Published on March 11, 2014
INTRODUCTION The first CAD-systems used by aerospace and automotive enterprises from the mid-1960s, were 2D systems – an electronic version of a drawing board. Soon it became clear that design should be based on 3D product models, whose 2D projections can be generated automatically However, simply adding a third coordinate to traditional 2D graphics results in modeling only a wireframe, which is not sufficient for calculating mass/volume characteristics of a future product This led to the evolution of solid modeling
INTRODUCTION A simple solid model had its own limitations It could not be easily manipulated or changed for implementing design changes Hence there was need to device a new method to allow the designer to easily manipulate the model as desired by him without loosing the design intent Hence came the parametric modeling
WHAT IS PARAMETRIC MODELING? The term parametric modeling denotes the use of parameters to control the dimensions and shape of CAD models. Parametric Design - a system that constructs relations among the geometry of different elements. When one element is changed, the geometry of the rest of the elements are changed as well.
PRIMITIVE ELEMENTS: 1. Dimensions can be linear and angular 2.Datums. Different CAD systems provide various types of datums, but typically datum planes and datum coordinate systems are provided. Datum lines and points are also possible. Generally, datums are coordinate systems, or parts of coordinate systems, that are used to control other coordinate systems or geometric entities. 3. Constraints can be geometric or algebraic relationships that the designer wants to impose on the geometry of CAD models. a) Geometric constraints are parallel, perpendicular, offset, tangent, and alignments. b) Algebraic constraints are equations that the designer adds to ensure that features sizes meet design requirements. For example, a part cross section may have to be a certain area.
NEED OF PARAMETRIC MODELLING 1.CONCEPT DESIGN- • Convey a visual representation of the idea or concept. • Create as many design concepts as possible. • Evaluate the concept that best captures specified criteria and aesthetic requirements. 2. BID AND PROPOSAL PROCESS- • Minimize the time and costs required to create the bid geometry • Submit models and geometry to support a proposed customer price • Accurately convey and communicate proposal requirements and costs • Improve accuracy of the prop osal to meet budget and schedule commitmentsParametric
3. DIGITAL PROTOTYPING- • Design, iterate, optimize, validate and visualize products before they are built • Rapidly create and explore design geometry • Enable fast changes to legacy and heterogeneous data 4. 2D DESIGN AND CONVERSION TO 3D- • Support quick 2D concept design and the creation of 2D engineering deliverables • Accelerate the 2D-to-3D conversion process to evolve 2D drawings into 3D models
5. REUSE LEGACY DATA- Reuse and maintain legacy 2D & 3D data to support current and future programsParametric
BENIFITS OF PARAMETRIC MODELING 3D modelling software can automatically update related parts of the model when design changes are made and there is full bi- directional associativity between parts, assemblies and drawings. It captures and stores the design intent of the designer so that any changes in the geometry will not affect the design intent for which the part was designed 3D systems provide easier design revisions Parametric modellers have a rollback feature that shows the sequence in which the model was created Adding design intent in the form of constraints between the model elements and saving them in the file together with the model simplifies future editing.
DESIGN INTENT In parametric modeling, dimensions control the model. Design intent is how your model will react when dimension values are changed.
DESIGN INTENT 2.50 4.00 1.25 2.50 The drawing shows the intent of the designer that the inclined plane (chamfer) should have a flat area measuring 2.5 inches and that it should start at a point 1.25 inches from the base of the drawing. These parameters are what the designer deemed significant for this model. Remember that the placement of dimensions is very important because they are being used to drive the shape of the geometry. If the 2.5 in. vertical dimension increases, the 2.5 in. flat across the chamfer will be maintained, but its angle will change.
DESIGN INTENT In this drawing, what is important to the designer is the vertical location and horizontal dimension of the chamfer, rather than the flat of the chamfer. 2.50 4.00 1.25 2.125 2.50 4.00 1.75 30.0O In the last drawing, the designer calls for a specific angle for the chamfer. In this case the angle of the chamfer should be dimensioned.
