Break a model into parts for 3d printing



I’m making parts for 3d printing that are too big for the printer. I first design the part and then make new drawings to break it into pieces for later assembly. Is there a way to simply break up a model in one file? I find it extremely difficult, for instance, to mirror interlocking geometries for attachment the way I’m doing it.


Yes. It can be done in a single model. Exactly how depends a great deal on the model you’ve drawn. Perhaps you could share it?


could you show an example of one design that needs to be split up? Just to get the feeling of “how difficult” the designs are. It shouldn’t be too difficult to break up an object into several parts.
I’m thinking of say two copies of a group ‘In Place’ and then painting each of the 3 groups a different color… Then work on each group, using the other(s) as a reference. hard to explain in words without your example.
Mirror interlock should be just a copy of the geometry into each “connecting” group.

oops, I shouldn’t pause typing. Dave beats me (to it) as usual.


So here is an example. I drew something the size it needed to be knowing it would not fit the printer.
I set a copy of it outside the ‘the plane’ here so you could see it better

Then I looked for a strategic place to “cut it” that would fit my printer… I did it right where another major structural member would already be to act as a splice. I did it by zooming in real close and drawing two parallel lines 1 mm apart and doing a push pull through them (the 1 mm clearance/meat removed makes them fit together better after printing)

So here it is in two parts now.

and printed out… Both half’s pushed together on the bench…

Finally the front part is in a partial assembly…

If you look at the top pics again, since this project is 5 foot long almost every single longitudinal part is in pieces and has to be spliced. They were all done the same way though. Two parallel lines 1mm apart and push/pull through the part.


test tray.skp (1.1 MB)
Here is a simple box with a “key.” I’d like to split the box on the horizontal line and be able to reassemble with the key. I then need the parts to be in separate files for printing.


test tray.skp (1.1 MB)

Here’s the corrected model with Solid Inspector applied. I’ve tried Robajohn’s trick but can’t seem to get the push/pull to actually slice the box.


test tray.1.skp (1.1 MB)

Okay! I got Robojohn’s trick to work. I can’t get a down to a 1mm gap, though, unless I expand the part to an extreme on the screen. That takes a lot of work but it does do the job. The next problem is that, with the screen that expanded, I can’t select one of the halves to cut and paste to a new file. The selection box goes way off the screen. Any ideas for this? (I used a much wider “slice” in my example.)


You can use a Section Plane to split the geometry.


WHOO HOOO! A new tool in the tool box! Thanks once again @box!


As far as I can tell, the section plane only hides the part of the model that is being “sectioned out.” Every action I try on the remaining section sees it as the original model. I don’t seem to be able to actually break the model into two parts. Do you have any ideas?


Did you use Create group from Slice and then explode the group so it’ll cut the shape?


Yes, I did a create group and then explode. Explode didn’t do anything that I can see.


Assuming its in the same context as the rest of the geometry, it will divide it so you can select just one part of it and make a component of the selection.


What is meant by “context?” I created the figure, did the slice, did the create group and then did the explode. Explode didn’t do anything. What am I missing?


Being in the same context means all of the geometry is either ungrouped or in the same group/component.

So you exploded the slice group like Box did? Then did you try selecting the top half and make a group of it?


I may have been unclear. When I did the slice, the top half became invisible. When I did the explode after creating the group (of the visible half), nothing happened (that I can see). I’ve tried selecting where the invisible part is, but nothing happens there, either.


After you create the “group from slice” you need to delete the section plane as Box did in his animation.


The only way I can see to delete the section plane is to erase it. Doing that restores the full model.


How to get through?

The section plane never actually splits the model. In this case you are only using it to define where to split the model with the slice. After you explode the “group from slice” you still have to select the section on top of the slince line and make it a group. Then select the bottom portion and make it a group.

Please! Go back and watch Box’s animation a few times. Do what he did. You can’t just arbitrarily leave out steps.

Or maybe it would just be easier for you to start over and draw the thing in sections from the beginning.


Well – there’s my problem. Box’s message only shows a picture on my computer, not an animation. I’m going to go look it up on another computer and see if it opens up as an animation there.

When I place the section plane where I want it, the upper part of the model becomes invisible, as described in the Sketchup tutorial.

I could do what you suggest, but then how would I learn? I’m a newbie, and I greatly appreciate your input. And I’m stubborn. Comes from being such an old fart.