Honeycomb Die EDM Slit Precision and Strength
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Solution Overview
Problem
Conventional honeycomb structure forming dies struggle to achieve high dimensional precision and isostatic strength, especially when forming pentangular or more polygonal lattice-like cells or cells with varying sizes, due to limitations in manufacturing methods such as grinding with disc grindstones, which result in irregular slit widths and increased risk of forming defects.
Innovation Solution
A die manufacturing method involving electric discharge machining with comb-teeth electrodes to form slits with predetermined widths and width-enlarged portions, ensuring precise alignment and gradual increase in slit width from the inner to the outer peripheral regions, thereby enhancing the strength and precision of the honeycomb structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional grinding with disc grindstones is used to form slits in the die, then the manufacturing process is simple, but the slit widths become irregular and dimensional precision deteriorates
Solution Approach 1:
The patent replaces the conventional mechanical grinding system with an electric discharge machining (EDM) system. The EDM process uses electrical discharges between electrodes to erode material, enabling precise formation of slits with controlled widths without the mechanical contact and irregularities associated with grinding. This substitution achieves superior dimensional precision while maintaining manufacturing feasibility through automated electrode positioning and discharge control.
Solution Approach 2:
The patent changes the fundamental processing parameter from mechanical removal (grinding) to thermal-electrical removal (electric discharge). By controlling discharge energy, electrode geometry, and processing conditions, the system achieves precise slit width control. The width-enlarged portions are formed by adjusting electrode dimensions and discharge parameters, enabling gradual width increases from inner to outer peripheral regions with high precision.
2Strength
If the thicknesses of cell partition walls are decreased to reduce weight and improve warm-up characteristics, then the heat capacity decreases and purification performance improves, but the breakdown strength against external pressure from the outer peripheral surface further lowers
Solution Approach 1:
The patent applies local quality by creating width-enlarged portions in the slits at specific locations (outer peripheral regions) while maintaining regular slit widths in inner regions. This results in partition walls with locally varied thicknesses: thinner in the center for weight reduction and heat capacity optimization, and thicker at the outer periphery for enhanced breakdown strength and resistance to external pressure. The die geometry is specifically designed to produce this non-uniform thickness distribution.
Solution Approach 2:
The patent introduces asymmetry in the slit design by creating width-enlarged portions that are positioned asymmetrically relative to the overall honeycomb structure. The slits have different widths at different radial positions, with the outer peripheral slits being wider than inner slits. This asymmetric slit width distribution directly translates to asymmetric partition wall thicknesses, optimizing the balance between weight and strength requirements.
3Reliability
If a structure wherein the outer peripheral surface of the honeycomb catalyst carrier is held is employed to improve holding area and resistance to vibration, then the isostatic strength can be improved, but the setting of the thicknesses of cell partition walls and honeycomb outer wall becomes more complex to achieve high dimensional precision
Solution Approach 1:
The patent replaces conventional mechanical forming methods with electric discharge machining to form the complex slit geometry. The EDM process can accurately reproduce the designed slit widths and width-enlarged portions without the tool wear, tool path errors, and dimensional deviations that plague mechanical machining. This enables precise control of partition wall thicknesses even in the complex outer peripheral regions where holding stability is critical.
Solution Approach 2:
The patent incorporates width-enlarged portions in the die slits as a preliminary design feature that pre-compensates for the holding requirements. By building in the thickness variation at the outer peripheral partition walls during the forming process itself, the structure achieves enhanced holding stability and vibration resistance without requiring post-forming adjustments or complex assembly operations.
4Strength
If outer peripheral slits have larger widths to increase the thickness of outer peripheral ribs, then the isostatic strength increases, but the slit width becomes irregular and forming defects increase
Solution Approach 1:
The patent uses electric discharge machining instead of mechanical grinding to form the slits with width variations. The EDM process eliminates the tool wear and mechanical runout issues that cause irregular slit widths in conventional grinding. By controlling electrode geometry and discharge parameters, the system achieves smooth, controlled transitions in slit width from regular to width-enlarged portions without the forming defects associated with mechanical methods.
Solution Approach 2:
The patent applies partial action by enlarging the slit width only in specific outer peripheral regions while maintaining regular widths in inner regions. This selective width enlargement provides the necessary isostatic strength enhancement at critical locations without unnecessarily increasing material removal or complexity throughout the entire die structure. The width-enlarged portions are precisely positioned to provide strength where needed while maintaining dimensional control.
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 the production of honeycomb structures with increased isostatic strength and dimensional precision, reducing the likelihood of forming defects and improving the overall quality of the honeycomb structure, particularly for applications requiring high precision and strength like catalyst carriers and diesel particulate filters.
Implementation Method 1
a first comb-teeth electrode provided with a plurality of thin-plate-like first projection electrodes corresponding to sides constituting the inner peripheral slit to form the slits including the inner peripheral slit and having a predetermined width by electric discharge processing; and after the first electric discharge processing, a second comb-teeth electrode provided with a plurality of thin-plate-like second projection electrodes corresponding to parallel sides constituting the width-enlarged portion to form the width-enlarged portion by electric discharge processing
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 1E
AI summary
There is described a die for (1) forming a honeycomb structure, comprising a platy die base member having a clay supply face (8) on one end to which a plurality of introduction holes (4) for introducing a mixed material containing ceramics are formed; a clay forming face (7) to which a plurality of slits (5) connected to the introduction holes (4) is formed on the other end face in lattice-like partition regions, and from which the clay is extruded to form a formed honeycomb article, at least a part of lattice-like partition regions defined by the slits being provided in such a position that the extended line of said at least part of a plurality of lattice-like regions overlap with the slits along the edges of the regions in a plane seen from a thickness direction (201) of the die base member, inner peripheral slits (50) formed in the inner peripheral region (22) of the clay forming face (7) and having a predetermined slit width, and outer peripheral slits (53) formed in the outer peripheral region (24) surrounding the periphery of the inner peripheral region and having a width-enlarged portion (52) having a width larger than that of the inner peripheral slit.