## Rules for Manual Scans

This topic discusses rules governing manual scanning using a hard probe on a portable device.

Rules for Manual Scans in General

The following description lists the rules that you need to follow to have manual scanning compensate correctly and with greater speed on Arm CMMs.

- You should not lock any axis during the scan. PC-DMIS takes the scan by crossing the probe over a keyed in Body Axis location. Each time the probe crosses this given plane the CMM takes a reading and passes it to PC-DMIS.

- On this type of scan you must type the InitVec and the DirVec values in the Part Coordinate System . This is required to work together with the Body Axis location.

- Make sure you type the Body Axis in the Part Coordinate System.

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. 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

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.