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Generation of optimal parting direction based on undercut features in injection molded parts
Abstract
An algorithm has been developed for the automated recognition of undercut features for determining the optimal parting direction of injection molded parts. On the basis of the 3-D solid model of a molded part described in Boundary Representation (B-Rep), the geometrical entities and the information of a solid model and their topological relationships are extracted. According to these information, the criteria under which the undercut feature is formed are set up and the undercut feature directions (the withdrawal directions of side-cores or side-cavities) are identified. The optimal parting direction is chosen based on the criterion of maximizing undercut feature volumes in each undercut feature group. Through the case studies on industrial parts, the methodology developed is found to be efficient and effective in determining the undercut features and the optimal parting direction automatically.mining the optimal parting direction of injection molded parts. On the basis of the 3-D solid model of a molded part described in Boundary Representation (B-Rep), the geometrical entities and the information of a solid model and their topological relationships are extracted. According to these information, the criteria under which the undercut feature is formed are set up and the undercut feature directions (the withdrawal directions of side-cores or side-cavities) are identified. The optimal parting direction is chosen based on the criterion of maximizing undercut feature volumes in each undercut feature group. Through the case studies on industrial parts, the methodology developed is found to be efficient and effective in determining the undercut features and the optimal parting direction automatically.
... Most of the research for die design of die casting is focused on determination of parting direction, parting line, parting surface determination, and gating system design only [2][3][4][5][6][7][8][9][10][11], whereas lesser attention has been given to address the issue of design of multicavity die casting die. Design of a multicavity die casting die depends on activities like determination of number of cavities, cavity layout design, core-cavity design, and side core design. ...
... Since SolidWorks is proprietary software, some of the data extraction from CAD file of the part is not feasible, which was therefore taken as input from the user. Furthermore, lot of efforts has been made by the researchers, to address the issues of undercut feature identification [5,6,9,10,29,30] and side core design [25,[28][29][30][31][32][33]. Identification of undercut features and their location in an automated manner would make the system more useful and increase the level of automation. ...
Design of a die casting die is a nontrivial task, which depends upon a number of influencing factors related to material, part geometry, manufacturing resources, cost, delivery time, etc. Complexity of this die design activity further increases in case of a multicavity die. Currently available die design systems lack in the level of automation and do not explicitly address multicavity die design. Present work is an attempt to develop a system, which facilitates computer-aided design of a multicavity die casting die. The objective of the proposed system is to automate the process of deciding number of cavities, design of cavity layout and die-base, and core and cavity creation for a multicavity die casting die. The proposed system, which we named Auto_Die_Caster, works as an add-on application to solid modeling software SolidWorks. The proposed system is divided into four modules, namely data initialization, cavity design, cavity layout and die-base design, and core-cavity design. Use of commercial software like SolidWorks as a platform both for part design and generation of die design eliminates loss of data which makes the proposed system quite useful in the industrial scenario. To demonstrate the capabilities of Auto_Die_Caster, it was tried for a number of die casting parts and the results are presented. Proposed system is a step forward to design manufacturing integration for die casting process. 2012 Springer-Verlag London.
... Most of the research for die design of die casting is focused on determination of parting direction, parting line, parting surface determination, and gating system design only [2][3][4][5][6][7][8][9][10][11], whereas lesser attention has been given to address the issue of design of multicavity die casting die. Design of a multicavity die casting die depends on activities like determination of number of cavities, cavity layout design, core-cavity design, and side core design. ...
... Since SolidWorks is proprietary software, some of the data extraction from CAD file of the part is not feasible, which was therefore taken as input from the user. Furthermore, lot of efforts has been made by the researchers, to address the issues of undercut feature identification [5,6,9,10,29,30] and side core design [25,[28][29][30][31][32][33]. Identification of undercut features and their location in an automated manner would make the system more useful and increase the level of automation. ...
Diecasting is one of the die-based forming methods which is used to manufacture large number of good quality parts in short time by high injection pressure of cast alloy. In reality die design of diecasting has been performed by die design experts, which is not well documented in books or literature. This study presents a systematic approach for cavity layout design system using some details of the part geometry. This methodology quantifies practical knowledge and experiences in die design as a formulating procedure. By using this methodology, it is possible for designers to make cavity layout design efficiently and would result in reduction of time and cost. This paper presents three stage methodology to complete cavity layout design of a die casting die. These stages include, layout requirements, factors affecting layout pattern and clearance database needed to arrange cavities within a single die base. Using this methodology an efficient system can be developed which would be used for automation of cavity layout design.
... Most of the research for the parting design of injection mold is focused on the determination of parting direction, parting line, parting surface determination, and gating system design only [1][2][3][4][5][6][7][8][9][13][14][15][16][17][18][19][20], Some research papers published on the mold design for die casting have also been discussed due to strong similarity between both the processes. The research work reported in recent years for the generation of the mold core and cavity has been summarized in the following paragraphs. ...
With the widespread application of mold CAD technology, it is a necessary design link for designers of mold enterprises to use three-dimensional software for mold parting design. Parting design is the most complex and key part of the whole injection mold design process. It is directly related to the success or failure of the whole mold design. In view of many problems existing in the current parting design system, such as frequent human–computer interaction, cumbersome operation, low efficiency, and heavy dependence on the experience and knowledge of designers and their software operation level, an automatic parting design algorithm based on the solid method is proposed and implemented in the developed mold automatic parting system (Auto_Mold_Parting). Experimental results show that this system can significantly decrease the time of design and guide users to quickly complete the design while reducing design errors to improve working efficiency by the automatic integration function.
... A lot of work is put into the reduction of tool complexity by changing the design of the part to avoid undercuts [22,23], optimizing the parting direction of the tooling [24] or employing forced demolding [25,26]. If none of these approaches is a proper solution for the desired complex part, the tooling has to be equipped with manually or automatically moved slides [25,27]. ...
The production of injection-molding prototypes, e.g., molded interconnect devices (MID) prototypes, can be costly and time-consuming due to the process-specific inability to replace durable steel tooling with quicker fabricated aluminum tooling. Instead, additively manufactured soft tooling is a solution for the production of small quantities and prototypes, but producing complex parts with, e.g., undercuts, is avoided due to the necessity of additional soft tooling components. The integration of automated soft slides into soft tooling has not yet been investigated and poses a challenge for the design and endurance of the tooling. The presented study covers the design and injection-molding trial of soft tooling with integrated automated slides for the production of a complex MID prototype. The design further addresses issues like the alignment of the mold components and the sealing of the complex parting plane. The soft tooling was additively manufactured via digital light processing from a silica-filled photopolymer, and 10 proper parts were injection-molded from a laser-direct structurable glass fiber-filled PET+PBT material before the first damage on the tooling occurred. Although improvements are suggested to enhance the soft tooling durability, the designed features worked as intended and are generally transferable to other part geometries.
