Helical Core Molding Using Rotating Self-Hardening Sand Die
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Solution Overview
Problem
The existing methods for molding helical-shaped cores for screw compressors require wide process margins and long processing times, and the removal of core dies from hardened sand molds is difficult due to high frictional forces, which impedes near-net-shape casting.
Innovation Solution
A core molding method involving the use of self-hardening sand mixed with a resin and hardener, where the core die is rotated during removal to optimize hardening time, frictional force, and strength, allowing for removal without sectioned surfaces or gradients, thereby reducing process margins and enabling near-net-shape casting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a core die has a removal gradient or sectioned surface to facilitate removal, then the core die can be easily removed from the core, but the process margin increases and near-net-shape casting is impeded
Solution Approach 1:
The invention changes the physical-chemical parameters of the sand material by using self-hardening sand that undergoes irreversible dehydration condensation reaction. This transforms the sand from a soft, easily removable state to a hardened state with sufficient strength to maintain core shape during removal, eliminating the need for removal gradients or sectioned surfaces while maintaining near-net-shape casting precision
Solution Approach 2:
The invention applies preliminary hardening action to the sand before core die removal. By allowing the self-hardening sand to harden for an optimized time period, the sand develops sufficient strength to support the core structure during die removal, preventing collapse without requiring geometric modifications to the core die
2Strength
If the core die contact area with the core is increased, then the molding support is improved, but the frictional force during die removal increases making removal difficult
Solution Approach 1:
The invention changes the friction parameter by utilizing the hardening transformation of self-hardening sand. As the sand hardens through irreversible dehydration condensation, its surface properties change, reducing the frictional force between the core die and the hardened sand, thereby facilitating die removal while maintaining adequate contact area for molding support
3Strength
If self-hardening sand is used and allowed to harden completely, then the core strength is sufficient to prevent collapse, but the frictional force increases making die removal more difficult
Solution Approach 1:
The invention replaces the mechanical approach of using removal gradients or sectioned surfaces with a chemical-physical approach. By utilizing the irreversible dehydration condensation reaction of self-hardening sand, the system achieves both sufficient core strength and reduced friction through material transformation rather than geometric modification
Solution Approach 2:
The invention applies preliminary optimization of the hardening time parameter to achieve the optimal balance between core strength development and friction reduction. By controlling the hardening duration, the sand reaches a state where it provides sufficient structural support while maintaining facilitative properties for die removal
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 method allows for stable removal of core dies from helical-shaped cores without collapsing the core, reducing process margins and enabling efficient near-net-shape casting by optimizing hardening time, frictional force, and strength during die removal.
Implementation Method 1
a resin serving as a bond required for coupling sand grains together and a hardener serving as a hardening catalyst cause an irreversible dehydration condensation reaction, so that the self-hardening sand hardens and contracts over time
Implementation Method 2
a frictional force exerted between the core and the core die during die removal, and strength of the core during die removal are optimized
Data Source
AI summary
When a core die is being removed from a core while being rotated around its axis, the hardening time of self-hardening sand, the frictional forces generated between the core and the core die during die removal, and the strength of the core during die removal are optimized.