- Practice · 4 marks
PDES, ACIS and Parasolid short notes
Short answer
PDES (Product Data Exchange using STEP) is a neutral standard for exchanging complete product data including shape, tolerances, and materials, which merged into ISO 10303 (STEP). ACIS and Parasolid are 3D geometric modeling kernels; ACIS (from Spatial) supports solid modeling with SAT files, while Parasolid (from Siemens) uses .x_t and .x_b files for precise solid exchange between CAD/CAM systems.
Write short notes on PDES, ACIS and Parasolid.
PDES
Product Data Exchange using STEP was a US initiative of the late 1980s (NIST and industry) to define a neutral way of exchanging complete product data, not only geometry. It was developed together with the ISO group working on STEP, and merged into ISO 10303 (STEP). It covers shape, tolerances, materials, assembly structure and life-cycle data, and was meant to replace IGES.
ACIS
ACIS (by Spatial Corporation; the name is commonly explained as "Alan, Charles, Ian's System", after its original developers) is a 3D geometric modelling kernel written in C++ and licensed to many software vendors. It handles wireframe, surface and solid (B-rep) modelling, Boolean operations, blending and offsetting. Its native file is SAT (ASCII) or SAB (binary), which is used to transfer solids between ACIS-based systems (for example SpaceClaim, BricsCAD, and early versions of AutoCAD and Autodesk Inventor).
Parasolid
Parasolid is a B-rep solid modelling kernel (originally from Shape Data, now Siemens). It supports solids, sheets, wires and free-form NURBS surfaces with robust Booleans. It is used in NX, SolidWorks, Solid Edge and many CAE/CAM tools. Its transmit file formats are .x_t (text) and .x_b (binary), which allow direct transfer of exact solid geometry between Parasolid-based software without loss.
| Item | Type | Native files |
|---|---|---|
| PDES | Data-exchange standard (became STEP) | STEP (.stp) |
| ACIS | Modelling kernel | .sat, .sab |
| Parasolid | Modelling kernel | .x_t, .x_b |
Kernel-based formats keep exact (not faceted) geometry, so they are better than STL for CAD-to-CAD exchange.
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