... Injection molding is typically limited to plastics (e.g., ABS or silicone), die casting to ductile metals (e.g., zinc or aluminum), and powder metallurgy to metal powder (sometimes mixed with a binder); manufacturability analysis within the appropriate tooling is focused primarily on being able to quickly and efficiently fill the mold with material and eject it safely. The manufacturability constraints then are in the form of feature restrictions (they must fit into and be easily removable from the tool), usually with a two-part tool, and the location of the tool parting line [175,[181][182][183] (Figure 2.5b shows one of the design results from Singh and Madan [175]). From a simple design perspective, powder metallurgy is often the least restrictive [32,184], as it can sometimes use a multi-part tool instead of the standard two-part used in injection molding and die casting. ...
Doctoral Dissertation: In the manufacturability-driven design (MDD) perspective, manufacturability of the product or system is the most important of the design requirements. In addition to being able to ensure that complex designs (e.g., topology optimization) are manufacturable with a given process or process family, MDD also helps mechanical designers to take advantage of unique process-material effects generated during manufacturing. One of the most recognizable examples of this comes from the scanning-type family of additive manufacturing (AM) processes; the most notable and
familiar member of this family is the fused deposition modeling (FDM) or fused filament fabrication (FFF) process. This process works by selectively depositing uniform, approximately isotropic beads or elements of molten thermoplastic material (typically structural engineering plastics) in a series of pre-specified traces to build each layer of the part. There are many interesting 2-D and 3-D mechanical design problems that can be explored by designing the layout of these elements. The resulting structured, hierarchical material (which is both manufacturable and customized layer-by-layer within the limits of the process and material) can be defined as a manufacturing process-driven structured material (MPDSM). This dissertation explores several practical methods for designing these element layouts for 2-D and 3-D meso-scale mechanical problems, focusing
ultimately on design-for-fracture. Three different fracture conditions are explored: (1) cases where a crack must be prevented or stopped, (2) cases where the crack must be encouraged or accelerated, and (3) cases where cracks must grow in a simple pre-determined pattern. Several new design tools, including a mapping method for the FDM manufacturability constraints, three major literature reviews, the collection, organization, and analysis of several large (qualitative and quantitative) multi-scale datasets on the fracture behavior of FDM-processed materials, some new experimental equipment, and the refinement of a fast and simple g-code generator based on commercially-available
software, were developed and refined to support the design of MPDSMs under fracture
conditions. The refined design method and rules were experimentally validated using a series of case studies (involving both design and physical testing of the designs) at the end of the dissertation. Finally, a simple design guide for practicing engineers who are not experts in advanced solid mechanics nor process-tailored materials was developed from the results of this project.
... Injection molding is typically limited to plastics (e.g., ABS or silicone), die casting to ductile metals (e.g., zinc or aluminum), and powder metallurgy to metal powder (sometimes mixed with a binder); manufacturability analysis within the appropriate tooling is focused primarily on being able to quickly and efficiently fill the mold with material and eject it safely. The manufacturability constraints then are in the form of feature restrictions (they must fit into and be easily removable from the tool), usually with a two-part tool, and the location of the tool parting line [124][125][126][127]. Powder metallurgy is the least restrictive [30,128], as it can sometimes use a fourpart tool instead of the standard two-part used in injection molding and die casting. ...
Design-for-manufacturing (DFM) concepts have traditionally focused on design simplification; this is highly effective for relatively simple, mass-produced products, but tends to be too restrictive for more complex designs. Effort in recent decades has focused on creating methods for generating and imposing specific , process-derived technical manufacturability constraints for some common problems. This paper presents an overview of the problem and its design implications, a discussion of the nature of the manufacturability constraints, and a survey of the existing approaches and methods for generating/enforcing the minimally-restrictive manufacturability constraints within several design domains. Four major design perspectives were included in the study, including the system design (top-down), the product design (bottom-up), the manufacturing process-dominant approach (specific process required), and the part-redesign approach. Manufacturability constraints within four design levels were explored as well, ranging from macro-scale to sub-micro-scale design. Very little previous work was found in many areas, but it is clear from the existing literature that the problem and a general solution to it are very important to explore further in future DFM and design automation work.
... Most of the researchers [8][9][10] concluded that the parting line is placed along the silhouette of the part in a direction of maximum projected area. The side core is employed to form the undercuts and the parting line splits at the undercuts is found by the researchers [11][12][13][14]. Hu et al. [1] employed a numerical simulation technique to design and optimize gating-system for thin wall die-cast components. ...
Multi-gates are often used in the die-casting die design to provide proper feed of the molten metal to the cavity for obtaining a sound casting. Although a number of systems for design of gating-systems are available they do not help much to design multi-gates. A computer aided system for gating-system for die-casting die-design with multi-gates is proposed in this paper. The proposed system helps to generate parameters of the multi-cavity die taking into account a multitude of factors, such as part design, material properties, process data and die-casting machine information. The parameters so generated are applied on selected gating-system feature existing in the library to complete the design of gating-system. The system generated results for industrial case-study parts are in tandem with the industry practices. The proposed system would greatly help bridge the existing gaps between design and manufacturing for die-casting die-design.
Copyright © 2016 by ASME Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature
Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
... However, no clear justification is given for choosing a particular direction in each of the individual cases. They have also suggested generating optimal parting direction by maximizing the undercut feature volumes in each undercut feature group in another closely related work [Fu99a]. ...
Often complex molded parts include undercuts, patches on the part boundaries that are not accessible along the main mold opening directions. Undercuts are molded by incorporating side actions in the molds. Side actions are mold pieces that are removed from the part using translation directions different than the main mold opening direction. However, side actions contribute to mold cost by resulting in an additional manufacturing and assembly cost as well as by increasing the molding cycle time. Therefore, generating shapes of side actions requires solving a complex geometric optimization problem. Different objective functions may be needed depending upon different molding scenarios (e.g., prototyping versus large production runs). Manually designing side actions is a challenging task and requires considerable expertise. Automated design of side actions will significantly reduce mold design lead times. This thesis describes algorithms for generating shapes of side actions to minimize a customizable molding cost function.
