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Laser Scanning
Produces More Accurate Space Planning Model in Less Time
 A
major worldwide automotive supplier was planning to begin producing a
fan in Asia that was already being produced in North America. Their
customer urgently required a solid model for space planning to confirm
the selected design. The fan had originally been designed in 2D,
therefore no 3D model existed. Redesigning the fan from scratch in 3D
would have required a complete design effort, requiring the work of
skilled designers and engineers for several weeks. Even with that effort
the resulting model would not have perfectly matched the parts produced
by the existing tooling. Reverse engineering the fan with a coordinate
measuring machine (CMM) would have also taken many weeks and would have
run the risk of not capturing the full complexity of the fan geometry.
To meet their
customer’s expectations, the supplier used a laser scanning service
bureau to capture millions of points that fully defined the geometry of
the fan in only a few days “The resulting solid model is a match to the
part being produced from the existing tool and the cost was less than
either redesigning the fan or reverse engineering with a CMM,” said a
designer for the company.
3D model needed of
fan designed in 2D
The fan mentioned
above was originally designed in 2D-Computer-Aided Design (CAD). The fan
is molded from an engineered polymer based on a tool design geometry
that compensates for shrinkage and warpage. In this case, engineers
created a solid model of the tooling for the 2D part design.
 The
tooling model was used by the company’s Asian operations to make molds
that produce parts with the same geometry as those produced in North
America. The challenge arose when their customer needed a solid model of
the fan for use in shape planning. Repeating the 3D design process would
have been very expensive because of the need to devote design and
engineering resources to the project.
The 3D design process
begins when engineers use one of several in-house programs to generate
airfoil shapes and extrude them to the complete blade shape. The blade
is duplicated and positioned around the hub of the fan to create the 3D
fan model. Many simulations of the fan’s operation are run to evaluate
and confirm its ability to meet customer performance specifications.
Once certain that the
design meets requirements, 2D and 3D models for manufacturing
documentation are generated. The design model is turned over to
manufacturing engineers who generate a new tooling model that represents
the geometry of the mold used to produce the fan. The tooling model is
then used to produce a first article which is used to confirm both
airflow and mechanical testing.
Problems with
redesign and manual digitizing
Other options include
digitizing the fan with a CMM but this has shown to be
time-consuming, labor-intensive, and captures only a limited number of
points. This results in a considerable amount of manual modeling
necessary to complete the model. The
amount of time required to digitize a fan with a CMM means that it is
usually only practical to capture a few thousand points. This is not
nearly enough to uniquely define the surface geometry of a complex
part. Another concern is the potential that manual operator involvement
can detract from the accuracy of the measurements.
The CMM operator would capture cross-sections
of the part and would rely on a CAD operator to manually develop smooth
surfaces to tie the cross-sections together. This process adds
considerably to the amount of time required for reverse engineering and
makes the accuracy of the finished model dependent upon the skill of
both the CMM operator and the CAD operator.
Laser scanning provides advantages
 The
company searched for a better way to meet the needs of their customers
and identified laser scanning as a possible solution. Laser scanning
systems work by projecting a line of laser light onto surfaces while
cameras continuously triangulate the changing distance and profile of
the laser line as it sweeps along, enabling the object to be accurately
replicated. The laser probe computer translates the video image of the
line into 3D coordinates, providing real-time data renderings that give
the operator immediate feedback on areas that might have been missed.
Laser scanners are able to quickly measure large parts while generating
far greater numbers of data points than probes without the need for
complex programming or part fixtures. Since there is no contact tip on a
laser scanner that must physically touch the object, the problems of
depressing soft objects, measuring small details, and capturing complex
free form surfaces are eliminated.
Instead of
collecting points one by one, the laser scanner picks up tens of
thousands of points every second. This means that the scanning of the
most complicated parts can often be accomplished in a few hours or less.
Laser scanning can collect data on parts that are so complex that they
would be practically impossible to digitize one point at a time.
Finally, the software provided with the scanner greatly simplifies the
process of moving from point cloud to CAD model, making it possible in
minimal time to generate a CAD model of the scanned part that faithfully
duplicates the original part. Special, but readily available, software
can be used to compare original design geometry to the actual physical
part, generating an overall graduated color error plot that shows in a
glance where, and by how much, surfaces deviate from the original
design. This goes far beyond the dimensional checks that can be
performed with touch probes on CMMs.
Selecting a
service bureau
 “We
used laser scanning in the past and discovered that it provides the
ideal solution to this problem,” the designer said. “However our
digitizing workload is not high enough to justify the purchase of a
laser scanner. In the past we have used the GKS Inspection Services
division of Laser Design, Inc. to provide laser scanning services. They
have always provided very accurate models at a reasonable cost on a very
timely basis. So it was natural to use them again on this project.”
“We made manual
measurements of a few key dimensions on an assortment of blades and
selected the blade that was closest to specifications,” the designer
continued. “We sent the fan to GKS Inspection Services. GKS
technicians scanned the surfaces on the ‘master’ blade and then
converted the resulting point cloud to a surface model as a SolidWorks
part. They sent a link and I downloaded the file. I was then able to
open the model in SolidWorks. It was clean, accurate and error free.”
3D models
meet customer requirements
The designer
used the resulting model to spin off models for several other versions
of the fans with different diameters. Then he generated the production
drawings and sent the 3D model and drawings to engineers within the
company. The engineers in turn provided the model to customers for use
in space planning. The model and drawings met the customer’s
requirements.
“The model was
far more accurate than would have been possible to create by other
methods,” the designer concluded. “It took only two weeks to provide
the model, including both the scanning time and the time required to
finish the model. This compares to at least three weeks that would have
been required to produce a similar model either by redesigning it from
scratch or by digitizing it with a CMM. Laser scanning ensures that the
model accurately matches the production parts. Clearly laser scanning
provides major benefits at multiple stages of the product development
process and we see many additional applications for this technology at
our company.”
For more information
about how GKS Inspection Services can improve your manufactured product,
save you money and decrease your development time, call Larry Carlberg
at 952-252-3433 or send an email to
measure@gks.com.
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