Osiervt,
Interesting project!

I have a question:
Why is the gantry made out of MDF and not EG ?

And a few remarks:
The support plates should be embeded in the EG casting and held by inserts, either welded or bolted to the support plates, this will simplify the casting process. The support plates should be have drilled and tapped holes to enable fastening of the linear rails,

Be careful with chamfering and pointed areas, they will hard to properly fill when pouring EG in the mold and edges with sharp angles are easy to break/shatter.

Good luck with your project

Best regards

Bruno