Journal of Engineering and Technology

ARTICLE
Year
: 2014  |  Volume : 4  |  Issue : 2  |  Page : 95--101

A Computer Aided Design Modeler for Designing the Plastic Components Using a Set of Programmatic Operations


Rajesh Kumar Bansal1, Punit Kumar2,  
1 Department of Mechanical Engineering, National Institute of Technology, Kurukshetra; Mechanical Engineering, PPIMT, Hisar, Haryana, India
2 National Institute of Technology, Kurukshetra, Haryana, India

Correspondence Address:
Rajesh Kumar Bansal
Department of Mechanical Engineering, National Institute of Technology, Kurukshetra; Mechanical Engineering, PPIMT, Hisar, Haryana
India

Abstract

Developments in the field of computer-aided design have targeted on reducing the time and efforts required of designer to define product models. Creating robust parametric [16] models is more time consuming especially as there can be hundreds of features and thousands of mathematical expressions to create. Even if combinations of low-level features [11] known as user-defined features are used, this process still involves inserting individual features into individual components and creating all the inter-part associativities. This work shows that programmatic operations designed for a specific product types (plastic components) can streamline the component-level design process much further because a single programmatic operation can create an unlimited number of low-level features modify geometry in multiple components and create new components. Results from user testing show that a set of high-level programmatic operations can offer savings in time and effort of over 70% and can be general enough to support user-specified component cross sections while leaving the majority of the primary design decisions open to the designer [13] .



How to cite this article:
Bansal RK, Kumar P. A Computer Aided Design Modeler for Designing the Plastic Components Using a Set of Programmatic Operations .J Eng Technol 2014;4:95-101


How to cite this URL:
Bansal RK, Kumar P. A Computer Aided Design Modeler for Designing the Plastic Components Using a Set of Programmatic Operations . J Eng Technol [serial online] 2014 [cited 2019 Sep 18 ];4:95-101
Available from: http://www.onlinejet.net/text.asp?2014/4/2/95/141177


Full Text

 1. Introduction



The parametric feature-based approach within computer aided design (CAD) applications has increased engineering efficiency dramatically [1] . Well-developed parametric models can be reused to produce many similar designs and can simplify the process of incorporating design changes [7] . In addition, associativity capabilities within modern CAD applications allow these parametric models to maintain relationships between features and components [10] , which extend the benefits to models of entire components. There are as well programming and scripting tools available that enable advanced users to programmatically perform most of the same interactive functions.

1.1 Objective

Objective is to show how the current modeling practices can be streamlined further through the use of product type-specific programmatic operations for plastic components that would combine the benefits of user-defined features (UDFs) and inter-part associativity and would function at a level much higher than inserting single features into individual components. This work defines a programmatic operation as one that can create an unlimited number of low-level features modify geometry in multiple components create new components establish inter-part expressions and create inter-part geometry links. Since products of a similar type have similar primary and secondary features programmatic operations can be written that can create most if not all of the CAD geometry necessary to define a product of a certain type. This is in affect reduce the time consuming for modeling element and decision making time. The specific test case that is used to demonstrate and validate this research is on various thin components showing different type of features. These particular parts are good candidates for this research because these types of parts are used repeatedly on a wide range of products. This research is therefore focus on the incorporation of thin components-specific design operations into an application that is interoperated with auto CAD.

The aim of this modeler is to develop a set of proof-of-concept applications that will streamline the design of thin parts. The objectives of the modeler are:

Create a framework of intelligent high-level programmatic operations that can be used to quickly design a wide range of thin manifold and non-manifold objects.Implement this framework specifically for plastic components.Show that the implementation of this framework decreases the design time without impeding innovation.

 2. Litereture Survey



Improvements to CAD have focused on reducing the number of user operations necessary to define the topology and geometry of products. Parametric modeling and relating parameters with equations are fundamental methods of reducing operations [14] . Once a parametric model is created, products with similar topology can be modeled simply by updating the key driving parameter values. Feature based design is another "one of the fundamental design paradigms of CAD systems" [9] . It allows the user to define and modify the model at a higher level than the point and curve entities. Even though feature-based parametric modeling increases the efficiency of CAD design, complex parts may require hundreds of features and thousands of parameters and so more advanced methods have been developed that modify geometry at an even higher level [12],[10] . A graphical user interface (GUI) supports the whole feature class definition process. Once defined, a feature class is automatically made available for use in a feature library of the modeling system [7],[5],[8] . UDFs "become full-privileged members of the feature collection of the system" [1] . Already commented that "if a powerful and convenient capability for UDFs can be provided and then the library of design-with features can be smaller and the need for combinatorial power is also reduced."

