3D PRINTING - REVERSE ENGINEERING
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The document discusses reverse engineering techniques. It describes reverse engineering as generating a CAD model from an existing physical part to reconstruct it. There are contact-based methods like coordinate measuring machines and non-contact methods like 3D scanners. 3D scanners use light or lasers to scan objects and generate CAD designs without contact. Reverse engineering is used to manufacture replacement parts, redesign products lacking documentation, or create cheaper alternatives.
3D PRINTING - REVERSE ENGINEERING
- 1. UNIT - 2 REVERSE ENGINEERING
- 2. Basic concept • Reverse Engineering (RE) is the process of generating a Computer Aided Design (CAD)model from an existing physical part. • It enables the reconstruction of an object by capturing the component's physical dimensions and geometrical features . • The main aim of reverse engineering is to reduce manufacturing costs of the new product, making it competitive in market.
- 3. Need for Reverse Engineering • Manufacture of service components after discontinuation of the product line. • Redesign of an existing design which lacks adequate product data documentation. • Corrupt data file or loss of CAD design for a product. • Generation of cheaper alternate products as a substitute for monopoly products.
- 4. Digitizing • Collecting data from physical part. • Used when drawing of object is not available. • Aim is to generate a 3D mapping of the product in the form of CAD file. • This requires acquisition of surface data, which is large number of points on the product surface. 4
- 5. Digitization techniques Non-contact reverse engineering digitization Techniques Contact reverse engineering digitization Techniques
- 6. Digitization techniques Contact method • Requires contact between the component surface & a measuring tool. • Uses Coordinate Measuring Machine (CMM), electromagnetic digitizer or sonic digitizers to get desired coordinates. Non contact method • Uses light as the main tool • Uses white light or laser scanners to scan 3D objects to generate CAD design. 6
- 8. CONTACT BASED • Contact based methods of reverse engineering have been available for nearly 40 years. • The first method of reverse engineering to be introduced was the coordinate measuring machine (CMM) • A CMM gives physical representation of a three dimensional Cartesian coordinate system
- 13. Types of CMM Configurations 1. Cantilever Type 2. Bridge Type 3. Column Type 4. Gantry Type 5. Horizontal Arm Type
- 14. Cantilever Type
- 15. Bridge Type
- 16. Column Type
- 17. Gantry Type
- 18. Horizontal Type
- 21. Noncontact Inspection Techniques Uses a sensor or probe located a certain distance away from the object being measured or gaged • Two categories: Optical – uses light to accomplish the inspection Non-optical - uses energy form other than light • Advantages of noncontact inspection: Avoids possible damage to surface of object Inherently faster than contact inspection Can often be accomplished in production without additional part handling Increased opportunity for 100% inspection
- 22. Optical Inspection Method- Machine Vision • It is the creation of image and the collection of data derived from the image and subsequent processing and interpretation od data by a computer from useful application. • It is also known as computer vision • Machine vision exists in 2D & 3D format with 2D being most common in industrial application. • Machine vision has 3 functions: Image acquisition and digitization Image processing and analysis Interpretation
- 23. Optical Inspection Method- Machine Vision
- 24. • Image acquisition and digitization It is performed by deploying a video camera to capture the image and use digitizing system to store image data for subsequent analysis. The camera is focused upon surface of item of interest and image consists of discrete pixel elements is captured by viewing area. Each pixel value has value proportional to light intensity of portion of scene. The intensity value of each pixel is converted into digital value by analog to digital converter.
- 25. • Image processing and analysis A number of technique have been developed so that data produced during first phase of machine vision may be processed. General techniques are called segmentation and feature extraction
- 26. • Interpretation Interpretation of the image is concerned with recognizing the object recognition, and/or pattern recognition. Two commonly-used interpretation techniques are Template matching:- a method whereby the features of the image are compared against corresponding features of a model or template stored in the computer memory Feature weighting:- technique in which several features are combined into a single measure by assigning a weight to each feature according to its relative importance in identifying the object, and where the resultant score is compared against an ideal object score stored in computer memory, to achieve proper identification
- 27. Non Contact Inspection method
- 30. 3D SCANNING • 3D scanners are tri-dimensional measurement devices used to capture real-world objects or environments so that they can be remodelled or analysed in the digital world. • The latest generation of 3D scanners do not require contact with the physical object being captured. REAL OBJECT 3D MODEL
- 31. Objects are usually Scanned in 3D for 2 Purpose 1. Extracting dimensions to reconstruct a CAD reference file for reverse engineering or rapid prototyping. 2. Measuring the object itself for analysis and documentation. It is done in application such as computer-aided inspection, digital archiving and computer-aided engineering analysis.
- 32. Two Categories of Scanners • White light and structured light systems • Scan arm and portable handheld scanners
- 33. How 3D Scanning Works • Scanning results are represented using free-form, unstructured three-dimensional data, usually in the form of a point cloud or a triangle mesh. Certain types of scanners also acquire color information for applications where this is important. • Images/scans are brought into a common reference system, where data is merged into a complete model. This process -- called alignment or registration -- can be performed during the scan itself or as a post-processing step. • Computer software can be used to clean up scan data, filling holes, correcting errors and improving data quality. The resulting triangle mesh is typically exported as an STL FILE or converted to NURBS surface for CAD modelling.
Editor's Notes
- #7: The choice of discretization method is based on speed & performance during digitization and avoidance of damage to the product.