Thermoformed Plastic Mould for Metal Casting
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Solution Overview
Problem
Existing casting processes, such as investment casting, face challenges with handling and damage of wax copies, and alternatives like polystyrene expanding during the burnout step, making it difficult to produce high numbers of products with changing designs efficiently.
Innovation Solution
A casting process using a form negative mould made from a plastic sheet via thermoforming, where a refractory layer is applied to create a ceramic mould, and molten metal is poured into the hollow space, allowing for the production of metal 3D products with complex designs in large quantities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a wax copy is used in investment casting, then the casting process can be performed, but the wax copy is difficult to handle and can be damaged before being surrounded by refractory material
Solution Approach 1:
The patent changes the material parameter from wax to polystyrene, which has different physical properties including higher strength and different thermal behavior. This material substitution resolves the handling difficulty while maintaining the casting functionality
Solution Approach 2:
The patent introduces an intermediary wax layer covering the polystyrene copy. This wax layer serves as a protective mediator that prevents damage during handling, while being removable during the burnout process, thus resolving the contradiction between strength and damage resistance
2Strength
If polystyrene is used as an alternative to wax, then the copy is stronger, but the solid polystyrene copy expands when heated in the burnout step and could damage the ceramic mould
Solution Approach 1:
The wax layer acts as an intermediary that melts first during burnout, creating space for the polystyrene to expand into without damaging the ceramic mould. The wax mediates between the strong polystyrene copy and the mould, preventing harmful expansion effects
Solution Approach 2:
The wax layer is applied preliminarily before the burnout process. It performs the preliminary function of controlling the expansion space during heating, preventing the polystyrene from expanding into the mould walls and causing damage
3Productivity
If traditional investment casting with wax copies is used, then casting can be performed, but it is laborious and not suitable for high-volume production of products with changing designs
Solution Approach 1:
The patent uses a master model to create multiple thermoformed plastic copies simultaneously. This copying approach enables high-volume production of identical parts while maintaining design flexibility, resolving the contradiction between productivity and process complexity
Solution Approach 2:
The patent replaces the manual wax modeling process with automated thermoforming of plastic sheets. This substitution of mechanical/manual processes with automated thermal-forming processes enables higher productivity while reducing labor intensity and complexity
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 method simplifies the mould creation process, reduces damage, and enables efficient production of metal 3D products with complex designs by using thermoformed plastic sheets and refractory materials, allowing for quick and cost-effective manufacturing of multiple products.
Implementation Method 1
providing a form negative mould of the 3D product comprising of a plastic sheet which sheet defines at its inner side a hollow space corresponding with at least the shape of one or more of the 3D products, by thermoforming using a master mould
Implementation Method 2
The ceramic moulds thus obtained are cured and subjected to a burnout step. In this step the wax melts and/or vaporizes and is able to leave the ceramic mould via the gating system leaving a hollow space corresponding to the 3D product. Next molten metal is poured into the opening of the gating system such that the metal fills the hollow space corresponding to the 3D product.
Data Source
AI summary
The invention is directed to a casting process to make a metal 3D product by performing the following steps, (a) providing a form negative mould of the 3D product comprising of a plastic sheet which sheet defines at its inner side a hollow space corresponding with at least the shape of one or more of the 3D products by thermoforming using a master mould, (b) applying a layer of refractory material on the exterior of the plastic sheet of the mould to obtain a ceramic mould having a hollow space, (c) pouring molten metal into the hollow space of the ceramic mould and allowing the metal to solidify, and. (d) removing the layer of refractory material to obtain the metal 3D product.