Starting a measurement routine with the probe inside
of the ClearanceCube volume, or initiating DCC motion inside the ClearanceCube
volume, are unsafe practices because the CMM
attempts to move to the closest ClearanceCube face.
If the ClearanceCube uses Tip Vector for Start/End Face
check box on the General tab in the Setup
Options dialog box (Edit | Preferences | Setup)
is selected, then the CMM attempts to move along the tip vector when inside
of the ClearanceCube volume. To avoid potential collisions, be sure to
first manually jog the position of the probe outside of the ClearanceCube
volume before entering DCC motion. Please account for this behavior in
your measurement routines.
The ClearanceCube is a three-dimensional box in the Graphic Display window that represents a protective envelope that surrounds the CAD model. During measurement routine execution, the probe moves along the tip vector to the offset distance of the ClearanceCube to the face of the cube to avoid colliding with the part. By default, ClearanceCube motion is disabled.
Sample ClearanceCube Surrounding the CAD Model
ClearanceCube only functions with single arm measurement routines. It does not support multiple arm measurement routines. If your measurement routine uses multiple arm mode, it only works with arm 1.
Differences from Clearance Planes
While this may have some similarities with clearance planes, it actually behaves quite differently and offers some advantages not available to clearance planes.
First, clearance planes are based on the part coordinate system, and if the part coordinate system changes, the clearance planes do not adjust accordingly. For example, if a Z+ clearance plane is set for 20 mm above the current Z=0 location, and you create a new part coordinate system by moving Z down by 30 mm, the clearance plane does not move, but is now at Z=50. However, if you use ClearanceCube, that box remains at the same relative distance from the CAD model, regardless of changes made to the part coordinate system.
Second, clearance planes rely on MOVE/CLEARPLANE commands being placed between features to move the probe to the defined clearance plane. Forgetting one of these move commands could result in an unintended collision with the part. The ClearanceCube functionality does not use clearance planes and so does not require move commands between features. In its simplest form, once you enable the ClearanceCube functionality, newly created features automatically cause the probe to move to the ClearanceCube before and after they are measured.
Using the ClearanceCube
When running, if the probe starts inside the ClearanceCube, a message appears that says: "Probe is currently located inside ClearanceCube. Move probe outside ClearanceCube and press OK to continue".
To use the ClearanceCube,
Select
Operation | Graphic Display Window | ClearanceCube, or from
the ClearanceCube toolbar, click the ClearanceCube Definition icon 
to open the ClearanceCube Definition dialog
box. This dialog box initially opens with the following interface.
See "(Simple)
ClearanceCube Definition" for detailed information.
ClearanceCube Definition dialog box
Select the
Activate ClearanceCube motion check box, or from the ClearanceCube toolbar, click the Activate
ClearanceCube Motion icon 
.
This mode disables clearance planes, and causes the measurement routine
to use the ClearanceCube motion instead. See the warning below.
Select the
Show ClearanceCube check box, or from the ClearanceCube
toolbar, click the Show ClearanceCube icon
to show the ClearanceCube
on the screen.
In the Offset
Value box, define an offset distance. You can also select the
Resize ClearanceCube check box, or from
the ClearanceCube toolbar, you can click
the Resize ClearanceCube icon 
to place the ClearanceCube in resize mode. When in resize mode and
the ClearanceCube is visible, you can click and drag a face of the
ClearanceCube and set offset distances per axis that way. A reddish
highlight indicates the face to drag.
If needed, set any advanced options by clicking Advanced, and then use the desired tabs to customize the ClearanceCube to your liking.
Click OK.
Add features into the measurement routine as usual.
If you activate ClearanceCube motion, it acts as a global setting to that measurement routine. This means that all clearance plane functionality for your measurement routine is disabled, even if individual features are specifically set to not use the ClearanceCube. ClearanceCube motion and clearance planes cannot coexist in the same measurement routine. Be sure to check for collisions before executing your measurement routine. See "Detecting Collisions" for more information.
More:
(Simple) ClearanceCube Definition
(Advanced) ClearanceCube Definition - Size tab