... Chen et al. 7 presented a ''visibility map'' to determine surface visibility in both global and local interference, which was then used to find the optimal parting direction of a 3D model. Fu et al. 8 proposed an algorithm that determined the optimal parting direction based on the number of undercut features and their corresponding volumes. Under the same rationale, Nee et al. 9 described a method to determine the parting directions of injection-molded parts. ...
A new slicing algorithm that uses multiple sets of cutting planes to automatically determine parting curves for three-dimensional parts is proposed. In this algorithm, one set of cutting planes is used to generate the slicing profiles, and two others are used to determine the intersection points with the inner and outer loops of the parting curves. The algorithm provides a highly effective solution for handling complicated models that contain free-form surfaces. The features of the algorithm are highlighted in three case studies using tessellated geometry in STL file format as the input. The resultant parting curves overcome many problems inherent in the current methods and can be used by various downstream computer-aided design systems for three-dimensional mold design.
... where V, E, and S represent the set of vertices, edges, and surfaces respectively [74]. The connection between various entities is shown in Figure A-1. ...
... Kharderkar et al. [3] described an algorithm to identify and display undercut features by implementing the Gauss map. Building upon these related techniques, Fu et al. [4] proposed an algorithm that determined the optimal parting direction in injection-molded parts by the number of undercut features and their corresponding volumes. Furthermore, Chen et al. [5] posed a method in which three possible parting directions were defined by surface normal vectors of a bounding box. ...
Multi-piece molding technology is an important tool in producing complex-shaped parts that cannot be made by traditional two-piece molds. However, designing multi-piece molds is also a time-consuming task. This paper proposes an approach for automatic recognition of mold-piece regions and parting curves for free-form CAD models. Based on the geometric properties of objects and mathematical conditions of moldability, a collection of feasible parting directions is formed from which the sets of visible-moldable surfaces are identified for each parting direction. Moldable surfaces that are partially visible to a particular parting direction are recognized and divided into fragments by silhouette detection and edge extrusion. A set of criteria is proposed to arrange tentative fragments, which can be simultaneously visible to several parting directions, into appropriate regions for mold pieces. Finally, the parting curves for mold pieces are extracted from the corresponding mold-piece regions. The proposed algorithm overcomes the problems found in previous multi-piece molds and at the same time achieves high accuracy and high performance. Examples of industrially complex models are used to demonstrate the performance and robustness of the proposed algorithm. The approach is generic in nature, allowing its application to be extended to any complex geometry in 3-D mold design.
... Fu et al. [12] developed an algorithm for generation of the optimal parting direction based on the minimum number of undercut features in injection molded parts. Undercut features are categorized based on the connectivity with the target surface and their geometrical information. ...
... Fu et al. [12] developed an algorithm for generation of the optimal parting direction based on the minimum number of undercut features in injection molded parts. Undercut features are categorized based on the connectivity with the target surface and their geometrical information. ...
The parting line decision for die-cast parts is a non-trivial task, which depends upon a number of factors related to the part geometry and the die-casting process requirements. This is a crucial decision which not only affects the design and manufacturing of the die-casting die but the part manufacturing as well. Normally, a die-casting die-design expert invests a lot of time, effort and resources to take this decision, which affects the part manufacturing lead time and cost. A systematic approach for automated determination of the parting line for die-cast parts is presented in this paper. Unlike the previous systems, which consider part geometric factors only, the system proposed in this paper also considers the die-casting process requirements to determine the parting line in a systematic and automated manner. Here we discuss classification of the die-cast part surfaces, identification of undercuts and protrusions, identification of parting line regions, and determination of the parting line. The system generates a number of feasible parting lines in a given parting direction after applying the die-casting process requirements. Finally, the most suitable parting line is determined from the feasible parting lines considering the industry best practices. The results obtained from the system are similar to those of the industry. The proposed system would prove to be a major step towards automation of the die-casting die design, leading to design–manufacturing integration of the die-casting process.
... Prismatic cut 8 2, 3, 4, 5, 6, 7 1 +y UF2 Cylindrical hole 7 45, 46 34 +x UF3 Cylindrical hole 34 45, 46 7 −x UF4 Cylindrical hole 10 11, 12 5 +z UF5 Cylindrical hole 5 11, 12 10 −z UF6 Cylindrical hole 13 14, 15 4 +x UF7 Cylindrical 14,15,11,12,17,18,23,24,26,27,28,29,30,31,32,33,34,45,46,35,36,37,38,39,40,42,43 side cores in this case, circular holes. This is to ensure that side cores remain with the core half side, which is a die-casting process constraint. ...
Determining parting direction and parting line for die-cast parts is a nontrivial task that not only depends upon shape and topology of the part, but also on many process related factors. Normally, a die-casting expert decides parting direction and parting line, intuitively taking into account a large number of factors, and this process can be time consuming and cumbersome in many cases. This study addresses automated determination of parting direction and parting line for a die-cast part from part CAD model. The proposed methodology takes STEP file of the part as input for extracting die-casting features, which consists of protrusion or depression regions of the part. These features are classified into those with single, double, or multiple withdrawal directions. Geometric reasoning is used for feature recognition, which includes nested and interacting features. Global visibility instead of local visibility is used for planning withdrawal direction, which makes the decision arrived by present system closer to industrial practice. Parting line is determined based on selected candidate parting direction considering process constraints and priorities. The contribution of this paper is in terms of development of an automated parting direction and parting line determination system, which is more comprehensive and overcomes limitations of the previous work. Results of this system have been validated with those arrived at by experts from the die-casting industry. Copyright 2007 by ASME.
... This approach, however , cannot identify directions as UFPDs when portions of a single " pocket " can only be formed by different halves of the mold, which unfortunately is not uncommon in industry. Graph-based algorithms recognized potential undercut features using boundary representation graphs1314151617 . This approach works for detecting depression or protrusion undercuts. ...
For molding and casting processes, geometries that have undercut-free parting directions (UFPDs) are preferred for man-ufacturing. However, existing approaches either cannot identify all UFPDs or cannot run at interactive speeds (the best exhaus-tive algorithm, unimplemented, runs at O(n 4) time theoretically). Our proposed feature-based approach avoids testing the whole Gaussian sphere of potential directions by first efficiently identify all UFPDs for individual features such as extruded and revolved features, thus significantly reducing test space and running time. In this paper, we describe a fast algorithm to find all UFPDs for solids of revolution. The algorithm is based on analyzing the constructing 2D generator profiles, building on our previous re-sults for 2-moldability analysis of polygons. The running time is O(n), where n is the geometric complexity of the 2D generator profile. For parts containing multiple solids of revolution, the set of possible UFPDs can be significantly reduced based upon an analysis of each such feature, efficiently identifying many as non-2-moldable or reducing the search space for exhaustive al-gorithms that find all UFPDs.
