Laser Scanning Improves
the Quality of Parts and
Processes
by Larry Carlberg, GKS Inspection Services
LL
aser scanning is gaining popularity every day as a key
tool in manufacturing’s quality assurance processes.
Maintaining and improving quality is of upmost importance in certain industries, because when parts fail, people are
in danger. Laser scanning assures and improves the quality of
manufactured parts and the manufacturing process in many distinct ways.
• Laser scanning is fast and accurate, reducing time to
market.
• Laser scanning measures the entire surface of an object,
improving inspection and verification. It reduces the
discrepancy between the as-designed part and the
as-built part.
• Laser scanning captures the profile of the whole part, so
parts can be “assembled” digitally to reveal interferences
and inaccuracies (out of spec sections) and create better
fitting assemblies.
• Laser scanning is highly automated and non-contact,
so there is no operator error or variation in operator
technique.
• Laser scanning allows designers to create true CAD
models for FEA testing of actual geometry to correct
problems before parts go into production.
• Laser scanning can be used to validate tooling, even
when no CAD model exists.
• Laser scanning can be used to help select a quality
vendor by comparing parts from multiple vendors to
validate their accuracy.
Laser Scanning is fast and accurate, reducing time to
market.
Part prototypes can be scanned in a matter of minutes for
product design and reverse engineering, or first articles can
quickly be inspected before going into full production to
correct problems, saving time and lowering the scrap rate.
High-speed line laser probes can capture over 100,000 points
per second and generate huge numbers of data coordinates.
The laser scanning process is highly automated and easy to
set up. The laser 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. Unlike
conventional CMM measurements, problems of missing data
on an irregularly shaped or hollowed out surface are reduced
or eliminated. The system measures fine details and complex
free-form geometry so that the object can be exactly captured
and used for applications such as inspection, design, and
reverse engineering.
3D laser scan data from physical parts can be used to
compare different versions of the parts or the same
part made from different materials to determine what
deviations, if any, occur when non-geometric elements
are modified. Laser scanning measures the entire surface of an object,
improving inspection and verification in first article inspection
as well as last article inspection. It reduces the discrepancy
between the as-designed part and the as-built part.
High-speed laser scanning captures the entire shape of an object,
not just select features like in traditional measuring methods.
Turbine Blade, three views
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The whole part is scanned, instead of a small percentage of
points, so it can be compared to the complete CAD design to
generate a comprehensive error report of discrepancies.
can also be performed on last articles. With this Last Article
Inspection Reporting (LAIR) scan, engineers can compare the
old part to the new part, making sure that every item, first to last
is within the required specifications and meets quality standards. When manufacturing processes change, speedy re-qualification
of the accuracy is required so that the system can return to
production as soon as possible. The LAIR can determine a go/
no-go status and make part-to-part comparisons.
First Article Inspection Reporting (FAIR) is a gradual process
that detects critical, major, and minor flaws in a part as it nears
the end of the development cycle. A very quick “pre-inspection”
using laser scan data can validate the form analysis of parts
before detailed measurements are taken on the first article. This assures that features are all in the right place, a step that
Laser scanning captures the profile of the whole part, so
can prevent wasted time and money on a worthless part.
parts can be “assembled” digitally to reveal interferences
For example, a part has 238 dimensions which are all satisfied, but
it also has features that are not dimensions because they are not
individually measurable. Out-of-spec problems may occur within
these “feature” areas and not be detected. Complex computerdesigned free-form shapes are hard to measure traditionally and
the results are often incomplete. Laser scanning verifies all of
the geometry to create a fully qualified part.
Laser scanning also reduces the discrepancy between the asdesigned part and the as-built part. A conventional first article
drawing may have over 700 dimensions, with two dimensions
out of tolerance. Tremendous time and man-power resources
could be wasted in measuring the whole part with conventional
touch-scanning methods trying to determine where those two
problem areas are located. Using actual original scan data to
create aninspection report shows how every physical dimension
stacks up against the CAD model.
and inaccuracies (out of spec sections) and create better
fitting assemblies.
Sometimes as a result of the manufacturing process, as-built
parts are out of spec from as-designed parts. When these
variations in shape create interferences between parts in an
assembly, laser scanning both parts can identify the problem
areas in a digital model, so engineers can decide the best tack to
take to correct the problem.
For example, in an assembly of parts with large curved contours,
two parts may require major portions of adjacent surfaces to
align in order to assemble and function properly. Assembled
parts are difficult to inspect fully and the shapes may be
distorted when forced together. Laser scanning can quickly
scan the individual parts to obtain accurate inspection data
and then “assemble” them digitally to allow each piece to be
compared to existing 3D models. One part’s virtual scan data
Comparison to CAD, three views
Laser scanning excels at capturing complicated geometric
aspects of parts, such as multiple cavities or surface textures.
