How to determine cavity volume casting mold

Hello everyone,

I have modeled out a casting mold that has both interior and exterior mold elements. What I want to do is figure out what the negative space volume is between them so I determine how much castable material I will need.

Attached is the .skp model for review,

I appreciate any insights you may have.

Thank you,

Forge plan.skp (550.7 KB)

Are you talking about the space between the inner and outer walls?

SketchUp can calculate the volume of a solid. You need to make a single solid that corresponds to the space that will get filled with the material.

So, open each component that borders the casting volume, select just the face(s) that are on the border, close the component and paste in place. When you have all of them copied out, you can select them and make a new component from them (it may help if you hide the other components using the outliner). You will probably have to reverse at least some of the faces so that their front sides face open air and their back sides face to where the casting material will go. Then add faces as needed to close the bottom of the mold.

If all goes well, the new component should show as a solid in Entity Info and its volume should be displayed there. If it doesn’t, you will need to track down the issues that prevent it from being a solid and correct them. Solid Inspector 2 extension can help with this.

Thank you for the insights!

I will attempt that method and see how it goes.

Its wrong way. Use solid tools. Create an additional solid from which you subtract both parts of the mold.

Edit: What was/is wrong, offensive in this post that it was hidden?

I suspect @slbaumgartner is offering advice and method after examining the existing included model, in which all the walls are isolated individually, and also not precisely aligned in a way that can make a solid. As the model exists, piecing together individual pieces ( or exploding everything) and stitching together individual faces to make a negative space may be the only way.


In case the model is haotic (like this one) copying and pasting walls is also a wrong solution. In this case, the best solution is start new with right workflow.

  1. Make a detal
  2. Make a mold - you can use JPP extension
  3. Add filler holes, vents, etc iff need
  4. Divide mold

Maybe I misunderstood
here are the volumes that I estimated