... Parting direction, parting surface, and undercut constitute the main parameters that significantly affects the mouldability and the manufacturing costs of a cast part. For a designed structure, the parting direction is usually obtained as the solution to an optimization problem so that certain criteria , e.g., number and volume of undercuts features, reach the optima ( Manoochehri 1996, 1997; Nee et al. 1997; Fu et al. 1999 ), hence minimizing the manufacturing costs. For the optimal design of a cast part in our present study, the parting direction af fects not only the manufacturing costs but also the working performance. ...
Parting direction is one of the main parameters that significantly affect mouldability and manufacturing costs of a cast part.
In conventional optimal design of cast part, a parting direction is pre-selected by a designer and fixed throughout the optimization.
However, when the optimization is performed with a different parting direction, the resulting design will also be different,
and more importantly it will end up with different working performance. Therefore, we take the parting direction as a design
variable in the optimization of a cast part so that the working performance can be optimized as much as possible. With these
goals, a level set based method is proposed for the simultaneous optimization of cast part and parting direction. In each
iteration, an optimal parting direction is first computed for the current structure, then the boundary of the current structure
is updated by a design velocity that guarantees the design be moldable with the optimal parting direction. Therefore, although
the parting direction may be changed during the optimization, the structure will always be moldable in the current parting
direction. Numerical examples are provided in 3D.
KeywordsCast part–Molding constraint–Parting direction–Structure optimization–Level set
... So, we will identify some of the important work in this field. Other work in the area of parting direction determination includes [10,16]. Representative work in parting surface and parting line design includes [18,32] and [34] respectively. ...
This paper describes algorithms for generating shapes of side actions to minimize a customizable injection moulding cost function. Given a set of undercut facets on a polyhedral part and the main mold opening directions, our approach works in the following manner: first, we compute candidate retraction space for every undercut facet. This space represents the set of candidate translation vectors that can be used by the side action to completely disengage from the undercut facet. As the next step, we generate a discrete set of feasible, nondominated retractions. Then we group the undercut facets into undercut regions by performing state space search over such retractions. This search step is performed by minimizing the given moulding cost function. After identifying the undercut regions, we generate the shapes of individual side actions. We believe that the results presented in this paper will provide the foundations for developing fully automated software for designing side actions.
... This approach, however, cannot find existing UFPDs when portions of a single " pocket " can only be formed by different halves of the mold. Graph-based feature recognition is another approach to finding undercuts [14,15,16,17,18]. However, this approach breaks down for complex interacting features. ...
For molding and casting processes, geometries that have undercut-free parting directions (UFPDs) are preferred for manufacturing.
Identifying all UFPDs for arbitrary geometries at interactive speeds remains an open problem, however; for polyhedral parts
with n vertices, existing algorithms take at least O(n
4) time. In this paper, we introduce a new algorithm to calculate all the UFPDs for extrusions, an important class of geometry
for manufacturing in its own right and a basic geometric building block in solid modeling systems. The algorithm is based
on analyzing the 2D generator profile for the extrusion, building on our previous results for 2D undercut analysis of polygons.
The running time is O(n
2logn) to find the exact set of UFPDs or O(n) to find a slightly conservative superset of the UFPDs, where n is the geometric complexity of the 2D generator profile. Using this approach, the set of possible UFPDs for a part containing
multiple extruded features can be reduced based upon an analysis of each such feature, efficiently identifying many parts
that have no UFPDs and reducing the search time for complete algorithms that find all UFPDs.
... In tandem with this, many researchers conducted research on undercut feature recognition. Fu et al. developed a methodology to categorize and recognize undercut features [1,2]. The undercut features are classified into different categories based on the edge number and edge characteristics of the target surface. ...
A methodology to deal with the automatic design of internal pins in injection mold CAD via the automatic recognition of undercut features is developed. The approach to automatically identifying the undercut features is first proposed. For the given parting directions, all the inner and outer undercut features are identified based on the topological relationship of geometrical entities. The outer edge loop, which represents the largest cross-section boundary along the given parting directions, is extracted and patched up. The surfaces of molding are then identified based on the classifications of their geometrical entities. To identify the deep inner undercuts in the molding, the projection of the main core, internal pins and their bounding boxes along the parting direction and the pin withdrawal direction are generated. Upon determination of whether the bounding boxes of any two internal pins and the main core projection have intersection area, the deep inner undercuts are located. The complete methodology is finally implemented and verified through case studies and the efficiency of the methodology in handling complex molded parts is thus illustrated.
Moulding refers to a set of manufacturing techniques in which a mould, usually a cavity or a solid frame, is used to shape a liquid or pliable material into an object of the desired shape. The popularity of moulding comes from its effectiveness, scalability and versatility in terms of employed materials. Its relevance as a fabrication process is demonstrated by the extensive literature covering different aspects related to mould design, from material flow simulation to the automation of mould geometry design. In this state‐of‐the‐art report, we provide an extensive review of the automatic methods for the design of moulds, focusing on contributions from a geometric perspective. We classify existing mould design methods based on their computational approach and the nature of their target moulding process. We summarize the relationships between computational approaches and moulding techniques, highlighting their strengths and limitations. Finally, we discuss potential future research directions.
Design-for-manufacturing (DFM) concepts have traditionally focused on design simplification; this is highly effective for relatively simple, mass-produced products, but tends to be too restrictive for more complex designs. Effort in recent decades has focused on creating methods for generating and imposing specific, process-derived technical manufacturability constraints for some common problems. This paper presents an overview of the problem and its design implications, a discussion of the nature of the manufacturability constraints, and a survey of the existing approaches and methods for generating/enforcing the minimally-restrictive manufacturability constraints within several design domains. Five major design perspectives or viewpoints were included in the survey, including the system design (top-down), product/component design (bottom-up), the manufacturing process-dominant case (product/component design under a specific process), the part-redesign perspective, and sustainability perspective. Manufacturability constraints within four design levels or scales were explored as well, ranging from macro-scale to sub-micro-scale design. Very little previous work was found in many areas, revealing several gaps in the literature. What is clearly needed is a more general, design-method-independent approach to collecting and enforcing manufacturability constraints.
