Understanding Engineering and CAD File Types in Construction and Product Litigation

In today’s complex construction and engineering disputes, attorneys are increasingly encountering technical design files as part of the discovery process. Most of these formats can be viewed directly within RelativityOne’s native viewer, allowing litigation teams to analyze engineering documents without needing the original design software. Understanding what these file types represent, and who could use them, is critical to interpreting the story behind the data.

.DWG files are the native drawing format for Autodesk AutoCAD and are among the most common files in construction and architectural matters. They contain detailed 2D or 3D design data, including layers, annotations, and object metadata. Attorneys may encounter them as the source files behind design plans, as-built drawings, or site modifications. The embedded metadata often includes timestamps and author information, allowing for analysis of who created or revised specific design elements.

.DXF (Drawing Exchange Format) files serve as a more open and shareable version of DWG drawings. They are often used when design data needs to move between software platforms or external teams. DXF files store vector-based geometry and are typically text-based, making them easier to preserve and search. In litigation, they are particularly useful when multiple contractors or engineers rely on different CAD systems.

.SLDPRT files originate from SOLIDWORKS and represent a single 3D component or part. These files contain precise geometric data, material specifications, and modeling features used in mechanical and product design. For attorneys, an SLDPRT file can demonstrate the intent and construction of an individual piece in a larger assembly — often relevant in product liability, equipment failure, or construction defect claims.

.SLDASM files are SOLIDWORKS assembly files that bring together multiple parts (.SLDPRT) into one complete system. They define how parts fit, move, and interact, showing the mechanical relationships between components. In disputes involving machinery, building systems, or manufacturing defects, reviewing an SLDASM file can reveal how a product or structure was designed to function — and where potential design flaws may have occurred.

.SLDDRW files represent the 2D drawing sheets generated from SOLIDWORKS models. These are the deliverable versions used for fabrication, review, and approval. They typically include dimensions, notes, and tolerances derived directly from the 3D model. Because they bridge design and production, SLDDRW files often surface in matters involving fabrication errors, documentation disputes, or change order verification.

.PRTDOT, .ASMDOT, and .DRWDOT files are SOLIDWORKS template formats used to standardize new parts, assemblies, and drawings. Each template carries preset properties such as title block layouts, units, and annotation styles. These files are valuable in discovery because they can show whether a designer followed the company’s established design standards or deviated from them, an important point in cases alleging procedural or quality control failures.

.STL files (Stereolithography) are used primarily for 3D printing and prototyping. They describe the surface geometry of an object using triangular facets but do not store material or texture data. In litigation, STL files can connect the digital design to a physical model or prototype, helping to validate whether a product was manufactured consistent with its approved design.

.3DXML is a lightweight 3D visualization format. It allows complex 3D models to be shared and viewed without exposing proprietary design parameters. Legal teams often use 3DXML files to review models in a readable, presentation-ready form suitable for expert analysis or courtroom exhibits.

.EDRW, .EPRT, and .EASM are read-only, shareable versions of drawings, parts, and assemblies. They enable easy review and markup without requiring full SOLIDWORKS access. These formats are particularly useful in discovery and production because they preserve visual accuracy while limiting exposure of sensitive design data. Attorneys should be aware that eDrawings can include embedded comments or redlines, which may be relevant evidence of design review discussions.

Compressed variants such as .EPRTX, .EDRWX, and .EASMX are optimized versions of the eDrawings formats, often smaller in file size and digitally signed to ensure authenticity.

Why It Matters

Each file carries metadata, authorship, and revision history that can reveal when changes were made, by whom, and under what standards. By leveraging RelativityOne’s built-in viewer and working with forensic or engineering experts, legal teams can transform these specialized files into accessible, defensible evidence that strengthens their understanding of the case.