Int J Adv Manuf Technol (2015) 81:1693–1703 DOI 10.1007/s00170-015-7327-4
ORIGINAL ARTICLE
A new method for casting process CAD based on multi-source neutral file Jianxin Zhou 1 & Tong Wang 1 & Hongtao Tang 2 & Yajun Yin 1 & Xu Shen 1 & Qin Zhou 1
Received: 24 November 2014 / Accepted: 15 May 2015 / Published online: 27 May 2015 # Springer-Verlag London 2015
Abstract Casting process CAD is the common basic problem in the foundry industry. With the innovation of computer technique and labor division between enterprises, the upstream and downstream enterprises adopt multi-source neutral file to exchange part drawings. The traditional design methods based on casting process CAD tools are not convenient; thus, the process design and production cycle of castings are extended. To handle this problem, a new method for casting process CAD system based on multi-source neutral file is proposed, which broadens the traditional application of casting process CAD system. The new method is supported by four key techniques, including the CAD bottom development, multi-source neutral file display, interactive drawing, and nonparametric drawing for casting process, which are described in detail. A practical casting process CAD system based on multi-source neutral file is successfully developed. Compared * Hongtao Tang
[email protected] Jianxin Zhou
[email protected] Tong Wang
[email protected] Yajun Yin
[email protected] Xu Shen
[email protected] Qin Zhou
[email protected] 1
State key laboratory of Materials Processing and Die and Mould Technology, Huazhong University of Science and Technology, Wuhan 430074, China
2
Hubei Digital Manufacturing Key Laboratory, School of Mechanical and Electronic Engineering, Wuhan University of Technology, Wuhan 430070, China
with the traditional method, the application of the two actual castings process design based on the new method illustrates that the time of drawing can significantly be reduced and the cycle of casting process design can be shortened. Keywords Casting process CAD . Multi-source neutral file . CAD bottom development . Interactive drawing . Non-parametric drawing
1 Introduction Casting process design is an essential part and a crucial link of the casting production. Casting process CAD is the design process that processes designers design the casting process parameter, gating system, riser system, chiller system, sand core, and casting cards with computer system based on casting part diagrams, technical requirements, design specifications, design charts, and so on. Professor J. T. Derry in Georgia Institute of Technology and R. D. Pehlke in University of Michigan of the USA first put forward the concept of casting process CAD at the 50th international foundry congress in 1983 and attribute it to the comprehensive application of calculated simulation, geometrical modeling, and process database [1, 2]. Then, the concept is further strengthened and becomes the focus of attention on the ensuing 52nd international foundry congress [2]. Since then, the study of the casting process CAD has quickly entered a period of rapid development. The mode of casting process design drawing transforms from traditional hand drawing into computer plotting [3]. At the beginning of the twenty-first century, the research of casting process CAD system appears in large numbers with CAD tends to the specialized development. For the current casting process CAD systems, these systems are mostly secondary development based on mainstream commercial CAD
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software (such as AutoCAD, UG, etc.). The designer calculates and designs the process according to the casting process manual, and then draws the casting process diagram [4–6]. The research and application of casting process CAD system can reduce the workload of the process designers, improve the scientificity and standardization level of casting process design, and provide convenience for product design, manufacturing, and management integration [7]. Electronic casting process diagram provides convenience to the conservation, management, and query. Traditional casting process CAD systems have played a significant role in a certain time and provided an excellent tool for casting process design. However, compared to the casting CAE, the study and application of casting process CAD systems are not successful, and one of the reasons is that multi-source neutral file is not supported [8, 9]. Multi-source neutral file contains three types: the first is the corresponding formats of product data exchange standards, including DWG, DXF, IGES, and STEP [10]; the second is PDF format; and the third is common image formats, including BMP, JPG, and PNG. Nowadays, more and more upstream enterprises deliver the drawings in
Trailer
Catalog
Pages Root
Page 1
Page 2
Outline Root
...
Bookmark1
Bookmark2
...
Fig. 2 The logical containment relationship of PDF neutral file object
multi-source neutral file to the foundry. Therefore, for the product with complex shape parts and relatively simple casting process diagram, most small and medium foundries must consume a large amount of manpower and time on drawing a variety of part diagrams in CAD software, and then draw the casting process diagram. Thus, it greatly extends the casting product design and production cycle.