Determination of pull directions for a freeform surface is a challenging problem because the number of normal vectors is unlimited for such type of surfaces. Consequently, researchers generally convert a freeform surface into planar faces to limit the number of normal vectors. This paper presents an approach using cascade filters of visibility maps to determine feasible pull directions for freeform surfaces such that the required accuracy is retained. Pull direction candidates are first generated using a modified regular placement method. Normal vectors are then extracted by a sampling box, and the number of normal vectors is optimized through a numerical approach. Significant normal vectors are then selected by a modified Barycentric method. A cascade filter of the visibility map is built using these vectors and used for the selection of feasible pull directions. A minimum number of sliders and cavities in molding are finally achieved using a clustering algorithm based on maximum intersections of visibility maps. A real-life part is created using commercial CAD software for performance evaluation of the proposed algorithm.
A hot forging process allows to produce parts of excellent quality and technical properties. Nevertheless, it is not possible to forge undercut geometries like piston pin bores, it is usually necessary to manufacture them in subsequent processes. Thus, an undercut-forging process was newly developed. Such a process requires a multidirectional forming tool, which is challenging due to a high clamping force of the tool during the process. With the research results, the requirements to the crucial tool components of heavy springs diminish, allowing using standard spring devices instead of large and expensive custom designed devices. The aim of this study is to analyze the clamping force, its origin, and influencing factors in order to facilitate the tool design. Therefore, in forming simulations the input parameters press velocity, initial temperature, and punch shape were investigated, and their effect on the clamping force was statistically evaluated. The press velocity has the major impact on the resulting clamping force. The initial part temperature and the shape of the punch tool showed minor but still significant effects. This combination of input parameters reduces the load and the stress on the tool, enabling to perform the process on smaller forging presses. Eventually, forging trials validated the results.
Automatic parting curve generation plays an important role in the realization of automatic injection mold design. We propose a hybrid visibility-based and graph-based approach to generate the parting curves of a solid part automatically. The approach consists of three steps: (i) construct a graph representation of the solid part, (ii) recognize mold piece region, and (iii) generate parting curve. In step (i), the surface visibility and edge convexity-concavity are attached to the graph. Visibility determination algorithms for various surface types and edge convexity-concavity calculation methods are also discussed. In step (ii), part surfaces are classified into concave-edge regions, inner-loop regions, and isolated surfaces. Concave-edge regions are decomposed into sub concave-edge regions based on graph-based algorithms that have linear time complexity. Concave-edge regions, inner-loop regions, and isolated surfaces are assessed to extract the cavity region, core region, and undercut regions. In step (iii), the boundary edges of each region are extracted to form parting curves. The approach has linear time complexity and is effective for complex solid products with planar surfaces, quadric surfaces, and free-form surfaces. Finally, two case studies are provided to validate the proposed approach.
Slider design is one of the vital tasks in achieving mold development automation. This paper proposes an approach to automating the determination of undercut regions and their releasing directions for complex parts in STL format. The end result of research will provide an impactful tool for manufacturing automation, and further enhance our advance mold design and manufacturing abilities. Specific research topics include: (1) automatic segregation of undercut regions and regular regions for each of the inner loops, (2) automatic selection of undercut regions for each of the inner loops, (3) automatic determination of releasing directions for each of the undercut regions, and (4) automatic grouping of undercut regions to produce sliders. Several real-life parts, such as cell phone component and car lamp component, are used as testing examples to implement the proposed approach and algorithms. While these example parts contain a large number of complicated free-form surfaces, the implementation results show that undercut regions and their releasing directions can be found within acceptable range of time.
In this paper a new method of automatic design for the layout and sizing of the ejector pins of the plastic injection mold, based on the discrete geometry of the plastic part, is presented. The proposed algorithm consists of a first phase of geometric analysis in which a node mesh corresponding to the surfaces to be molded by the lower mold cavity is generated. Then the variations of the difference in thickness of the part for each pair of mesh nodes are evaluated, locating areas with varying thicknesses and resembling this geometric value at discrete nodes that are stored in arrays. Two sub-algorithms of discrete geometric recognition enable the location of the nodes which can be points of expulsion. Ejection points will correspond to those nodes which have a maximum in the parameter regarding concentration of nodes near walls, ribs, protrusions, etc. The dimensioning of the ejector pins is performed by an optimization algorithm with three objective functions, ensuring that the system of forces in the ejection of the part will be balanced. This new method improves on the methods used so far as it does not require heuristic methods to achieve the result and does not use the method of identifying features for the geometric recognition of the surface of the plastic part, avoiding the problems of dependency from the modeler and analysis of complex features. It takes the part in discrete format as input data, analyzing in this way the geometry externally, obtaining the advantage of the possibility of implementing the algorithm in any CAD modeler. The proposed algorithm is applicable to any geometry because it works regardless of the CAD system in which the piece has been designed. Finally, the system provides as a result the layout with the location and the diameter of the ejectors on the part while ensuring a suitable distribution of balance of ejection forces. The solution of the algorithm is shown superimposed on the part as a map of ejection. The results of the algorithm can be exported and stored for use in other applications and parametric injection mold CAD systems.
In this paper a new methodology of automated demoldability analysis for parts manufactured via plastic injection molding is presented. The proposed algorithm uses as geometric input the faceted surface mesh of the plastic part and the parting direction. Demoldability analysis is based on a sequential model to catalog nodes and facets of the given mesh. First, the demoldability of nodes is analyzed, subsequently, from results of previous nodes analysis, facets of the mesh are cataloged in: demoldable (facets belong cavity and core plate), semi-demoldable (plastic part manufactured by mobile mechanisms, side cores) and non-demoldable (plastic part not manufacturable). This methodology uses a discrete model of plastic part, which provides an additional advantage since the algorithm works independent of the modelling software and creates a new virtual geometry providing information on its manufacture, exactly like CAE software. All elements of the mesh (nodes and facets) are stored in arrays, according with their demoldability category, with information about their manufacture for possible uses in other CAD/CAE applications related to design, machining and costs analysis of injection molds.
