Core Competence, and Much More by aqv56188


									Core Competence, and Much More
Nemak discovers that 3D imaging with laser
triangulation offers a more accurate approach to core
inspection, at a fraction of the cost and with more
efficiency than a two-dimensional view.

                                                                                                        Continuous 3D surface
                                                                                                        maps of the core’s exterior
                                                                                                        depict height variations
                                                                                                        in color. The maps are
                                                                                                        created by coordinating
                                                                                                        data assembled from
                                                                                                        three-dimensional images
                                                                                                        of the core, captured as
                                                                                                        the robotic handlng device
                                                                                                        transports it from the
                                                                                                        coremaking machine to the
                                                                                                        molding line.

                                                                                                                                                                                                                                                              Diagram by Vista Solutions

        emak had been monitoring sand         specting cores is a more productive effort      to present the part to the vision system.       Scarlett, vice president at Vista Solutions.    had recently achieved authorized integra-     own robot, worked through the problems
        cores for its aluminum cylinder       than inspecting the casting interiors, but                                                      “There were a handful of other groups all       tor status with Sick AG (,       and algorithms associated with inspection,
        head and engine block casting op-     after eight years of use Nemak was looking      3D development                                  specifying the latest cameras in another        a well-known maker of the IVC-3D inte-        and they virtually committed to giving us
        eration using a two-dimensional,      for an update for its 2D system.                   It’s widely believed that 2D inspection is   four-camera configuration. We contacted         grated vision camera with laser triangula-    the order on the spot.”
grayscale inspection system, because this        Vision-system integrator Vista Solutions     cheaper than 3D approaches, but that over-      the purchasing manager at Nemak and said        tion.
is an effective way to track the interior     ( suggested that a        looks the capabilities of 2-GHz micropro-       that we were declining to quote because we         According to Vista v.p. Mike Sirizzotti,   Pass/fail inspection
formation of its castings.                    three-dimensional imaging system using          cessors and low-cost field programmable         believed that grayscale was not the right ap-   “we told Nemak, ‘If you really want to in-       For about 10 years Nemak had been in-
   Cores are made of compressed and           laser triangulation could provide a more        gate arrays (FPGA), which put the power         proach to solve this problem.                   spect this core, you need volumetric defect   specting cores using four analog cameras to
bonded sand, and then carefully placed        accurate inspection system at a fraction of     of a mainframe computer into handheld               “But,” Scarlett recalls telling the Nemak   information, and not just area.’ So, we ob-   capture four separate images that revealed
within a sand mold. Once molten aluminum      the cost of the two-dimensional view, and it    devices.                                        officials, “if you’re open to suggestions,      tained some sample cores, and we knew         12 breather tabs on one side of a core. In this
is poured into the mold, the cores hold the   promised to ease timing constraints later in       “Nemak contacted us about a little over a    let’s look at different solutions.”             as soon as we’d seen a screenshot (from       system, a robot would extract the core from
spaces where cavities form in the finished    the production process by inspecting cores      year ago and said it was time to update their       Vista Solutions is “vendor and technol-     the IVC-3D) that this was the right way to    the machine, position it in front of the cam-
casting after the aluminum solidifies. In-    “on the fly,” rather than having a robot stop   core inspection system,” explains Dean          ogy agnostic,” but the Windsor, ON, group       approach the problem. We set it up on our                               continued on p. 50

