ECAD to MCAD transfer redraws board

Created: March 25, 2021 | Updated: August 12, 2021

This article describes why a transfer from ECAD to MCAD redraws board shape and loses board constraints.

Starting in Version: 20.1
Up to Version: Current

Solution Details

Constraints applied to the board outline:

A Mechanical Engineer (ME) can apply a constraint from an element of the board outline to another element or to an enclosure or to a component. CoDesigner does nothing with such constraints. However, if the board outline is changed on the ECAD side, the sketch of the board part will be redrawn in MCAD and all of the edge IDs will be changed.  

Any change to any part of the board outline in ECAD will result in the entire board being redrawn in MCAD, and all board edge IDs changing. If there was a constraint applied to those edges or to the derived surfaces, those constraints will be broken. The board will stay in place in MCAD, and if necessary, the constraints can be manually restored. But considering that it takes time, it’s better to make changes to the board outline on the MCAD side only.


One method how to handle this is to synchronize changes among Mechanical Engineers (please keep in mind that CoDesigner is not a tool for transferring changes among MEs in any case):

The exchange is directional. The data sent from Electrical Engineer (EE) to ME is handled by CoDesigner separately from the data sent from ME to EE. In other words, CoDesigner is a tool for sending changs from EE to ME and back, it's not a storage system and not a tool for interacting between MEs.

To allow other MEs to see your changes, please simply save your PCB assembly to some common storage available for both, in the same way as you would for any other assembly. Or, pull changes on the ECAD side and then push an updated design back to all MCADs.

Constraints applied to the components:

The mechanical engineer can apply a constraint from a component: to the board; to an enclosure; or to another component. These constraints will stay healthy if the model of that component can be found locally (if the PCB assembly is not built from scratch in a different folder, or if a common folder is set up for storing models). However, if a component is moved on the ECAD side, the placement change on the MCAD side may not correspond to that movement and should be checked manually (CoDesigner will notify you in this situation). For components with an ECAD footprint, the component standoff (location relative to the board surface in the Z direction) will always be defined by the position of the STEP model in the footprint.  CoDesigner will always attempt to override any conflicting MCAD constraints on a Pull into MCAD.

Note: Be careful with where the mates/constraints are applied. For example, if you have not secured the PCB assembly within the device assembly and then applied a constraint/mate between a PCB component and the enclosure, it may cause unpredictable changes in your design.

Here's a video that may be of interest:

Maintaining MCAD Constraints During Exchange

Further information on this topic, please refer to our documentation:!working-with-constraints-and-dimensions-in-mcad

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