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ORIGINAL ARTICLE Algorithm for automatic parting surface extension in the mold design navigating process Wen Ren Jong however this may result in the inefficiency to make full use of the designer s capacities As the entire mold design and manufacturing process covers a wide range and has complex operations with out the control of project management and knowledge management enterprises cannot improve the overall competitiveness The mold design navigating process is applied to connect the entire design process save the design information of various stages in a database and Fig 4 EvalOutline functional relation diagram Fig 5 Integration of design and knowledge management Int J Adv Manuf Technol feedback information at the proper time Meanwhile using a feature oriented design the features obtained at the conceptual design stage can be reused in the de tailed mold design stage Then by project control and collaborative capabilities a small number of experienced engineers can be in charge of the important early stages Fig 6 Historical knowledge base Fig 7 Parting line loop Int J Adv Manuf Technol such as the conceptual design and project analysis while engineers with less experience can collaborate at the detailed mold design stage In this way the employ ees capabilities can be fully used and the model devel opment process can be accelerated Through the secondary development interface provided by the CAD software the design navigating process is developed for engineers to directly operate the CAD software accord ing to the process Figure 3 shows some user interfaces of this mold design navigating process As such the automatic parting surface process proposed in this study utilizes the feature oriented concept of the system to complete the construction of the parting surface and integrate it into the design navigating process 2 3 Secondary development Most CAD software has a corresponding secondary devel opment toolkit API for users to conveniently develop customized functions The Pro ENGINEER CAD system provides three development language environments includ ing Pro Toolkit Pro J Link and Pro Web Link Pro Toolkit is a development language based on C and it is the develop ment environment with the most supporting functions Pro J Fig 8 Extending rule of the parting line going through XY axes Fig 9 Pro Web Link get parting line which goes through the X axis and Y axis Int J Adv Manuf Technol Link is Java based Although the functions provided by Pro Web Link are not comparable with those provided by the former two languages Pro Web Link still provides hundreds of commonly used functions that can directly communicate and operate in the CAD environment In addition it is a web based development language and its programming codes can be directly written in the JavaScript environment As a result it has the capacity for online access and storage of CAD instructions Hence this study mainly used Pro Web Link for the secondary development interface The entire mold design process includes many tedious and repetitive operations such as file input size computa tion interference checks and graphic capture as well as operations including the assembling saving of file and regenerating relevant models Automatic processing through programming can eliminate many redundant operations Taking geometric outline computation as an example al though CAD provides many corresponding tools it requires numerous mouse clicks and selections to get the results Through the direct writing of measuring tools using Pro Web Link it takes only one click and selection by the users to obtain the dimensions of the geometric shape The system then automatically determines the proper size of the mold core cavity In this way it can accelerate the model design process and reduce human errors Figure 4 illustrates the geometric shape computation functional relation diagram The Pro Web Link guideline manual 17 can help users determine the corresponding purpose of the functions According to the EvalOutline method the function requires the presentation of the spatial matrix of the model pfcTransform3D as well as the feature removal item types pfcModelItemTypes The computation of the model size requires the geometric shape only and the unnecessary coordinates points and axes can be removed using pfcModelItemTypes The EvalOutline method is classified into the category of the pfcSolid Therefore it should be determined by its equivalent relations and the pfcModel type should be identified The relevance of the pfcBaseSession can thus be obtained Using the parental relationship with pfcSes sion the type of MpfcCOMGlobal necessary for the initial announcement can be obtained accordingly Such hierarchical relational search and type declaration can realize the access capabilities of CAD functions 3 Automatic parting surface design The automatic parting surface planned in this study was built in the mold navigating process 13 At the initial conceptual design stage design navigating cou pled with design historical knowledge base helps the planning of the parting line and feeds the results back Fig 10 Parting surface extending sequence Fig 11 Pro E curve equation Int J Adv Manuf Technol to the historical knowledge base for reference during the next design At the mold design stage the concep tual design is employed to establish the parting line features and determine the direction and geometrical relationship of the parting line using Pro Web Link Coupled with the customized user defined features in Pro ENGINEER the main parting surface is automati cally developed and established 3 1 Conceptual design Mold conceptual design requires a thorough analysis of the model and decision making of the follow up mold design In the mold industry the conceptual design stage is often assigned to senior development engineers Without a systematic knowledge management if the senior engineers leave the design experience and knowledge cannot be