Choosing a 3D CAD Program for Moulding Design

Data management with revision controls, which is standard in some programs and an extension in others, helps CAD programs efficiently track model changes throughout the design process (including naming conventions) and monitors the historical and present activity with each design. If an engineer is working on a model, other engineers are prevented from unknowingly accessing the design and potentially overriding the work of the initial engineer. Furthermore, if modifications are made to a complicated assembly that contains additional sub-assemblies, everything above it in its design tree is affected. The intelligence of the data management system allows it to automatically update any other pertinent areas in the assembly that the change in geometry affects.

There are also productivity tools within many programs that allow for things like geometric and feature comparisons between versions; analysis of thickness, draft, symmetry, and other design validations; and Bill of Materials (BOM) generation, among many other functions.

Neutral File Formats

When transferring a 3D model from its native CAD program to an alternative program, the solid model information may remain intact; however, depending on the format, some of the design elements may be lost in translation. That is why when designers are sharing part files between multiple systems, they'll often export their models in a neutral file format that is not bound to a particular vendor, but rather controlled industry groups. The primary file formats with vendor-neutral data are STEP (Standard for the Exchange of Product model data) and IGES (Initial Graphics Exchange Specification), and, to a greater extent with additive manufacturing, STL (Stereolithography).

if you're submitting a neutral file to be manufactured at Protolabs, we accept both STEP and IGES files for injection-moulded parts. With that said, Protolabs accepts nearly all file formats. (Note that STL files are limited to our additive and machining services.)

Smart vs. Dumb Models

When you're moving between two programs—regardless of whether it's uploaded into Protolabs' system or imported into your own—the loss of design intelligence can create what is called a dumb solid. When in this state, the model no longer contains its parametric attributes. If the face on one side of a part is moved, it no longer automatically moves any of the other features that are affected. You may be able to recalculate dimensions to create the change, but dragging a face to a new dimension will not propagate to the other design features it affects, so you're limited in that regard. CAD files that work within the same program typically retain that parametric knowledge.

Proposed Revisions

No matter what file format is uploaded at Protolabs, we provide automated design analysis on that model within 24 hours. We also have a feature in the design analysis that not only pinpoints potential mouldability issues, but when a model requires only minor changes—e.g., draft on thin/thick sections—we'll provide proposed revisions on a second model. Our quoting software documents and illustrates exactly what the new model changes are, and you can either accept it or upload a new model. If a SolidWorks part file was submitted, we'll retain and make changes directly within the smart model before sending it back to you. If any other CAD program was used, you'll have the option to download either a STEP or IGES file.

Protolabs-accepted 3D CAD file formats are listed online at protolabs.co.uk, and if you have a question about a particular program or format, please contact a Customer Service Engineer at +44 (0) 1952 683047 or [email protected]