Vacuum Plaster Casting Mold Fabrication for Aluminum Alloy
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Solution Overview
Problem
Current plaster mold investment casting methods face challenges in ensuring the quality and qualification rate of surface roughness for large-inner-cavity and complicated-structure aluminum alloy castings with thin walls, particularly due to air entrainment, premature solidification, and inadequate air exhaust in large-area partitions or partially closed blind cavities.
Innovation Solution
A method involving the use of a wax pattern cleaned with acetone and industrial ethanol, combined with vent holes and waterproof-breathable membranes, and a vacuum-based mixing and grouting process using asynchronous mixing tanks to achieve efficient air exhaust and continuous production, ensuring high surface quality and dimensional accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If plaster slurry is mixed and poured at atmospheric temperature and pressure, then the mixing and pouring process is simple, but air entrainment occurs inside the slurry causing defects in the casting mold
Solution Approach 1:
The patent applies vacuum environment (inert atmosphere principle) during mixing and pouring processes. The mixing tank and pouring process occur under vacuum conditions, replacing atmospheric air with vacuum environment to prevent air entrainment in the plaster slurry, thereby eliminating the harmful effect while maintaining process feasibility
Solution Approach 2:
The patent replaces conventional atmospheric mixing and pouring with vacuum-based mixing and pouring systems. The vacuum mixing tank and vacuum pouring apparatus substitute the traditional atmospheric process, using pressure differential instead of mechanical stirring alone to achieve air-free slurry preparation and delivery
2Object-affected harmful factors
If ultrasonic treatment is used to clear air entrainment in plaster slurry, then some air bubbles are removed, but the casting mold solidifies prematurely during the gas clearing process
Solution Approach 1:
The patent removes air bubbles from plaster slurry during the mixing stage itself, before the slurry is poured into the mold. The vacuum mixing process pre-clears the slurry of entrained air, eliminating the need for subsequent ultrasonic treatment that would cause premature solidification. This preliminary action prevents the harmful effect before it can impact the mold
Solution Approach 2:
The patent replaces ultrasonic treatment with vacuum-based air removal during mixing. Instead of using ultrasonic waves that cause premature solidification, the system uses vacuum pressure differential to remove air bubbles during the mixing process, achieving bubble clearing without the harmful side effect
3Object-affected harmful factors
If conventional vacuum molding is used for plaster casting mold, then air entrainment is reduced, but the process requires repeated opening and closing of vacuum chamber doors reducing productivity
Solution Approach 1:
The patent merges the mixing and pouring operations into a single integrated vacuum environment. Both the mixing tank and pouring process occur within the same vacuum chamber without breaking the vacuum seal, combining multiple operations that were previously separated into distinct steps requiring chamber access
Solution Approach 2:
The patent maintains continuous vacuum conditions throughout the entire mixing and pouring process. The vacuum seal is never broken during these operations, allowing continuous production without repeated opening and closing of chamber doors, thereby maintaining both air-free conditions and high productivity
4Shape
If plaster mold investment casting is used for large-inner-cavity and complicated-structure aluminum alloy castings, then complex geometries can be achieved, but surface roughness quality and dimensional accuracy deteriorate due to poor mold fitness
Solution Approach 1:
The patent applies vacuum environment during mold fabrication to prevent air entrainment and ensure complete mold filling. The vacuum conditions eliminate air pockets that would cause defects in complex geometries, thereby improving surface roughness quality and dimensional accuracy while maintaining the ability to produce complex shapes
Solution Approach 2:
The patent replaces atmospheric mixing and pouring with vacuum-based systems that provide better control over slurry delivery and mold filling. The vacuum pouring apparatus ensures complete filling of complex cavities without air entrapment, improving the fitness of the mold to the pattern and resulting in better surface quality and dimensional accuracy
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 effectively reduces air entrainment and premature solidification, improving the surface finish and dimensional accuracy of aluminum alloy castings by controlling pressure differences and using independent vacuum environments for mixing and grouting, resulting in reduced defects and enhanced production efficiency.
Implementation Method 1
sticking and covering the upper and lower surfaces of the holes with circle TPU waterproof-breathable membranes
Implementation Method 2
turning on the valve of the plaster slurry transfer tube, so that within 3 s～5 s after the discharge valved pipeline at the bottom of each of the left and right mixing tanks is turned on, the plaster slurry enters into the sand box to be filled in the lower tank via the sand box feed inlet under the action of gravity and pressure difference
Implementation Method 3
a spiral stirrer is installed in the center of the upper cover of each of the left and right mixing tanks, and the spiral stirrer can rise and fall vertically along the axis line of the mixing tank
Implementation Method 4
the plaster slurry enters into the sand box to be filled in the lower tank via the sand box feed inlet under the action of gravity and pressure difference
Data Source
AI summary
The application provides a plaster casting mold fabrication method for a complicated structure aluminum alloy casting with a large inner cavity and a thin wall, in which, a wax pattern is cleaned with a mixture; closed blind cavity and large plane unbeneficial to plaster mold-filling of the wax pattern are used to exhaust air by using vent holes and waterproof-breathable membranes in cooperation with each other; under pressure difference, plaster powder and mixed aqueous solution are vertically splashed and mixed in a mixing tank to reduce dust discharge; asynchronous mixing and grouting can be realized by left and right mixing tanks in an upper tank of a vacuum tank. The present application can effectively remove the surface parting agent, increase the wettability of the plaster paste and the wax pattern surface, and improve the surface finish of the casting mold.