Fig. 1 The framework of casting process CAD
Casting process CAD system Point/line/circle/rect/a rc/text basic drawing
Load multi-source neutral format file System basic service
Save customized format file
Size marking, edit of graphics
CAD interactive drawing
Non-parametric drawing
CAD basic drawing
Image recognition on multi-source neutral file
Casting process graphic drawing
Zoom, undo, redo, print, redraw
Parting surface drawing
Gating system drawing
Chill drawing
Draft drawing
Process card
Parting line drawing
Pad drawing
Sand core drawing
Machining allowance drawing
Process description
Joint allowance drawing
Riser system drawing
Repairing hole drawing
Roughness drawing
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Therefore, the study of the amalgamation between multisource neutral file and CAD has been carried out. It is divided into two categories at present. (1) For the study of CAD data exchange, Vergeest and others have established B spline curve and expression language of interfaces based on STEP standards [11]; Tanaka and others have studied the quality of STEP data exchange in the collaborative design process [12]. These studies select the common CAD data exchange standards like STEP, IGES, DXF, etc. They focus on the technical details and set out to improve the quality of data conversion from the details, but these methods are always limited by the source CAD system. With the escalation of the CAD systems, these CAD systems are not convenient or need continuous upgrades. (2) Such kind of research work focuses on releasing the drawings in PDF neutral file through CAD system. It does not directly use multi-source neutral file like PDF as the source drawings for process design and deeply integrated the multi-source neutral file and the design, drawing of CAD system. Meanwhile, the part drawing in PDF and image format files cannot be selected and edited, and the study is a blank on how to accurately pick up the primitives such as points, lines, and so on in PDF and image formats. The casting process primitives with many types and the complex shapes lead to the overly strict parametric design. It is another reason why the application of casting process CAD system is unsuccessful. When designing and drawing the complex casting process primitives such as the gating system, riser system, and so on, the primitives have many control points whose sequence and parameter relationship are very strict for localization. The design and drawing of complex primitives will be in trouble under the strict parameter design environment of mainstream CAD software. Therefore, it has great significance that breaking the restriction of the current design basis document formats and strict parameterization to achieve fast and accurate casting process drawing and design.
Fig. 3 The flow chart of rendering page based on PDF neutral file
Create context variable when rendering document
For small and medium casting enterprises, 2D drawings are widely used in the actual casting process design. So in this paper, 2D drawing is the researching focus. For the long cycle of casting process design and drawing under multi-source neutral file in current foundry enterprises, a new method for casting process CAD system based on multi-source neutral file is proposed. The system formed by this new method can be utilized to open the part drawings in multi-source neutral file provided by customers. And, its drawing functions can be utilized to rapidly and accurately draw up the primitive graphics and casting process graphics, which greatly reduce the time of casting process design and improve the productivity of the enterprises. Therefore, the research of the new system has the important scientific significance and practical value of engineering for small and medium casting enterprises.
2 Framework According to the actual needs of casting enterprises and deficiencies of existing methods of casting process CAD systems, the casting process CAD system is developed based on the new method in this research. Firstly, it could open multisource neutral format file of part as the background of the drawing of casting process. Secondly, it must have basis and practical CAD drawing functions such as point, line, circle, rect and arc drawing, size marking, and edit of graphics. Thirdly, it must have practical casting process design and drawing functions containing drawing of the parting surface, gating system, riser system, sand core, process card editing, and so on. The framework of casting process CAD system designed based on the new method is shown in Fig. 1. The four key techniques are described in the following section in detail.
