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BIO-PARTS
Tooth: Bio-parts can be scanned to an accuracy of better
than +/- 25 microns (+/- 1 thou)
with the Model 150C. Motion control software guides the sensor around
the bio-part keeping the sensor aligned nearly perpendicular to part surfaces.
Since the Optimet confocal optics sensor can measure surfaces even at
steep angles to the illuminating beam, tiny nooks and crannies of bio-parts
can be accurately portrayed. Bio-parts can be displayed in either
datacloud or topography map formats.
Figure 1. Tooth Datacloud
Figure 2. Tooth Topography Map
MACHINED PARTS
Bore Groove: Five axis motion control also helps to inspect
dimensions that are otherwise
difficult to inspect. The figure below shows the groove that holds in the
circlip on a piston's pin bore. The depth of the groove must be deep
enough to prevent the circlip from falling out and ruining the engine.
Since the Optimet sensor scans co-axially, accurate dataclouds can measure
the region around the groove despite obstructions from other parts of the piston.
Figure 3. Pin Bore Groove
Scanning the groove results in the datacloud shown in isometric below.
The scan is 1 mm wide by 6 mm long and measures the bottom of the pin bore
seen in the figure above. The bevel on the pin bore is to the right
of the figure. The scan direction is indicated by the small red
arrow. Note that a small portion of the groove was occluded by the
groove's lip.
Figure 4. Groove Datacloud
Since the width of the scan is narrow compared to the pin bore diameter, the
surfaces can be modeled as simple planes and cylinders. Below, the groove
is modeled as a cylinder even though data points cover only about
a third of the cylinder's circumference. The narrow section of the pin
bore and bevel datacloud have been modeled as planes. Dimensions were
set up to measure the distance from the pin bore surface to the bottom of the
the groove cylinder -- the groove's depth.
Figure 5. Cylinder Fit to Groove
Instead of fitting a cylinder to the groove,
CAItech software
can alternatively fit a sphere to the groove. In the figure below, a
sphere has been least squares fit to the groove datacloud. This is
equivalent to placing a ball with a variable radius in the pin bore groove so
that it fits the best way. The sphere has been made transparent to show
the fit to the groove datacloud. Notice that only the central part of
the sphere touches the groove datacloud.
Figure 6. Sphere Fit to Groove
ELECTRONICS PARTS
Die Bead: Although the Model 150C has the capability of
inspecting parts as large as
150 mm, it can also inspect small parts accurately. In the figure below
it inspects an electronic die with beads at both ends. The die is 3 mm
(0.12") wide by 16 mm (0.64") long. It is fixtured by vacuum chuck to the
machine's turntable. The inspection task is to find the variation in
bead height relative to the die surface.
Figure 7. Die Datacloud
The bead at one end of the die is shown in more detail below. Here
the die has been least squares fit to a plane. The bead datacloud has been
sliced into ten narrow cylider slices, each just 0.3 mm (12 thou) wide.
The top of each cylinder slice is least squares fit to the corresponding slice
of the bead datacloud such that the top of each slice is the same height
as the bead at that location.
Figure 8. Bead Slices Fit to Cylinders
In the table below, the bead slice's cylinder radius is subtracted from the
die height to give the height of that bead segment above the die surface.
The bead heights vary only slightly despite large variations in cylinder radius
and center. Variation of only a micron can be seen because hundreds of
data points were averaged into each cylinder slice.
Figure 9. Bead Height Variation
Connector: Another important type of electronic part is a
connector. The
connector shown below in isometric is about 20 mm (0.8") by 12 mm
(0.5"). It has 16 contacts: eight upper contacts above the plastic
base and eight end contacts protruding from the end of the base. The
inspection task was to determine the shape of the formed metal
contacts relative to the top plane of the base.
Figure 10. Connector Isometric
In the figure below,
CAItech's software has extracted one of the contacts
from the connector's datacloud of the figure above. The connector view
has been changed to see the connector in a front view. The shape of
the contact is clearly seen despite being only 0.5 mm (20 thou) wide.
Figure 11. Single Contact Extracted
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