• NX Tutorial NX Tools PDTM

NX QuickTip - How to use the NX Tool PDTM (PMI Dimension and Tolerance Modeler)

In our last QuickTip we introduced you to the NX tools including the PDTM (PMI Dimension and Tolerance Modeler) and showed you where to find and how to install them in NX.

However, the question that remains is: How and for what do I use the PDTM? Therefore it is important to know about PMI's and what they are needed for.

What are PMIs and what are they needed for?

PMIs are Product Manufacturing Information that are attached to the 3D model or assembly during the construction process and stored within the file.

PMIs include the following

  • Surface information
  • Geometric dimensions and tolerances
  • Form and position tolerances
  • Text notes
  • Machining method (reaming, drilling, milling, etc.)

These dimensional and manufacturing tolerances, which are normally only available in a drawing, are specified as the PMIs of the 3D model and allow it to provide manufacturing-relevant information on which other processes such as CAM and CMM can be based in order to automate the manufacturing processes.


Why do you need tools like the PDTM?

Design usually works with nominal dimensions, taking tolerance specifications into account. In CAM programming, however, the middle dimensions on the tolerance center are often used for programming.

If the PMIs are attached directly to the 3D object in CAD, the manufacturing process can be optimized by using this information to further consistency and automation.

PMIs Nominal dimension vs. Middle dimension

Nominal dimension vs. Middle dimensions

In the case that a component has dimensions whose nominal dimensions are not at the center of the tolerance, Siemens provides a tool in NX, the PDTM, to correct the dimensions in the 3D model. This tolerance middle dimension module automatically shifts the contours of the component including the adjacent geometries to the tolerance center according to the PMI specifications. 

Alexandra DeYoung shows you in this tutorial how to use the PDTM in NX :

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Alexandra DeYoungAlexandra DeYoung
Junior CAX Consultant
E-Mail: alexandra@amscollective.com

Author of this Article

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