3D Printed Mold Porous Surface for Sink Mark Prevention
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Solution Overview
Problem
The existing method for manufacturing three-dimensional shaped objects using selective laser sintering often results in 'sink marks' during resin molding due to stress-induced volumetric shrinkage, leading to defective moldings.
Innovation Solution
A method is developed where a three-dimensional shaped object is created with a low-density solidified portion having a solidified density between 50% to 90%, allowing gas to flow through and apply pressure, thereby preventing sink marks by forming a porous surface that can be used as a metal mold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a three-dimensional shaped object is used as a metal mold for resin molding, then the molding process can be performed, but sink marks occur due to stress-induced volumetric shrinkage during resin solidification
Solution Approach 1:
A porous layer is formed on the surface of the three-dimensional shaped object that will contact the resin. This porous structure allows gas to pass through during molding, enabling pressure equalization that prevents sink marks while maintaining the structural integrity of the mold
Solution Approach 2:
The surface density of the three-dimensional shaped object is modified by controlling the solidification process. A porous layer with controlled porosity (5-50%) is created on the surface, while the internal structure maintains higher density. This parameter change allows gas permeability at the surface while preserving structural strength
2Strength
If the surface of the three-dimensional shaped object is made dense for structural strength, then the object can support molding loads, but gas cannot flow through to apply pressure and prevent sink marks
Solution Approach 1:
The three-dimensional shaped object is divided into two distinct zones: a porous surface layer (5-50% porosity) for gas flow and pressure application, and a dense internal structure (higher than 90% density) for structural strength. This segmentation allows each zone to fulfill its specific function without compromising the other
Solution Approach 2:
Different density/porosity characteristics are applied to different parts of the object. The surface layer has controlled porosity to allow gas flow, while the internal structure maintains high density for strength. This local quality differentiation resolves the contradiction between gas permeability and structural strength
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 prevents sink marks and allows for more flexible molding processes by applying pressure through the gas flowing through the low-density solidified portion, enhancing the quality of the molded articles.
Implementation Method 1
irradiating a predetermined portion of a powder layer with a light beam, thereby allowing sintering of the predetermined portion of the powder or melting and subsequent solidification thereof
Implementation Method 2
a part of a surface portion of the three-dimensional shaped object is formed as a low-density solidified portion whose solidified density ranges from 50% to 90% so that an application of pressure can be performed by a gas flowing through the low-density solidified portion
Data Source
AI summary
There is provided a method for manufacturing a three-dimensional shaped object, the method comprising the repeated steps of: (i) forming a solidified layer by irradiating a predetermined portion of a powder layer with a light beam, thereby allowing a sintering of the powder in the predetermined portion or a melting and subsequent solidification thereof; and (ii) forming another solidified layer by newly forming a powder layer on the resulting solidified layer, followed by the irradiation of a predetermined portion of the powder layer with the light beam, wherein a part of a surface portion of the three-dimensional shaped object is formed as a low-density solidified portion whose solidified density ranges from 50% to 90% so that an application of pressure can be performed by a gas flowing through the low-density solidified portion.