Integrating the Physical and Virtual With 3-D Inspection Technologies
Using offline programming, laser scanning and an inspection management tool reduces inspection time dramatically.
Trends in product development include using more and more 3-D modeling technologies and digital mockups. Parts and components are described in 3-D digital, allowing freedom to design free-form surfaces. Three-dimensional geometric inspection uses 3-D digital reference to validate any kind of geometry - in particular, free-form surfaces for which you are not able to use traditional techniques.
CMMs or arms are driven by the CAD definition to verify particular 3-D features or 3-D points. The main limitation of conventional techniques is that an inspection of complex parts will need one to four hours to verify the parts on the CMM, based on the number of measurements requested. This delay will limit that technique to offline inspection - not allowing online inspection. The objective of inspection is to be as close as possible to the production line to be able to perform corrective actions as quickly as possible.
The challenge in geometric inspection will be reducing that acquisition and analysis cycle time to change the setup or production parameters as soon as a default is identified.
Reducing Inspection Time from Measurement to Analysis
Specialized software will help to control and perform the acquisition
as well as analyze the results of measurement. By using offline
programming and an inspection management tool, it is possible to reduce
inspection time dramatically.
Using Laser Scan Technology and 3-D Inspection
Touch-probe inspection will take two points per second; the latest
laser scan technology will allow 30,000 points per second with five
microns of resolution (see Figure 1).
With this new-generation laser scanner, you will be able to measure
more than 10,000 points per second without contact. Advanced,
specialized inspection software and prelude inspection will allow you
to analyze the result of the measurement and compare it with the CAD
file.
The following application was completed with advanced, specialized inspection software by a major American car manufacturer:
- The external frame of a sunroof was digitized with a high-density, laser-based point cloud scanner.
- The data point cloud was loaded into the specialized inspection software and aligned to the original CAD model using a reference point alignment technique (RPS) (see Figure 2).
- A comparison and measurement analysis was performed:
- a. Color mapped to compute the global deviation between the point cloud and the CAD model (see Figure 3).
- b. Used 3-D calipers to measure the distances between two points and to compute deviation on these points (for width/height).
- c. Performed a cross-sectional analysis.
- Generated complete reports including color maps, annotated snapshots, tabular report, and an animated report in AVI format for the production and design department.
- Further analysis will be performed to determine if the deviations come from the design or the assembly process (see Figure 4).
Specialized inspection software will allow you to execute a series of measurements automatically using the advanced macro programming language. This function allows you to execute a complete inspection - from the first alignment to the generation of complete reports - in less than three minutes from one click of a mouse.
Application Benefits
- Inspection of a sunroof frame was nine times faster with a 3-D digitizer and inspection software as compared with traditional CMM-based inspection techniques.
- Data acquisition with a 3-D digitizer was performed in only fifteen minutes instead of one hour with a CMM.
- Reduced time for data analysis, calculation and reports.
- Provided accurate information to the quality engineers and feedback to the production and design department.
- Increased the number of parts being inspected, enhancing the overall quality and reliability of the product.
