When starting a new Enventive Concept project, the user faces an important decision in order to optimize the tolerance analysis of their product: should they start from a blank sheet or import their existing geometry from CAD?”
Actually, four different approaches are possible:
- Starting from scratch
- Importing geometry from CAD and constraining the functional geometry
- Importing and automatically constraining CAD geometry
- Mixed approach
1- Starting from scratch
Following this approach, the user manually enters all required functional information in a new Enventive Concept model. Rather than representing all the elements in the CAD model, the user only needs to enter the functional elements for the specific GD&T (geometric dimensioning and tolerancing) study. The following figure illustrates this approach for studying the functional elements of a brake cylinder:
At first sight, it may seem that this approach is not the most efficient to create a new project, and it indeed isn’t the method of choice among many new Enventive Concept users. However, we see that more advanced users tend to use this approach, as they create models earlier in the design process before CAD models are finalized.
Pros: Quick to enter only functional geometry, the user must think about each dimension and its effect on the product’s design
Cons: Lack of visual information
2- Importing “locked” geometry from a CAD model
One of the drawbacks of the previous approach is the lack of visual information that helps product managers, colleagues, clients, suppliers and anyone involved in the process. to quickly understand the model. To provide this visual information in an Enventive Concept model, users can import geometry from an existing CAD model using a STEP/IGES file.
Using this approach, the user exports a 2D section of the part to a STEP/IGES file, and then imports the file into Enventive Concept as “locked” geometry, which essentially means that the geometry does not include any dimensions and acts as if it’s fully constrained (which essentially means that the geometry does not include any dimensions or constraints and the geometry is ignored by the Solver). The user “unlocks” and dimensions only the functional entities, leaving the rest of the geometry that has only a visual purpose “locked.” The following video illustrates this approach using the same CAD model as in our previous example:
Pros: Visual aid to assist in understanding the part, reuse of existing CAD data, more intuitive for new Enventive Concept users
Cons: Exporting an appropriate view of the geometry from the CAD model may be more time-consuming than just sketching the functional geometry from scratch for experienced Enventive Concept users
3- Importing and automatically constraining CAD geometry
Enventive Concept includes an automatic constraining wizard that automatically assists the user in constraining imported CAD files. This tool can save considerable time applying the datums, dimensions and constraints needed to fully define an imported model.
Pros: The wizard helps inexperienced users and quickly performs repetitive tasks
Cons: Not as flexible as other methods
4- Mixed approach
This method is an alternative mixed approach that uses the information of the CAD file as a “background” image. Then, the user draws the functional geometry on top of that image.
Pros: Suitable for very large models with only a few functional entities (e.g., complex plastic injected parts)
Cons: All the constraints applied to the background image must be removed; otherwise, the tolerance analysis results could be incorrect
The best approach to choose depends on the complexity of the model and the user’s own preferences.
In all cases, Enventive Concept is not just another verification tool for use at the end of the design cycle, but rather a conceptual design tool that helps users discover issues before detailed design begins, thus saving them time and money.