PMI
What is PMI (Product and Manufacturing Information)?
PMI, or Product and Manufacturing Information, refers to essential non-geometric data attached to a 3D CAD model that is crucial for product manufacturing. PMI contains all the information that a machinist, machine shop, or machining facility needs to manufacture, measure, and inspect a part—without the need for separate 2D drawings. PMI is a key element of model-based definition (MBD), an approach where the 3D model serves as the sole source of information throughout the entire manufacturing industry process.
PMI from the manufacturing industry’s perspective
In a machine shop, PMI makes it possible to conduct CNC machining, CAM programming, and measurements directly from the 3D model. PMI may include geometric tolerances, nominal dimensions, surface roughness requirements, material specifications, as well as various manufacturing and process notes. When this information is a built-in part of the CAD model, it reduces errors commonly caused by interpreting traditional engineering drawings.
PMI and Geometric Tolerances
One of the most important aspects of PMI is GD&T, or geometric dimensioning and tolerancing. With PMI, tolerances, datums, and measurement requirements can be directly associated with model surfaces and features. This is especially critical in CNC machining and CMM inspections, where tolerances can be read straight from the model without manual entry.
PMI in CAD, CAM, and CMM Systems
PMI acts as a bridge between CAD design, CAM programming, and measurement processes. Many CAM applications can directly use PMI data for toolpath generation. Likewise, CMM measurement programs can utilize PMI to automatically generate inspection routines, speeding up quality assurance at the machine shop and reducing human interpretation errors.
PMI and Data Transfer in Manufacturing
PMI can be transferred between different systems using neutral file formats like STEP and JT. This is crucial in subcontracting chains, where CAD models are passed from designers to machine shops and on to inspection. PMI ensures that all parties see the same product definition, regardless of the software in use.
PMI and Model-Based Definition (MBD)
PMI is a core component of model-based definition, where the 3D model replaces traditional 2D drawings. In the MBD approach, PMI acts as a digital product definition used by machinists, CAM programmers, and quality control across the entire product lifecycle. This supports the manufacturing industry’s shift toward automation and Industry 4.0 practices.
Summary
PMI, or Product and Manufacturing Information, consists of manufacturing data embedded into a 3D CAD model that supports machining, inspection, and quality assurance without separate 2D drawings. PMI improves data transfer in machine shops, reduces errors, and enables more efficient CNC machining as part of a model-based definition workflow.