In this paper, a new method for demoldability automatic analysis of parts to be manufactured in plastic injection is presented. The algorithm analysis is based on the geometry of the plastic part, which is discretized by a triangular mesh, posing a hybrid discrete demoldability analysis of both the mesh nodes and facets. A first preprocessing phase classifies mesh nodes according to their vertical dimension, assigning each node a plane perpendicular to the given parting direction. By selective projection of facets, closed contours which serve as the basis for calculating the demoldability of the nodes are created. The facets are then cataloged according to demoldability nodes that comprise demoldable, non-demoldable and semi-demoldable facets. Those facets listed as semi-demoldable are fragmented into demoldable and non-demoldable polygonal regions, causing a redefinition of the original mesh as a new virtual geometry. Finally, non-demoldable areas are studied by redirecting the mesh in the direction of the sliding side, and again applying the processing algorithm and cataloging nodes and facets. Resoluble areas of the piece through mobile devices in the mold are obtained. The hybrid analysis model (nodes and facets) takes advantage of working with a discrete model of the plastic part (nodes), supplemented by creating a new virtual geometry (new nodes and facets) that complements the original mesh, providing the designer not only with information about the geometry of the plastic piece but also information on their manufacture, exactly like a CAE tool. The geometry of the part is stored in arrays with information about their manufacture for use in downstream applications.
Injection moulding process is a vast and advantageous process in the field of science and technology. Injection moulding process gives birth to vast application which replaces not only industrial products and parts but also capture home appliances and the products of our day to day life. But from the technology point of view we are still using hit and trial methods. In industries, workmen and craftsmen who are engaged in these operations are only expertise but to a certain extent they are also dependent on hit and trial methods which sometimes increases the manufacturing cost of the product. There is a need to develop a technology which guides the designer that what methods he has to follow to design a particular product. There are basically three step in the injection moulding cycle. Firstly, design of sprue which are tapered to increase the rate of flow. Secondly, design of runner whose efficiency is pre determined and fixed. Efficiency here refer to smoothness or least obstruction provided to the flow material. Thirdly, selection of the gate which pour the flow material finally into the cavity. Selection of gate is quite a difficult task for the designer; only skilled crafts-men can handle easily. Now again the problem arrives to assemble these the three steps according to the type of cavity. In this paper i tried to develop a system with the help of CAD/CAM which facilitates the user to work on injection moulding operations starting from the cavity to the selection of gates and then to the efficiency of runner and finally to sprue. This results time reduction in designing process and to a certain extent reduces manufacturing cost also.
The gating system design for a die-casting die is a non-trivial task that involves a number of steps and computations, in which many factors related to part design, material, and process need to be accounted. In case of a multi-cavity die-casting die, the non-triviality of the gating system design increases manifold. The main contribution of this article is to develop a computer-aided system for design of gating system for multi-cavity die-casting dies. The proposed system applies design knowledge and rules, accounting for various influencing factors to design gating system elements and generate their computer-aided design models in an efficient manner. To demonstrate the capabilities of the developed system, the results for an industrial case study part are presented. We expect that the proposed system would help reduce manufacturing cost and lead time, alongside bridging gaps between design and manufacturing of the die-casting process.
In computer-aided design for moldings, automatic generation of parting curves is a crucial design task that has an influence on the entire mold structure. This article proposes a hybrid approach for determining the parting curves of free-form computer-aided design models. Based on the analysis of the geometric properties of specific entities and mathematical conditions, different sets of moldable surfaces for two-half molds and side cores are identified. All surfaces that do not contribute to the parting curves can be subtracted from these surface sets. The proposed parting curve is generated based on the combination of both the outermost boundary edges and the visible silhouette segments of the relevant surfaces. By the techniques of silhouette detecting, edge projecting, and ray testing, the proposed algorithm overcomes the problems found in conventional research that cannot guarantee that the outermost curves generated are the actual silhouette of a free-form surface. In addition, by eliminating all irrelevant surfaces and without using the surface approximation method, the proposed approach achieves the goals of obtaining high accuracy coupled with high performance. Two examples of industrial models are used to demonstrate the performance and robustness of the proposed algorithm. The approach is generic in nature, which allows it to be applied to any complex geometry in three-dimensional mold design.
This article describes automated identification, classification, division and determination of release direction of complex undercut features of die-cast parts. The proposed system uses the concepts of visibility and accessibility to identify undercut features from a B-rep model of a die-casting part. The undercut features are then classified using a rule-based algorithm. Thereafter, the identified complex undercut features are separated into simple ones. Finally, the release direction for each simple undercut feature is determined and those having common release direction are grouped. The proposed system is implemented on case study die-cast parts, and the results are verified. This article would help bridge the design-manufacturing integration gaps in the die-casting process.
Runner and gating system design is one of the important activities of die-casting die design. In normal practice, a die-casting expert makes use of the expertise gained taking care of many factors, such as material properties, industry best practices and physics of the process to determine the runner and gating design parameters. These parameters are then optimized by conducting process flow simulations on a computer and dry runs on a die-casting machine, which usually requires a number of iterations. These iterative activities increase the manufacturing lead time and makes the die-casting die-design a tedious process. A system which could reduce the iterations and make the design process more efficient is highly desirable. This paper presents a computer-aided system for runner and gating system design for a die-casting die. The system first generates runner and gating system parameters based on part, material and machine information. The system makes use of a runner and gating system feature library that has been built in this research. Lastly, the user decides the placement of the runner and gating system, along the parting line of the die-cast part. The results obtained from the system for some industrial die-casting parts are as per the practices being followed in the industry.
This paper presents an efficient method to generate packaging space that can be used to create molded foam. This method first reduces the number of facets presenting the product and then detects heights of supporting lines from an evenly spaced mesh grid on the bottom space of a pre-defined bounding box. The height of each supporting line is further relaxed and smoothed to form the final supporting surface. Based on the supporting surface, an STL format is created so it can be fabricated using RP machines. Three examples are presented to demonstrate this method.
This article describes automated identification, classification, division and determination of release direction of complex undercut features of die-cast parts. The proposed system uses the concepts of visibility and accessibility to identify undercut features from a B-rep model of a die-casting part. The undercut features are then classified using a rule-based algorithm. Thereafter, the identified complex undercut features are separated into simple ones. Finally, the release direction for each simple undercut feature is determined and those having common release direction are grouped. The proposed system is implemented on case study die-cast parts, and the results are verified. This article would help bridge the design-manufacturing integration gaps in the die-casting process.
In this paper, a new approach for moldability analysis is presented. A new algorithm based on a discretization method using storage arrays is developed. The discretization method consists of slicing a CAD part model and analyzing 2D intersection profiles by scanning lines along the parting direction and side demolding directions. The intersection points obtained are classified according to the value of their coordinates and assigned to different areas of the mesh. A hierarchical classification in terms of demolding is also proposed. A set of classification criteria for transforming a discrete points mesh into the desired demolding map is introduced. The stored boundary points are evaluated through a new reallocation algorithm of points in mesh in order to compare each point with the remaining points included in the higher order hierarchy demolding zone. The algorithm then reassigns boundary points to a set of hierarchically classified mold zones, and calculates the parting line subsequent to the parting direction. The proposed method allows the moldability analysis to be performed on any system, and no other internal information of the solid is required. Solid geometry remains stored in arrays for further work. This volume discretization method improves the efficiency of the process since it is defined by a much more simple conception by means of massive data storage arrays whose elements are the coordinates of the part boundary points. The resulting demoldability map is displayed on the same CAD part analyzed, providing designers with an evaluation tool which assists them in taking decisions about the mold design.
