DESIGN FOR MANUFACTURING (DFM) GUIDE

CAD for Manufacturing

Your 3D CAD model is the blueprint for your physical part. This guide covers best practices for creating models that are clear, accurate, and optimized for manufacturing.

The Golden Rule: The Model is the Truth

The single most important principle is that **your 3D CAD model should be the "source of truth" for the part's geometry.** While a 2D drawing is essential for communicating tolerances, threads, and finishes, the physical shape of the part will be manufactured directly from the 3D data you provide.

Ensure that all features, including fillets, radii, and draft angles, are fully modeled in your 3D file. Do not rely on a note in a drawing to add a geometric feature that isn't in the model itself.

A detailed 3D CAD model of a car, representing the source of truth for manufacturing

Modeling for Your Intended Process

Modeling for Injection Molding

When modeling a part that will eventually be molded, you must incorporate DFM rules for molding. Use your CAD software's tools to add draft to all vertical faces, ensure wall thickness is uniform, and add generous radii to all corners.

Modeling for CNC Machining

When modeling for machining, think about how a cutting tool will access the features. Design internal corners with the largest possible radius. Avoid deep, narrow pockets. And remember that the tool cannot create sharp internal corners—they will always have a radius.

Exporting for Success

Best Export Practices

Use STEP for Machining/Molding: The STEP (.step, .stp) format is the best universal format for these processes as it contains precise geometric data. Export using the AP214 or AP242 protocol.
Use STL for 3D Printing: STL is the standard for printing. When exporting, choose a high-resolution setting (a low deviation or angle tolerance) to ensure curved surfaces are smooth.
Check Model Scale and Units: Ensure your model is exported at a 1:1 scale and that the units (e.g., mm vs. inches) are clearly defined. All of our systems operate in millimeters (mm).
Single Solid Body: Ensure your final exported model is a single, solid, "watertight" body, not an assembly of multiple surfaces or bodies.

CAD Preparation FAQ

Why can't I just send my native SolidWorks / Fusion 360 / etc. file?

While we can often open native files, providing a neutral format like STEP guarantees compatibility across all of our different software systems (for quoting, CAM programming, and inspection). It eliminates the risk of translation errors that can sometimes occur when opening a native file in a different software version.

How do I check if my STL file is "watertight"?

Many CAD programs have built-in mesh analysis tools. There are also free external tools like Meshmixer or Microsoft 3D Builder that can automatically diagnose and often repair issues like holes or inverted normals in an STL file.