Create a drawing paper for rendering page 1
Convert the rendered draw paper to bitmap
Rendering page to the specified device
Open the file stream 2
Load the specified page of the document
5
Set the size of the document page 3
7
6
Release the occupied resources of the drawing paper
8
Close the document 4
9
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3 Key techniques
Page space
3.1 CAD bottom development
Window origin
For CAD software products, CAD has been developed for decades [13, 14]. With the rapid development of computer technology in the late twentieth century, there have been a number of outstanding commercial soft wares such as AutoCAD, CAXA, KMCAD, InteCAD, ZWCAD2D, PICA D, and so on. Over the past decade, Autodesk’s AutoCAD software has occupied the main absolute guide status in the 2D graphics market in china [15]. In the study, some complex functions were avoided in these large CAD systems [16]. Some core modules which contain the basic graphic drawing, size marking, and text edit are laid out. By the object-oriented system design method, the data architecture of the new system is established. The casting process graphics are quickly drawn based on the new CAD system. 3.2 Multi-source neutral file display The multi-source neutral file formats include a variety of formats. These file formats follow inconsistent graphic data exchange standards. This paper focuses on the display technology of the neutral file based on PDF and image. The PDF neutral file was developed by Adobe Company. It is based on the PostScript language image model. It is an encapsulation file with texts, fonts, formats, colors, and graphic images which are independent of devices and
window
Device space Viewport origin
viewport
Fig. 5 The transformation from page space to device space
resolution ratio. The texts, colors, and image information can be clearly and accurately displayed in the file. And, the PDF neutral file is independent on the operating system platform. So, it becomes not only an ideal document format published on the internet as an electronic document but also a common format of part drawings provided by customers in mini-medium foundry industry [17–20]. The drawing of a variety of CAD design softwares can be saved as PDF neutral file, so it is easy to be viewed and printed. A PDF neutral file largely contains four parts: file header, file body, cross-reference table, and file trailer. But from a logical view of document, it should consist of the trailer, catalog, outline, and pages, as shown in Fig. 2 [21]. In this study, the flow chart of rendering page based on PDF neutral file is shown in Fig. 3 (http://www.mupdf.com).
Input device
Fig. 4 The process of interactive drawing
Microcomputer
Printer
Keyboard
Mouse
Graphics tablet
Light pen
Realtime modification
Situ observation
People
Monitor
Process drawing
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Fig. 6 The feature point is captured when the cursor is moving Fig. 8 The image recognition of part drawing background
Picture neutral file includes BMP, JPG, PNG, and other formats. Picture neutral file is not only a format without platform but also one of the formats widely used in small and medium enterprises. The bitmap information of the picture format can be analyzed by using GDI+. The picture file object can be loaded, stored, and performed other operations [22]. 3.3 Interactive drawing Interactive drawing is that when the designer draws graphics by using the computer system, information can be exchanged between people and computer and the complex drawing task can be finished. The interactive drawing system consists of software and hardware. The process of interactive drawing is shown in Fig. 4. Excellent CAD drawing software needs powerful interactive function. This system introduces coordinate transformation technique, feature points capturing technique, object pickup technique, rubber band technique, and image recognition technique. The following paper will describe the various techniques in detail. 1. Coordinate transformation technique Coordinate system is defined by determining the relationship between the logical coordinate and the device coordinate. The logical coordinate is the coordinate rendered graphics when the user stores the file. And, the device coordinate is based on the coordinate of the
Fig. 7 The drawing of line and circle based on the rubber band technology
display. The transformation from page space to device space is shown in Fig. 5. In this paper, the display of multi-source neutral file, the drawing of graphics, and the change of view are related to the coordinate conversion. The mutual transformation of logic (window) coordinate and device (viewport) coordinate is shown in formula (1, 2, 3, 4). The variable control is a control factor of view. The variables xViewOrg and yViewOrg represent the origin of the viewport coordinate system. The variables xWinOrg and yWinOrg represent the origin of the window coordinate system. xWindow ¼ ðxViewport−xViewOrgÞ*control þ xWinOrg
ð1Þ
yWindow ¼ ðyViewOrg−yViewportÞ*control þ yWinOrg
ð2Þ
xViewport ¼ ðxWindow−xWinOrgÞ=control þ xViewOrg
ð3Þ
yViewport ¼ yViewOrg−ðyWinOrg−yWindowÞ=control
ð4Þ
Fig. 9 The image recognition with the rubber band interference
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Fig. 12 Non-parametric drawing steps of waist riser
Fig. 10 The image recognition with eliminating the rubber band interference
2. Feature points capturing technique The precise drawing is an important issue to be considered for interactive drawing. When the mouse is moved close to the primitive feature points (midpoint, endpoint, center point, etc.) during the drawing process, the distance is very small to a certain extent, and then this feature point can be captured. In the meantime, the corresponding information for the feature point can be simultaneously displayed, thereby improving the accuracy of the drawing. The feature point is captured when the cursor is moving, as shown in Fig. 6. 3. Object pickup technique The object pickup is very important and is the basis of the object parameterization, deletion, and movement. The object pickup is divided into two parts: a single-object pickup and multiple-object pickup. Take point pickup, for example, when the distance of the dynamic movement point of the mouse to the selected point is less than or equal to the set accuracy of the field (d), this point is successfully picked up. In other words, when the dynamic
movement point of the mouse P(x1,y1) satisfies the formula (x1−x2)2 +(y1−y2)2
