The need for safety, security and the protection of people working in facilities around the world is continually increasing. To that end, 3M’s Occupational Health and Environmental Safety division (OH&ES, St. Paul, Minnesota) was tasked with developing a new face shield for welders.
About halfway through the design and prototyping phase, Paul Martinson, product development specialist, and the team realized they needed to improve the aesthetics of the design. “We weren’t happy with where we were at,” says Martinson. “The concept to CAD [computer-aided design] and to rapid prototypes was not working, so a change had to be made. We needed to make a major correction to the design in the middle of project execution. That is why new CAD data was needed.”
The traditional design trial-and-error method of altering the CAD model was too time consuming and expensive for the project’s targeted release and budget. “We decided to take an approach like the automotive industry does and make a clay model of the shield to address aesthetic concerns,” says Martinson.
A clay model would be quick and easy to modify as feedback was gathered from the design team. It also delivered the concept in a full-size 3-D format vs. working with more traditional 2-D industrial design sketches, which can be hard for some people to use in visualizing the true look. The model would increase the speed and accuracy with which changes could be implemented in the shield to bring the project back in line with the design intent.
“We had a window of opportunity at this late stage of the design process to make the aesthetic corrections we felt were needed to create the best product possible,” says Martinson. “In order to keep the design going, we had certain goals we had to hit.”
Taking another cue from the automotive industry, Martinson and the team decided to use 3-D noncontact laser scanning to create the modified CAD model to move forward with the project. A 3M co-worker who had successfully used the method on projects in the past referred him to GKS Inspection Services (Minneapolis). Reverse engineering by noncontact laser scanning is an ideal application for scanning a soft pliable material such as clay because the scanner never touches the surface to distort the dimensions or damage the fine details.
Scanning the ModelMartinson sent a picture of the clay welding shield mock-up to GKS, so the feasibility of the project could be discussed. The idea was to scan the left half of the model, and from that use the point cloud to guide the creation of the new surfaces in CAD and mirror them to the other side, thus saving scan time and ensuring a balanced design. Also, the 3M CAD engineer needed 3-D curves created at some of the surface intersections and orientated to an origin at a specified location.
After a brief conversation, Martinson brought the modified clay shield with half the part finely sculpted to GKS the next morning because he was a local customer. Martinson waited while a technician performed the scan and left a few hours later with the ASCII point data and a surface model exported in STEP format on a CD. Martinson, who had not seen 3-D laser scanning before, found it to be “a phenomenal tool.”
Scanning was set up to capture the left side with the details defined and just past the centerline of the part. “This data allowed us to model the geometry and mirror about the centerline,” says Carlberg. Because the laser scanning system projects a line of laser light onto surfaces while cameras continuously triangulate the changing distance and profile of the laser line as it sweeps along, the problem of missing data on an irregularly shaped surface is eliminated. The laser line moves back and forth until the complete part is scanned. The system measures fine details and captures complex freeform geometry so that the object can be exactly replicated. Laser scanners measure articles quickly, picking up tens of thousands of points per second, and generating huge numbers of data points without the need for templates or fixtures.
GKS used the RPS-450 laser on the Surveyor 3500 equipped with a heavy-duty Aerotech rotary stage. This combination of equipment allowed GKS to quickly and accurately digitize all the surfaces required for the project, including those that might have been missed due to the sagging of the clay model. Reference features were used to align the assembly because the clay was pliable. When the scanning was complete, GKS used editing tools available in Geomagic Studio processing software to avoid double layers in the scan data that may have occurred because of the sagging. Double layers in the scan data would have resulted in errors on the surfaces.
Efficiency AchievedMartinson returned to 3M offices in a few hours with the CD containing the complete scan data and CAD model of the redesigned face shield. After Martinson went over the data with his CAD engineer, he requested some additional files his group needed to complete their requirements. Within 24 hours of initial contact, Martinson had the CAD data of the redesigned shield with the key points and features. From there, the 3M designers could finalize the design in 3-D CAD, which would be used directly to cut the molds for the face shield.
“We definitely cut our time and costs with laser scanning,” says Martinson. “The traditional trial-and-error method of CAD iterations is expensive and takes much more time. I estimate we saved from $3,000 to $5,000 in CAD modeling time by using GKS and 3-D laser scanning instead.”
The face shield redesign was required because of aesthetic considerations, so details were of utmost importance and 3-D laser scan data is intrinsically very accurate and detailed. The subtleties were not lost in the CAD generated from the laser scan files.
Within two days Martinson had created a rapid prototype of the face shield and was able to obtain confirmations from all parties involved at 3M. “With a major design correction coming half-way through the project, it was difficult to stay on track and within budget,” says Martinson. “For us, laser scanning at GKS was the creative tool that got our program back on target time-wise and financially.”
- GKS Inspection Services, a division of Laser Design Inc.