Ceramic Extrusion Mold Surface Flattening and Coating
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Solution Overview
Problem
Conventional molds for extrusion forming of ceramic honeycomb structures suffer from forming defects and wear issues, particularly around the outer peripheries, due to unevenness in the die surface caused by ECM processing, leading to non-uniform clay supply and reduced isostatic strength.
Innovation Solution
A mold with a die surface flattened to a surface roughness (Ra) of 0.05 µm to 10 µm, coated with a Ni-based first coating film and a W3C-based second coating film, to ensure uniform clay flow and enhanced wear resistance, thereby reducing forming defects and improving isostatic strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the die surface is processed by ECM to create back holes, then the die can supply clay to the honeycomb structure, but the die surface becomes uneven with height differences exceeding 65μm causing forming defects
Solution Approach 1:
The die surface is preliminarily flattened by removing protrusions before clay extrusion begins. This preliminary action prevents the formation of gaps between the die and back pressing plate, ensuring uniform clay supply from the start of the process and eliminating forming defects in the outer peripheral portions of the honeycomb article.
Solution Approach 2:
The surface roughness parameter of the die is changed from a state with height differences exceeding 65μm to a flattened state where protrusions are removed. This parameter change ensures that the die surface maintains proper contact with the back pressing plate throughout the clay supply process, preventing non-uniform extrusion.
2Manufacturing precision
If the die surface is flattened to reduce height differences, then forming defects decrease, but the die wear resistance may be reduced
Solution Approach 1:
The die is constructed as a composite structure with a base material providing structural strength and a separate coating layer providing wear resistance. The coating layer is applied after the ECM processing and flattening, allowing the die surface to be flattened for precision while the coating maintains wear resistance during operation.
Solution Approach 2:
Different regions of the die have different properties: the bulk material provides structural support while the surface coating provides wear resistance. The flattened surface area contacts the back pressing plate to prevent forming defects, while the coating layer protects this contact area from wear during clay extrusion.
3Stability of the object's composition
If the height difference between protrusions and recesses is reduced to 65μm or less, then uniform clay flow is achieved, but the die requires additional processing steps
Solution Approach 1:
Only the protrusions on the die surface are selectively removed, while the recesses and back holes are preserved. This selective extraction approach achieves the necessary surface flatness for uniform clay flow without requiring complete resurfacing or additional complex processing steps.
Solution Approach 2:
The protrusion removal is performed as a preliminary step before die assembly and clay extrusion. By flattening the surface in advance, the need for complex adjustment mechanisms or additional processing during operation is eliminated, simplifying the overall device 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
The solution significantly decreases forming defects near the outer peripheries and enhances wear resistance, allowing for the production of ceramic honeycomb structures with high density and precision, maintaining stable isostatic strength over time.
Implementation Method 1
the die is coated with a first coating film disposed on a base material made of a stainless steel and containing Ni as a main component and a second coating film further disposed on the first coating film and containing W 3 C as a main component
Data Source
Figure 1
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AI summary
There is provided a mold for extrusion forming of ceramic articles which is excellent in wear resistance and can remarkably decrease forming defects in the vicinity of outer peripheries thereof. The mold for the extrusion forming of the ceramic articles includes a die 1 having a plurality of back holes 9, and slits 8; a back pressing plate 12 and a back spacer 13 to adjust the amount of the kneaded clay to be supplied; and a pressing plate 11 and a spacer 10 to regulate the shape and size of the formed ceramic article. At least a portion of the supply end 22 of the die 1 which overlaps with the back pressing plate 12 is flattened, and a surface roughness (Ra) thereof is in a range of 0.05 µm to 10 µm.