Contact Regions and Contact Groups

The Welding cost models rely on the following important GCD types that are specific to the Assembly process group:

Adhesive Bonding and Fay Sealing also rely on ContactRegion GCDs.

ContactRegion GCDs

A ContactRegion represents a single continuous area of contact between two parts (where each of the two parts is a non-assembly, that is, a leaf-level Subcomponent in the assembly Subcomponent tree). Each of the two parts bears the Lies On relation to the ContactRegion. If there is a Weld on or near the edge of a ContactRegion, the Weld bears the Lies On Relation to the ContactRegion (which helps the cost model estimate clamping requirements).

Under the Joining node in the Geometric Cost Drivers pane, ContactRegions are divided into Top Level ContactRegions and Lower Level ContactRegions. The Top Level ContactRegions are those that are in a Top Level ContactGroup (see below). The rest are Lower Level ContactRegions.

Certain operations, such as Adhesive Bonding and Fay Sealing, are performed on ContactRegion GCDs. In addition, the Clamping operation of the Pick and Place process is performed on ContactGroup GCDs, which represent groups of ContactRegions.

Site administrators can use the following site variables to configure the extraction of ContactRegion GCDs and their associated relations:

  • maxGapForContactRegionMm: By default, parts are considered to be in contact with each other if they are within 1mm of each other. Site administrators can override the default with the site variable maxGapForContactRegionMm. Set the site variable to the maximum distance at which parts should be considered to be in contact.

  • maxDistanceFromWeldToRegionMm: By default, a Weld is considered to Lie On a ContactRegion if the Weld and the ContactRegion are within 10mm of each other. Site administrators can override the default with the site variable maxDistanceFromWeldToRegionMm. Set the site variable to the maximum distance at which a Weld should be considered to Lie On a ContactRegion. If you use Pro Welds, set this to a value greater than 0. If you use only virtual welds, set this to 0.

  • minContactRegionLengthMm: By default, aPriori will not recognize an area of contact as a ContactRegion GCD when the contact length is less than 1.00 mm. Administrators can override the default with the site variable minContactRegionLengthMm. Such small contacts likely are unintentional modeling errors or do not represent valid joining surfaces.

  • minContactRegionAreaMm: By default, aPriori will not recognize an area of contact as a ContactRegion GCD when the contact area is less than 0.10 mm2. Administrators can override the default with the site variable minContactRegionAreaMm. Such small contacts likely are unintentional modeling errors or do not represent valid joining surfaces.

ContactGroup GCDs

A ContactGroup represents all the regions of contact between a pair of siblings in the Subcomponent tree. The Top Level ContactGroups are those that represent the regions of contact between pairs of top-level Subcomponents. The rest are Lower Level ContactGroups.

In the example below, Part B contacts Part A in two places, so there are two ContactRegions in the ContactGroup for Parts A and B.

The Clamping operation of the Pick and Place process is performed on ContactGroup GCDs, in order to model clamping in preparation for welding.

Here is an example that further illustrates the relationship between ContactRegions and ContactGroups: The image below shows an assembly. Parts P1, P2, P3, P4, P5, and P6 represent Subcomponents that are not themselves assemblies. The assembly also has an assembly subcomponent (in green) that includes P1, P2, and P3; and assembly also has an assembly subcomponent (in blue) that includes P4, P5, and P6.

Given the regions of contact shown in the image, aPriori forms a single ContactRegion between each of the following pairs of parts:

  • P1-P2

  • P2-P3

  • P3-P6

  • P6-P5

  • P5-P4

  • P4-P1

In addition, aPriori forms the following ContactGroups:

  • ContactGroup for the green Subcomponent and the blue Subcomponent: includes ContactRegions P3-P6 and P4-P1.

  • ContactGroup for P1 and P2: includes ContactRegion P1-P2.

  • ContactGroup for P2 and P3: includes ContactRegion P2-P3.

  • ContactGroup for P6 and P5: includes ContactRegion P6-P5.

  • ContactGroup for P5 and P4: includes ContactRegion P5-P4.

There is no ContactGroup for P1 and P3, because they are not touching. Similarly for P4 and P6.

There is no ContactGroup for P1 and P4, because they are not siblings in the Subcomponent tree (they do not share a parent). Similarly for P3 and P6

Here is another example: The diagram below represents an assembly. Parts P1, P2, P3, P4, P5, and P6 represent Subcomponents (in blue) that are not themselves assemblies. Subcomponents SA1, SA2, and SA3 represent Subcompoenents (in red) that are assemblies.

Given the regions of contact shown in the diagram, aPriori forms a single ContactRegion between each of the following pairs of parts:

  • P1-P2

  • P2-P3

  • P3-P4

  • P2-P5

  • P4-P6

In addition, aPriori forms the following ContacGroups:

  • ContactGroup for SA1 and SA2: includes ContactRegions P1-P2, P2-P3, and P3-P4.

  • ContactGroup for P2 and SA3: includes ContactRegion P2-P5.

  • ContactGroup for P4 and SA3: includes ContactRegion P4-P6.

For every assembly, there is one contact group for each pair of Subcomponents that meet the following conditions:

  • The Subcomponents are siblings in the assembly Subcomponent tree (that is, they have the same parent Subcomponent).

  • The Subcomponents are touching each other.

In this case, both Subcomponents bear the Lies On relation to the ContactGroup.

A ContactGroup, G, for a given pair of assembly Subcomponents, S1 and S2 represents all ContactRegions, R, such that both the following hold:

  • S1, or a part descended from S1, bears the Lies On relation to R.

  • S2, or a part descended from S2, bears the Lies On relation to R.

In this case, every such R bears the Lies On relation to G.