maintained and accumulated Therefore this study employed a historical knowledge base in the parting line planning of the conceptual design stage to systematically summarize historical de sign When engineers are planning the parting line it can provide reasonable suggestions and reduce design errors and change time as well as feedback reasonable design results to the historical database for future refer ence in cases of similar models Thus the historical knowledge base can be updated along with the design projects and the design technology and experience can be accumulated As shown in Fig 5 with the help of a historical knowledge base the design results are achieved by the design navigating process The design results are added Fig 12 Curve loop direction Fig 13 Comparison of extending sequence and parting line segment directions Int J Adv Manuf Technol into the historical knowledge base to help in the development of similar models forming a knowledge accumulation and inheritance loop Figure 6 illustrates the interface of the his torical knowledge base for reference in the design navigating process 3 2 Mold design The proposed automatic parting surface design mainly uses the parting line features generated from conceptual design to develop the surface and the parting line as shown in Fig 7 is based on the curve loop generated by the geometric edges of model In the mold design of this study we determine the direc tions and geometric positions of curve segments by the secondary development language Pro Web Link and de fine the extension directions of the segments using Z axis as the mold opening direction with rules as below Rule 1 The extending directions of segments at four posi tions in a model parting line are definite at the beginning namely the parts going through the X Table 1 Rules of the starting and ending points of the parting line symmetrical method Zone 1Zone 2Zone 3Zone 4 Start pointEnd pointStart pointEnd pointStart pointEnd pointStart pointEnd point Clockwise parting line loopt01 0t00 0t00 0t01 0t00 0t01 0t01 0t00 0 Counterclockwise parting line loopt00 0t01 0t01 0t00 0t01 0t00 0t00 0t01 0 Table 2 Rules of the starting and ending points of the parting line clockwise method Zone 1Zone 2Zone 3Zone 4 Start pointEnd pointStart pointEnd pointStart pointEnd pointStart pointEnd point Clockwise parting line loopt00 0t01 0t00 0t01 0t00 0t01 0t00 0t01 0 Counterclockwise parting line loopt01 0t00 0t01 0t00 0t01 0t00 0t01 0t00 0 Fig 14 Extending direction analysis Int J Adv Manuf Technol axis and Y axis as shown in Fig 8 curves 1 and 3 extend to the directions of X and X respectively and curves 2 and 4 to the directions of Y and Y respectively Hence this study uses the X axis andY axis todividethe partinglineintofourregions as the basis for the extension direction of the parting surface Figure 9 shows how to get the four seg ments using Pro Web Link code Rule 2 After finding four fixed line segments this study attempts to extend the parting surface by two approaches including the symmetrical method andtheclockwisemethod Thesymmetricalmethod extending sequence is 1 X axis to Y axis zone 1 2 X axis to Y axis zone 2 3 X axis to Y axis zone 3 and 4 X axis to Y axis zone 4 with Y axis as the symmetrical axis as shown in Fig 10a The clockwise method extends clockwise from the starting point at Y for one round back to Y as shown in Fig 10b The user may choose one of the methods for parting surface extension Rule 3 Parting line is a closed curve loop and all the curves in Pro E have directions with parameter t as a line segment construction equation The range of t value is from the starting point at 0 0 to the ending point at 1 0 as shown in Fig 11 According to this rule the parting line loop can be constructed in the clockwise direction as shown in Fig 12a or in the counterclockwise direction as shown in Fig 12b The parting loop direction will affect the judgment of the line seg ment directions as illustrated in rule 4 Rule 4 Due to the fixed parting surface extending sequence the judgment of the starting and ending point of the parting line cannot fully rely on the rules of Pro E but additional rules for judgment With the symmetrical method as an example if the parting loop is clockwise since it extends from X to Yin zones 1 and 4 for counterclockwise judgment which is the opposite to the direction of the parting line loop as shown in Fig 13 the curve parameter t01 0 should be used as the starting point and t00 0 as the ending point when judging the starting and ending points of the parting line in zones 1 and 4 Nevertheless in the Fig 15 Extending rule 1 Fig 16 Extending rule 2Fig 18 Extending rule 4 Fig 17 Extending rule 3 Int J Adv Manuf Technol Table 3 Extending rules of each zone the symmetrical method Zone 1Zone 2Zone 3Zone 4 Initial extending direction X X X X End point extending direction Y Y Y Y Checked componentYYYY Table 4 Extending rules of each zone the clockwise method Zone 1Zone 2Zone 3Zone 4 Initial extending direction Y X X Y End point extending direction X Y Y X Checked componentXYYX Fig 19 Extending direction check procedure Int J Adv Manuf Technol case of the clockwise method as the entire parting line is judged in clockwise sequence all the line segments in four zones use parameter t01 0 as the starting point when the parting line loop is constructed in a clockwise manner On the contrary it uses t01 0 as the starting point The summary of the judgment of the starting and ending points of the line segments by two extending methods is as shown in Tables 1 and 2 Rule 5 The judgment of the extending direction of the parting line segments in various zones is based on Fig 20 Corner compensation Fig 21 Symmetrical parting surface extension breakdowns Int J Adv Manuf Technol the starting directions of the zones followed by the judgment of the secondary direction The line segment direction judgment rule uses the line connecting the starting point to the ending point of the line segment as the direction