|
The company has
provided blowmolding systems and services for more than three decades for
companies producing everything from milk bottles and automotive parts to
pharmaceutical vials and industrial trash cans. The company offers a very
wide range of plastic blowmolding and structural foam solutions. The
company also offers comprehensive moldmaking services that begin with an
understanding of the blow mold process and the intricacies of the
customer’s specific equipment and resin choice. Before mold construction
even begins, the company helps create or optimize the container or part
design for the blowmolding machinery being used. Once the mold is
completed, the manufacturer can test-run it on the machine process for
which it was designed to ensure real-world performance meets requirements.
Need for reverse engineering
The first step in
the mold design process is to define the geometry of the container being
produced. The traditional method is to produce a clay model called a
stone. The geometry of the stone is typically extremely complex, with many
different contoured surfaces blending together to create a stunning,
modernistic look. Of course, today most beverage manufacturers use solid
modeling instead of the stone as the master geometry used to guide the
bottle manufacturing process. But even many of the bottle manufacturers
that have switched to solid modeling have discovered that it’s usually
easier to obtain just the right look for a bottle by adding and removing
material to a clay model than it is by manipulating a solid model on the
computer screen. Then again there are many situations where manufacturers
simply want to produce a new mold for an existing bottle that was created
without the use of computer aided design (CAD). In all of these
situations, the ability to convert the physical model to CAD geometry is
critical to achieving just the right look in the finished bottle.
The CMMs that the
blow mold manufacturer used in the past did not provide the ideal solution
to this problem. A CMM’s key advantages include the ability to measure
individual points to a high level of accuracy and to move from sample
location to location under computer control. But as the beverage container
geometry has grown increasingly complicated, the number of points required
for accurate measurements is increasing at an exponential rate. Millions
of points are required to accurately model geometrically complicated
bottles. The result is that the time needed to capture points one by one
has grown to weeks for complicated parts. Another problem is that the
contact probe used to capture points on a CMM runs the risk of creating an
indentation in the stone or plastic container that could detract from the
accuracy of the measurement or even damage the model.
The advent of laser scanning
Fortunately, the
technology of laser scanning has emerged in recent years to present a
viable alternative. Laser scanners work by projecting a line of laser
light onto surfaces, while cameras continuously triangulate the changing
distance and profile of the laser as it sweeps along, enabling the object
to be accurately replicated. They collect thousands of points every second
at a high level of accuracy so they are able to accurately digitize
complicated parts. The elimination of the need to maintain contact with
the workpiece also means that the results are independent of the skill of
the operator.
With a relatively
small number of parts that need scanning every year, engineers felt that
it didn’t make sense to rush into a purchase of a machine. The company
would have faced the risk that the machine could become obsolete before it
had paid for itself as well as the challenge of training operators and
maintenance staff. So they looked for a service bureau that could provide
the high accuracy and fast turnaround the company needed on nearly every
project. The company had a bad experience with the first service bureau
they tried because it was unable to meet the tight deadline. “We searched
on the Internet for a different vendor and discovered GKS
Inspection Services,” said
the Product Design Engineer. “The people I talked to there demonstrated
their interest in my requirements and the willingness to help me through
every step of the process. Their prices were very good and through the
numerous projects we had done with them they have always met the delivery
dates they promised.” The engineer also liked the fact that GKS Inspection Services
is one of the leading manufacturers of laser scanning equipment so they
have continual access to the latest technology which they use to ensure
accuracy and fast-turnaround.
Digitizing a dairy container
The first part
the company sent to GKS Inspection Services was a plastic container for which the
customer ordered a new mold. The plastic bottle was a 26-ounce
single-serve diary container that was too soft to accurately digitize with
a CMM. He shipped the bottle to GKS Inspection Services whose engineers then scanned
the part, generating a point cloud with the millions of points needed to
accurately define the complex surface geometry of the part. Each
individual point was accurate within 20 microns and the surfaces generated
from the point cloud were accurate to at least 0.004 inch. GKS Inspection Services
engineers used Raindrop Geomagic software to convert the point cloud to a
surface model. They then exported the surface model as an IGES file and
imported it into CATIA, one of the CAD software packages used by the
manufacturing company. Within two days from the time they had received the
bottle, they had emailed a CATIA surface model to the Product Design
Engineer.
Since this was
the first time the company had worked with GKS Inspection
Services, it wanted to
double-check the accuracy of their work. After receiving both the model
and the bottle back from them, a series of measurements were made with
calipers, height gauges and shadowgraphs. The same measurements were made
on the surface model from the file they had sent in CATIA. Then, to be
sure that they had accurately captured the contours, the engineers
generated a number of cross-sections in actual size, printed them out, and
cut out the part of the drawing that represented the bottle. These
drawings were then fit to the bottle, which GKS Inspection
Services had by this time
returned. The company was please to see that the sections that had been
cut out matched the bottle perfectly. The company also liked the fact that
this scan, as well as all of the ones it has had done since, cost less
than $2000.
Since that initial project, the company has
sent about a half a dozen other stones or containers to GKS
Inspection Services for
digitizing. All in all, GKS' service bureau has met our needs
for fast and accurate reverse engineering of existing products and models.
Their willingness to work with us to ensure that we get exactly what we
need in a timely manner has helped us meet the needs of our customers.
|
