Starrett on Coordinate Measuring

Machine Frame Construction

Bearing Systems

Scales

Manual and DCC

Probing

Software

Service and Support

Products

In order to be useful, CMM software must be intuitive, powerful, and reliable.

A graphical user interface should provide simple, direct access to common CMM operations such as probe calibration, part coordinate system creation, feature measurement and tolerance evaluation. It should not be so limited that a user is forced into a CMM language environment for all but the simplest of tasks. It should provide the ability to automatically measure features, given nominal information.

Feature measurement is the focal point of CMM operation. A window like this provides direct access to all frequently-used measuring functions.

One of the most time consuming and error-prone aspects of creating an inspection program is the entry of feature nominal and tolerance information. On some systems the only way to do this is to enter the data from the keyboard. A much more efficient and accurate way is to access the data directly from the CAD design file in a 3-D graphic environment. Access to the CAD data should not be limited to the nominal design information, but should also be able to obtain geometric tolerancing requirements directly from the drawing. The system should be able to understand IGES, DXF and other widely used CAD formats. It should also be possible to view measured and constructed features in a 3-D graphic window for comparison with a design model, or for reverse engineering purposes.

Another important aspect to consider is mathematical analysis and display of results. The algorithms used for feature calculation must be accurate, stable, and work over a wide range of shapes and aspect ratios. The same is true for the algorithms used for probe calibration, part coordinate system creation, feature construction and tolerance evaluation. In addition, these algorithms should follow the guidelines provided by the relevant geometric dimensioning and tolerancing standards.

Result information is most useful when presented in clean, tabular form, customized to a manufacturer's own needs. For more detailed analysis of particular geometry problems, a 3-D graphical display of actual samples with respect to the given tolerance zones is highly valuable. In addition, certain types of tolerance evaluation, such as position of a hole pattern, or profile of a complex surface are best evaluated using 2-D or 3-D best fit or soft gage algorithms which can minimize the error between a set of sample points and a set of features or surfaces.

Reverse engineering is best accomplished by sending measuring results directly to a CAD environment where editing, trimming, and detailing can be used to create a complete design file.

For users who want to take advantage of software language features such as looping, variables, arrays, and mathematical formulas, a modern programming environment is essential. The environment should provide the ability to single step the program, set breakpoints, and examine user variables. It should be simple to add and delete lines, cut and paste blocks of code, and use search and replace functions. The most powerful environments allow program changes on-the-fly and the ability to undo back to any previous point for error recovery and experimentation.

For software to be truly user friendly, all these capabilities must work together at the same time, so that the operator can choose the best tool for each action without penalty of having to start over, or to shutdown one system and startup another.

Finally, a good CMM software system is robust and stable. It should be easy and intuitive to perform common operations. When mistakes are made, the user must be given the opportunity to back up and try again.