48   FOUNDRY MANAGEMENT & TECHNOLOGY                                                                                            APRIL 2008    WWW.FOUNDRYMAG.COM                                                                       FOUNDRY MANAGEMENT & TECHNOLOGY                49
                        Quality control

continued from p. 49                                                                                                                                                                                  the ABB robot could pass the part at a con-    The camera collects up to 5,000 profiles per
eras, stop momentarily while the images                                                                                                                                                               stant speed in front the camera, so we could   second, processing them in real time on the
were captured and collected, and then pass                                                                                                                                                            using timing to create the 3D surface map,     FPGA and microprocessor, and composit-
the core along. Depending upon whether a                                                                                                                                                              rather than physical position using an en-     ing them into a continuous 3D surface map
core failed or passed its inspection, it would                                                                                                                                                        coder,” DeGroot recalls.                       of the core’s surface. On the map, height
be trafficked either to a reject conveyor or                                                                                                                                                             The camera builds a 3D surface map by       is displayed as intensity — in the case of
on to a conveyor leading to the aluminum                                                                                                                                                              combining “profiles,” individual images        grayscale display — or as color, in the case
casting line.                                                                                                                                                                                         that reveal the position of the laser line.                            continued on p. 52
   Because the six-axis ABB robot had to
stop and hold the core in front of the cam-
eras, the inspection routine imposed a few
extra seconds into the coremaking process
while the handling device decelerated,
stopped, and accelerated again.
   Each breather tab measures approxi-
mately 1 cm in diameter and less than 2
cm tall. In order to produce an acceptable
casting, Nemak’s manufacturing process           The robot holds the core while the camera captures an image of it for                                The camera is housed near the core
requires only that a majority of the tab be      inspection.                                                                                          machine, to inspect the finished
present to achieve a good aluminum part.                                                                                                              cores as they are transferred to the
The older system, and all of the other pro-      cate the presence of a breather tab.              IVC-3D 200 holds a CMOS sensor offering a          mold.
posals Nemak fielded, suggested upgrad-             The Vista Solutions proposal also called       maximum profile width of 1,024 pixels and
ing the camera technology but staying with       for a static inspection station served by the     a red diode laser-line generator in a single
grayscale imaging and geometric pattern          ABB robot. A Sick IVC-3D 200 camera was           housing. A laser line is directed straight at
searches, to identify key features that indi-    mounted just to the side of the robot path. The   the object under inspection while the CMOS
                                                                                                   camera is placed slightly off the optical axis.
                                                                                                       In this configuration, displacement of the
                                                                                                   laser line in the acquired image indicates dif-
                                                                                                   ferences in height. A bandpass filter placed
                                                                                                   under the IVC-3D 200’s protective window
                                                                                                   filters out wavelengths other than those emit-
                                                                                                   ted by the laser-line generator. This reduces
                                                                                                   the need for additional vision-specific light-
                                                                                                   ing, as well as the system’s footprint and the
                                                                                                   vision system’s component checklist.
                                                                                                       The camera also houses an 800-MHz mi-
                                                                                                   croprocessor with FPGA acceleration. Ac-
                                                                                                   cording to the system developers, this makes
                                                                                                   it possible to process images entirely at the
                                                                                                   camera head, using Sick’s IVC Studio object-       A Sick IVC-3D 200 camera is
                                                                                                   based image-processing library, or to send the     mounted in the path of the robot
                                                                                                   image to a separate processing station.            that handles cores, and is fitted
                                                                                                                                                      with a laser-line generator, in a
                                                                                                   The new approach                                   single housing. The data it captures
                                                                                                       Once the robot retrieves the first core from   is used to compile a 3D surface
                                                                                                   the mold, the controller sends a query signal      map of the core.
                                                                                                   across a relay to one of six programmable
                                                                                                   I/O ports on the IVC-3D 200. If the system         captured from a single image.
                                                                                                   is ready for inspection, a signal is sent to the      Keith DeGroot, Vista Solutions manager
                                                                                                   robot controller for the process to begin.         of application engineering, reports that in
                                                                                                       Then, the robot takes the core from the        designing the system a important consider-
                                                                                                   machine and moves it across the camera’s           ation was whether or not to use an encoder
                                                                                                   field of view (200×600-mm), at a distance          to track the position of the core as it moved
                                                                                                   that allows the full width of the core to be       in front of the camera. “We determined that

