Current Help System: PC-DMIS CMM (View Core Help)

#### Rules for Manual Scans in General

Manual scans should be done along the machine axis (the X, Y, or Z axis).

For example, your part requires a scan along the surface of a sphere. To do this scan:

1. Lock the Y axis. This is done by using a lock switch on your CMM. This switch can be set to ON/OFF to prevent/allow movement in a particular axis.

2. Begin scanning in the +X direction.

3. Unlock the Y axis, and move to the next row along +Y or -Y.

4. Lock the Y axis again.

5. Scan back in the reverse (-X) direction.

When multiple rows of manual scans are being done, we recommend that every other scan line be reversed.

For example (continuing the scan of the sphere as outlined above):

1. Begin the scan along the surface in the +X direction.

2. Move to the next row and scan along the -X axis.

3. Continue to switch the direction of the scan as needed. The internal algorithms depend on this kind of regularity and could give poor results if the scheme is not followed.

Compensation Limitations

In previous versions there was a 3D check box that let you take hits in a three-dimensional manner. Starting with version 4.0, the 3D check box has been removed. PC-DMIS now automatically applies this functionality whenever you perform supported manual scans using a hard probe.

With Fixed Distance, Fixed Time / Distance, and Fixed Time scan, PC-DMIS automatically lets you take manual hits in a three-dimensional manner, in any direction. This is useful when scanning using free moving manual CMMs (such as a Romer or Faro arm) whose axes cannot be locked.

Since you can move the probe in any direction, PC-DMIS cannot accurately determine the proper probe compensation (or the Input and Direction vectors) from the measured data.

There are two solutions to the compensation limitations:

- If CAD surfaces exist, then you can select FINDNOMS from the Nominals list. PC-DMIS will attempt to find the nominal values for each measured point in the scan. If the nominal data is found, then the point will be compensated along the found vector, allowing proper probe compensation; otherwise, it will remain at Ball Center.

- If CAD surfaces do not exist, then probe compensation will not occur. All data will remain at Ball Center with no probe compensation occurring.