A declarative approach to the description of feature classes is presented as an alternative to their previous procedural proposal, within the features testbed [4] . A number of primitive geometric constraints are established on feature geometric entities (e.g., faces and edges), in order to define the volumetric shape of the UDF and are combined in a directed graph [2] . Another, more recent [9] , who explicitly deal with the conceptual definition of UDF prototypes for a feature library. Analogous to the semantic constraints first proposed in Ref. [3] and elaborated in Ref. [6] . Complex assembly designs and component-level designs are streamlined by the programmatic operations; a single programmatic operation can create an unlimited number of low-level features, modify geometry in multiple components and create new components [18] . An algorithm based on primitive fitting for segmenting thin-plate is discussed [19] and can be used for solid model reconstruction in the simulation driven design process. The use of 3D CAD in mechanical product design has become a standard practice [15],[16],[17] . 3D CAD model comparison is presented [20] . A wide variety of use cases for 3D CAD model, difference calculation methods and identifying key characteristics and limitations.

 3. Design Methodology



This works purposed a set of steps that can be used to design a specific type of product (plastic products). The objective of this work is to prove that such a set of programmatic operations can reduce the time and expertise required for defining the geometry and topology of such parts. These method is developed using the C++ programming language and ACIS (Alan, Charles, Ian's System) geometrical kernel. Qt is used for GUI and openGl is used for graphical representation.

The steps used in designing are grouped in following four operations:

Operation 1: To create part and draw basic sketch using sketch feature.Operation 2: To make created the sketch into thin solid by applying offsetting.Operation 3: To add detail features such as chamfers, blend, bend, handle, hole, loft, cap etc.Operation 4: To export file in different formats such as .stl (STereoLithography) and .pmp (plastic modeler part).

Application procedure for the plastic modeler represents a set of steps associated with above different operations.

Operation 1: To create part and draw basic sketch using sketch feature:

Create a new document-New feature is created by radio button as shown in [Figure 1].{Figure 1}

Create and control sketch:

Open sketch feature-radio burrton to create a new sketch is shown in [Figure 2] below.Draw different sketches using different sketchers are used. Types of sketchers such as line, polyline, arc, circle, polygon and nurbs are shown in [Figure 3].{Figure 2}{Figure 3}

Sketch drawn by using nurbs sketcher is shown in [Figure 4] and [Figure 5].{Figure 4}{Figure 5}

Operation 2: To Convert sketch into thin solid by applying offsetting:

Select the created sketch and select feature such as thin extrude or thin revolve for creating solid body by converting 2D sketch in 3D model. These features provide offsetting options. By using these features [11] , thin solids can be created.Applying revolve feature by giving revolve angle (360°), output generated is shown in [Figure 6].{Figure 6}

Operation 3: In the third operation detail features such as chamfers, blend, bend, handle, hole, loft, cap etc., are generated. The entity such as face, edge, vertex required to generate the feature is selected thin 3D body.

Edge is selected for applying the feature chamfer on the edge as shown in [Figure 7].Give required parameters such as distances from the corner (in case of chamfer) as shown in [Figure 8].Apply created feature.{Figure 7}{Figure 8}

After applying chamfer feature by giving distance from corner output generated is shown in [Figure 9].{Figure 9}

Operation 4: To export file in different formats such as .stl and .pmp.

After creating the final plastic model in the modeler, the output is sending to rapid prototyping in different file formats such as .stl and .pmp file formats.

 4. Implementation



Plastic modeler is developed for designing and manufacturing of the plastic components. The data structure for the proposed plastic modeler contains four modules:

User interface module.Sketcher module.Feature module.ACIS base module.

