, connecting the free-lying surface present on the core with the prototype at a temperature that is higher than the decomposition temperature of the polymer layer by decomposing the layer, removing the decomposed layer and optionally removing the additional layers so that the hard material layer lies freely with the microstructured surface. The hard material layer is applied with a thickness of 100-1000 mu m. The coated model bevels on the core. The hard material layer is applied in an inert gas atmosphere or under vacuum and is electrically or chemically reinforced. A barrier layer, which is not attacked chemically or electrically, is applied on the metallic layers with a layer thickness of 3-8 mu m. The hard material layer and/or the reinforcement are machined on the free-lying surface facing the microstructured surface to produce a cast shell with a defined surface contour. The free-lying surface is soldered, adhesively bonded and/or sintered with the prototype by the application of pressure. The adhesive has a higher decomposition temperature than the polymeric layer. The free-lying surface and/or the prototype are chemically, physically or electrically coated. The cast shell and the prototype are pressed under pressure at a temperature that is lower than the melting temperature of the prototype and the cast shell, which is thermostatically pressed before the connection of prototype for the reduction of the stresses.