In the current mould-making industries, the challenge is to shorten the mould lead-time while maintaining the desired quality. This is one of the main demands from customers so as to maintain a competitive edge over the competition. While mould industries are always improving on their systems to cater to the rapidly changing plastics industry, one of the common issues that are still plaguing them is the management of large quantities of data within a mould project. In the current practice of local mould-making industries, almost all the data for the mould design, manufacture and testing stage are often either confused or duplicated unnecessarily. As a result, it becomes less responsive when changes are required since manual decision-making and sorting of these data are required. With the increasing complexity of plastic part design, the corresponding mould design, manufacturing, and testing data also increase in both quantity and complexity. The usual method of managing these data would take up a substantial amount of time. This issue could be resolved by incorporating a data management system that specifically caters to mould-making industries into their practice. This paper presents a framework for how the data from the different stages of the mould project could be managed more efficiently through the use of templates. This framework is divided into modules to cater for the various stages of the mould project. A case study is presented to illustrate the proposed framework for mould data management.
We consider the problem of whether a given geometry can be molded in a two-part, rigid, reusable mold with opposite removal directions. We describe an efficient algorithm for solving the opposite direction moldability problem for a 2D "polygon" bounded by edges that may be either straight or curved. We introduce a structure, the normal graph of the polygon, that represents the range of normals of the polygon's edges, along with their connectivity. We prove that the normal graph captures the directions of all lines corresponding to feasible parting directions. Rather than building the full normal graph, which could take time O(n log n) for a polygon bounded by n possibly curved edges, we build a summary structure in O(n) time and space, from which we can determine all feasible parting directions in time O(n).
In the design of plastic injection molds, the depressions and protrusions (DP) preventing the removal of molded part from
mold are referred to as undercuts. This paper describes an approach to recognize DP feature within the curvature region representation
based on the curvature properties of entities in B-rep model. The recognized depression features and the concave transitions
between protrusion features are potential undercuts which affect the choice of parting directions of the molded part. The
possible withdrawal directions of the potential undercuts are derived by geometric reasoning and visibility map computation.
This method can recognize isolated and intersecting features with planar, quadric, and freeform surfaces. The identified potential
undercuts with their possible withdrawal directions can provide decision support information for mold design such as selecting
parting direction, parting lines and surfaces, etc. The case study is presented to verify the feasibility of the developed
method.
KeywordsInjection molding-Freeform feature recognition-Undercut-Withdrawal direction
This paper presents an automated method to generate thin-walled packaging structures with reinforcement. This method first
obtains a thin-walled design space compose of hexahedral elements, which covers the models to be packaged without undercut
effect. After the proper boundary conditions are assigned by designers, topology optimization is applied to identify the optimal
placement of reinforcement. This automated method can also be used to generate foam packaging structures. Design examples
are presented to demonstrate the efficiency of this method.
In casting, molding and forming processes, the surface geometries of the fabricated products are formed/molded by different functional components of tooling. In plastic injection molding, they are molded by core, cavity or side-cores. In die and mold CAD, how to identify the product surfaces formed/molded by the corresponding tool components for a given product CAD model is critical, as it affects the determination of parting directions, parting lines and parting surfaces, the generation of core and cavity blocks, and finally the design of side-cores and their actuating mechanisms. In this paper, the concepts of surface visibility, demoldability, and moldability are first presented and formulated. The surfaces formed/molded by core, cavity and side-cores are then defined based on the plastic injection molding process. The methodology to identifying and classifying them is further developed. By employing the proposed notions of the demoldability map of surfaces and undercut features, the most preferred demolding direction, the grouping of undercut features, and how to conduct the side-core design is articulated succinctly, and the detailed procedures and processes are presented. Through an industrial case study, the developed methodology for side-core design is systematically presented and the feasibility of the developed approaches is verified.
Due to the large variety of CAD systems in the market, data exchange between different CAD systems is indispensable. Currently, data exchange standards such as STEP and IGES, etc. provide a unique approach for interfacing among different CAD platforms. Once the feature-based CAD model created in one CAD system is input into another via data exchange standards, many of the original features and the feature-related information may not exist any longer. The identification of the design features and their further decomposition into machining features for the downstream activities from a data exchanged part model is a bottleneck in integrated product and process design and development. In this paper, the feature panorama is succinctly articulated from the viewpoint of product design and manufacturing. To facilitate feature identification and extraction, a multiple-level feature taxonomy and hierarchy is proposed based on the characteristics of part geometry and topology entities. The relationships between the features and their geometric entities are established. A litany of algorithms for the identification of design and machining features are proposed. Besides, how to recognize the intersecting features or compound features based on the featureless chunks of geometry entities is critical and the issue is addressed in the paper. A multi-level compound feature representation and recognition approach are presented. Finally, case studies are used to illustrate the validity of the approach and algorithms proposed for the identification of the features from CAD part models in neutral format.
We present new programmable graphics hardware accelerated algorithms to test the 2-moldability of geometric parts and assist with part redesign. These algorithms efficiently identify and graphically display undercuts as well as minimum and insufficient draft angles. Their running times grow only linearly with respect to the number of facets in the solid model, making them efficient subroutines for our algorithms that test whether a tessellated CAD model can be manufactured in a two-part mold. We have developed and implemented two such algorithms to choose candidate directions to test for 2-moldability using accessibility analysis and Gauss maps. The efficiency of these algorithms lies in the fact that they identify groups of candidate directions such that if any one direction in the group is undercut-free, all are, or if any one is not undercut-free, none are. We examine trade-offs between the algorithms' speed, accuracy, and whether they guarantee that an undercut-free direction will be found for a part if one exists.
There usually exist narrow-long-deep areas in mould needed to be machined in special machining. To identify the narrow-deep
areas automatically, an automatic narrow-deep feature (NF) recognition method is put forward accordingly. First, the narrow-deep
feature is defined innovatively in this field and then feature hint is extracted from the mould by the characteristics of
narrow-deep feature. Second, the elementary constituent faces (ECF) of a feature are found on the basis of the feature hint.