50    FOUNDRY MANAGEMENT & TECHNOLOGY                                                                                                 APRIL 2008      WWW.FOUNDRYMAG.COM                                                                        FOUNDRY MANAGEMENT & TECHNOLOGY             51
                                                              Quality control

                                                                                                                                                                   “During our trials with the 3D system, the    internally and externally.”
                                                                                                                                                                false trials were attributed to multiple han-       According to the system integrators, the
                                                                                                                                                                dling of the parts that caused them to fail on   installation has been so well accepted that it
                                                                                                                                                                their third trial,” explains says Nemak’s lean   may lead to further applications. “We’re in
                                                                                                                                                                manufacturing coordinator, Mandy Karnib.         talks with Nemak to look at deploying more
                                                                                                                                                                “In short, the 3D laser system has been ex-      ‘black box’ solutions based on this architec-
                                                                                                                                                                tremely beneficial in allowing us to signifi-    ture at other Nemak facilities,” says Dean
                                                                                                                                                                cantly reduce our breather-core scrap, both      Scarlett.

                                       Two sections of the surface map show the elevated                      An example of a core as it is held for
                                       tabs (highlighted in green) that rise above the surface                3D inspection.
                                       of the core; areas where the tabs are missing will fill
                                       with molten aluminum, forming a defective casting.                     text files,” DeGroot explains. “We can dial
                                                                                                              up the IP of the camera and view the latest
                                                                                                              images, and results for each task, whether
                                                                                                              it passed or failed, etc. The system itself
                                                                                                              doesn’t have a monitor or keyboard. We
                                                                                                              program the camera by taking a laptop to
                                                                                                              the camera and uploading the program de-
                                                                                                              veloped in IVC Studio. You can leave the
                                                                                                              laptop there, if you want to display the cam-
                                                                                                              era in real time, but it’s not necessary.”
                                                                                                                 Moving to a scanning mode called for
                                                                                                              some robot reprogramming, because the ABB
                                                                                                              device no longer had to present the part at
                                                                                                              the inspection station. However, this allowed
                                                                                                              the robot to move more quickly, and directly
                                                                                                              from the press to the output conveyor.
                                                                                                                 Sirizzotti says the time savings was not
                                                                                                              significant for coremaking productivity, but
                                                                                                              helped to ease some production restraints
                                       The robot holds the core while the camera captures an                  later in the casting process.
                                       image of it for inspection.                                               Although the combination of optics,
                                                                                                              camera field of view, and size of the core,
                                       continued from p. 51                                                   established a minimum spatial resolution of
                                       of false-color surface map display.                                    0.2 mm for inspecting the breather tabs, Ne-
                                          In addition to the six discrete, programmable I/O ports, the IVC-   mak ‘tweaked’ the threshold to catch larger
                                       3D 200 offers an RS-422 interface for encoders, and a RS-485 out-      defects in the tab structure, which improved
                                       put for PLC communication. The latter wasn’t needed for Nemak’s        the system’s throughput.
                                       application (the ABB robot is in the workcell), but the camera there      In tests, the Vista Solutions/Sick system
                                       includes a 10/100 Ethernet port and internal web server. DeGroot       showed a total effectiveness of 98.17% on 10
                                       says he connected the IVC-3D 200 to the plant’s local area net-        parts: six were good parts, four had known
                                       work and set up the camera to store result data and images on the      faults. None of the errors allowed failed parts
                                       network’s FTP server, for remote viewing by plant personnel, and       to pass. Similar grayscale systems gener-
                                       debugging by Vista Solutions, if necessary.                            ated 85% effectiveness, and passed parts that
                                          “We can save images on the plant network, but we typically save     were known to be defective.

52   FOUNDRY MANAGEMENT & TECHNOLOGY                                                           APRIL 2008     WWW.FOUNDRYMAG.COM                                                                           FOUNDRY MANAGEMENT & TECHNOLOGY                53

To top