When evaluating a part that will be used in production, automated
capability studies can be run, which set defined parameters of
tolerance intervals to be applied to all the samples examined. Typical parts could use the line-laser scan files to conduct many
checks including form analysis, optimization, tool wear, and
trend analysis.
In addition to scanning first articles to make sure they are
in spec through the manufacturing process, laser scanning
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can be overlaid on the other’s until they are aligned correctly
in the model. Interference locations are graphically depicted in
error reports. From the reports, tooling modifications to get the
parts to fit can be determined.
Sometimes assembled parts will perform correctly even
though they may be somewhat out of the ideal tolerance. 3D
laser scanning determines whether tolerances can be loosened
and made easier to achieve, and still be acceptable to the
functionality of the assembly.
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Cross Section Error Maps
Laser scanning is highly automated and non-contact,
so there is no operator error or variation in operator
technique.
The laser scanning process is highly automated which insures
consistency and quality of the data obtained. Since it is a noncontact measuring method, there are no variations in practices
or techniques from operator to operator, or pressure differences
that may generate different readings in traditional touch-probe
measurement. Laser scanning allows extremely consistent
checking of parts by removing the human error factor. Accept/
reject decisions are automated into the scanning software.
Laser scanning allows designers to create CAD models
for FEA testing to correct problems before parts go into
production.
Since many manufacturing steps can lead to “as-built” parts
falling away from the CAD model’s “as-designed” specifications,
FEAs performed on the original CAD model are not valid. To
obtain FEA results that are true to reality, manufactured parts
can be laser scanned to generate a CAD model that represents
the true geometry of the completed part. The model created
from 3D laser scan data provides an accurate as-built model on
which to conduct the tests, yielding more accurate simulation
results to predict stress locations for the product and increase
confidence levels in the integrity of the part.
With the abundance of 3D data from the laser scanner the
engineer can develop and validate processes such as twist
and warp, wall thickness, and form analysis with Geometric
Dimensioning and Tolerancing (GD&T). GD&T defines the
nominal or as-intended geometry of parts and assemblies, so
that the allowable variation in form and size of features, and
orientation of features can be determined.
Laser scanning can be used to validate tooling, even when
no CAD model exists.
In any manufacturing process tooling is needed to create
parts and certain features of parts. Injection molding tools
are often validated with laser scanning, as are punch dies and
compression tools. Tools may also be scanned for wear or to
predict wear, and aid in repairing, maintaining, or changing out
tools to keep them dimensionally correct. Non-contact laser
scanning is the ideal method to check the accuracy of the whole
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mold or die. Undercuts and negative geometry do not pose
problems in gathering complete data sets. Legacy parts sometimes have no CAD models, or the mold has
been manually modified over time. Either the altered mold or
the part created from it, or both can be laser scanned to update
incorrect or obsolete CAD models to the true representation of
the as-built object. Up-to-date documentation is a valuable asset
for manufacturers, and essential in many regulated industries.
Laser scanning can be used to help select a quality vendor
in comparing parts from multiple vendors to validate their
accuracy.
Laser scanning can alert a manufacturer to variations in parts
when using several vendors, or help find the best supplier
if certain constraints apply such as geographic location,
availability, or cost. Companies can inspect parts provided by
different suppliers with laser scanning to measure whose are
in spec and whose are out of spec, and by how much. Fully
automated laser scanning provides consistent measurements,
avoiding errors introduced when parts are measured manually,
which can be greater than or equal to the tolerances.
Since laser scanning captures the whole part, accurate
tolerances can be applied and the best quality precision parts
can be chosen. The scan data removes the guesswork from the
selection process in wondering which vendor’s part is better, so
there is no controversy in making an informed decision.
Summary of Laser Scanning Benefits
When 3D laser scanning can take on so many roles in improving
the quality of a manufactured part and the manufacturing
process itself, its value is enormous to its user. No matter what
the application of laser scanning in the manufacturing process,
it produces the rewards of shorter lead times, better accuracies,
simplicity of operation, and confidence in part quality. Larry Carlberg is the Service by Bureau Manager of GKS Inspection
Services, a division of Laser Design, Inc. Carlberg is a graduate
engineer and has been involved in the manufacturing world for over
35 years, beginning in pattern-making and prototyping. He has spent
the last 12 years advancing laser scanning for quality inspection and
reverse engineering applications. For more information visit www.
GKSInspection.com
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