Allan D. Spence

This paper proposes a novel framework for high resolution printing, detection, tracking, and registration of deformable grids. The undeformed dot feature grid is created on the target surface using a flat bed inkjet printer. After deformation, the surface is imaged using close-range monocular vision, and the dots are detected and localized to sub-pixel accuracy. A novel, deformation invariant grid registration topological map and associated algorithms are used to track features between subsequent video frames. By matching the map to the undeformed grid geometry, stretching or compression of the distance between the dots can be used to compute the material strains. Accuracy, repeatability, and computation time for several image based dot feature detectors are compared, and experimental laboratory results demonstrate consistent robustness of the method under practical imaging conditions.

Spatial visualization skills are the aptitudes needed to mentally process three-dimensional images of objects. These skills are important to successful design engineers of all disciplines and are closely correlated to student performance in undergraduate engineering programmes. This paper reports on the metrics, curriculum, and teaching methods that have been implemented at McMaster University to improve the visualization skills of first year engineering students and modernize the course content of the mandatory first year engineering design and graphics course. Strong improvements in visualization test scores has been observed from the first week through to the last week of the course. To automate grading, the visualization tests have been implemented on WebCT. The WebCT-based visualization tests and results will be shared with other CDEN members upon request.

Reproduction of hand crafted 3D shape geometry is an important industrial concept design step employed for items ranging in size and function. Adding surface art work would extend concept design to include essential product information. This paper describes an equipment and workflow implementation for simultaneously reproducing both 3D shapes and art work. The handcrafted shape is laser digitized to obtain the XYZ geometry coordinates plus the surface gray level. The resulting point cloud is processed and converted to an STL file for plastic rapid prototyping, while the surface gray level information is resampled to fit the smoothed surface and match the reproduction ink jet printing system resolution. Developed software automatically calculates the dot pattern to reproduce the art work onto the correct prototyped surface location. An actual sample produced using the system is shown.

The need to simultaneously measure sheet metal geometry and strain arises during research, die tryout, statistical process control production part approval, or in response to manufacturing exceptions. Several optical systems have been developed for strain and geometry measurement of small specimens. Large scale geometric measurement is possible using coordinate measuring machines equipped with touch probes. This Technical Brief summarizes the extension of these methods using three dimensional gray level point clouds obtained from either laser digitizers or an in-house developed stereo vision system.

Mechanical engineering graduates are expected to possess a working knowledge of modern Computer Aided Design/Computer Aided Manufacturing/Computer Aided Engineering (CAD/CAM/CAE) tools. The instructional challenge is to balance fundamentals with applications, and theory with practice. Many courses teach CAD from a mathematical base. This approach emphasizes “what do you know” evaluation without addressing “what can you do” expectations of both students and employers. This paper approaches instruction from a product centric perspective that, with each step, progressively builds skills and knowledge from mechanical dissection and solid modeling fundamentals towards original product design, prototyping, and testing. In first year, student teams dissect a product and produce solid model parts and assemblies. The upper year courses require product design to the prototype stage, with consideration of optimization and manufacturing issues. Incorporated subject material includes organizational behavior and team building, solid modeling theory, finite element analysis, CNC machining, rapid prototyping, and moldable part design. Implementation experiences in actual courses are described and discussed. Suggestions are provided for others contemplating similar initiatives.

Stamped automotive sheet metal parts must be measured for correct part shape, as well as for compliance to forming strain limits. Despite recent technological advances, use of non-contact, optical measurement techniques still has not replaced conventional touch probe and manual methods. This paper reports our recent laboratory experiences using two different non-contact solutions for sheet metal and grid digitizing. In the first solution, an electrochemically etched circle grid is first applied to the blank part. After forming, a CMM mounted triangulation laser digitizer measures the part coordinates and gray level. A parallel computer is used to accelerate data processing. The second solution begins with a square grid, and uses close-up passive stereo CCD cameras for digitizing. Both tailer-welded and constant thickness steel blanks are measured, and the resulting data is graphically presented in an easily interpreted format.