Splitting and separating model for 3D printing

I know this question has been asked a few times in this forum over the years, but none of the answers seem to be complete. I have a model I designed for my 3D printer that’s just a bit too big. I need to not only split the model in two pieces, but it needs to be split at a point I designate and I need to separate the two halves so that they can be saved as separate STL files.

One solution said that I should create a “cutting plane”. Well, drawing a rectangle and manually trying to move it to the model at an exact position seems very awkward. Is there a trick I missing?

My understanding is that the technique is as follows:

  1. Turn the model into a group
  2. Place the cutting plane in place inside the model.
  3. Select all, and do Intersect Faces with Selection

But the rest doesn’t seem to work. If I explode the group, how do I separate the model into two pieces?

If you share the SKP file it would be possible to give you complete, exact instructions.

Probably are missing a trick. Moving the moving the rectangular cutting plane should just be a simple Move operation. Once you start moving it, you should be able to drop it exactly where you want to cut the model.

items_events_omens.skp (30.9 KB)

I’m hoping for generic instructions that I can use any time. Creating the cutting pane of the correct size is still awkward, as it’s hard to position the first corner and then draw the rectangle in the correct orientation and sufficient size.

There are other applications that are intended to making things printable. They can make a model be hollow for example, and can cut up the model too.

The two I use are Cura and Meshmixer. Here’s an article on what you want to do, using Meshmixer:


I would prefer to make the cut in Sketchup so that I can continue working on it if necessary.

One way to pull a model apart that’s fairly easy on the brain is to copy the model and the cutting plane and paste-in-place them into two new documents (easy on a Mac with multiple windows), then cut and throw away the unwanted parts of each half knowing that you’re not editing the original. Then Save As each document as their own parts which is what you’re looking for to print.

How do I use the cutting pane to only select the half that I want to get rid of?

Surely there’s a more elegant way of breaking a model apart?

First intersect the model with the plane, then use selection tools to select the unwanted half, but not the common parts to both right on the cutting plane, and delete them. Switching to orthographic view sometimes helps with that selection.

Basically you just need to create the geometry at the point you want to split it, then select and group both sides and repair any holes made in the process. This shape is straightforward because you have a point to work from and can align it to the axis.
Note I make two groups within the original group, then explode it to get rid of it, you don’t have to do it that way but it works for this example.