By means of extending and clipping the ECF, the feature faces are obtained incrementally by geometric reasoning. As a result,
basic narrow-deep features (BNF) related are combined heuristically. The proposed NF recognition method provides an intelligent
connection between CAD and CAPP for machining narrow-deep areas in mould.
Le sens est un concept couramment utilisé en sciences de gestion. Face au constat de la pluralité des attributions du terme " sens " dans la littérature et au flou théorique entourant son utilisation au sein des recherches en sciences de gestion, nous proposons une nouvelle construction du concept de sens en faisant émerger cette construction de l'étude empirique du sens donné à des projets de construction de centres commerciaux par les acteurs de la région Ile-de-France d'Immochan, filiale immobilière du groupe Auchan. La grille de lecture que constitue l'opérationnalisation du concept de sens nous permet de réaliser des analyses comparatives entre les acteurs des projets ainsi qu'à travers le temps dans le déroulement des projets. L'appréhension de la subjectivité des acteurs est ainsi cadrée par une grille d'analyse rigoureuse. Cet outil nous permet d'analyser trois phénomènes empiriquement constatés : l'influence de l'orientation des acteurs sur leur comportement, la mal-être des responsables de projet et l'utilisation de l'analogie pour donner sens au projet.
Au travers d''une étude menée avec des membres de projets de construction de centres commerciaux de la région Ile-de-France d''Immochan, filiale immobilière du groupe Auchan, ce travail propose une nouvelle approche du concept de sens utilisable pour les sciences de gestion. Après avoir défini et opérationnalisé le concept de sens, trois essais sont menés afin de comprendre en quoi cette nouvelle approche du sens peut apporter un éclairage nouveau pour le management de projet. L''orientation des acteurs des projets, le mal-être des responsables de projet et l''utilisation de l''analogie pour donner sens au projet sont ainsi décryptés au travers du concept de sens. Des implications managériales et théoriques sont avancées grâce aux résultats mis en évidence, et un outil de représentation du sens au travers d''une cartographie est proposé. Les notions de perte de sens et de non sens sont discutées au regard de notre approche du concept de sens.
Starting with the motivation to provide manufacturing feedback to designers and to reduce bottlenecks in the design-manufacturing transition, algorithms for constructing molds and dies are presented. The concept of “virtual manufacturing” serves as the umbrella for this work. Computational prototypes, rather than hardware prototypes, can greatly speed product development, process design, and process tooling development. The work presented here contributes directly to all three areas, since automated tool construction enables accurate, detailed Design-for-Manufacturing feedback to aid product development, enables process design through simulation, and provides an initial tool design that can be enhanced by a tool fabricator.
A series of algorithms are presented for the automated construction of tools from a purely geometric reasoning viewpoint. Starting with a solid model of a component, undercuts are found and classified, then moving tool sections are constructed. For external undercuts, accessibility directions are found and are used to construct tooling side actions. Automated undercut accessibility determination has not been previously previously reported in the literature. For internal undercuts, form pins are constructed that access the undercut through the core of the tool. Undercut classification is important since their cost implications can be reported back to the component designer during design. Two examples illustrate the application of the algorithms.
This paper deals with a processing system for extracting undercut in mold designing. The development of such a system involves the solution of two problems. One is how to extract those parts which may form undercuts-the parts that may be called “potential undercuts” -from the shapes of moldings. The other is how to determine on the optimum direction of withdrawal of moldings. In solving the first problem, we worked out a new method for extracting potential undercuts; this method comprises the determination of three-dimensional convex hull and set operations. The approach to the second problem was the use of the simplex method, one of the nonlinear optimization methods, to find the optimum direction of withdrawal of moldings. A case study was then conducted to verify the usefulness of the processing system thus developed.
Selection of an optimal parting direction in mold and die design is considered. Based on the condition for demoldability, two levels of visibility—complete and partial—are defined for a surface. If a surface is completely visible along a certain direction, it can be separated from the mold along the opposite direction. If a surface is not completely visible and theregore cannot be separated from the mold along any direction, it can be decomposed into two portions: those that are separable and those that are undercuts; the former is based on complete visibility and the latter on partial visibility. Algorithms are given for computing the undercut volumes of a polyhedral surface with respect to a particular parting direction and for selecting a parting direction that minimizes the number of undercuts.
The design of parts for economical manufacture by injection molding is an important element in the broader design strategy known as design for manufacturing (DFM). This paper provides an insight into the process of developing a DFM model for injection molding and into the use of such a model in the context of part design. The costs due to the mold making, the costs due to processing and the costs due to material are determined by the features of the part design, and models are presented to demonstrate these dependent relationships. The knowledge for the model databases was gained through extensive interactions with mold makers and molders. An example of the use of the models is also presented and discussed in detail.
A scientific approach is presented and the related logic developed for design of parting surfaces of patterns, moulds and dies used in the manufacture of cast, forged, injection-moulded and die-cast components. This has enabled computer-aided generation of parting surfaces and the determination of projected area, flatness and draw for a parting surface, identification of surfaces to which draft is provided, recognition of component segments causing undercuts, testing for dimensional stability, and location of flash, machined surfaces and feeders. Influencing criteria for parting-surface design have been formulated and developed into algorithms implemented on a personal computer. This approach greatly aids the engineer in rational decision making, paving the way for a systemized code for parting-surface design.
On the basis of the condition for demouldability, two levels of visibility, complete and partial visibility, are defined. The viewing directions from which a surface is completely visible can be represented as a convex region on the unit sphere called the visibility map of the surface. Algorithms are given for dividing a given object into pockets, for which visibility and demouldability can be determined independently, for constructing visibility maps, and for selecting an optimal pair of parting directions for a mould that minimizes the number of cores. An example illustrates the algorithms.
The application of a sweep operation to a solid (a solid sweep) results in a complex solid that can be used for obtaining the core and cavity of injection-moulded or die-cast components. The paper describes a method that is based on solid-sweep operations for modelling mould geometry without the creation of undercut or detached objects. In particular, algorithms based on heuristic search techniques for selecting the parting direction are presented. These algorithms can be used for the selection of the parting direction of a simple 2-piece mould or a mould with external side cores. With the proposed solid-sweep operation, they form a basis for automation of the mould design process.
A method for generation of parting surface for injection moulds
- S T Tan
- M F Yuen
- W S Sze
- K W Kwong
Computer aided-parting surface generation
- B Ravi
- M N Srinivasan
- B Ravi
- M N Srinivasan