4.1 User interface module

Contains classes used for building user interface. User interface module provides the following functionality:

The application menu contains file-related commands and options to customize.The quick access toolbar contains the file-related shortcuts.The design window contains your model. If you are in sketch mode, it also contains the sketch grid to show the 2D plane on which you are working. It also provides different views for model observation.Tree window: This shows you each of the objects in your design. You can expand or collapse the nodes of the tree, rename objects, create, modify, replace and delete objects, as well as work with components.Scene window: This window shows graphical objects. You can select different objects from this window and also create.

4.2 Sketcher module

Contains classes used for creating new sketches. The Sketcher module provides following tools,

Line tool to sketch lines in 2D.Circle tool to sketch circle in 2D by using various options such as a circle by center point and Radius, circle by 3 points, circle by 2 points etc.Ellipse tool to draw ellipseArc tool to create an arc with known center point and end points.Spline tool to sketch splines in 2D such as beziers and nurbs.Polygon tool to draw a rectangle by using various options such as the center point and one corner point, rectangle by 3 points, rectangle by 2 corner points and different polygons.Patterning tool to draw circular and linear patterning.

4.3 Feature module

Contains classes used for generating different modeling features such as extrude, revolve blend, sweep etc. Feature module contains classes, which provides different modeling features such as extrude, revolve, cap, handle, hole, loft, bend.

4.4 ACIS base module

The 3D ACIS modeler (ACIS) is a geometric modeling kernel. ACIS is used by to develop the plastic modeler, designing software. ACIS provides the underlying 3D modeling functionality. ACIS features an open, object oriented C++ architecture that enables robust, 3D modeling capabilities. ACIS is used to construct applications with hybrid modeling features, since it integrates wire frame, surface and solid modeling functionality with both manifold and non-manifold topology and a rich set of geometric operations. Contains classes used for creating actual geometrical and topological entities using ACIS. The ACIS base module handles the interaction between ACIS kernel and our application. This module generates all geometrical and topological entities from ACIS kernel as requested by the user and provides data for displaying them.

 5. Case Study Algorithms



The algorithms used in plastic modeler for modeling the cup with circular and elliptical handles.

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[INLINE:2]

[INLINE:3]

[INLINE:4]

[INLINE:5]

The input values are given in [Figure 10]a.{Figure 10}

The output is shown in [Figure 10]b.

First make a copy of selected body and then create rotational transformation by using ACIS function rotate_transf and apply this transformation on the new body by using ACIS api_translate_entity.

The inputs values and outputs for feature translate are shown in [Figure 11]a-c.{Figure 11}

 6. Results



To determine whether the objectives of this research are meat and to what extent they are or are not successful, two elements of the objectives are evaluated:

Observed the time saving.The range of design supported by this plastic modeler.

To verify the proposed methods, a set of modeling tasks are performed using both the traditional approach and the approach implemented by this modeler. It has been founded that the number commands, mouse clicks and the completion time has been significantly reduced with this proposed method is shown in [Table 1].{Table 1}

Designer can choose from a finite set of options, can modify the parameters of the decision and can change anything about the decision within the normal design limits

6.1 Test case: Model-cup

Required steps for creating cup are shown in [Figure 12].{Figure 12}

The output of the plastic modeler is shown in [Figure 13]a-c.{Figure 13}

 7. Conclusion



This modeler can create the inter-part associativities and expressions that are necessary in parametric assembly modeling and are able to generate larger sets of geometry since UDFs cannot use their own entities as inputs to their other features. Another important advantage of the plastic modeler presented here is that they drastically reduce user error and can be executed by a trainee designer. During testing, many of the operations have to be repeated or corrected because the wrong input values and geometry is selected. Programmatic methods do not have these problems. In addition, the associative links between components assure that design changes are properly propagated throughout the assembly automatically. This further reduces design time and modeling errors. The objectives of this plastic modeler is to show that high-level, product type-specific operations (programmatic operations) can accelerate the design of a wide range of plastic components and assemblies and that these operations will decrease the design time without impeding innovation. A method is developed to define the operations and assembly using a framework of C++ programming language and ACIS geometrical kernel. Qt is used for GUI and OpenGl is used for graphical representation. This modeler supports a large number of products

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