### Working with Contact Path Properties

Probe Toolbox—Contact Path Properties tab

This tab becomes visible when you have the Auto Feature dialog box open and a contact probe is enabled.

The Contact Path Properties tab contains several items that allow you to change various hit properties for a number of supported Auto Features that use contact probes.

Hint: A useful way of visualizing how these properties affect the measurement is to display pathways and hits by using the Show Hit Targets Toggle icon .

Depending on the type of feature in the Auto Feature dialog box, this tab may change to contain one or more of the following items:

Item | Supported Auto Features | Description
Hits | Line, Plane, Circle, Ellipse, Round Slot | This defines the number of hits that will be used to measure the feature. The number of hits specified will be equally spaced between the starting and ending angle indicated.

Circle or Ellipse | If the start and end angles are the same, or differ by a multiple of 360°, then only one hit will be taken at the mutual starting and ending point.

Location of Hits | A - Starting Angle

Round Slot | If an odd number of hits is entered, PC-DMIS will automatically add one to the value. This allows for an even number of hits in the measurement of the slot. Half of the hits will be taken on the semi-circle at each end of the slot. A minimum of six hits is required.
Plane | The minimum number of hits needed to measure a plane is three. However, the total number of hits for the plane feature is generated by the product of the values in the Hits and Levels boxes. Therefore, a value of 2 in the Hits box with a 3 in the Levels box would generate a total of six hits.
Line | You can type any number of hits. Depending on the type of line and the value entered, PC-DMIS does the following: If you are creating a bounded line, then PC-DMIS uses the calculated length of the line and spaces the number of hits equally along the line so that the first and last hits are at the Start and End points.

If it is an unbounded line, then PC-DMIS uses the typed length value and spaces the number of hits equally along the line's direction vector.

Note: If you don't type a length value (or the value is zero), PC-DMIS uses the current probe tip's diameter as the distance between points.

Hits (Total) | Sphere | This is the same as described in Hits except that this defines the total number of hits that will be used to measure the feature among all available levels. You need at least four hits to measure a sphere.
Depth | Edge Point, Line, Circle, Ellipse, Round Slot, Square Slot, Notch Slot, Polygon | This defines where PC-DMIS will take hits on the feature itself and its surrounding sample hits.

Edge Point, Notch Slot | If one, two, or three sample hits are indicated, then the depth value will be applied from the measured surface value.

Depth for Edge Point | A - Target hit B - Sample hit C - Depth

Circle, Ellipse, Round Slot, Square Slot, Polygon | For these features, the depth value is usually applied as a positive offset distance along the IJK centerline vector. The vector originates at each feature's center point. While negative depth values are allowed, this is not recommended for contact-based measurements of these features. For example, consider these two cases:

- Case 1: If the nominal center point is at the base of the external feature, the depth would be the distance from the bottom of the feature.

- Case 2: If the nominal center point is at the top of the external feature, the depth would be the distance from the top of the feature.

A negative value in the first cases would cause the probe to move into the surface material surrounding the feature, possibly causing a collision.

A negative value in the second case would be desired for the probe to properly contact the feature, whereas a positive depth value would move the probe above the feature where no material would exist for the probe to contact.

Important Considerations:

Centerline vector (IJK): The vector of the feature should point away from the plane in which the feature lies (2D feature). If sample hits are involved (for 2D or 3D features), that vector should reflect the approach vector for those sample hits.

Height or Length: If the feature has a length or height with a negative value, the vector orientation is flipped.

The orientation of the vector along which the positive depth is applied (IJK’) will change based on these conditions:

External features:

IJK’ = IJK in case the features has a Height/Length >= 0;

IJK’ = - IJK in case the features has a Height/Length < 0.

Internal features:

The IJK’ for internal features points in a direction opposite that of external features.

Line | The distance is applied as a positive value along the perpendicular vector to the line vector and edge vector. The line's depth depends on the direction of the hits in relation to the current coordinate system. For example, if you have a typical orientation (X/Right, Y/Back, and Z/Up), and you take your first and second hits from left to right on the model, then you need to use a positive depth value. However, if you take your first and second hits from right to left on the model, then you need to use a negative depth value.

Starting Depth | Cylinder, Cone | For features with multiple levels, this defines the starting depth of the first level of hits. It is an offset from the top of the feature. All other levels will be equally spaced between the Starting Depth and Ending Depth. View Demo
Ending Depth | Cylinder, Cone | For features with multiple levels, this defines the ending depth of the last level of hits. It is an offset from the bottom of the feature. All other levels will be equally spaced between the Starting Depth and Ending Depth.
Pitch | Circle, Cylinder | For threaded holes and studs, the Pitch value (also known as "threads per inch") defines the distance between threads along the axis of the feature. This allows for more accurate measurements of threaded holes and studs. If the value is anything other than zero, PC-DMIS staggers the feature's hits along the feature's theoretical axis, spacing them around the feature using the Start Angle and End Angle values in the Auto Feature dialog box.

Circle | In order to follow a standard (clockwise) thread pattern, you need to reverse the starting and ending angles (i.e. 720 - 0) and in order to cause the measurement to reverse from a rising pitch to a falling pitch (up/down), you need to negate the value of the pitch.

Example: If measuring a circle with four hits equally spaced around the circle, the first hit will be at the starting angle at the input depth. The second hit will be at a 90 degree rotation to the first and a depth of (depth – ((hitnum-1)/tothits * pitch)). The third hit would be 180 degree rotation from the first hit with a depth of (depth – ((hitnum-1)/tothits * pitch)). The remaining hits follow this same pattern.

Cylinder | Example: If measuring a cylinder with two levels of four hits equally spaced around the cylinder, the first hit in each level will be at the starting angle at the input depth. The second hit will be at a 90 degree rotation to the first hit and a depth of (Depth - (hitnum-1)/# hits per level * pitch). The third hit would be 180 degree rotation from the first hit with a depth of (Depth - (hitnum-1)/# hits per level * pitch). The remaining hits follow this same pattern.

Hits Per Level | Cylinder, Cone | This defines the number of hits per level that will be used to measure the feature. A value of four would mean four hits per level. Note: At least six hits and two levels are necessary to measure a cylinder or cone (three hits at each level).
Levels | Cylinder, Cone, Sphere | This defines the number of levels that will be used to measure the feature. Any integer greater than one can be used. The first level of hits will be placed at the Starting Depth. The last level of hits will be placed at the Ending Depth. For a cylinder or cone, the levels will be equally spaced between the Starting Depth and Ending Depth of the feature.

For a sphere, the levels will be equally spaced between the Start Angle 2 and End Angle 2 value in the Auto Feature dialog box.

For a plane, the number of levels and the number of hits are used to determine how many total hits will be used to generate the auto plane.

Hits Per Side | Polygon | This defines the number of hits taken per side on a Polygon feature.