PARAMETRIC MODELING The true power of parametric modeling shines through when design changes need to be made. The design modification is made by simply changing a dimension. Since the counterbore is associated with the top surface of the ring, any changes in the thickness of the ring would automatically be reflected on the counterbore depth. 60 10 15 30Pattern: 8 Holes
SKETCH GEOMETRY Line Sketch Tool
GEOMETRIC CONSTRAINTS APPLIED FIRST Geometric Constraint Tools What do you think we do next?
DIMENSION CONSTRAINTS APPLIED SECOND Dimension Constraint Tool
PROFILE CHANGED TO ISOMETRIC Right mouse click, select Home View or use shortcut key F6 or Click on Home icon by View Cube
EXTRUSION PARAMETERS SET Extrusion Dialogue Box Select Extrude from Create panel
CREATE NEW SKETCH PLANE Sketch plane selected with left mouse click Sketch Button
View Face SKETCH GEOMETRY Normal View selected with View Face tool or by clicking on front of View Cube
FEATURE PARAMETERS SET Isometric (Home) view selected, Extrusion dialog box set Choose cut operation here
WHY PARAMETRIC MODELING? Determine the shape and size of the geometry at any time during the design process. This part should be 5 in. long, not 3 in. How can we fix this without redrawing it?
VIRTUAL REALITY To understand what is AUGMENTED REALITY first we need to see what is Virtual reality? Virtual reality is using computer technology to create a simulated, three-dimensional world that a user can manipulate and explore while feeling as if he were in that world. It includes: Three-dimensional images that appear to be life-sized as seen by the user. The ability to track a user's motions, particularly his head and eye movements, and correspondingly adjust the images on the user's display to reflect the change in perspective An effective VR experience causes you to become unaware of your real surroundings and focus on your existence inside the virtual environment. DEFINITION : Augmented reality (AR) is a field of computer research which deals with the combination of real-world and computer-generated data.
AUGMENTED REALITY VR technologies completely immerse a user inside a synthetic environment. While immersed, the user cannot see the real world around him. In contrast, AR allows the user to see the real world, with virtual objects superimposed upon or composited with the real world. AR supplements reality, rather than completely replacing it. It creates the illusion that the virtual and real objects coexisted in the same space. Augmented reality adds graphics, sounds, haptic feedback and even smell to the natural world as if it exists.
WHAT IS REAL AND WHAT IS NOT Real desk with virtual lamp and two virtual chairs (ECRC)Is this VR or AR?
WHY AR? AR enhances a user’s perception of interaction with the real world. The virtual objects display information that the user cannot directly detect with his own senses. The information conveyed by the virtual objects helps a user perform real-world tasks. AR is a specific example of what is known as Intelligence Amplification (IA): using the computer as a tool to make a task easier for a human to perform.
Characteristics: Optical vs. Video Optical see-through HMD conceptual diagram Video see-through HMD conceptual diagram AR can be accomplished using either optical HMD or video HMD HMD:-HEAD MOUNT DISPLAY
Main classes of applications: 1. Medical 2. Manufacturing and repair 3. Annotation and visualization 4. Robot path planning 5. Entertainment 6. Military aircraft APPLICATIONS
TYPICAL APPLICATIONS:- 1.Medical. The system can be used in pre-operative planning of a laparoscopic surgical procedure in order to find both the right points to introduce the surgical instruments and the best path to reach the organ concerned in the surgical operation. 2.Educational purpose A very handy tool for instructors and faculty members for subjects involving complex understandings. APPLICATIONS
Head Up Guidance System (HGS) (Flight Dynamics Inc.) Boeing 737 cockpit with Head- up Display (HUD) (Flight Dynamics Inc.) APPLICATIONS:AIRCRAFT
Nightvision system in the 2000 Cadillac DeVille (Cadillac.com.) APPLICATIONS: NIGHT VISION
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