What’s New in SOLIDWORKS 2024 – A Mold-Maker’s Delight: Subtract Bodies, Make Main Body Transparent

Article by Ben Colley updated November 9, 2023


In this post, I want to highlight a SOLIDWORKS 2024 enhancement that gets to the most basic form of CAD modeling.

One of the oldest and most elemental concepts in CAD is Boolean operations – combining geometrical entities through either addition or subtraction to get to a desired shape. (The term “Boolean operations” may evoke haunting memories for engineers of their Calculus 3 days and the creation of solids through antiderivatives… luckily SOLIDWORKS does all the math and we can laugh while we hit a single button that accomplishes an hour’s worth of hand calculations.)

Intelligent features like Extrude, Loft, Sweep, advanced surfacing, etc. have modernized our thinking of part creation beyond the simple concept of putting primary solids together to approximate a finished product; but that doesn’t mean Boolean operations – simply adding and subtracting shapes from each other – no longer have a place in SOLIDWORKS modeling. Indeed, SOLIDWORKS users who design molds or products with complex interior features, such as engine blocks, use simple geometric additions and subtractions every day. If you work with these kinds of operations in SOLIDWORKS, then the enhancement I’m going to highlight here is for you.

The enhancement is to the “Subtract” portion of the Combine Bodies command. Where before this command was a little bit of a chore to use, in SOLIDWORKS 2024, subtracting bodies is a breeze. I could have really used this enhancement in years past when I would design molds for poured materials in SOLIDWORKS. My general workflow for mold design (not referring to the Mold Making arm of the SOLIDWORKS software) was as follows:

  1. In SOLIDWORKS, I’d model the finished part as it would look when drawn out of the mold. I would generally create a configuration for the cast part that didn’t include any post-operations like drilling, milling, etc.
  2. If I was designing for a poured material that would go through some expansion or contraction, I’d use empirical data to determine any necessary scaling, so the finished part would harden to the correct dimensions.

    simple mold design process in solidworks

    Basic mold design

  3. I’d model a block that fit the properties of the actual stock that would be used to create the mold (I used a CNC router to cut molds)
  4. I’d use the Subtract operation in the Combine Bodies command to subtract the finished components from the mold stock (the Main Body in the Combine command – the body that remains after completing the subtraction), creating a reverse impression of the finished parts.
  5. Depending on the complexity of the finished part, I’d break up the stock into segments, so that the mold could be separated along all necessary parting lines.
  6. I’d plan ahead for any alignment pins, clamping, etc. for the molding process, and include that in the model.

This worked effectively for me, but there was a slight limitation in the software when carrying out the Subtract operation. Before 2024, the main body remained opaque and selectable onscreen after it was chosen as the main body. If the cores (the bodies that needed to be subtracted from the mold) were fully enclosed or flush with the extents of the stock, it was somewhat difficult to select the inner bodies while within the Combine command. Often, I could see portions of the inner bodies in the graphics area, but when I tried to click on them as “Bodies to Subtract”, the software would think I was selecting the Main body again, and it would clear out my selection.

SOLIDWORKS combine subtract bodies before 2024

SOLIDWORKS combine subtract bodies before 2024

To successfully get the correct selection of main and subtracted bodies, I would usually have to expand the Feature Manager back out, expand the “Bodies” folder, and sort out the bodies there. It wasn’t a terrible hassle, but it was a lot of clicks, and a source of frequent minor annoyances.

The Enhancement: Make Main Body Transparent

In 2024, we’ve been given an improvement to the Combine command that makes body subtractions much easier.

Note, the easiest ways to get to the Combine Bodies command are to…

  • Select the bodies from the feature tree that will be involved in the Combine, right-click one of the bodies, and “Combine” will appear as an in-context command.
  • Use the S-Key shortcut bar or W to activate a command search, and search for the “Combine” command. Optionally, add it to a toolbar if you use Combine often.
  • Insert > Features > Combine…

The enhancement in 2024 is a new checkbox that shows up when using the Subtract operation in Combine bodies. It’s such a subtle enhancement, but I think it’s going to have a huge impact. The checkbox shows up beneath the “Main Body” selection and says “Make main body transparent”.

solidworks 2024 make main body transparent

Make main body transparent

With this check box activated, the “Main Body” goes transparent (as expected) and cannot be re-selected from the graphics area while the command is active. The implications of this are:

  1. Interior bodies have complete visibility as soon as the main body is selected.
  2. There’s no chance of accidentally unselecting the main body.
  3. The interior bodies are a piece of cake to select from the graphics area. No more having to re-open the FeatureManager and navigate through folders.


The addition of a simple checkbox hardly seems like an earth shattering software enhancement, but in this case, that simple checkbox is going to make life easier for lots of SOLIDWORKS users. It’s refreshing to see that SOLIDWORKS R&D is still looking and listening for ways they can make even the most elemental aspects of the software better for everyone, even after the program’s been around for nearly three decades.

Keep an eye out on our blog and Tech Tips YouTube channel for more content on all the exciting enhancements in SOLIDWORKS 2024!

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Ben Colley