Rules Applicable During Type B Checks

Model Reference Manual

Clash Detection : Specifying How Branches Are Checked : Rules Applicable During Type B Checks

The following sections define the rules that MODEL applies during the clash-checking process when the BCHECK option is in force. They include examples of the sorts of design errors that would remain undetected in the clash report. The term ‘clash’ is used in these examples to refer to all types of interference; in practice, some of these may be reported as touches, depending upon the touch specifications in force.

Clashes Within a Single Branch

Rule: If the leave point (p-leave) of an upstream component or tube coincides with the arrive point (p-arrive) of a downstream component, and there is no intervening Tube, the two components will not be checked for clashes between them.

This rule is intended to suppress clashes when two components or tubes within a branch are separated by one or more zero-length components that have no Geomset.

For example:

Clashes Between a Branch and a Nozzle

Rule: If a branch head or tail and a nozzle are properly connected and the p-arrive or p-leave of the final component coincides with the branch head or tail, then no clash will be reported.

This rule is intended to suppress clashes when a nozzle and a pipe component or tube are separated by one or more zero-length components.

For example:

The rule would, however, cause the following (unlikely) clash to be ignored:

Clashes Between Two Branches

Rule 1: If two branches are connected together end-to-end and the p-arrive/p-leave of two components or tubes coincide with their respective branch head/tail (whichever is the connected end), then no clash will be reported.

This rule is intended to suppress clashes similar to those described for clashes within a single branch, except that the relevant components or tubes may now be from different, but connected, branches.

For example:

Rule 1 would, however, allow some clashes due to routing errors to be ignored. For example:

Rule 2: If the head/tail tube of one branch is connected to a set-on tee or olet (having no geometry other than a sphere) in a second branch and the p-arrive/p-leave of the connected component in the main branch coincides with the p-arrive/p-leave of the tee’d component in the side branch and the latter point is also the HPOS or TPOS of the side branch, then no clashes will be reported between the head/tail tube of the tee’d component and the tube on either side of the tee/olet in the main branch.

This rule is intended to suppress clashes when a side branch is connected to a zero-length component in another branch.

For example:

Rule 2 would, however, allow the following clash to be ignored: