Use .stp AND .pdf to get the best casting price from your RFQ
Computer aided design has come a long way in recent years, and continues to evolve. 3D models have become the norm, and there are many benefits to working with them. They make parts much simpler to visualize. It is easier to understand coring requirements, perform casting weight calculations and parting line and draft analysis. But even though 3D models contain a lot of great information, a reliable companion 2D drawing is still needed.
The 2D drawing applies information that's difficult, if not impossible, to get from the 3D model. Material specification, inspection requirements, datum structure and targets, critical dimensions, basic tolerances and GD&T, identification locations, and finishing requirements are all derived by the 2D. With this in mind, most drawings have evolved into several different views with datums and targets called out plus a list of notes. It is not uncommon to have more notes than dimensions on a drawing.
Often, a note will read something like the following: “CAD database is to be used for manufacturing and/or tooling of this part. Any geometry not defined or dimensioned on the drawing is to be derived from the database matching the rev level of the drawing”. Verbiage like this allows for much cleaner drawings since the engineer only has to convey critical dimensions and tolerances. The model can inform everything else.
For quoting purposes, while we can work with either 2D or 3D alone, it benefits you the customer to provide both. 3D without 2D can lead to surprises in tolerances, among many other things. 2D without 3D, especially with complicated designs and a lack of dimensions, make it difficult to determine desired parting lines and coring requirements. As companies try to compress the manufacturing timeline, they tend to want to send the design out for a quote once the 3D is complete, or close to complete, without waiting for the 2D. It is wise to keep in mind that this approach can lead to surprises down the line.
Providing both formats is your best bet, if you want the best price.
Vice President, Engineering
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