Arnout Temminck

Best practice MBD CAD to CAM

Discussion created by Arnout Temminck on Feb 22, 2021
Latest reply on Feb 22, 2021 by Arnout Temminck

Hello all,


I'm sort of struggling to find the optimal link between a 3D SOLIDWORKS MBD CAD model and CAM. The main issue is whether the CAD model is a 1:1 match of the desired end-product. In general, we tend to make a nominal model of our design and add additional information such as tolerances. The problem with this workflow is that asymmetric tolerances, such as the bilateral ones together with the fits, will result in a mismatch between the desired geometry of the manufactured end-product and the geometry of the CAD file.


For example, let say want to manufacture the following part:


This part has 7 dimensions, all with asymmetric tolerances. The geometry of the model, however, consists of the nominal dimensions (the dimensions present in sketches), like shown in the picture below


CAM uses CAD geometry as input so CAM wants to generate a program to manufacture the part with the nominal dimensions (picture 2). However, most of the time we want to manufacture the part with dimensions that are the mean values of the tolerance ranges so like this.



The mapping from pictures 1&2 to picture 3 is often a manual task. I was hoping that SW MBD has a possible solution for this problem. I know that you can provide the CAD model with DimXpert's size and location dimensions. Like this


And I know that CAM programs like SolidCam and CAMWorks can handle DimXpert dimensions with asymmetric tolerances via the Tolerance Based Machining tool. However, we don't use these CAM programs, and even if we will use these, then suppliers of our company still struggle with this issue if they also don't make use of one of these CAM packages. 


The solution for this problem, I think, is that SOLIDWORKS will help us in making a tolerance-centered model. Now, the CAM programs essentially must come up with a solution to map the dimensions. Wouldn't it be more convenient that such a task is performed at the source?, so within SOLIDWORKS. So for example within SW MBD there is a new option that enables the CAD geometry to be rebuild, based on the DimXpert dimensions with asymmetric tolerances. So that Dimxpert information can overrule sketch information. This way all CAM packages can be provided with tolerance-centered models. 


Another solution for this problem is that SW would provide us with a better link between sketch dimensions and DimXpert dimensions. Because sketch dimensions directly determine the geometry. And you can also provide sketch dimensions with tolerances, and there even exist tools that can map sketch dimensions to the mean values of the tolerance range. Like this.


However, as mentioned earlier you cannot create a link between a sketch dimension and a dimxpert dimension.


Lets say i have a sketch dimension of 40g6, i can add a DimXpert size dimension and manually add there the g6 tolerance as well, so both the sketch dimension and the dimxpert dimension are 40g6. However this is always a manual task and errors will occur if one edits one of these dimensions and forgets the other one.


I think the best solution would be a new tool within solidworks that regenerates the CAD file's geometry based on the additional information of the DimXpert dimensions. So a make a 40 dimension in the sketch, make a size dimension in DimXpert and add the tolerance g6 in dimxpert. Run this new tool, so when I measure the cad file, I measure 39.983 instead of 40 and 40g6 is display instead of 39.983.



Does anyone of you also have the same problem? Or even better, has found a solution for this problem.


Also, can maybe someone like Oboe Wu also share his option about this topic. That would be really appreciated!




Kind regards, 

Arnout Temminck