Migrating to Minimally Annotated Drawings

References Cited

3D Visualization, Mechanical Computer Aided Design (MCAD), Model Based Definition (MBD), Model Based Enterprise (MBE)

Studies Cited

The ROI of MBD Study

While a lot of attention is focused on replacing drawings with annotated models, that’s not the only engineering documentation initiative organizations are pursuing. One initiative that is in practice is to release a 2D graphical drawing and a 3D model as a set. The advantage here is to rely on the ability of the 3D model to convey the complete and detailed geometric form of a component while allowing the 2D graphical drawing to define the measures and thresholds within which a component meets quality standards.

These two deliverables work in conjunction to achieve the function of engineering documentation. The following examples illustrate how the two are used side-by-side downstream.

While a lot of attention is focused on replacing drawings with annotated models, that’s not the only engineering documentation initiative organizations are pursuing. One initiative that is in practice is to release a 2D graphical drawing and a 3D model as a set. The advantage here is to rely on the ability of the 3D model to convey the complete and detailed geometric form of a component while allowing the 2D graphical drawing to define the measures and thresholds within which a component meets quality standards.

These two deliverables work in conjunction to achieve the function of engineering documentation. The following examples illustrate how the two are used side-by-side downstream.

  • Tooling Design: Those developing molds, dies and casting tooling can accurately develop cavities within the tooling based on the 3D model. They then make changes to the tooling based on the tolerances and surface finishes defined in the 2D graphical drawing.
  • Generating NC Toolpaths: Machinists can directly, and frequently automatically, generate toolpaths using the 3D model in CAM software applications. They then reference the 2D graphical drawing for tolerances, surface finishes and other details to refine the speeds, feeds and tools used during the operation.

Using such a method theoretically offers a straightforward benefit: less time is required to detail a fully annotated drawing, only documenting the aspects of the design that needs to be measured for conformance. Findings from this research study do, in fact, verify this benefit. The amount of time estimated to create the minimal drawing dataset averages 5.2 hours, a significant amount less than the 8.8 hours estimated to create the fully annotated drawing dataset. Additionally, those using this approach realize a small reduction in clarification requests for engineering documentation (23% vs. 15%), as the 3D model can provide clarification.

Finding: Migrating to Minimally Annotated Drawings

Finding: Migrating to Minimally Annotated Drawings

Figure 2: On the left is the average of the estimate to create the fully annotated drawing dataset by All Respondents cohort. On the right is the average of the estimate to create the minimally annotated drawing dataset by the Drawing-Reliant cohort. Details on calculations of the estimate, assignment of respondents into cohorts and the drawing datasets are detailed on The ROI of MBD Study page.

There is, however, a flaw in using this approach. A 2D graphical drawing that has been exported or saved into a neutral or other format can still be edited without updating the 3D model. When under tight time constraints, as is often the case in product development projects, this is seen as an easy fix requiring little time. Taking this approach, however, leads to diverging definitions in the 3D model compared to the 2D graphical drawing. This leads to costly errors downstream. For example, parts coming out of tooling made with the 3D model will not conform to quality standards when measured against the 2D graphical drawing. Responses from this research report verify this as there is no practical difference between organizations that primarily release drawings, defined as the Drawing-Based cohort in Appendix B, and organizations primarily releasing models and drawings, defined as Model-Based cohort in Appendix B in reducing ECOs (20% vs. 21%), decreasing non-conformances (16% vs. 16%) and reducing scrap (16% vs. 16%).

Finding: Benefits of Migrating to Minimally Annotated Drawings

Finding: Benefits of Migrating to Minimally Annotated Drawings

Table 1: Comparison of benefits realized across the Drawing-Reliant and Model-Reliant cohorts. Details on calculations of the estimate, assignment of respondents into cohorts and the drawing datasets are detailed on The ROI of MBD Study page.

Ultimately, transitioning from releasing fully annotated drawings to releasing a combination of minimally annotated drawings and a 3D model provides benefits to the engineering organization in terms of time spent on engineering documentation, but little else for the whole company.