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A tool and die design company has improved on
the traditional approach by using a laser probe to scan the die surface
while viewing the reflected light with a camera that captures millions
of points in minutes. With laser scanning, most all die components can
be scanned in under an hour to an accuracy of 0.0005 inches, enabling
the stamping companies to generate additional revenues by getting the
dies into production faster.The company’s primary business is designing
metal stamping dies, special machines, and fixtures. The company’s
designers have over 70 years of combined experience in the tool and die
industry in designing progressive dies, transfer dies, blank dies,
compound blank and pierce dies, draw dies, form dies, line dies, and
model trim dies for the automotive, appliance, lawn and garden, and
heating/ventilation/air conditioning industries. The company also
designs special machines including material handling systems,
metalworking machines, assembly machines, and lubrication machines.
Need to quickly digitize die components
“Many of the metal-stamping dies used in the
United States to produce automotive components are supplied by overseas
resources,” said the company’s Owner/Designer. “A high percentage of
these dies are delivered to domestic stamping companies without accurate
die design information or 3D surface data need to build replacement
components. A major reason for this is that the tooling is typically
hand-worked at the overseas tool shop during the die tryout, debug, and
part quality inspection process. With short tooling delivery leadtimes,
this leaves no time for reverse engineering of the final “as-built”
tooling configuration before shipment. The digitized data may be used
for several different purposes such as the machining of a spare stock
cage die component or the replacement of a broken or worn out
component.”
This leaves the domestic stamping company to
deal with the challenge of getting the critical die components reverse
engineered either before the die goes into production or between
production runs. In either case, the existing die components are usually
available only for a very short period of time before they are needed to
make production parts. The dies are usually sent out to die engineering
firms or tool & die shops that use CMM’s to capture their geometry point
by point. But it has become increasingly difficult to utilize CMM’s for
this purpose as the complexity of dies tends to increase with each new
model introduction. At a minimum, tens of thousands and, in some cases,
millions of points are needed to accurately define the die geometry. The
result is that the amount of time needed to capture points one by one
has grown considerably.
The company’s Owner/Designer found himself
facing a particular challenge when a customer asked him to digitize four
die components with trim lines and pockets for die button inserts. These
components require a high degree of reverse engineering accuracy because
the die has only 0.002 inch punch-to-die clearance. Another challenge
was that most of the holes in the components are on compound angles. It
would have taken a huge amount of time to reverse engineer these parts
to the required levels of accuracy using a CMM. Also, the parts were
somewhat worn so the model produced by reverse engineering needed to be
updated to eliminate the wear. In this case the Owner/Designer only had
three days to work with the parts before they needed to be returned to
the stamping company.
Switching from CMM to laser scanning
He searched for a better way to meet the
needs of his customer and identified laser scanning as a possible
solution to this problem. 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 templates or 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 reverse engineering of the most complicated parts can often
be accomplished in less than an hour. Laser scanning can reverse
engineer parts that are so complex that they would be practically
impossible one point at a time. Finally, the software provided with the
scanner greatly simplifies the process of moving from point cloud to
computer aided design (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.
Scanning four components in less than one day
The Owner/Designer researched the Internet
for laser scanning systems with the idea of purchasing a system to
provide in-house reverse engineering services. “I found the website of
Laser Design Inc. (Minneapolis, Minnesota) to be very comprehensive and
contacted the president of the company, Marty Schuster, regarding my
idea of purchasing a laser scanning system,” he said. “Schuster
suggested that I use their GKS Inspection Services division, a laser
scanning service bureau, to familiarize myself with the process. I
emailed him pictures of the four components that needed to be quoted. I
received a quote and contracted with GKS Inspection Services to scan the
components. I personally delivered the components to GKS and observed
the scanning of the components. Each component only took about 30
minutes to scan. In a single day the operator scanned all four
components generating point clouds for each with millions of
coordinates. I returned home the next day with the die components,
making it possible to deliver them to my customer ahead of schedule.”
After the Owner/Designer left, GKS Inspection
Services’ engineers uploaded the point clouds into Geomagic Qualify
software from Raindrop Geomagic, Research Triangle Park, North Carolina.
They used this software to convert each point cloud to a surface model
of the part geometry and also to correct the model to account for die
wear. The software also allows the user to create a graphical comparison
called a color error map of the manufactured part vs. the CAD model, by
displaying differences between the two in a range. This makes it
possible to easily compare the as-built die to the original part
geometry to see what changes were made during the debugging process.
“The new high definition laser scanning systems available
today in conjunction with high-end data processing software have given
the metal stamping industry the resources to provide very quick and
accurate reverse engineering data for the manufacturing of complex
surfaced die components,” the Owner/Designer concluded. “The ability to
accurately digitize the existing component to within 0.0005 inches and
then, if necessary, virtually recondition the component using the tools
within the data processing software have dramatically improved this
process. The higher scanning speed provided by the new method is another
important advantage. An average-sized die component can typically be
scanned on all surfaces in about 30 minutes and a large component
generally takes less than an hour. This compares to several hours or
days that are typically required to digitize similar parts on a CMM.”
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