CAD Modeling from Sample Process
The steps of digitizing a physical sample with 3D scanning and creating its technical drawing.
The most reliable way to make a sample without technical drawings or digital data re-manufacturable is the 3D scanning-supported CAD modeling process. This process meets many different engineering needs — from spare part production to mold design preparation, from transitioning to serial production to quality verification.
Why CAD Modeling from a Sample?
Parts with lost or never-created technical drawings are very common in industrial manufacturing. Spare parts of obsolete machinery, existing production parts without drawings, or products to be transitioned from handmade prototypes to production preparation fall into this category. Creating CAD data from a sample enables these parts to be reliably integrated into the production chain.
Step 1: Sample and Project Evaluation
The process begins with a technical examination of the sample. At this stage, part dimensions, geometric complexity, surface condition, and material properties are evaluated. The expected CAD output level (surface model or solid model), tolerance requirements, and final use purpose are also clarified at this stage. The project scope is shaped based on this evaluation result.
Step 2: 3D Scanning
The sample is digitized using a 3D scanner with red laser or blue laser technology. The entire surface of the part is scanned from different angles to obtain complete point cloud data. Under suitable conditions, scanning can be performed at accuracy levels down to ±0.03 mm/m; however, this value varies depending on part geometry and surface conditions. On-site scanning can also be evaluated depending on part size and location conditions.
Step 3: Point Cloud and Mesh Processing
The raw scan data is processed using specialist software such as Geomagic Design X. At this stage, a noise filter is applied, data obtained from different scanning positions is aligned, and a closed mesh model is created. Mesh quality directly affects the accuracy of the subsequent CAD modeling step.
Step 4: CAD Model Creation
A manufacturable model is built in CAD software such as Siemens NX, SolidWorks, or Cimatron using the mesh data as reference. Surface modeling or parametric solid modeling can be preferred based on project requirements. For projects transitioning to mold design, manufacturability, draft angles, and parting line requirements are observed at this stage.
Step 5: Deviation Analysis and Validation
When required within the project scope, a deviation comparison analysis is performed between the completed CAD model and the 3D scan data. This analysis numerically shows how closely the modeling represents the sample and verifies whether tolerance requirements are met. This validation step is particularly valuable in mold revision or serial production preparation processes.
Step 6: Output and Delivery
Delivery can be made in various output formats depending on project scope and need:
- STEP — the most common CAD delivery format due to universal compatibility
- IGES — suitable for data exchange between different CAD systems
- Parasolid — preferred especially in Siemens NX and SolidWorks workflows
- PDF technical drawing — can be prepared for projects requiring 2D projections and dimensioning
- Deviation / tolerance comparison report — for quality verification and production tracking processes
What You Want to Know.
- Are worn or broken parts suitable for CAD modeling?
- The current condition of the part is evaluated at the start of the project. Partially worn parts can usually be scanned and the CAD model can be completed using symmetry, reference geometry, or engineering decisions. In cases of heavy damage, the project scope and approach must be clarified in advance.
- Can the CAD model obtained from a sample be used directly in mold design?
- Yes, this approach is the most common continuation of reverse engineering projects. A CAD model created with manufacturability in mind can be used as the starting data for the mold design process. If transitioning to mold design, observing draft angle, parting line, and production requirements during the CAD modeling stage provides benefits.
- What is the process if multiple identical samples exist?
- If multiple samples are available, the part with the best geometry is selected for scanning. Alternatively, scanning multiple parts and using the most suitable geometry as a common reference can also be evaluated. This situation is discussed at the start of the project.
- Which file formats can be sent for CAD modeling?
- If available, existing 3D scan files (STL, OBJ), part images (JPG, PNG), old technical drawings (PDF, DWG, DXF), and any reference CAD files (STEP, IGES, Parasolid, SLDPRT) can be shared. If no digital data exists, the project can be started with only the physical sample.
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