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Potential problems with Retooling using CAD model converted from STEP to parametric 1

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Jonathan Tang

Mechanical
Dec 5, 2020
5
I am working on a resin change to a part that potentially needs small redesigns. We only have an imported STEP model of the part so making the changes would be a lot of effort.
We reached out to a vendor to recreate the STEP file into a parametric file with a design model history for me to edit. However, for certain features, he's going to only be able to match 99%.
From what I understand, when retooling happens, they use the new CAD model to create a CAD tool and retrace the cavities (All the portions already cut would just be retraced).

Question is:
1. Would the areas with 99% match, mess up the retooling?
2. How is the conversion to a parametric file even done with such accuracy?

SIDE NOTE QUESTION:
I need to perform impact analysis on this part on Solidworks FEA. I only have experience with static loading analysis. Does anyone have guidance or a source to learn this?
 
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Jonathan Tang,

Can you get a properly dimensioned drawing of the part? This makes re-modelling easier, and you kind of need tolerances to do manufacturing. Your phrase "99%[ ]match" means nothing to me other than that you are guaranteeing and error of some sort.

Impact analyisis: Is this safety critical? Are you qualified to do it? Can you do it by hand? We have a forum1183.

--
JHG
 
drawoh,

No, we don't have a properly dimensioned drawing of the part. There are organic surfaces so we reference the CAD file for the full geometry. I think by 99% match, he really just means the parametric file won't be an exact match to the original step file. And this is most likely going to be the portion of the model with organic curves. Will retooling with this non 1:1 model cause issues?

Thanks for the simulation forum, I didn't know about it. We will be testing the parts with a drop tower so that will be the ultimate decider if the parts pass. But it would be beneficial to accurately simulate the impact before making design changes.
 
I have had to recreate many parts in SW using STEP files as the only input. Some things are easily measured and can be exactly duplicated. Other things like the organic surfaces are going to end up being a best guess, especially if they were produced using hard to control features like sweeps or lofts or use splines instead of radii.

If you work closely with your tooling vendor this doesn't need to be a problem. Just indicate in detail what is supposed to have changed and tell them to disregard anything else on the swoopy surfaces (technical term). They aren't going to want the update process to be more involved than it needs to be so they won't be running cutters over all surfaces of the tool if you only moved a mounting boss.
 
If you are that worried about it just import the STEP file and modify it. If the changes are small enough to be made in the tool you don't need a fully parametric model. Just add the new material to the imported dumb solid.

This will actually be a more accurate representation of the design intent which is take this geometry without changes and add these new features.
 
A happy medium could be taking the difficult to recreate organic forms and extracting them from the step model and incorporating them into a parametric model that lets you adjust other features while the organic stuff stays static.
 
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