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Using CAD models in 4.1 and above; importation and transformation
Written by James Mannes   

The software developers at Wilcox have been hard at work to improve PC-DMIS for the last few years. With their hard work they have added many new features that may not be known to the average programmer. This flexibility is making the usage of the software easier and easier for the seasoned programmer. At one time the programmer would have to hunt down an engineer that had some knowledge of CAD software if a “tweak” was need to an .iges or .step model. As of the PC-DMIS 4.1+ version(s), the CMM programmer can easily manipulate the models from within the software.

As an example, many times a program will have been created in standard units and the next CAD model given to the CMM programmer will have been exported from its native software in metric units. This change may have been intentional or an oversight, but either way, it would have a required a rewrite of the program or the very least for someone that had access to the native CAD software to export in the proper units. All of this manipulation can cause errors. PC-DMIS now allows the CMM programmer the ability to import .iges and .step files regardless of the units used for its’ creation.

Another improvement in PC-DMIS is the ability to “transform” the CAD data once the .iges or .step file has been imported. Similar to the units of measurement issue, sometimes a CAD model can be imported and the origin of the part may not be where the blueprint states it should be. In many cases there are a number of authors that work on a CAD model. Each one of those authors opens, saves, and closes the CAD model numerous times in its’ life and at some point the origin is either moved or re-oriented upon a new model being created.
It is at this time that the ability of PC-DMIS to “transform” the model is a welcome option for the CMM programmer. In the example, notice that the trihedron is set such that the +x axis is pointing downward, the +y axis is facing to the left, and the +z axis is pointing away from the operator.

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If the part were to be set up on a CMM as seen here the axis could be manipulated so that they mimic the CMM axis.

This is done via the “transform” option. This option is accessed from the file pull down menus…OPERATION| GRAPHICS DISPLAY WINDOW|TRANSFORM…

The Cad model is able to be manipulated by rotation, translation, and even scaling the model down. Two of the options will explained in this article, the ability to translate and the rotation function.

Referring to the original model, if the part were to be set up just as it is seen in the example, the programmer would be able to manipulate the axis’ so that x, y, z  matched the CMM. This could be done when the program is initially being created, or if needed, when a new CAD model is introduced.


To do this is just a few simple steps. First, with the TRANSFORM window open, insert a value into the “Rotate” box. In this case it will be 90 degrees. An axis for rotation must also be chosen. In this case it will be the Z axis that will be the axis of rotation.

As can be seen, the x axis has now been rotated the appropriate direction. In order to finish the rotational portion of the transform function, one more step is needed. A rotational angle of -90 degrees must be input into the “Rotate” box and the x axis must be chosen. This will allow the trihedron to be rotated about the x axis such that the z axis is now positioned correctly for staging on the CMM.

Here is what the CAD model will look after the translations have been successfully carried out.

Most of the time those steps would be sufficient to continue creating the new program or using the CAD model to add measurements to an existing program. But, consider this, what if the CAD modeler also moved the location of the Y axis also?

What if the Y axis used to be where the yellow arrow is pointing and this is a completed program that just needs some new features, from the new CAD model added? Well, then the “translate” feature found in the TRANSFORM option.

The Y axis of the trihedron can be moved to the front face. In this case, the Y axis happens to be 10.885mm from the front face. This option is accessed from the file pull down menus…OPERATION| GRAPHICS DISPLAY WINDOW|TRANSFORM…

Here the transformation has taken place and the programmer can continue programming without having to wait for hours or days to get the CAD model updated.

James Mannes is the Leading Senior Layout Technician at the EST Co. Inc located in Grafton, WI with 15 years in metrology, and a past contributor to the CMI testing process for ASQ. James is also available for contract work and consulting. Contact James at jmannes@gmail.com

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