Checking for Clearance and Interference in an Assembly

It is a common occurrence for components to interfere with one another in your design. In some situations, this may even be intended. But when parts interfere, Pro/ENGINEER does not display warning messages.

The Model Analysis tool in Pro/ENGINEER can be used to determine where the interference is occurring, and if it is desired. You can calculate clearance or interference between any combination of parts, sub-assemblies, surfaces, cables, or entities in an assembly by clicking Analysis > Model Analysis. In this tip, a bulldozer assembly (Figure 1) is used to illustrate the techniques involved in checking for clearance and interference. 

Checking for interference:

First, check for interference by looking at the hidden/no hidden line. If this area does not look correct, it is an indication there is interference (Figure 2). If you want to check your entire assembly for interference, a global interference check is required:

• Select Analysis > Model Analysis and look for the Model Analysis dialog box 
• In the Type box select Global Interference 
• Click Sub-assemblies only under the Setup section if you do not want to check individual parts within the sub-assembly
• Select Parts only if you want to check interference of parts regardless of what assembly they belong to
• Surface quilts can also be included by clicking Include under the Quilts section (leave Exclude selected)
• Now, under Display click Exact result and then click Compute 
• In the Results section clicking a pair of interfering parts will highlight them on the screen, one in green and the other in yellow 

Figure 3 shows that the "canopy.prt" and "seat.prt" interfere. The region of interference is highlighted in red, and the volume of the interference is displayed in the Results area.

Checking for clearance:

If two parts do not interfere, there is clearance between them. A global clearance check can be performed to see if there are any pairs of components that have clearances of less than a specified distance: 

• In the Type box select Global Clearance and under Setup select Parts Only 
• In the Clearance box, type 0.00, then select Compute 
• Select Pairs Clearance in the Type box if you want to check individual pairs of sub-assemblies, parts, surfaces, cables, or entities

For example, to determine if the right tread of the bulldozer is interfering with the plow:

• Select Pairs Clearance in the Type box and in the From box select Whole Part 
• Select the "right_tread.prt", and leave the default Exclude selections for Quilts and Facet 
• Repeat the procedure for the To box and select the "plow.prt"
• Click Compute and you will see two red vertices connected by a red line at the area of minimum clearance. 
• A new To object can be selected if desired 

Figure 4 shows the point where the clearance is at a minimum. If these two parts had interfered, the interference would appear in the Results area. 

In Figure 5, the display of the cable connecting the plow to the engine does not look correct in a no-hidden line view. This is indicative of possible interference.

Follow the steps below to calculate the clearance or interference between any combination of surfaces, cables, or entities (points, curves or edges):

• Select Pairs Clearance from the Type box
• With Whole Part selected from the From box select the "engine.prt" (leave Exclude selected for Quilts and Facet) 
• In the To box, select Cable and then select the cable feature from the screen. The Results area reports Clearance= -0.643. (showing an interference). The cable is passing through the engine part, and should be rerouted to avoid the interference. 

Note that this interference was not detected with a global interference check. The only way to check for cable interference is to use Pairs Clearance. 

Although not used in this example, it is also possible to determine which components of an assembly interfere with a given volume:

• Select Volume Interference from the Type box and choose a closed surface quilt. Closed quilts are entirely purple. If the surface feature contains magenta edges, it is not fully closed.

Figure 1


Figure 2


Figure 3


Figure 4


Figure 5