A geometric tolerance sets the allowable variation of a length,
angle or position of a feature, or the acceptable relationship
between multiple features.
To add a tolerance, you must specify its type (such as length or
perpendicularity), the range of acceptable results (that is, the
tolerance's minimum and maximum values), and the features to which
it is applied. For example, you can set the length tolerance of a
segment to be between 90 and 100 pixels, or you can set the
perpendicular tolerance between 2 segments to be between 89.95 and
90.05 degrees. Optionally, you can set warning thresholds to alert
you when the resulting tolerance is close to, but outside of, a
passing range.
The status of the geometric tolerance returns Pass or Warning if the tolerance
meets the specified pass or warning requirements, and Fail if it does not, as
illustrated below.
Note that the tightest range specifies values that Pass. A warning value is not
considered a pass, so the warning ranges fall above or below the
Pass range's
Value max and
Value min
settings, respectively.
The following illustration lists the geometric tolerance types.
Note that information on how to define each tolerance is available
at design-time from the
Quick Access pane or the Construction
control panel.
Angle-based tolerances
Dimension and position based tolerances
Angularity
DistanceMin/DistanceMax
PositionX/PositionY
Perpendicularity
Length
Straightness
Parallelism
Radius
Roundness
Concentricity
Using the
Project toolbar
The following is a basic methodology for defining geometric
tolerances using the
Project toolbar:
Add a tolerance using the Add angle tolerance
() or Add dimension/position
tolerance () toolbar buttons.
Select the Tolerance type from the
dropdown menu (for example, DistanceMin).
The Construction
control panel will then appear, giving contextual information as to
which features are supported for the chosen tolerance type. For
instance, the DistanceMin tolerance can be
based on almost any 2 features, with the exception of lines.
Select the features on which to apply the tolerance (for
example, a segment and a circle). To do so, in the image, click on
a feature or its callout to add it to the list of Base features in the
Construction
control panel.
Click on the green checkmark in the Construction
control panel to confirm the Base features. The tolerance
is added. Note that the
Configuration pane updates to display the tolerance
options, where you can input specific tolerance values.
Specify the tolerance's minimum and maximum values.
For example, for a DistanceMin tolerance, you
could set the minimum and maximum values to 90 and 100 pixels,
respectively. If you do not specify warning values, the status of
the features on which the minimum distance tolerance is applied
will return a Pass if the distance is
within this range; features with a distance below 90 or above 100
pixels will return a Fail.
Optionally, specify the tolerance's minimum and maximum warning
values.
For example, set the minimum and maximum warning distance values
to 85 and 105 pixels, respectively. Distances between a warning
value and its respective minimum or maximum tolerance, set in step
5 above, will return a Warning status.
Using the
Configuration pane
You can add geometric tolerances directly from the
Configuration pane as follows:
Click on the Add... button in the
tolerances section of the
Configuration pane.
Select the Tolerance type (for example,
Length).
Select the feature category (From features) for which to
validate the tolerance (for example, Segment, Circle, or Arc).
For some tolerance types, this narrows down the possible features
upon which you can apply the tolerance (in step 4 below), leaving
only applicable features.
Select the features (Select features) on which to
apply the tolerance (for example, one specific segment, circle, or
arc).
Click on the Add button. The tolerance is
added. You can typically add, edit, delete, or rename tolerances
from the
Configuration pane.
Specify the tolerance's minimum and maximum values.
Optionally, specify the tolerance's minimum and maximum warning
values.
Note that, when adding a tolerance, some features are not
available from the
Configuration pane. For example, features added with the
Measurement
step are not listed in the Add tolerance page of the
Metrology step's
Configuration pane. To add a tolerance using these
features, you must do so interactively using the
Project toolbar method described above.
Setting
an angularity tolerance
An angularity tolerance validates that the angle between 2
features falls within the specified angular range (for example,
that 2 lines intersect at an angle between 25° and 35°). You can
add an angularity tolerance between the following features: 2
lines, 2 points, 2 segments, or between a linear feature (segment
or line) and an edgel feature. In addition, you can add an
angularity tolerance for one segment.
2 line features.
To validate the angularity between 2 line features, Matrox
Design Assistant considers the angle between the lines to be,
counter-clockwise, from the first line to the second line. The
angularity status will fail unless the angle falls within the
minimum and maximum pass values set for the tolerance. To designate
the valid angular range, set the Value min and Value max tolerance limits
as angles applied counter-clockwise from the first line to the
second line, around the intersection point of the 2 lines.
The order in which you select the lines can affect your results.
For example, the same line pair is measured differently, depending
on which line is selected first.
2 point features.
An angularity tolerance between 2 points is measured from the
first to the second point, applied in a counter-clockwise
direction. The start point for the angle is an imaginary axis
originating from the first point, parallel to the X-axis of the
point's reference frame.
2 segment features.
To validate the angularity between 2 segment features, Matrox
Design Assistant internally connects each segment at their start
point and considers the angle from the first to the second segment,
applied in a counter-clockwise direction. The angularity status
returns a Pass
if the angle falls within the minimum and maximum pass values set
for the tolerance. To designate the valid angular range, set the
Value min and
Value max
tolerance limits as angles applied counter-clockwise around the
start point of the first segment. Note that Matrox Design Assistant
does not physically rearrange the specified segments, it only
orients them internally to measure the required angles.
The following animation illustrates angularity between 2 segment
features.
Each segment's start point, as well as the order in which you
select the segments when adding the tolerance, can affect your
results. For example, the same 2 segments are measured differently,
depending on which segment is selected first.
To find which end of a segment is the start point, click on its
callout, and note the listed StartPosition and
EndPosition in
the
Quick Watch flyout panel. If necessary, click on the
filter button at
the top-right of the panel; then, choose the Advanced display mode to see
these properties.
A linear feature (segment or line) and an edgel feature.
For one linear feature (segment or line) and one edgel feature,
Matrox Design Assistant validates the edgel feature's width. The
width is measured from a projection of the edgel feature onto an
imaginary line that is perpendicular to the specified angle
(ReferenceAngle). The angle
is in the counter-clockwise direction relative to the linear
feature. To designate the valid width range, set the Value min and Value max tolerance limits
in the
Configuration pane. Typically, you should set the minimum
width value to 0. The width of the projection is in pixel or world
units. Note that the second feature specified must be edgel.
Using
multiple geometric tolerances
To accurately represent a relationship between features, you
might have to validate the features with multiple geometric
tolerances. For example, to verify the following result, you can
set a 30° angularity tolerance between 2 segments.
However, using only the angularity tolerance, each of the
following results has a valid tolerance status.
In this case, you need to add an additional tolerance to check
the location of the segments. To do so, add 2 constructed point
features at the start of each segment. You can then add a distance
tolerance for these 2 points, ensuring they are at the same
location. To satisfy the required feature relationship, both the
angularity status of the segments and the distance status of the
points must be valid.