vector to capture its XYZ components for extending parting surface judgment as shown in Fig 14 The basic rule of extending is to extend the subsequent parting lines on the basis of the starting line extending direction of each zone If the subse quent parting line cannot follow the initial extend ing direction it will change to the direction of the ending point direction With zone 1 as an exam ple as the starting line direction is Y the parting surface extends in the direction of X and then the subsequent line segments may extend in the fol lowing directions 1 Line segment Y component 0 this indicates that the parting line segment will extend in the direction of Y therefore the extending direction of the part ing line is X as shown in Fig 15 2 Line segment Y component00 and Z component 0 it will go on extending in the direction of the initial extending direction as shown in Fig 16 3 Line segment Y component00 and Z component00 this is the line segment on the Z projection plane initial axis and is unable to extend in the initial extending direction In this case there will be two possibilities one is not to extend and the other is to extend in the direction of the ending point In this case the line segment should be kept before judging the subsequent parting line seg ments With the kept curve we can find out the Fig 22 Clockwise parting surface extension breakdowns Fig 23 Surfaces copy Int J Adv Manuf Technol parting surface extending in the direction of the initial extending direction In this way it can be judged that the kept parting line need not extend the parting surface On the contrary the kept parting line should extend in a different direc tion All the kept line segments should be ex tended in the direction of the ending point extending direction as shown in Fig 17 4 Line segment Y component 0 this means that the parting line segment has not extended in the direc tion of X and that the rest of the parting line seg ments should be extended to the direction of the ending point Y as shown in Fig 18 The summary of extending rules is as shown in Fig 19 and Tables 3 and 4 We check whether the directional components of the parting line segments of each zone are consistent with the starting directions of the line segments If so the parting surface extends to the initial extending direc tion If not the parting surface extends to the end point extending direction Rule 6 According to the above extending rules the model parting surface is extended into four zones However in the case of the parting surface of the parting line segments in the XY directions it cannot extend to the parting surfaces of the four corners of the model Hence in this study we capture the last parting line segment of the first direction and its extended parting surface when the parting surfaces of each zone are changing directions Meanwhile the edge of this part ing surface which goes through the end point of this parting line and has the same normal Fig 24 Trim boundary Fig 25 Clamshell phone bottom housing Int J Adv Manuf Technol vector with the second parting surface direc tion will be obtained to extend in the second direction to get the four parting surfaces of the four corners of the model as shown in Fig 20 The extending sequences by two parting line extension methods are broken down as below Figure 21 illustrates the parting sur face extension breakdowns by the symmetri cal method The parting surface extends from X and X to Y and Y in the extending sequence of zone 1 zone 2 zone 3 zone 4 Figure 22 illustrates the parting surface extension breakdowns by the clockwise meth od The parting surface extends from the di rection of Y in the sequence zone 1 zone 2 zone 4 zone 3 clockwise The direction of all extending actions is all determined by customized Pro Web Link functions while the extending operations are automatically com pleted by the user defined features In this study the parting surface extension meth od is the copy extend method which manually cop ies the model contour by the parting line as shown in Fig 23 The algorithm proposed in this study is then applied to find out the edges in line with the parting line features on the surfaces using the sec ondary development language for surface exten sion The advantage of this method is that the surfaces extended from the line segments belong to the same group of surfaces for the direction separation of mold core cavity By using the CAD function of surface merge the ups and downs of the parting surface can be trimmed First trimming the surfaces is performed between the model and mold core cavity boundaries as shown in Fig 16 then the parting surface and trim boundary surfaces are merged as shown in Fig 24a b The trimmed parts can then be expanded by the filling method to Fig 26 Clamshell phone bottom housing the parting line going through XY axes Fig 27 Clamshell phone bot tom housing shut off surface filling Int J Adv Manuf Technol Fig 28 Clamshell phone bottom housing parting surface establishment process Fig 29 Clamshell phone bot tom housing mold core cavity separation Table 5 Comparison of mouse clicks case 1 clamshell phone bottom housing TraditionalAutomatic Copy neighboring surfaces 66 Extend the parting surface162 27 parting curves 1 use the secondary development as one key functionality Total clicks1687 Int J Adv Manuf Technol Fig 30 Bar type phone bottom housing bottom housing Fig 31 Bar type phone bottom housing the parting line going through XY axis Int J Adv Manuf Technol merge with the original parting surface to get the final trimmed parting surface as shown in Fig 24c d This can save mold manufacturing time and improve the service life of the mold 4 Case study This study conducted case studies on establishing the main parting surfaces for two mobile phone housings and carried out mold core cavity separation with the resulting parting surface design 4 1 Case 1 Figure 25 illustrates the first case study of this research the planning of the bottom housing of the cla