Help me split my solid


First off, let me tell you that i am a complete noob with SketchUp, so I hope this makes it possible for me to ask stupid questions :slight_smile:

Here is what i am cracking my head with - i have this model.

It consists of two components. I need to unite these two and then make a cut along the curve in the top corner to the right:

As you can see, i put the square which i was going to use with the Intersect with model command, but i can’t get the face of this square along the curved line.

I know that i can use Solid Tools, but the end result i get with solid tools is too weird. I need the cut to happen along the curved line on the inner side and on the outer side i need it to be 45 degrees. These two pieces will then be ‘printed’ on a CNC machine out of wood.

What is the best way to do this?

Can you upload your model here (the .skp file) not just an image, to make it easier to help you?

Yes, absolutely.

K-402 Wood community.skp (245.6 KB)

Does it have to be the case that the vertical and horizontal profiles differ in both size and rotation angle?

The front corners also do not match. No wonder the result of the split is strange.

Hm, interesting.

The difference in size and rotation angles are intentional. But the front corners not matching is an issue that needs fixing.

What would be the best way to fix it? I know, I can make the whole thing 2D again, apply corrections to the geometry and push it again, but that is very time consuming and lacks precision. Maybe I should place crossing guiding lines and then use resize tool?

As for the making a 45 degree angle cut - the to of choice would be intersecting with the face of a rectangle?

чт, 31 дек. 2020 г., 14:32 Guntis Konstants via SketchUp Forum <>:

Just move it.
It’s worth noting that the bounding box doesn’t fit the shape, so it is off axis somehow. The two angles make it a rather odd shape, something that doesn’t work with a saw and two bits of wood.

There is a famous Irish saying about giving directions which begins “If I were you , I wouldn’t start from here.” I wonder if that is apposite here?

You might do better by explaining what it is you were trying to achieve as an end result rather than how others would use your method of getting there. It looks like you may be just trying to make a mitre cut. If so, there are better ways.

If you align the corners, as @Box showed, then due to the difference in profiles, the joint will not be nice either, although the splitting planes of both parts will be correct.

I have to agree with @simoncbevans that it would be nice if you could say what you really want to get.

If it is to be, for example, a picture frame made from pre-cut moulding, the the FollowMe tool would do a good job of making the whole frame in one go. Then to separate it into pieces just select the whole of one edge profile and make it a component. Copy and rotate or mirror it to replace loose geometry on the opposite edge, then repeat for the other sides.

Like this, for example, using your profile:

K-402 Wood community JWM.skp (258.3 KB)

I’m wondering what is the intention?

To meet at a clean 45 degree miter, the shapes must be the same. To meet at other angles, one must be developed properly from the other. In other words, perhaps what you are seeking to do is impossible…

The two profiles aren’t quite matching, even at the recess. Is one supposed to be a scaled down version of the other? Or at least, the curved part?

Here I’ve overlaid the horizontal profile on top of the vertical one.

If you were to get the rebates to match, re-extrude the pieces, align them correctly, then Intersect Faces/With model would create the mitre intersections, and a bit of clean up would get you a clean corner.

Something like this - clean on the inside, at least:

Not so tidy round the back!
K-402 Wood community JWM 2.skp (328.9 KB)


Thanks a lot of so much help. Wasn’t expecting it, frankly.

The end result of this endeavor is a replica of an acoustic horn for music system and/or home theater. The original is made of some sort of plastic, i am trying to model a replica out of wood. The first part of the horn is straight sided, the last part is curved as in the model. I am attaching a model with the straight side as well, so that you can see the whole thing together.

I need a way to CNC curved sides, make a miter joint and glue the curved parts on the straight sided parts.

A high frequency driver is then put on the apex of this horn. On two of the straight sided sides (laying horizontally in the model) i will be putting two woofers, which will ‘fire’ through two ports each. The whole thing will then be put in the cabinet. So i decided to model it first, produce plans and ask local carpenter to produce this speaker for me.

K-402 Wood.skp (302.1 KB)

Now i am thinking how to make a miter angle.

Here is what i get with ‘intersect with model’:

What would be the right way to put a face that will make an angle and match with upper part of the round over?

There are many questions here.

Do you really need these side gaps? If so, how deep should they be?


Does only the geometry of the curved surfaces matter, or must all the surfaces of the part be exactly as in the model?

I also have doubts about the acoustic properties of the replicated system, because the sound depends not only on the geometry, but also on the materials used.

No, those gaps are left not intentionally. I was trying to delete parts of the component after intersecting it with model and deleted those that i need as well.

Well, the first two thirds of the horn are designed to be made from plywood of 12mm thickness. I will also add braces to make it stiffer. Curved part must be made from several pieces of plywood glued together and then CNCed to needed form.

As for acoustic properties of the horn - the geometry of this horn is proven. Materials are chosen to be very stiff and i will be adding braces so that the horn doesn’t resonate. I hope this will be enough.

I was able to get almost the same form with Curviloft-Loft plugin as in your screenshot. The only problem with the one that i get is that the edges are too smooth. This is the first time i am using this plugin, can you point me into the right direction so that i could make them not as smoothed:

I used default settings of the plugin.

And another question - how did you actually split the model as shown on the right side of your screenshot?

:flushed: This helps explain something I’ve been having trouble with.

Hide Rest of Model and Hide Similar Components show up in both Model Info>Components and in View menu>Component Edit. I didn’t realise that changing the setting in the View menu changes the Model Info, and accordingly the behaviours are preserved in the Template or File, rather than with the programme. For me, it’s a hot tip. Thanks.

They’re the same settings, actually. I have keyboard shortcuts set up for them which is very handy because I can change them while I’m in the middle of editing a component if I need to.

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I simplified the profile a bit to make tinkering easier:

I can’t get my head around how I can match them so that diagonals do not show up when I use Curviloft, so that i get a nice miter. Plus, the first 12mm of the profile should stay perpendicular to the plywood part of the horn.

It is very difficult to get the correct shape if the geometric construction is not done correctly from the very beginning.

If the two profiles are compared, it can be seen that corners C, D and E are not equidistant from the front line.

In order for the profiles to split correctly, adjustments must be made to one of them. Either vertical (red lines) or horizontal (green lines).

Even if it is fixed, the next problem will occur on the arched (invisible) edges. Horizontal profile has 24 faces, but vertical - 27 faces, and their boundaries do not match.

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